Extracellular Polymeric Substances from Bacillus subtilis Associated with Minerals Modify the Extent and Rate of Heavy Metal Sorption

详细信息    查看全文

• 作者：Robert Mikutta ; Anja Baumg盲rtner ; Axel Schippers ; Ludwig Haumaier ; Georg Guggenberger
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：April 3, 2012
• 年：2012
• 卷：46
• 期：7
• 页码：3866-3873
• 全文大小：329K
• 年卷期：v.46,no.7(April 3, 2012)
• ISSN：1520-5851

文摘

Extracellular polymeric substances (EPS) are an important source of organic matter in soil. Once released by microorganisms, a portion may be sorbed to mineral surfaces, thereby altering the mineral虁s ability to immobilize heavy metals. EPS from Bacillus subtilis were reacted with Ca-saturated bentonite and ferrihydrite in 0.01 M KCl at pH 5.0 to follow the preferential uptake of EPS-C, -N, and -P. The sorption kinetics of Pb²⁺, Cu²⁺, and Zn²⁺ to the resulting EPS-mineral composites was studied in single and binary metal batch experiments ([metal]_total = 50 渭M, pH 5.0). Bentonite sorbed much more EPS-C (18.5 mg g^鈥?) than ferrihydrite (7.9 mg g^鈥?). During sorption, EPS were chemically and size fractionated with bentonite favoring the uptake of low-molecular weight components and EPS-N, and ferrihydrite selectively retaining high-molecular weight and P-rich components. Surface area and pore size measurements by N₂ gas adsorption at 77 K indicated that EPS altered the structure of mineral-EPS associations by inducing partial disaggregation of bentonite and aggregation of ferrihydrite. Whereas mineral-bound EPS increased the extent and rate of Pb²⁺, Cu²⁺, and Zn²⁺ sorption for bentonite, either no effect or a decrease in metal uptake was observed for ferrihydrite. The extent of sorption always followed the order Pb²⁺ > Cu²⁺ > Zn²⁺, which also prevailed in binary Pb²⁺/Cu²⁺ systems. In consequence, sorption of EPS to different minerals may have contrasting consequences for the immobilization of heavy metals in natural environments by inducing mineral-specific alterations of the pore size distribution and, thus, of available sorption sites.