Biosorption of As(III) and As(V) from aqueous solutions by brown macroalga Colpomenia sinuosa biomass: kinetic and equilibrium studies

In this research, capability of brown macroalga Colpomenia sinuosa for biosorption of arsenic [As(III) and As(V)] from aqueous solutions was investigated in a single-component batch system. Kinetic experiments indicated that As(III) and As(V) biosorption by C. sinuosa was rapid, and that 90–98% of equilibrium capacity of biosorption in 30 min was reached. Biosorption kinetics of As(III) and As(V) by the biomass at different concentrations were well described in terms of pseudo-second-order rate model (R 2 > 0.999 and ϵ% < 12.1%). In the pH range of 2–9, the optimum pH values for As(III) and As(V) biosorption were determined to be 6 and 2, respectively. The optimal pH of As(V) biosorption is highly acidic and its provision in operating the process would be difficult. Isotherm experiments were conducted in initial ion concentration range of 2–100 mg/L. The isotherm data were fitted to the Langmuir, Freundlich, Langmuir–Freundlich, and Redlich–Peterson models. Isotherm data of As(III) biosorption were found to be in the best fitness with the Freundlich–Langmuir model (R 2 > 0.996 and ϵ% < 4.2%) while the Langmuir model (R 2 > 0.995 and ϵ% < 5.6%) described the isotherm data of As(V) biosorption better than the other isotherm models. According to the Langmuir model, the maximum biosorption capacities (qm ) of As(III) and As(V) were obtained to be 95.6 and 59.9 mg/g, respectively. This study indicated that C. sinuosa biomass could be used as an efficient biosorbent for removal of As(III) and As(V) from aqueous environments.