the mechanism of d- metal ions sorption from aqueous media … · 2016. 11. 22. · 121...

Draft

The mechanism of d- metal ions sorption from aqueous

media and chelating sites structures of modified heterocyclic

biopolymers

Journal: Canadian Journal of Chemistry

Manuscript ID cjc-2016-0194.R1

Manuscript Type: Article

Date Submitted by the Author: 09-Jul-2016

Complete List of Authors: Kozlov, Vladimir; Ivanovo State University of Chemistry and Technology Nikiforova, Tatiana; Ivanovo State University of Chemistry and Technology Islyaikin, Mikhail; Ivanovo State University of Chemistry and Technology Koifman, Oskar; Ivanovo State University of Chemistry and Technology

Keyword: d-metal, cellulose modification, sorption mechanism

https://mc06.manuscriptcentral.com/cjc-pubs

Canadian Journal of Chemistry

Draft

1

The mechanism of d- metal ions sorption from aqueous media 1

and chelating sites structures of modified heterocyclic biopolymers 2

3

Kozlov V.А., Nikiforova Т.Е., Islyaikin М.К., Koifman O.I. 4

Ivanovo State University of Chemistry and Technology 5

Sheremetevskiy Avenue, 7, Ivanovo, Russia 6

7

8

9

10

11

corresponding author: Tatiana E. Nikiforova, e-mail: [email protected] 12

tel. 8(4932) 939331 13

14

15

16

17

18

19

20

21

22

23

24

25

Page 1 of 30



Draft

2

Sorption of d-metal ions (Cu2+, Fe2+ and Ni2+) from aqueous media using modified 26

heterocyclic biopolymers takes place with the participation of sorption sites – acidic groups: 27

α-hydroxycarboxylic (monobasic, bidentate), hydroxamic (monobasic, bidentate), and 28

aldehyde bisulphite (dibasic) in the form of chelate metal complexes, whose structures were 29

determined through the use of computational quantum chemistry on some modeled 30

compounds. 31

Ion exchange mechanism of the components of hetero-phase system in electroneutral, 32

molecular form reflects the implementation of the general laws of thermodynamics – Gibbs' 33

phase rule, law of mass action, law of equivalent proportions, and law of conservation of 34

charge at electroneutrality of phases. 35

Sorbents functional groups act as sorption sites whose filling goes in accordance with 36

their amount, denticity, basicity and ability of metal cations to complex formation and 37

solvation. The amount and the nature of acid sorption sites of sorbents permits to compare 38

their initial and maximum sorption abilities. 39

40

Keywords: d-metal, cellulose modification, sorption mechanism. 41

42

43

44

45

46

47

48

49

50

Page 2 of 30



Draft

3

Introduction 51

Chelate metal complexes are very common in natural processes, they have a unique 52

and specific features that allows them to act in the photosynthesis of carbohydrates 53

(chlorophyll) and in animals breathing processes (heamin) whereby the pyrrollic rings act as 54

ligands in the macrocycle. These natural polipyrrollic ligands contain four pyrrollic rings in 55

their unit structure (porphyrins) which are embedded in the biopolymer structures. Denticity 56

of such sorption sites in the macroheterocycles is 4. However, the study of the peculiarities 57

and the mechanism of the chemisorptions of metal cations to form chelate metal complexes 58

can be made easier by beginning with one of the most common polyheterocyclic sorbent – 59

cellulose, which has a simpler functional acid groups-sorption site with denticity not 60

exceeding 2, cellulose being the most available polyheterocyclic biopolymer and its modified 61

forms can be used as sorbents. 62

The sorption of heavy metal ions by biopolymers on the basis of β-D-glucose is of 63

great importance in various fields of science and technology. Cellulosic materials are 64

promising sorbents for the sorption of heavy metal ions; derived from available, cheap, 65

renewable and biodegradable natural resources.[1-3] 66

Among the requirements placed on sorbents, the most important are high sorption 67

capacity in relation to a wide spectrum of metal ions or selectivity to ions of one metal, ability 68

to speedily and strongly bind metal ions, possibility of regeneration (recycling), 69

environmental friendliness, cheapness and high availability. Most authors see the low sorption 70

capacity while using cellulosic biopolymer sorbents as the main problem. It should be noted 71

that the most profitable use of cellulose sorbents is in the purification of very dilute solutions, 72

which allows achieving very low concentration of metal ions.[4]

73

Presently in the literature there is a large number of experimental data on the sorption 74

of metal ions from aqueous solutions of their salts by various cellulose-containing materials, 75

Page 3 of 30



Draft

4

also in recent years there has been a rapid growth in researches touching the use of cellulosic 76

materials in the natural state as well as in their modified forms for the sorption of heavy metal 77

ions from aqueous media.[5-8]

78

Thus, in the removal of divalent metals of the natural form of jute fibers its sorption 79

capacity decreases as follows: Cu (4.23 mg⋅g-1

) > Zn (3.55 mg⋅g-1

) >Ni (3.37 mg⋅g-1

). Lignin 80

isolated from paper wastes, removes heavy metal ions from aqueous solution of their salts in 81

the following sequence: Pb(II) > Cu(II) > Cd(II) > Zn(II) > Ni(II).[9]

In the study of Zn(II) and 82

Pb(II) on the fibers of coconut palms,[10]

it was found that the sorbent has a stronger affinity 83

for Pb(II) ions than for Zn(II) ions. The sequence of increasing sorption effectiveness of metal 84

ions using wastes of grapefruit follows this: Pb(II) > Cu(II) > Ni(II) > Cd(II).[11] 85

Variety of agricultural wastes are used in sewage treatment of Pb(II), Cd(II), Hg(II), 86

Cu(II), Ni(II), Cr(III) and Cr(VI) ions: peanut shells and walnut husk, green almond, tea 87

leaves, olive oil production wastes, jute fiber, sunflower stalks, tobacco leaves and maple 88

peels, oak, spruce. While the sorption values can vary within a wide range depending on the 89

raw material used: 0.3-14.3 mg⋅g-1

for Cu(II), 0.4-10.8 mg⋅g-1

for Cd(II) and 1.47-10.9 mg⋅g-1

90

for Cr(III) ions.[2] 91

In addition to experimental data accumulated, the theoretical understanding of the 92

mechanism of heavy metal ion sorption processes was formed taking in account the nature of 93

functional groups (sorption sites) of polysaccharides, their interaction with metal ions, also 94

the influence on sorption process by various factors, like pH, solution temperature, 95

concentration of strong electrolyte, etc.[12] 96

During the development of new sorbents it is important to find a polysaccharide 97

material treatment method aimed at improving their sorption properties in relation to heavy 98

metal ions. 99

Page 4 of 30



Draft

5

Works[13-17] suggest different methods used in modifying cellulose-containing 100

polymers by using mechanical, physical, biochemical and physico-chemical types of 101

treatment. The main goal of modification is to increase the internal adsorption surface, the 102

availability of active groups, also creation of new sorption-active sites on the sorbent surfaces 103

