Study of the kinetics of arsenic removal from wastewater using Bacillus arsenicus biofilms supported on a Neem leaves/MnFe2O4 composite

Abstract

The pollution caused by arsenic is major environmental problem, vital to be resolved. New technologies, easy for implementing and adapting to any system, require extraordinary consideration and are motivation of this research. The performance of a biofilm of Bacillus arsenicus MTCC 4380 supported on Neem leaves/MnFe2O4 composite on scavenging of As(III) and As(V) was evaluated. Optimum conditions of biosorption/bioaccumulation were determined as a function of contact time and temperature. The equilibrium was achieved after about 240min at a temperature of 30°C and biosorbent dose of 0.9g/L. Non-linear regression analysis was done for determining the best-fit kinetic model based on three correlation coefficients and three error functions and also for predicting the parameters involved in kinetic models. The results showed that both Brouers–Weron–Sotolongo and Avrami models for both As(III) and As(V) were proficient to provide realistic description of biosorption/bioaccumulation kinetic. Applicability of mechanistic models in the current investigation exhibited that the rate governing step in the biosorption/bioaccumulation of both As(III) and As(V) was film diffusion rather than intraparticle diffusion. The evaluated thermodynamic parameters ΔG0, ΔH0 and ΔS0 exposed that biosorption/bioaccumulation of both As(III) and As(V) was feasible, spontaneous and exothermic under investigated conditions. The activation energy (Ea) calculated from Arrhenius equation indicated the nature of biosorption/bioaccumulation being ion exchange type. Increasing concentration of As(III) and As(V) moreover improved the initial sorption rate h, from 3.86 to 694.03mg/gmin and 4.72–520.39mg/gmin, respectively. The outcomes attained are very favourable and inspire the usage of this biofilm in environmental applications.11NL/MnFe2O4 composite (MNL).