Bioremediation of As(III) and As(V) from wastewater using living cells of Bacillus arsenicus MTCC 4380

Abstract

The biosorption characteristics of As(III) and As(V) using living cells of Bacillus arsenicus MTCC 4380 strain as biosorbents was investigated in the present research. Cell surface of B. arsenicus MTCC 4380 was characterized utilizing FT–IR and SEM–EDX. The maximum removal% of As(III) and As(V) by living bacterial cells were found to be 93.478 and 95.615, respectively at optimum conditions of pH adjusted to 7.0 at biosorbent dose of 2g/L, contact time of 90min and temperature of 30°C. To determine the most appropriate correlation for the equilibrium curves applying the method of the non-linear regression for curve fitting analysis, isotherm studies were performed for both As(III) and As(V) using 30 isotherm models. For initial arsenic concentrations of 50–2000mg/L, batch biosorption data of live biomass preferred to be simulated with Brouers–Sotolongo, Sips and Fritz–Schlunder–V isotherm models for As(III) while those for As(V) fitted Holl–Krich and Fritz–Schlunder–V isotherm models well. On the basis of R2¯ values the highest fitted model order among one and two parameter models is Langmuir model with a maximum adsorption capacity of 978.29824mg/g for As(III) and 894.13462mg/g for As(V). Based on the equivalent adsorption capacity values the higher fitted model order among three, four and five parameter models is Toth model with a maximum adsorption capacity of 1394.36585mg/g for As(III) and 1261.80096mg/g for As(V). Adsorption energy (15.811388KJ/mol for both As(III) and As(V)) and Temkin isotherm constant (19.99513J/mol and 20.9188J/mol for As(III) and As(V), respectively) calculation using Dubinin–Radushkevich and Temkin isotherm models indicated that the biosorption processes were chemical (ion exchange), spontaneous and exothermic in nature. Desorption study exhibited that over 88.372% and of As(III) and 91.231% of As(V) could be desorbed from composite with 0.05M NaOH solution.