(surface functionalization). Chemical modification allows significantly increase the sorption 104

capacity of natural sorbents by using inexpensive and readily available reagents. 105

Two main approaches can be used for the conversion of cellulose containing materials 106

to biosorbents having the ability to effectively remove heavy metal ions from aqueous 107

solutions. First of the approaches is based on the methods by which macromolecules of 108

cellulose are directly modified leading to the creation of functional groups in its structure, 109

having the ability to participate in chelation or ion exchange with heavy metal ions of aqueous 110

solutions. The other approach is associated with polymer analogous transformations by 111

grafting of certain monomers to the cellulose macromolecules, having direct sorption 112

reactivity towards to heavy metal ions or allowing further functionalization of the grafted 113

polymer chains to form chelating structures. 114

The first approach includes operations such as delignification, hydrolysis, oxidation, 115

attachment of carboxyl, sulfo-, nitro-, phosphate-, amino-groups, etc. with the use of various 116

reagents: alkali solutions such as sodium, potassium and calcium hydroxides,[18, 19]

mineral 117

acids (hydrochloric, nitirc, phosphoric, sulfuric),[20] organic acids and acid anhydrides 118

(tartaric, citric, succinic),[21, 22] oxidizing agents (hydrogen peroxide, potassium 119

permanganate, potassium metaperiodate), [23, 24] and organic compounds of different classes 120

(ethylenediamine, formaldehyde, epichlorohydrin, methanol, amino acids, acrylonitrile), 121

reactive dyes (monochlorotriazine types), enzymes and others used in the removal of soluble 122

organic compounds, decolouration of treated water solutions and increasing the effectiveness 123

of metal ions sorption.[25] 124

Page 5 of 30



Draft

6

Literature review shows that in a vast majority of papers, the Langmuir's model has 125

been used to describe the sorption equilibrium of polysaccharide-based sorbents, due to high 126

correlation coefficient values (0.97 – 0.99), the Freundlich's model, Dubinin-Radushkevich's 127

models and others has been used also. Thus the Langmuir model has been successfully used 128

in processing the isotherms of Cd(II) and Pb(II) ions sorption on grape bagasse,[26] Ni(II) and 129

Cd(II) ions on stems of water hyacinth,[27] Cu(II) и Zn(II) ions on lignocellulose substrate 130

based on wheat bran,[28] Cd(II) ions on coconut shell fibers. [29] 131

For the description of the experimental isotherms of Сu(II) and Cd(II) ions sorption on 132

rice husk, Demirbas[2] used Langmuir and Freundlich's adsorption models. Review of research 133

on Cr(III) ions[30] also shows that the most frequently used model for processing of heavy 134

metal ions' sorption data are the Langmuir's and Freundlich's models. Isotherms of Th4+ and 135

UO22+ ions sorption on chitosan, transversely cross linked by epichlorohydrin, and 136

chitosan/clinoptinolite composite, were processed with three models - Langmuir's, 137

Freundlich's and Sips'.[31] It is noted that the experimental data were more accurately 138

described by the Langmuir's model. 139

In review[32] it is noted, that, despite the fact that the Langmuir model does not provide 140

information on the sorption mechanism, it is usually correctly (with a correlation coefficient 141

close to unity) allows to describe the experimental isotherm of heavy metal ions sorption by 142

cellulose biosorbents and to determine the maximum sorption capacity of sorbents. 143

To determine the peculiarities of the mechanism of metal cations removal from 144

aqueous media as a chemisorptions process, it is particularly important to trace the influence 145

of the components nature of the hetero-phase system (salts, acids, the cellulose functional 146

groups) on the thermodynamics of metal cations sorption process. 147

In the works[17, 33, 34] hypothetical sorption site structures were used, which now 148

necessitates the need of representing ion exchange mechanism as a chemisorptions process on 149

Page 6 of 30



Draft

7

cellulosic sorbents, that will involve the computation of the chelate structure of some modeled 150

compounds sorption sites. In the same place of importance and urgency, stands the 151

development of scientific foundations, focusing on the chemical modification and 152

clarification of the specifics involved in sorption of heavy metal cations from aqueous media 153

by natural and modified sorbents. 154

The aim of this work was to study the peculiarities of the mechanism of the processes 155

of protodesorption and sorption of metal ions Cu(II), Ni(II) and Fe(II) from aqueous solutions 156

by cotton cellulose and its chemically modified samples with acidic sorption sites of different 157

basicity and denticity, having the ability of bonding with cations forming chelate metal 158

complexes and the determination of their structures through the use of computational quantum 159

chemistry on the modeled compounds. 160

Experimental 161

Sorption kinetics was investigated by a method of limited solution volume. To obtain 162

the kinetic sorption curves, the samples of a sorbent (m; 0.1 g) were placed into several flasks 163

filled with 10 ml (vol) of aqueous solution of metal sulphate and kept under stirring at 273 K 164

from 5 minutes to 24 hours. The initial concentration (C0) of metal ions was 1.5・10–4

mol l–

165

1. The solution was separated from the sorbent by filtration at definite time intervals; the 166

current concentration of metal ions (Cτ) was determined by atomic absorption spectroscopy 167

(Saturn-2000 apparatus). 168

To obtain the sorption isotherms, the samples of a 0.1 g sorbent (m) were placed into a 169

series of flasks, and the metal sulphate aqueous solution (10 ml portions by volume) was 170

added into these flasks with initial concentrations (C0) ranging from 1.5・10–4 to 5・10–2 mol 171

l–1. The geterophase sorbent – water solution of the metal sulphate system was used to achieve 172

the equilibrium state at 273 K. The solution was then separated from the sorbent by filtration. 173

Page 7 of 30



Draft

8

The equilibrium concentration of metal ions in solution (Cs) was determined by atomic 174

absorption spectroscopy. 175

The sorption capacity (Aτ) of sorbents at any given period was calculated according to 176

the following formula: 177

Vm

ССА ⋅

−=

)( 0 ττ (1) 178

After establishing the equilibrium in the system, the equilibrium concentration of 179

metal ions in the solution (Cs) was measured, and equilibrium sorption capacity of sorbents 180

