A Heavy Metal Biotrap for Wastewater Remediation Using Poly-γ-Glutamic Acid

Poly‐γ‐glutamic acid (γ‐PGA) obtained from Bacillus licheniformisATCC 9945 was evaluated as a potential biosorbent material for use in the removal of heavy metals from aqueous solution. Copper (Cu2+) was chosen as the model heavy metal used in these studies since it is extensively used by electropla...

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Bibliographic Details
Published in:	Biotechnology progress Vol. 22; no. 2; pp. 523 - 531
Main Authors:	Mark, Sonny S., Crusberg, Theodore C., DaCunha, Christopher M., Iorio, Alexander A. Di
Format:	Journal Article
Language:	English
Published:	USA American Chemical Society 01-03-2006 American Institute of Chemical Engineers
Subjects:	Absorption Bacillus licheniformis Biological and medical sciences Biotechnology Cations - chemistry Conservation of Natural Resources Filtration Fundamental and applied biological sciences. Psychology Hydrogen-Ion Concentration Kinetics Metals, Heavy - chemistry Osmolar Concentration Polyglutamic Acid - chemistry Polymers - chemistry Solutions Temperature Waste Disposal, Fluid Water Supply Glutamic acid polymer Waste water Heavy metal
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Summary:	Poly‐γ‐glutamic acid (γ‐PGA) obtained from Bacillus licheniformisATCC 9945 was evaluated as a potential biosorbent material for use in the removal of heavy metals from aqueous solution. Copper (Cu2+) was chosen as the model heavy metal used in these studies since it is extensively used by electroplating and other industries, has been the model for many other similar studies, and can be easily assayed through a number of convenient methods. Cu2+‐γ‐PGA binding parameters under varying conditions of pH, temperature, ionic strength, and in the presence of other heavy metal ions were determined for the purified biopolymer using a specially designed dialysis apparatus. Applying the Langmuir adsorption isotherm model showed that γ‐PGA had a copper capacity approaching 77.9 mg/g and a binding constant of 32 mg/L (0.5 mM) at pH 4.0 and 25 °C. Cu2+‐γ‐PGA adsorption was relatively temperature independent between 7 and 40 °C, while an increase in ionic strength led to a decrease in metal ion binding. Cd2+ and Zn2+ ions compete with Cu2+ for binding sites on the γ‐PGA biopolymer. Metal uptake by γ‐PGA was further tested using a tangential flow filtration apparatus in a diafiltration mode in which metal was continually processed through a dilute solution of γ‐PGA without allowing for equilibrium to be established. The circulating polymer solution was able to complex metal as well as successfully prevent passage of unbound copper ions present in solution through the membrane. Using 500 mL of a 0.2% γ‐PGA solution, up to 97% of a 50 mg/L copper sulfate solution processed at a flow rate of 115 mL/min was retained by the polymer. For a 10 mg/L solution of Cu2+ as copper sulfate, filtrate concentrations of Cu2+ never rose above 0.6 mg/L while processing 2.5 L of dilute copper sulfate.
Bibliography:	istex:BEACC659BF5A0B628C93D923079457B460562FBB ark:/67375/WNG-462MCND4-9 ArticleID:BTPR60040 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	8756-7938 1520-6033
DOI:	10.1021/bp060040s