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.