(As) was calculated as follows: 181

Vm

ССА S

S ⋅−

=)( 0 (2) 182

Sorption degree α was determined using equation (3) 183

%1000

0 ⋅−

=С

СС Sα (3) 184

The pH of solutions was calculated using a pH meter. 185

The number of carboxyl groups in the original cellulose molecule was determined by a 186

classical method based on the interaction between acid groups and calcium acetate and by 187

titrimetric determination of the acetic acid evolved. Its content per unit mass was taken equal 188

to the value of the carboxyl group acidity [4]: 189

[ ] gCVCOOH NaOHNaOH /⋅=− , (4) 190

where VNaOH is the volume of NaOH for titration (ml); CNaOH is the concentration of NaOH 191

solution (mol l–1

) and g is the weight of the sorbent. 192

The content of aldehyde groups in native and oxidized cotton cellulose was 193

determined by iodometric titration. 194

[ ] %,1000

100)(51,14

q

banCOH

⋅

⋅−⋅⋅=− (5) 195

Page 8 of 30



Draft

9

where a is the volume of hyposulphite solution for titration in a control experiment (ml); b is 196

volume of hyposulphite solution for titration in a basic experiment (ml); q is weight of a 197

cotton cellulose (g); n is the normality of hyposulphite solution and E–COH (= 14.51) is the 198

gram equivalent of aldehyde groups involved in the reaction. 199

The relative error of the experiments was calculated based on equilibrium and kinetic 200

experiments in which each point represents an average value taken from three parallel 201

experiments. The error in determining the concentration of metal ions using the Saturn-2000 202

apparatus was 3%, and the experimental error did not exceed 10%. 203

Results and discussion 204

With the purpose of improving the equilibrium-kinetic characteristics of the sorbent 205

also for the validation of the mechanism of heavy metals sorption from aqueous media, 206

chemical modification was carried out by selectively oxidizing the cotton cellulose with 207

sodium metaperiodate forming dialdehyde cellulose. The periodate ions interact with 208

cellulose without destruction of fibres. The action of sodium metaperiodate on cellulose 209

resulted in the oxidation of two neighbouring alcoholic groups in C2 and C3 to aldehydes with 210

the simultaneous rupture of the carbon–carbon bond. A dialdehyde cellulose is thus formed. 211

In this case, however, there is no oxidation of primary alcoholic group.[35] 212

The condition of selective oxidation of cellulose used, was performed is such a way, 213

that the number of aldehyde groups formed were practically equal to the number of carboxylic 214

groups in the initial cellulose. Further modifications were carried out by the quantitative 215

conversion of aldehyde groups to other acidic types. 216

1. To hydroxamic acidic groups: 217

NH2OH·HCl H2O2 218

НООС(НО)СН-Cell-СН=О → НООС(НО)СН-Cell-СН=NOH → 219

→ НООС(НО)СН-Cell-СONHOH; 220

Page 9 of 30



Draft

10

2. To aldehyde bisulphite acidic groups: 221

NaHSO3 + {НООС(НО)СН-Cell-СН=О → НООС(НО)СН-Cell-HС(OН)SО3Na}. 222

In the aqueous phase, due to the high dielectric constant and sufficiently high donor-223

acceptor activity of water, surface inactive substances dissociate to ions as a result of 224

electrolytic dissociation. It can be said that the metal cations and protons in the aqueous media 225

exist in the state of hydrated complexes [M·(H2O)n]2+ and [H·(H2O)n]+. 226

Furthermore, the state of the metal cation and proton in the phase of the cellulose 227

sorbent needs to be ascertained from the standpoint of chemical structure theory. Cellulose in 228

the aqueous solution swells and due to electron-donor groups can sorb protons. In such a case 229

the sorbents sorption space in the acid pH range will be filled exponentially, starting from the 230

more active groups -СОО− with the formation of salt groups (-СОО)2М or acidic groups in 231

the form of –СООН, whose structures will be largely dependent on the neighbouring electron 232

donating groups. In cellulose α-hydroxylcarboxylic groups –CНOНСООН or α-233

alkoxycarboxylic groups –CНORСООН can act as dentate groups in the formation of chelate 234

five-membered H- and metal complexes of monobasic, bidentate type (N = 1, n = 2). 235

The conjugation effect of carbonyl (>С=О) and N- hydroxyamide (-NH–ОН) groups 236

of the hydroxamic acid group (-CONHОН) gives it an acidic property comparable to that of 237

carboxylic acids. Supposing that the proton of hydroxyl is more acidic, and the oxygen of 238

carbonyl takes part in the formation of dentate bonds. However it is still not clear which of the 239

protons in N-hydroxyamide groups is more acidic and which of the oxygen in (-CONHОН) 240

groups is more susceptible to dentate bond formation with electron accepting agents (cations 241

М2+ or protons Н+). However such an acidic group as –CONHОН should have the properties 242

of a monobasic (N = 1), bidentate (n = 2), with the tendency of forming a five-membered 243

chelate of H- and metal complexes. 244

The resemblance of sorption sites structures of the modified cellulose, proffers a 245

Page 10 of 30



Draft

11

similar character to the α-hydroxylcarboxylic (-CНOНСООН, N = 1, n = 2) and N-246

hydroxycarbamide (-CONHОН, N = 1, n = 2) groups during interfacial ion exchange 247

interactions with 2Н+ and М

2+, while the characters of hydroxamic (-CONHОН, N = 1, n = 2) 248

and hydroxymethylsulphonic (-CHOH-O2O−, N = 2, n = 2) would be different. 249

In this work cellulose samples with the following sorption sites were used: 250

(I) An unmodified one containing α-hydroxycarboxylic acid groups: 251

[НООС(НО)СН]-Cell; 252

(II) A modified one containing α-hydroxylcarboxylic and hydroxamic acid groups: 253

[НООС(НО)СН]-Cell-[СОNНОН]; 254

(III) A modified one containing α-hydroxylcarboxylic and aldehyde bisulphite acid 255

groups: [ООС(НО)СН]-Cell-]СН(ОН)SO3Na]. 256

The above samples were used in receiving sorption isotherms of copper, iron and 257

nickel ions from the aqueous solutions of their sulphate salts at pH 6 (Fig. 1-3). 258

Earlier[17] it was shown experimentally, that sulphate- anions from acidic aqueous 259

solutions are not sorbed by cellulose sorbents, which allows to view the sorbents as cation 260

exchanging gel sorbents. 261

In cellulose sorbents, the anion forms of acidic carboxylic functional groups bond with 262

cations as salts, forming carboxylates in the acidic pH region: рН = рКа-соон ± 2, this gives the 263

ability to study М2+/2Н+and М2+/2Na+ ion exchange in the acidic region (рН 2-6). 264

The thermodynamics of interfacial metal cation exchange is usually viewed in a 265

context of mechanism without the participation of anions in the process, with the assumption 266

that the multiplier of the activity coefficients of cations in the phases equals to unit. 267

Scheme I. Ion exchange of metal cations М2+

/2Na+ 268

М2+ + {Сell-(CHOH-COONa)2 ↔ Сell-(CHOH-COO)2М} + 2Na+ 269

Ion exchange М2+/2H+ 270

Page 11 of 30



Draft

12

М2+ + {Сell-(CHOH-COOH)2 ↔ Сell-(CHOH-COO)2М} + 2Н+. 271

From the study of protodesorption mechanism[33] it was shown, that cations can not 272

pass through the interfacial border without their anionic carriers, therefore the interpretation 273

of the mechanism of protodesorption in the form of purely ion exchange (Scheme I) can not 274

be substantiated with experiment. 275

Thus it was offered mechanism of ion-molecular type, with the participation of cations 276

and their anionic carriers as salts or acidic molecular forms of the independent components in 277

the heterophase system (aqueous solution of salts and acids - cellulose sorbent) with 278

electroneutrality of the phases. It can be viewed in the scheme II.[33] 279

Scheme II. МSO4 + {Сell-(CHOH-COOH)2 ↔ Сell-(CHOH-COO)2М} + H2SO4 280

---↕-- К=1 К = Кан2so4--↕--- 281

М2+ + SO42- 2Н+ + SO4

2- 282

283

МCl2 + {Сell-(CHOH-COOH)2 ↔ Сell-(CHOH-COO)2М} + 2HCl 284

---↕--- К=1 К = Канcl ---↕--- 285

М2+ + 2Cl- 2Н+ + 2Cl- 286

The justification of ion-molecular mechanism has been made from the point of view of 287

