Biochar Properties & Production Techniques

Sorptive removal of salicylic acid and ibuprofen from aqueous solutions using pine wood fast pyrolysis biochar

ByMatthew Essandoh , Bidhya Kunwar , Charles U. Pittman Jr. , Dinesh Mohan , Todd Mlsna

Presented byMuhammad Zeeshan Ul-HaqAbstract

Pine wood biochar, prepared at 698 K with a residence time of 2030 s in an auger-fed reactor, was used as a 3-dimensional adsorbent to remove salicylic acid and ibuprofen from aqueous solutions. This biochar was characterized by FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, surface area determination, and zero point charge measurements. Batch sorption studies were carried out at pH values from 2 to 10, adsorbate concentrations from 25 to 100 mg/L and temperatures from 298 to 318 K. The adsorption of both adsorbates was highest at low pH values, dropped as pH increased and then exhibited a second increase related to the pKa of these carboxylic acid adsorbates. This was followed by a further drop at high pH. Conjugate acid/base equilibria of the adsorbates and the phenolic hydroxyl and carboxylic acid biochar sites versus pH dominated the mechanism. Sorption followed pseudo-second order kinetics. Sorption was evaluated from 298 to 318 K using the Freundlich, Langmuir, RedlichPeterson, Toth, Sips, and RadkePrausnitz adsorption isotherm models. Langmuir adsorption capacities for both salicylic acid and ibuprofen were 22.70 and 10.74 mg/g, respectively. This low surface area pinewood biochar (1.35 m2/g) can adsorb far more adsorbate compared to commercial activated carbons per unit of measured surface area. Methanol stripping achieved 93% and 88% desorption of salicylic acid and ibuprofen, respectively, from the spent biochar, and 76% and 72% of the initial salicylic acid and ibuprofen adsorption capacity, respectively, remained after four full capacity equilibrium recycles.IntroductionWastewater pollution is an urgent environmental concern. The negative effects of pollution on both humans and the environment have become a subject of intense discussion. Pharmaceutical pollutants are increasingly important and require immediate attention . Pharmaceutical products enter the aquatic environment through municipal waste water treatment, plant effluent, animal excreta, direct discharge of pharmaceuticals into waterbodies, and septic tank leakage. Negative effects on humans and animals include the suppression of embryonic cell growth in humans, the incapacitation of liver and gills in fish, and the inhibition of Gram-positive bacteria. Despite public concerns about the negative effects that pharmaceuticals have on aquatic ecosystems, there are currently no federal laws defining the amount of these chemicals permitted in waste water streams or in drinking water.

Introduction (contd..)Ibuprofen 2 is a non-steroidal anti-inflammatory drug with a wide global consumption. It is produced on an industrial scale as a race-mate which is generally excreted in the form of conjugates such as 2-[4-(2-hydroxy-2-methylpropyl)phenyl]propanoic acid, 2-[4-(2-carboxypropyl)phenyl]propanoic acid, and 2-phenylpropanoic acid. Ibuprofen is known to have endocrine disruptive activity . Aqueous solutions of these pharmaceutical pollutants have been treated by physical, biochemical and chemical processes . However, these techniques can be expensive. Thus, low cost methods to remove pharmaceutical contaminants from aqueous solution will be well embraced. Low cost adsorbents can be employed to remove recalcitrant compounds from aqueous solution inexpensively and can be effective for removing both organic and inorganic contaminants .

MethodThe biochar used for adsorption experiments was produced as a byproduct of bio-oil produced by fast pyrolysis of pine wood chips in an auger-fed reactor at a temperature of 698 K using a feed rate of 12.5 kg/h . The residence time of the pine wood chips in the hotzone was 2030 s and the approximate gas residence time in the reactor was 2 s. The chips were preheated to between 383 and 393 K, and a proprietary heat transfer method was used to speed the temperature rise to 698 K in the hotzone. The powdered biochar was collected from the system by capturing it in an enclosed pot after moving past the hotzone. After subsequent removal from this container at room temperature, it was washed several times with distilled water to remove salt impurities and water-soluble organic residuals. Biochar was sieved to a particle size distribution of 100600 lm (0.10.6 mm), and moisture was removed by heating to 383 K for 12 h. The adsorbent was then stored in a closed vessel at 338 K for several days until needed.Biochar PropertiesHigh carbon content (60 95% C)Resistant to biodegradationSignificant adsorptive qualities (similar to activated carbon)Nutrients (& contaminants) essentially lock on to the structureIncreases moisture holding capacityEnhances microbial biomass

Biochar Properties:Process ConditionsEnhanced biochar yields from:Lower temperatures ( pH of the solution, the surface of the biochar will be positively chargedSEM Images

SEM images of the biochar. The biochar has a macroporous surface texture.pH effect on adsorptionAt higher pH, (pH greater than the pKa of the adsorbates), both adsorbates are increasingly present as their carboxylate anions (RACOO_). Simultaneously, the biochar becomes increasingly negatively charged as pH rises (pH > pzc), causing increased electrostatic repulsion of adsorbate carboxylate anions and decreasing the adsorption capacity. This trend is seen from pH 2 or 3 through 10. However, both adsorbates show a region of intermediate pH values where adsorption increases, maximizes and then continues to drop as pH increases. These adsorptions peak at about pH 8 for ibuprofen and 6 for salicylic acid, where both adsorbates are 99.9% in their carboxylate anion forms (each approximately 3 pH units above their pKa). For example, at pH values above 8, almost all salicylic acid (pKa = 2.98) exists as RCOO_ and the surface of the bio-char will have a substantial negative charge density. Thus, little salicylic acid can adsorb.

