Characterization of Pb biosorption by psychrotrophic strain Pseudomonas sp. I3 isolated from permafrost soil of Mohe wetland in Northeast China.

Due to the long and severe winter in Northeast China, wastewater containing lead (Pb) is treated inefficiently, resulting in irregular disposal. In order to solve this problem, a Pb-resistant psychrotrophic bacterium, Pseudomonas sp. I3, was isolated from permafrost soil of Mohe wetland and served as biosorbent for Pb removal under 15 °C. The minimum inhibitory concentration of strain I3 for Pb was 7.5 mM, which was higher than that of Escherichia coli DH5α (1.5 mM). However, acid digestion results showed that these two bacteria had a comparable biosorption capacity for Pb, suggesting no direct relationship between biosorption ability of bacteria and their metal-resistance. Acid digestion results also proved that intracellular Pb accumulation was mainly contributed to the distinct performance between living and non-living biosorbents, which was further confirmed by the analyses of TEM-EDS. Results of FTIR revealed that functional groups including CH, CO, CN, NH, COO and SO were participated in the biosorption process of the tested biosorbents no matter bacteria were living or not. The effects of environmental factors including pH, temperature, biomass dose, operation time and initial Pb concentration were investigated through a batch of biosorption experiments. The equilibrium data for living and non-living biosorbent were well fitted to Langmuir model with their maximum Pb biosorption capacities of 49.48 and 42.37 mg/g, respectively. The kinetic data for each biosorbent were well described by pseudo-second order kinetic model. Overall, Pseudomonas sp. I3 seemed to be an effective biosorbent for cleansing Pb from contaminated wastewater at low temperature.