Gibbs phase rule applied to the system of DoF (Degree of Freedom) = 1: four components 288

(water, acid, salt, cellulose), with 2 independent components (K = 2: water and acid) 289

connected together through concentration, two phases (P = 2: aqueous solution - cellulose 290

sorbent), and with only one variable parameter (n = 1) – acid concentration, constant 291

parameters of the system are - temperature, pressure, salt concentration (interface indicator), 292

module (sorbent/solution). Such a system is (F = К + Р + n = 2 – 2 + 1 = 1) monovariant. The 293

values of other parameters in the system will depend on the acid concentration. 294

Schemes I and II are alternatives to the sorption mechanism and they are mutually 295

Page 12 of 30



Draft

13

exclusive in occurrence. To proof, which one of them is substantiated through experiment 296

(purely ion exchange М2+/2Н+ by scheme I or ion exchange with the participation of acidic 297

and salt components in their molecular forms МSO4/H2SO4 or МCl2/2HCl by scheme II), we 298

need to determine the degree of hydrogen ion participation in the reaction of protodesorption 299

of cations for the multicomponent, monovariant, heterophase system. 300

In scheme I (the ion exchange М2+/2Н+) the indicator of the degree of proton 301

participation is supposed to be 2. In scheme II (the ion exchange МSO4/H2SO4) the indicator 302

of the degree of sulphuric acid participation should be 1, and proton ½. In the ion exchange 303

with МСl2/2HCl participation it should be 2, and proton ¼. [17, 33] 304

For checking the correlation of sorption sites structure specifics with the sorption of d-305

metal cations from the two - phase system “aqueous solution of salts - cellulose sorbent”, the 306

sorption isotherms received at рН 6 (Fig. 1-3) were used, where all the acidic functional 307

groups of the cellulose sorbents taking part in the sorption at their first stage of dissociation, 308

were in the active anion-salt state (-СНОНСОО−, -СОNНО−, -СНОНSO2O−), while the metal 309

cations in the aqueous phase were in the thermodynamically stable hydrated state of 310

М(Н2О)n]2+. This allows to write down the process of filling of the sorbents anionic sorption 311

sites in the region of saturation: 312

a) For the one-staged dissociation type of the monobasic bidentate functional groups 313

МSO4 + {Cell-[(СНОНСООNa)2] ↔Cell[(СНОНСОО)2M]} + Na2SO4 (stage I) 314

МSO4+ {Cell-[(СОNНОNa)2] ↔ Cell-[(СОNНО)2M]} + Na2SO4 (stage I) 315

b) For the dibasic groups of a two-staged dissociation type. 316

МSO4+ {Cell(HСОНSО2ОNa)2 ↔ Cell[(HСОНSО2О)2М]} + Na2SO4 (stage I) 317

МSO4+ {Cell[(HСОНSО2О)2М] ↔ Cell[(HСОSО2О)М]2} + H2SO4 (stage II). 318

The amount of the cellulose α-hydroxylcarboxylic groups (monobasic bidentate) is 319

practically equal for modified samples, so such characters of isotherms result solely from the 320

Page 13 of 30



Draft

14

difference apparent in the sorption sites nature of the samples: hydroxamic groups (monobasic 321

bidentate) - sample 2; aldehyde bisulphite groups (dibasic bidentate) – sample 3. 322

0 10 20 30 40 50 60

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

А,

mo

l . k

g-1

С . 103, mol . l-1

1 23

323

Fig. 1. 324

Differences in the nature of the acid groups of the sorbents have allowed to reveal the 325

mechanism peculiarities of cations М2+

chemisorption with their participation in the initial 326

(Henry's region) and ending (saturation region) sections of the isotherms helping in recording 327

the dependence of sorption on chemical structures of sorption sites: [17] 328

1) Isotherm section of the Henry's region. At the initial linear segment of the sorption 329

isotherm heavy metal ions sorption must occur proportionally with respect to the number of 330

sorption sites (Сss) and the bond strength of the d-metal cations attached to it. The later will be 331

proportional to the denticity of the ligand n′D – number of coordinate bonds of cation - 332

sorption site. In such a case, the sorption (A) must be described with a relationship, in which 333

the Henry's constant КH will be proportional to the product of the number of sorption sites and 334

their denticity: Сss·n′D for all the sorbents sorption site (finite discrete integral ∑). Based on 335

the sorption sites structures one can say the denticity of α-hydroxylcarboxyl group equals two, 336

n′D = 2, (bidentate, monobasic), for hydroxamic group - n′D = 2 (bidentate, monobasic), and 337

for the aldehyde bisulphite group, for the first filling stage - n′D = 1 (monodentate, 338

monobasic). 339

Аini = КH·Сs = α·(∑Сss·n′D)·С s. = tgα·Сs. 340

Page 14 of 30



Draft

15

where α is a proportionality coefficient, Cs is the concentration of metal cations in aqueous 341

solution, Сss is the concentration of sorbent sorption sites, КH·is the Henry's constant. 342

0 10 20 30 40 50 60

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

А, m

ol

. kg

-1

С . 103, mol . l

-1

12

3

343

Fig. 2. 344

0 10 20 30 40 50 60 70

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

А,

mo

l . k

g-1

С . 103, mol . l

-1

1 23

345

Fig. 3. 346

In such a case the calculated tangents of the slope angles α·(∑Сss·n′D) for the initial 347

linear sections of sorption isotherms characterize Henry's law constants for each of the three 348

type of samples. These relationships are observed from experiment and computed data (Fig. 349

1-3), with the condition, that the number of each sample sorption sites is practically equal, but 350

with variations in their denticities at the first sorption stage: 351

(КHII):(КHIII): (КHI) = (α∑Сss·n′DI +α∑Сss·n′DII):(α∑Сss·n′DI +α∑Сss·n′DIII): (α∑Сss·n′DI) ≈ 352

≈ (2+2):(2+1):(2) ≈ (2):(1,5): (1). 353

Page 15 of 30



Draft

16

In this case the tangents of the slope angles follow the sequence tgαI I> tgαIII > tgαI 354

(Fig. 1-3) and the calculated quantities of Henry's constants follow suit as (KHII) > (KHIII) > 355