Effect of solution pH on adsorbate adsorptionSolution pH plays a crucial role in ibuprofen and salicylic acid adsorption from aqueous solution. The percent removal of both ibuprofen and salicylic acid is higher in acidic solutions than in the basic region

pH effect on adsorption

Temperature effect on adsorption

Adsorption at 318 K at different ibuprofen [pH = 3, amount of biochar was 4 g/L] and salicylic acid [pH = 2.5, amount of biochar was 4 g/L] concentrations.Temperature effect on adsorption

Adsorption at 318 K at different ibuprofen [pH = 3, amount of biochar was 4 g/L] and salicylic acid [pH = 2.5, amount of biochar was 4 g/L] concentrations.

Repeatability

Biochar recycling using an adsorbent dose of 4 g/L and an adsorbate concentration of 100 mg/L, at a pH of 2.5 for

salicylic acid and pH 3 for ibuprofen at 318 K. Methanol (20 mL _ 2) was used as a stripping agent.ConclusionsFast pyrolysis pinewood biochar was characterized and this biochar successfully adsorbed ibuprofen and salicylic acid from aqueous solutions. Adsorption of both ibuprofen and salicylic acid followed pseudo-second order kinetics. Adsorption was favored at low pH values because the chars pHpzc is 2 relative to the pKas of ibuprofen (4.91) and salicylic acid (2.98). Adsorption capacities were 22.70 and 10.74 mg/g at 318 and 308 K, for salicylic acid and ibuprofen, respectively. Despite low surface area, the biochar (19% O) appears to adsorb by imbibing water and adsorbate within its solid structure. Methanol was able to achieve 93% and 88% desorption of salicylic acid and ibuprofen, respectively, from the spent biochar. Additionally, 76% and 72% of the biochars initial adsorption capacity for salicylic acid and ibuprofen, respectively, remained after four full capacity equilibrium recycles.References Y. Zhang, S.U. Geiben, C. Gal, Carbamazepine and diclofenac: removal in wastewater treatment plants and occurrence in water bodies, Chemosphere 73 (2008) 11511161. F.A. Caliman, M. Gavrilescu, Pharmaceuticals, personal care products and endocrine disrupting agents in the environment a review, Clean Soil Air Water 37 (2009) 277303. F. Pomati et al., Effects of a complex mixture of therapeutic drugs at environmental levels on human embryonic cells, Environ. Sci. Technol. 40 (2006) 24422447. K. Fent, A.A. Weston, D. Caminada, Ecotoxicology of human pharmaceuticals, Aquat. Toxicol. 76 (2006) 122159. K.T. Elvers, S.J.L. Wright, Antibacterial activity of the anti-inflammatory compound ibuprofen, Lett. Appl. Microbiol. 20 (1995) 8284. T. Heberer, Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: a review of recent research data, Toxicol. Lett. 131 (2002) 517. T.A. Ternes, Occurrence of drugs in German sewage treatment plants and rivers, Water Res. 32 (1998) 32453260. H.-R. Buser, T. Poiger, M.D. Muller, Occurrence and environmental behavior of the chiral pharmaceutical drug ibuprofen in surface waters and in wastewater, Environ. Sci. Technol. 33 (1999) 25292535. A. Ziylan, N.H. Ince, The occurrence and fate of anti-inflammatory and analgesic pharmaceuticals in sewage and fresh water: treatability by conventional and non-conventional processes, J. Hazard. Mater. 187 (2011) 2436. D. Mohan, A. Sarswat, Y.S. Ok, C.U. Pittman Jr., Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent a critical review, Bioresour. Technol. 160 (2014) 191 202. C.U. Pittman Jr. et al., Characterization of bio-oils produced from fast pyrolysis of corn stalks in an auger reactor, Energy Fuels 26 (2012) 38163825. B. Kunwar, T. Mlsna, Upgrading bio-oil with a combination of synthesis gas and alcohol, Energy Fuels 58 (2013) 9092. M. Rondon, J. Lehmann, J. Ramirez, M. Hurtado, Biological nitrogen fixation by common beans (Phaseolus vulgaris L.) increases with bio-char additions, Biol. Fertil. Soils 43 (2007) 699708. D.A. Laird, The charcoal vision: a winwinwin scenario for simultaneously producing bioenergy, permanently sequestering carbon, while improving soil and water quality, Agron. J. 100 (2008) 178181. D. Mohan, S. Rajput, V.K. Singh, P.H. Steele, C.U. Pittman Jr., Modeling and evaluation of chromium remediation from water using low cost bio-char, a green adsorbent, J. Hazard. Mater. 