Pb2+ biosorption from aqueous solutions by live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2

• Published in: PloS one Vol. 15; no. 1; p. e0226557
• Main Authors: Hu, Xin, Cao, Jiachang, Yang, Hanyu, Li, Dahui, Qiao, Yue, Zhao, Jialin, Zhang, Zhixia, Huang, Lei
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 2020; Public Library of Science (PLoS)
• Subjects: Adsorption; Aqueous solutions; Binding sites; Biology and Life Sciences; Biosorption; Cadmium; Chemical engineering; Chemistry; Copper; Drug dosages; Earth Sciences; Electron microscopy; Experiments; Fourier transforms; Functional groups; Heavy metals; Hydrocarbons; Hydrocarbons - metabolism; Hydrogen-Ion Concentration; Infrared analysis; Infrared spectroscopy; Laboratories; Lead; Lead - analysis; Lead - isolation & purification; Lead - metabolism; Medicine and Health Sciences; Metal ions; Methods; Microscopy; Nickel; Optimization; pH effects; Photovoltaic cells; Physical Sciences; Research and Analysis Methods; Response surfaces; Rhodococcus; Rhodococcus - chemistry; Rhodococcus - growth & development; Rhodococcus - metabolism; Scanning electron microscopy; Temperature; Transmission electron microscopy; Wastewater treatment; Water - chemistry; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0226557

In this study, the Pb2+ biosorption potential of live and dead biosorbents of the hydrocarbon-degrading strain Rhodococcus sp. HX-2 was analyzed. Optimal biosorption conditions were determined via single factor optimization, which were as follows: temperature, 25°C; pH, 5.0, and biosorbent dose, 0.75 g L-1. A response surface software (Design Expert 10.0) was used to analyze optimal biosorption conditions. The biosorption data for live and dead biosorbents were suitable for the Freundlich model at a Pb2+ concentration of 200 mg L-1. At this same concentration, the maximum biosorption capacity was 88.74 mg g-1 (0.428 mmol g-1) for live biosorbents and 125.5 mg g-1 (0.606 mmol g-1) for dead biosorbents. Moreover, in comparison with the pseudo-first-order model, the pseudo-second-order model seemed better to depict the biosorption process. Dead biosorbents seemed to have lower binding strength than live biosorbents, showing a higher desorption capacity at pH 1.0. The order of influence of competitive metal ions on Pb2+ adsorption was Cu2+ > Cd2+ > Ni+. Fourier-transform infrared spectroscopy analyses revealed that several functional groups were involved in the biosorption process of dead biosorbents. Scanning electron microscopy showed that Pb2+ attached to the surface of dead biosorbents more readily than on the surface of live biosorbents, whereas transmission electron microscopy confirmed the transfer of biosorbed Pb2+ into the cells in the case of both live and dead biosorbents. It can thus be concluded that dead biosorbents are better than live biosorbents for Pb2+ biosorption, and they can accordingly be used for wastewater treatment.