(KHI), showing that they correlate well enough. 356

With the stage-wise filling mechanism observed in the initial linear section (Henry's 357

region), the sorption isotherm of sorbent (II) lies above that of sorbent (III) due to the fact that 358

n′DII>n′DIII for the first stage. 359

2) Isotherm section of the saturation region. This is the final, almost linear isotherm 360

section (saturation region), in which all the sorption sites almost completely filled out. In this 361

case, the total sorption А∞ of each sorbent sample will be determined by the maximum 362

sorption value in all their steps of filling, so it should be proportional to number (Сss) of 363

sorption sites and their basicities (NB) for all sites (∑): 364

А∞ = α·(∑ Сss·NB). 365

The modified sorbents contain α-hydroxylcarboxylic groups (Сss, NBI = 1, nI = 2, Сеll-366

CHOH-COO−) in combination with an equal amount of immobilized sites having different 367

basicities: hydroxamic acid (Сss, NBII = 1, nII = 2, Сеll-CONHO−) and aldehyde - bisulphite 368

groups (Сss, NBIII= 2, nIII = 2, Сеll-HСОНSО2О−). The isotherm of sorbent (III) lies higher 369

than that of sorbent (II), А∞III > А∞II (Fig. 2, 3). As a result the isotherms for all the cations 370

will intersect which matches the experimental and estimated results. The ratio of estimated 371

maximum sorption values А∞ for the three samples with an equal number of sorption sites but 372

with different basicities (NI = 1, NII = 1, NIII = 2) should follow this sequence: 373

А∞I:А∞II:А∞III ≈ (α∑Сss·NB1):(α∑Сss·NB1+α∑Сцс·NB2):(α∑Сss·NB1+α∑Сss·NB3 ) ≈ 1 : 2 : 3. 374

This is in good agreement with the experimental А∞I:А∞II:А∞III = 0.4:0.8:1.2 (Fig. 1-3) and 375

estimated values of the limiting sorption received from the Langmuir's model. А∞I:А∞II:А∞III = 376

0.53:0.92:1.52. 377

Page 16 of 30



Draft

17

3) Sorption isotherms of the sorbents with the similar nature. Samples of sorbents I 378

and II have the similar nature (nDI = 2, NBI = 1 for α- hydroxycarboxyl and nDII = 2, NBII = 1 379

for hydroxamic groups) but different in their sorption site amounts СssI ≈ Сss for sorbent I and 380

СssI + СssII ≈ 2Сss for sorbent II. In such a case, with КLI ≈ КLII from the Langmuir's model 381

which is fair approximation for the same and equivalent sorption sites, we can expect them to 382

have comparable values of tangents of the slope angles tgα1:tgα2≈(КHI):(КHII) ≈ 1:2 for the 383

initial section of their isotherms and for their limiting sorption values tgα1:tgα2 ≈ 384

(КLI·А∞I):(КLII·А∞II) ≈ А∞I:А∞II ≈ 1:2, which correspond to that of experiments (Fig. 1-2). 385

Samples I and II have the same mechanism of sorption, because they are of the same 386

denticity and the same basicity of sorption sites, both for the initial, middle and final sections 387

of their isotherms. 388

4) Sorption isotherms of the sorbents with the different nature. For samples II and III, 389

sorption isotherms are convex, different in forms and intersecting with each other (А∞II < 390

А∞III, Аini-II > Аini-III), having differences in their mechanisms of filling for the initial 391

(denticities dominate: that is the bond strength with cations), middle and final section of 392

sorption isotherms (basicitiy of sorption sites is the dominating factor, that is the number of 393

bonds to each adsorbed cation). In such a case, the ratio of denticity to basicity of the 394

available sorption sites at the initial segment will favour the hydroxamic site (n/N = 2/1), 395

while the final isotherm segment will favour aldehyde bisulphite sites (N/n = 2/1). It is 396

evident that their isotherms will intersect, because of these differences in their sorption sites. 397

Despite a significant difference in basicities and denticities of the sorption sites of 398

samples II and III, description of intersecting isotherms involving the law of mass action 399

(Langmuir's model) gives reliable results of the maximum sorption values. They are 400

proportional to the basicity of sorption sites (NBI = 1, NBII = 1, NBIII = 2) for samples with 401

equal sorption site amounts (Сss). 402

Page 17 of 30



Draft

18

(А∞II):(А∞III) ≈ (α∑ Сss ·NBI + α∑Сss ·NBII) : (α∑Сss ·NBI + α∑Сss ·NBIII) ≈ 2:3. 403

The estimated (calculated) data based on the number and structure (denticity and 404

basicity) of sorption sites and experimental data obtained by processing of isotherms of metal 405

ions (Сu2+, Fe2+, Ni2+) sorption are in good agreement with each other: (А∞II):(А∞III) ≈ 2:3 406

(estimated) ≈ (0,92):(1,52) (Langmuir's model). While the values of the constants КL obtained 407

for samples II and III are significantly different (КLII = 279) > (КLIII = 83). With the same 408

amount of sorption sites and different denticity (n′II = 2 and n′III = 1 for the initial section of 409

isotherm) and basicity of sorption sites (NBII = 1 and NBIII = 2), these differences in the 410

constants suggests great influence of the nature of functional groups on the shape of the 411

sorption isotherms. 412

The shape of the initial section of the isotherm (tgα = KH) is determined by the metal 413

cation binding strength, and the more adsorption centers number and their denticity, the 414

greater the tangent of slope angle of the initial section of the isotherm (the higher the Henry's 415

constant KH), the contribution of the basicity of sorption sites (the degree of sites filling) thus 416

negligible. 417

Maximum sorption value is achieved at the final section of the isotherm (saturation 418

region) and is determined by the amount and and basicities of the available sorption sites. In 419

this region the role of their denticities (bond strength) will be negligible. In this region the 420

role of their denticities (bond strength) will be negligible. The quantitative characteristics of 421

initial and final sections of the sorption isotherms, reflect the specifics associated with the 422

nature, structure and characteristics of sorption sites structures. 423

The values of the maximum sorption for all sorbents with different sorption sites 424

follow this relationship А∞II < А∞III while reversed to that of Langmuir's constants КLII > КLIII. 425

Differences in sorption sites of a particular sorbent is highly cited as an argument 426

against the applicability of the Langmuir's model for explaining the sorption processes. 427

Page 18 of 30



Draft

19

The limitations of the Langmuir's model are valid for weak interactions at sorption like 428

universal solvation or quasi chemisorptions of nonpolar substances. In a case of distribution 429

of particles between phases (ion exchange) with strong (specific) interactions in the phases, 430

the Langmuir's model will correspond to the law of mass action in this case. With the 431

correlation coefficient close to unity, this shows the good applicability of the Langmuir's 432

model to explaining ion exchange processes on sorbents, both for similar or different sorption 433

sites types. 434

The posed interpretation for the sorption mechanism for the similar sorption site types 435

(I, II) and the different site types (II, III) of sorbent samples is fully consistent with 436

thermodynamics of reversible processes, whereby the sorption of ions and ion exchange can 437

be considered as a variety of chemical processes occurring between the components of the 438

heterophase system with the participation of the sorbent's active groups in these processes. 439

Such approach to elucidation of the mechanism of chemisorptions of metal cations 440