188 (2011) 319333. C.E. Brewer, K. Schmidt-Rohr, J.A. Satrio, R.C. Brown, Characterization of biochar from fast pyrolysis and gasification systems, Environ. Prog. Sustainable 28 (2009) 386396. F.-M. Pellera et al., Adsorption of Cu(II) ions from aqueous solutions on biochars prepared from agricultural by-products, J. Environ. Manage. 96 (2012) 3542. H. Sun, W.C. Hockaday, C.A. Masiello, K. Zygourakis, Multiple controls on the chemical and physical structure of biochars, Ind. Eng. Chem. Res. 51 (2012) 35873597. H. Guedidi, L. Reinert, Y. Soneda, N. Bellakhal, L. Duclaux, Adsorption of ibuprofen from aqueous solution on chemically surface-modified activated carbon cloths, Arabian J. Chem. (2014). H.P. Boehm, Surface oxides on carbon and their analysis: a critical assessment, Carbon 40 (2002) 145149. W.T. Tsai, C.Y. Chang, C.H. Ing, C.F. Chang, Adsorption of acid dyes from aqueous solution on activated bleaching earth, J. Colloid Interface Sci. 275 (2004) 7278. ReferencesA.S. Mestre, J. Pires, J.M.F. Nogueira, A.P. Carvalho, Activated carbons for the adsorption of ibuprofen, Carbon 45 (2007) 19791988. S. Lagergren, Zur theorie der sogenannten adsorption geloster stoffe, K. Sven. Vetenskapsakad. Handl. 24 (1898) 139. Y.-S. Ho, Review of second-order models for adsorption systems, J. Hazard. Mater. 136 (2006) 681689. Z. Aksu, D. Akpinar, Modelling of simultaneous biosorption of phenol and nickel(II) onto dried aerobic activated sludge, Sep. Purif. Technol. 21 (2000) 8799. R.S. Summers, Strategies and Technologies for Meeting SDWA Requirements, Technomic Publishing Company Inc., Lancaster, 1993. J.M. Montgomery, Water Treatment Principles and Design, Wiley-Interscience, New York, 1985. K.Y. Foo, B.H. Hameed, Insights into the modeling of adsorption isotherm systems, Chem. Eng. J. 156 (2010) 210. D. Mohan, A. Sarswat, V.K. Singh, M. Alexandre-Franco, C.U. Pittman Jr., Development of magnetic activated carbon from almond shells for trinitrophenol removal from water, Chem. Eng. J. 172 (2011) 11111125. M. Otero, C.A. Grande, A.E. Rodrigues, Adsorption of salicylic acid onto polymeric adsorbents and activated charcoal, React. Funct. Polym. 60 (2004) 203213. R.G. Combarros, I. Rosas, A.G. Lavin, M. Rendueles, M. Diaz, Influence of biofilm on activated carbon on the adsorption and biodegradation of salicylic acid in wastewater, Water Air Soil Pollut. 225 (2014) 1858. J. Huang, G. Wang, K. Huang, Enhanced adsorption of salicylic acid onto a b- naphthol-modified hyper-cross-linked poly(styrene-co-divinylbenzene) resin from aqueous solution, Chem. Eng. J. 168 (2011) 715721. F. Liu, M. Xia, Z. Fei, J. Chen, A. Li, Adsorption selectivity of salicylic acid and 5- sulfosalicylic acid onto hypercrosslinked polymeric adsorbents, Front. Environ. Sci. Eng. 1 (2007) 7378. A.S. Mestre et al., Waste-derived activated carbons for removal of ibuprofen from solution: role of surface chemistry and pore structure, Bioresour. Technol. 100 (2009) 17201726. R. Baccar, M. Sarra, J. Bouzid, M. Feki, P. Blanquez, Removal of pharmaceutical compounds by activated carbon prepared from agricultural by-product, Chem. Eng. J. 211212 (2012) 310317. S.P. Dubey, A.D. Dwivedi, M. Sillanpaa, K. Gopal, Artemisia vulgaris-derived mesoporous honeycomb-shaped activated carbon for ibuprofen adsorption, Chem. Eng. J. 165 (2010) 537544. I. Langmuir, The adsorption of gases on plane surfaces of glass, mica and platinum, J. Am. Chem. Soc. 40 (1918) 13611403. H.M.F. Freundlich, Over the adsorption in solution, J. Phys. Chem. 57 (1906) 385471. R. Sips, On the structure of a catalyst surface, J. Chem. Phys. 16 (1948) 490 495. O. Redlich, D.L. Peterson, A useful adsorption isotherm, J. Phys. Chem. 63 (1959). 10241024. C.J. Radke, J.M. Prausnitz, Adsorption of organic solutes from dilute aqueous solution on activated carbon, Ind. Eng. Chem. Fundam. 11 (1972) 445451. J. Toth, State equations of the solidgas interface layers, Acta Chim. Acad. Sci. Hung. 69 (1971) 311328.