Metal removal from multi-metal solutions by metal-tolerant Stenotrophomonas maltophilia isolated from river sediment

The efficacy of S. maltophilia in removing Pb2+, Cu2+, Zn2+ and Cd2+ from multi-metal solutions was determined by comparing against single-metal solutions. Results showed that the removal of the cations was higher in single than multi-metal solutions with mean uptake of 70 mg g(-1) of metals removed compared to less than 10 mg g(-1) metals, respectively. Biosorption of Pb2+ was the highest in both single (70.89 mg g(-1)) and multi-metal solutions (8.05 mg g(-1)). Metal removal by S. maltophilia in multi-metal solutions was influenced by different pH and adsorbent dosages used, in which pH 7 and low adsorbent dosages (0.10-0.50 g) led to higher amount of metals removed (pH 7: 3.26 -12.28 mg g(-1); 0.10-0.50 g: 2.30-8.71 mg g(-1)). ATR-FTIR analysis revealed that metal-binding sites for S. maltophilia were attributed to functional groups such as hydroxyl (-OH), amine (-NH2) and carboxyl (-COOH). Biosorption by S. maltophilia was found to comply with pseudo-second order, suggesting that the biosorption process is chemically rate-limited. This study showed that the metal-tolerant S. maltophilia has good potential as biosorbent for removal of metals, with recommended dosage and pH at 0.10-0.50 g and pH 7, respectively.