M2+ from aqueous media by cellulose sorbents, based on knowledge of the nature, quantity 441

and structure of the sorption sites and the solvation of ions in the phases allows to identify the 442

causes of noncompliance or compliance involved in the description of sorption isotherms 443

through various theories of sorption and to determine the limits of their application, especially 444

for the models most frequently used for explaining the sorption of metal cations from aqueous 445

media. 446

Sorption equilibrium depends on the nature both of sorbate and phases. Phases and 447

their constituent components act as reagents that quantitatively and qualitatively affect the 448

solvated-complexes of cations in the phases of sorption sites. 449

The salts of Cu(II), Fe(II) and Ni(II) sulphates are strong electrolytes, in water they are 450

in the form of hydrated ions. In the solid phase of the sorbent, they are in the coordinated – 451

salt forms bonded to the anionic sites of the sorbent. Such solvated complexes in the phases 452

Page 19 of 30



Draft

20

differ in energy and structure. That is reflected on their salts solubility in the aqueous phase 453

and on the distribution of cations in the hetero-phase system “aqueous solutions of salts - 454

cellulose sorbent”. 455

In aqueous solutions of metal sulfates with higher solubilities, the cations are largely 456

hydrated and, as a consequence, it will be more difficult to sorb them. The series of salt 457

solubility and sorption of the cations are inversely related. 458

These allows to interpret the mechanism of the processes of metal cations sorption 459

from aqueous media by natural and modified cellulose as a conjugated and equivalent ion 460

exchange process, with the acidic groups acting as sorption sites, forming coloured and 461

colourless chelate metal complexes with Cu2+, Fe2+, Ni2+: 462

In the α-hydroxylcarboxyl groups: 463

MSO4 + {Сell-(CHOH-COOH)2 ↔ Сell-[(CHOH-COO)2M]} + H2SO4 464

colourless colourless 465

In the hydroxamic groups: 466

MSO4 + {Сell-(CO-NH-OH)2 ↔ Сell-[(COH=N-O)2M]} + H2SO4 467

colourless coloured 468

Colours of the complexes are reddish-brown with iron(II) and green with copper(II). 469

In the aldehyde-bisulphite groups (substitution in I and II dissociation steps): 470

MSO4 + {Сell-(CHOH-SO3Na)2 ↔ Сell-[(CHOH-SO3)2M]} + Na2SO4 471

MSO4 + {Сell-[(CHOH-SO3)2M] ↔ Сell-[(CHO-SO3M)2]} + H2SO4 472

colourless colourless 473

The sorbent with hydroxamic groups forms coloured complexes of the chelate type 474

with d-metal ions Сell-[(COH=N-O)2M. The colour appears as a result of the formation of 475

five-membered chelate rings, with the ring atoms forming a complex due to the charge 476

transfer during metal–ligand interactions with the participation of a π-conjugated system 477

Page 20 of 30



Draft

21

between key atoms of the ligand and d-atomic orbitals of the metal ions. Sorption of metal 478

ions by cellulose on the α-hydroxylcarboxyl and aldehyde-bisulphite groups was not 479

accompanied by a colour change of the sorbent. Colourless chelate charge-transfering 480

complexes are formed in the absence of conjugation in the systems between the key atoms 481

(O) of the ligand, due to the presence of (>СН–) in the chain as in the case of α- 482

hydroxylcarboxylic (НО-С′Н-СОО–) and aldehyde-bisulphite (НО-С′Н-SО2О-) groups. 483

Since the difference in denticity, basicity and the amount of sorption sites of sorbents 484

has a different and significant impact on the initial section (region of Henry's law) and 485

maximum (saturation region) of the sorption isotherms (Fig. 1-3), this allows to perform 486

targeted modifications of cellulosic materials used for various purposes and in various 487

technologies for the removal of heavy metals from aqueous media both for the static and the 488

dynamic conditions. 489

Sorbents with polydentate, monobasic sorption sites are more efficient when removing 490

the d-metal cations from dilute aqueous solutions and sorbents with the same amount as 491

above, but with polybasic sorption sites will be more effective for sorption of d-metals cations 492

from concentrated aqueous solutions. 493

Computational quantum chemistry modeling method was performed on some modeled 494

compounds having functional groups of the same type as that of the used sample sorbents: 2-495

hydroxyethanoic acid, N-hydroxylacetamide and sodium ethanalbisulphite. 496

The quantum chemistry computation were performed using the DFT method with the 497

B3LYP method of Hybrid Functional Theory with the 6-31+G(d, p) basis sets with the help of 498

the software package Firefly 8.1.0 with full optimization of the geometric parameters and the 499

verification of the conformity of the found minima of the potential energy surface by critical 500

conditions. Preparing of the input data, and the processing and visualization of results were 501

performed with help of the software ChemCraft. 502

Page 21 of 30



Draft

22

The fragment of the carboxylic acid with the hydroxyl group in α-position is an almost 503

planar cyclic five-membered chelate H-complex in which the proton of the carboxyl group is 504

linked to the oxygen of the alcohol group by an intramolecular hydrogen bond. This type of 505

configuration is more polar than other configurations. It helps to strengthen the acidic 506

properties of such fragments. 507

Following the above statement; the carboxylic group in the polysaccharides which also 508

has electronegative groups (НО- hydroxyl and RO- alkoxyl) in the α-position is supposed to 509

support the cyclic five-membered H-chelate structure and increased acidity (рКа-СНОНСООН ≈ 510

4). It is advisable to present such structures with reflection of the nature of the neighbouring 511

groups participating in the formation of the dentate bonds of H- or metal complexes type in 512

the form of a Cell-(CHOH-COOH) or as shown on the modeled compound CH3-CHOH-513

COOH. 514

Conformational structure of propene-1-triol- 1,1,2 is a tautomer

of lactic acid, H- chelated form of which has two flat cycles (five-

membered and four- membered).

Usually compounds with a hydroxyl group at double bond or with two hydroxyls at 515

one carbon atom are very unstable and immediately reform to the carbonyl structures, while 516

the hydrogen atoms in the α-position retain their predisposition to the keto- enol tautomerism. 517

Сell-[СНОН-СООН] ↔ Сell-[СОН=С(ОН)2] 518

Mobile hydrogen atoms of cyclic chelate form 2 intramolecular bonds giving some 519

amount of stability to the enol structure. However, judging from the total energy of the 520

isomers such tautomeric entriol structure is less stable than the structure of the lactic acid 521

fragment. Thus the structure of cellulose sorbents sorption sites is the chelated structure of α- 522

hydroxycarbonic acids fragment. 523

Page 22 of 30



Draft

23

In N- hydroxyacetamide, the hydrogen at the amide nitrogen atom is mobile, which 524

allows it to be involved in keto-enol tautomerization with the formation of the enol structure 525

in the form of alkanoloxime. 526

R-[СО-NH-OH] ↔ R-СОH=N-OH 527

Both tautomers have the cyclic five-membered H-chelate form, which are stabilized by 528

intermolecular hydrogen bonds. Judging from Etot, the structure of N- hydroxyacetamide is 529

somewhat more stable than the acetoxime structure, the hydrogen of such stable acidic group 530

have a more high positive charge of (0.386 and 0.359, respectively). Thus hydroxamic 531

functional groups of the modified cellulose are in the form of five-membered chelate structure 532

