DEPT of- CHEMICAL TECHNOLOGYUniversity of Calcutta

Hydrophobic Biopolymers for Adsorption of Dyes in Water

Water pollutants are classified as Inorganic pollutant (heavy metals and its ions & non metals)

Organic pollutant(dyes , pesticides, hydrocarbons)

Biological pollutant( viruses bacteria )

DYES ARE HAZARDOUS BECAUSE

1. Most dyes are non biodegradable ,causing ,skin irritation , having carcinogenic action.

2. Some of them and their breakdown products are toxic (eg-TOXIC AMINES etc).

3. Several dyes causes damage of DNA that can lead tumors (eg- DIRECT BLACK 38 AZO DYE)

EXAMPLE OF SOME COMMON DYES

The major sources of dyes pollution are

1. Textile industries2. Paper industries 3. Rubber industries4. Plastic industries5. Paints industries6. Leather industries

Treatment methodology1. Irradiation.2. Oxidative process.3. Fenton process.4. Ozonation.5. Oxidation with NaOCl.6. Adsorption with solid adsorbents.7. Distillation.8. Reverse osmosis.

Amongst all methods Adsorption is preferred because:

1.The cost effectiveness of adsorption process > Other process. 2. Ease of operation & availability of wide range of adsorbents. 3. Effective in removal of organic, inorganic, & biological pollutants.

What is adsorption?

It is a surface phenomenon between adsorbent and adsorbate.

A molecule adhered to the solid surface is called an adsorbate ,and the solid surface is called adsorbent .

Adsorption takes place by physical forces but sometimes ,weak chemical bondings also participate in adsorption process.

Adsorption is controlled by various parameters such as TEMPERATURE, NATURE OF ADSORBATE AND ADSORBENT, PH , CONCENTRATION,CONTACT TIME, PARTICLE SIZE

To design a stirred vessel for a given degree of separation, the knowledge of adsorption equilibrium (in terms of adsorption isotherm ) and properties of solid and solute is required.

Property of a good adsorbent:

(1)Selectivity.(2) Adsorption capacity.(3) Reversibility of adsorption.(4) Particle size and its distribution.(5) Porosity.(6) Specific surface area.(7) Structural strength and stability..

BIOPOLYMER AS ADSORBENT

Advantages of biopolymers as adsorbent –(1)Biopolymer are biodegradable ,safe, and nontoxic in

nature. (2) Low cost and industrially available. (3) Selective.(4) Many are stable in water environment & Stable in

acid & base environment.(5) Satisfactory adsorption capacity.(6)Capable to remove pollutant even at low

concentration

Examples of Biopolymers which can be used as adsorbent.

1. Poly(glutamic acid) - polypeptide

3. Chitosan

4. Guar gum

2. Cellulose biopolymer

Cross-linked Polyglutamic Acid

Chitosan

Hydrophobic modification in cellulose biopolymer

Conclusion

The property of biopolymers are so ideal to make them as a candidate for fast and low expensive water treatment technology. Also there is a scope of further research on biopolymer for water treatment on a large scale . Some work has been carried out on this issue, and still there is a need for the development of novel biopolymer with increased affinity, capacity, selectivity, and capability to work at column operation.

References

1. Dye adsorption characteristics of magnetite nanoparticles coated with a biopolymer poly(cglutamic acid) B. Stephen Inbaraj a, B.H. Chen a,b,

2. Dithiocarbamated chitosan as a potent biopolymer for toxic cation remediation Adnan Khan, Syed Badshah, Claudio Airoldi 2011.∗

3. Competitive Sorption-Desorption Behavior of Triazine Herbicides with Plant Cuticular Fractions MICHAL SHECHTER,† BAOSHAN XING,‡ FRANK-DIETER KOPINKE,§ AND BENNY CHEFETZ*,†

4. A preliminary spectroscopic investigation on the molecular interaction of metal–diphenylthiocarbazone complex with cellulose biopolymer and its application S. Kalidhasana, A.S. KrishnaKumara, Vidya Rajeshb, N. Rajesha,∗

5. Poly (glutamic acid)--an emerging biopolymer of commercial interest. Bajaj I Singhal R. Source Food Engineering and Technology Department, Institute of Chemical Technology, Matunga, Mumbai 400 019, India

6.   Physical chemistry , by P.C. Rakshit 7 ed7. Coulson and Richardson’s CHEMICAL ENGINEERING VOLUME 2 FIFTH EDITION8. UNIT OPERATIONS OF CHEMICAL ENGINEERING Warren L. McCabe &Smith 7 ed9. B. K. Dutta mass transfer.