(Cell-(СО-NH-OH). 533

The most stable of tautomeric and conformational structures of the anionic 534

hydroxamic acid group, is structure (1). Relative energies, Erel, of tautomers 1 and 4 are very 535

close. This allows the thermodynamics of dissociation of the most stable form of hydroxamic 536

acid to be modeled on the modeled compound (R- = CH3-) in the chelate form: 537

{R-(СО-NH-OH)cis -↔ R-(СОН=N-OH)cis-} ↔ R-(СО−=N-OH) cis- + Н

+ 538

(1) (4) (1′) 539

The “acid” hydrogen bonded to the nitrogen atom of the amide fragment is the one 540

that take part in the acidic dissociation of the hydroxamic acid groups (-СО-NH-OH), whose 541

acidic properties are strengthened by the electron accepting inductive influence from the 542

neighbouring hydroxyl group and also the shifting of electrons of σ- and π- bonds from 543

nitrogen to the carbonyl oxygen. This unusual type of acid dissociation through the tautomeric 544

acid forms (1) and (4) to the anionic form (1') is due to the fact that it preserves the 545

heterocyclic five- membered chelate form, which is stabilized by intermolecular hydrogen 546

bond. 547

Page 23 of 30



Draft

24

The chelate metal complex on the modeled compound

(Cell-…= CH3-).

The formation of chelate metal complexes is also accompanied by the substitution of 548

proton of the hydroxyl of (>N-ОH group) by cation of the most stable chelate H-form (1) with 549

the simultaneous transfer of the proton from nitrogen to the carbonyl oxygen, keeping the 550

form of the cyclic five-membered chelate structure unchanged: 551

М2+ + {Сеll-(СО-NH-OH)2 cis- ↔ Сеll-[(-СОН=N-O‾)2M2+] cis- + 2Н+. 552

The transfer of cations from one phase to another occurs together with their anions at 553

the electroneutrality of phases, in a form of the equivalent exchange of charged particles. In 554

this case, the acetalaldehyde bisulphite – anion can exist in the sorbent phase only with 555

oppositely charged ions in the form of sodium acetalaldehyde bisulphite. The structure of 556

such anionic form and the form of its sodium salt are similar. 557

The mechanism of thermodynamics of interfacial transfer of cations as electroneutral 558

salt or acidic components in the heterophase system (scheme II), permits the passage of the 559

process of ion exchange with unstable intermediates. In the first and second dissociation 560

stages, with the participation of its dibasic sorption sites in the aldehydebisulphite group 561

complete substitution takes place of, firstly; Na+, and later Н+ and their subsequent removal in 562

conjugation with sulphate ions to the aqueous phase. While in the organic phase the neutral 563

chelate metal complex of copper(II) in the ratio of 1:2 (in the first stage of substitution) and 564

1:1 (in the second stage) is formed based on coordination bond type, whose structure in the 565

modeled compounds are of the type: 566

Page 24 of 30



Draft

25

It should be noted, that the sorption of ions on the aldehyde bisulphite sorption sites 567

always leads to the formation of chelate metal complexes both at the first stage (initial section 568

of isotherm) and the second stage of substitution (final section of the isotherm). During the 569

first stage of substitution М2+ ions form a practically planar complex with four- membered 570

chelate cycles and a coordination number of 4, in which all the four coodinate bonds are 571

practically equal. Since the hydroxyl group of aldehydebisulphite anion having a lower 572

electron donating capacity relative to water, doesn't take part in the coordination bond with 573

copper. In the second stage of sorption, copper ion forms a neutral, chelate and polar complex 574

with coordination number of 2 of a practically planar five- membered cycle. 575

CONCLUSIONS 576

Sorption isotherms of d-metal cations are accurately described with active masses law. 577

In the process of sorption, the functional groups are independent sorption sites, their filling 578

being in accordance with their amount, basicity, dentate and the ability to dissociate. Ratios of 579

values of maximum adsorption capacities and Henry's constants are in good agreement with 580

the amount and basicity of the same type and different types of functional groups for the 581

cellulose samples investigated, which allows to predict the relative shapes of the isotherms 582

and sorption capabilities of sorbents. 583

The chelate structures with H- and metal complexes on acidic sorption sites were 584

computed with the methods of quantum chemistry on modeled compounds, by adhering to 585

chemistry's best practices. 586

Hydroxamic groups form coloured chelate metal complexes Cell-[(COH=N-O-)2M] 587

with Cu2+, Fe2+, Ni2+ cations. The colouration results from π-conjugation between key atoms 588

of oxygen in the four- atoms chain, during complex formation with charges transfer. 589

Acknowledgements 590

The work was supported by the Russian science Foundation, agreement № 14-23-00204. 591

Page 25 of 30



Draft

26

References 592

1. Hubbe, M.A.; Hasan, S.H.; Ducoste, J.J. BioResources, 2011, B(2), 2181. 593

URI: http://www.lib.ncsu.edu/resolver/1840.2/2621 594

2. Demirbas, А. J. Hazard. Mater. 2008, 157, 2209. 595

http://dx.doi.org/10.1016/j.jhazmat.2008.01.024. 596

3. Kumar, U. Sci. Res. Essays, Agricultural products and by-products as a low cost adsorbent 597

for heavy metal removal from water and wastewater: A review, 2006, 1(2), 033. 598

http://www.academicjournals.org/article/article1380188016_Kumar.pdf 599

4. Kelly-Vargas K.; Cerro-Lopez M.; Reyna-Tellez S.; Bandala, E.R.; Sanchez-Salas, J.L. 600

Physics and Chemistry of the Earth. 2012, 37, 26. 601

http://dx.doi.org/10.1016/j.pce.2011.03.006 602

5. Hamissa, A.M.B.; Lodi, A.; Seffen, M.; Finocchio, E.; Botter, R.; Converti, A. Chem. Eng. 603

J., 2010, 159, 67. http://dx.doi.org/10.1016/j.cej.2010.02.036 604

6. Aydın, H.; Bulut, Y.; Yerlikaya, C. J. Environ. Management, 2008, 87, 37. 605

http://dx.doi.org/10.1016/j.jenvman.2007.01.005 606

7. Sud, D.; Mahajan, G.; Kaur, M.P. Bioresour. Technol., 2008, 99, 6017. 607

http://dx.doi.org/10.1016/j.biortech.2007.11.064 608

8. Ngah, W.S.W.; Hanafiah, M.A.K.M. Bioresour. Technol., 2008, 99, 3935. 609

doi:10.1016/S1003-6326(14)63137-X 610

9. Guo, X.; Zhang, S.; Shan, X.Q. J. Hazard. Matter., 2008, 151, 134. 611

http://dx.doi.org/10.1016/j.jhazmat.2007.05.065 612

10. Conrad, К.; Hansen, H.C.B., Bioresour. Technol., 2007, 98, 89. 613


11. Bayo, J. Chem. Eng. J., 2012, 191, 278. http://dx.doi.org/10.1016/j.cej.2012.03.016 615

12. Nikiforova, T.E.; Kozlov, V.A. Protection of Metals and Physical Chemistry of Surfaces, 616

Page 26 of 30



Draft

27

2011, 47(1), 20. http://dx.doi.org/10.1134/S2070205110051016 617

13. Meena, A.K.; Kadirvelu, K.; Mishraa, G.K.; Rajagopal, C.; Nagar, P.N., J. Hazard. 618

Mater., 2008, 150(3), 604. http://dx.doi.org/10.1016/j.jhazmat.2007.05.030 619

14. Nikiforova, T.E.; Kozlov, V.A. Russian Journal of General Chemistry, 2011, 81(10), 620

2136. doi: 10.1134/S1070363211100173. 621

15. O'Connell, D.W.; Birkinshaw, C.; O'Dwyer, T.F. J. Chem. Technol. and Biotechnol., 622

2006, 81(11), 1820. http://dx.doi.org/10.1002/jctb.1609 623

16. Nikiforova, T.E.; Kozlov, V.A.; Bagrovskaya, N.A.; Rodionova, M.V., Russian Journal of 624

Applied Chemistry, 2007, 80(2), 236. http://dx.doi.org/10.1134/S1070427207020139 625

17. Nikiforova, T.E.; Kozlov, V.A.; Loginova, V.A. Adsorpt. Sci. Technol., 2014, 32, 389. 626

http://dx.doi.org/10.1260/0263-6174.32.5.389 627

18. Sciban, V.; Klasnja, M.; Skrbic, B. J. Hazard. Mater., 2006, 136, 266. 628


19. Memon, S.Q.; Memon, N.; Shah, S.W.; Khuhawar, M.Y.; Bhanger, M.I. J. Hazard. 630

Mater., 2007, 139, 116-121. http://dx.doi.org/10.1016/j.jhazmat.2006.06.013 631

20. Kumar, U.; Bandyopadhyay, M., Bioresour. Technol., 2006, 97, 104. 632


21. Arslanoglu, H.; Altundogan, S.; Tumen, F., Bioresour. Technol., 2008, 99, 2699. 634


22. Junior, O.K.; Gurgel, L.V.A.; de Melo, J.C.P.; Botaro, V.R., Melo, T.M.S.; de Fernas, 636

G.R.P.; Gil, L.F. Bioresour. Technol., 2006, 98, 1291. 637


23. O’Connell, D.W.; Birkinshaw, C.; O’Dwyer, T.F., Bioresour. Technol., 2008, 99, 6709. 639


24. Nada, A.M.A.; Adel, A.M., J. Appl. Polym. Sci., 2007, 105(2), 412. 641

Page 27 of 30



Draft

28

http://dx.doi.org/10.1002/app.25895 642

25. Zheng, L.C.; Dang, Z.; Yi, X.Y.; Zhang, H., J. Hazard. Mater., 2010, 176(1-3), 650. 643


26. Farinella, N.V.; Matos, G.D.; Arruda, M.A.Z. Bioresource Technol., 2007, 98, 1940. 645


27. Correa, M.L.; Velásquez, J.A.; Quintana, G.C. Ind. Eng. Chem. Res., 2012, 51(38), 647

12456. http://dx.doi.org/10.1021/ie301156y 648

28. Jolly, G.; Dupont, L.; Aplincourt, M.; Lambert, J., Environ. Chem. Lett., 2006, 4(4), 219. 649

http://dx.doi.org/10.1007/s10311-006-0051-4 650

29. De Sousa, D.A.; de Oliveira, E.; da Costa Nogueira, M.; Esposito, B.P. Bioresour. 651

Technol., 2010, 101, 138. http://dx.doi.org/10.1016/j.biortech.2008.08.051 652

30. Miretzky, Р.; Cirelli, A.F., J. Hazard. Mater., 2010, 180, 1. 653


31. Humelnicu, D.; Dinu, M.V.; Drâgan, E.S., J. Hazard. Mater., 2011, 185, 447. 655


32. Farooq, U.; Kozinski, J.A.; Khan, M.A.; Athar, M., Bioresour. Technol. 2010, 101(14), 657

5043. http://dx.doi.org/10.1016/j.biortech.2010.02.030 658

33. Nikiforova, T.E.; Kozlov, V.A., Protection of Metals and Physical Chemistry of Surfaces, 659

2015, 51(4), 510. http://dx.doi.org/10.1134/S2070205115040206 660

34. Nikiforova, T.E.; Kozlov, V.A. Protection of Metals and Physical Chemistry of Surfaces. 661

2012, 48(6), 620. http://dx.doi.org/10.1134/S207020511206007X 662

35. D. Klemm, B. Philipp, Т. Heinze, U. Heinze, and W. Wagenknecht, Comprehensive 663

Cellulose Chemistry. Vol. 1: Fundamentals and Analytical Methods, 1998, Wiley-WCH, 664

Weinheim, Germany. 665

666

Page 28 of 30



Draft

29

Table 1 667

Parameters of the Adsorption Isotherms Calculated using the Langmuir Equation 668

Sorbent Cation 1/(А∞⋅К), 103

1/А∞ R

А∞,

mol⋅kg-1

К

(I) Initial

Cu2+ 8,59±0,74 1,81±0,03 0,99 0,55 210

Fe2+

8,98±0,66 1,87±0,03 0,99 0,53 189

Ni2+

9,89±0,95 1,99±0,04 0,99 0,50 201

(II) Modified sample

containing

hydroxamic groups

Cu2+

3,85±1,54 1,04±0,09 0,98 0,96 270

Fe2+

3,91±0,83 1,09±0,04 0,99 0,92 279

Ni2+ 3,98±1,22 1,12±0,06 0,99 0,89 281

(III) Modified

sample containing

aldehyde-bisulphite

groups

Cu2+ 5,99±1,51 0,59±0,07 0,98 1,69 98

Fe2+ 7,95±1,38 0,66±0,05 0,99 1,52 83

Ni2+ 15,86±2,50 0,68±0,07

0,97 1,47 43

669

670

671

672

673

674

675

676

677

678

679

Page 29 of 30



Draft

30

Figure captions 680

Fig. 1. Sorption isotherms of Cu2+(1), Fe2+ (2), Ni2+ (3) ions by unmodified 681

cellulose 682

Fig. 2. Sorption isotherms of Cu2+(1), Fe2+ (2), Ni2+ (3) ions by samples of 683

cellulose containing hydroxamic acid groups 684

Fjg. 3. Sorption isotherms of Cu2+(1), Fe2+ (2), Ni2+ (3) ions by samples of 685

cellulose containing aldehyde–bisulphite groups 686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

Page 30 of 30



the mechanism of d- metal ions sorption from aqueous media … · 2016. 11. 22. · 121...

Documents