Removal of low concentration of As(V) from groundwater using an air injected electrocoagulation reactor with iron ball anodes: RSM modeling and optimization

Abstract

The present study deals with removal of arsenic from groundwater containing <=45 µg As(V) /L by a new air injected electrocoagulation (EC) reactor using iron (Fe) ball shape electrodes. The effects of initial pH (pH_i), applied current (i), operating time (t_EC), size of Fe ball anode (d_p), initial As(V) concentration (C_o), height of Fe anode (h) and air flow rate (Q_air) in the reactor as well as their interactions on effluent arsenic concentration and arsenic removal efficiency are investigated using a three level factorial design viz, response surface methodology (Box-Behnken statistical experiment design). Analysis of variance for all variables (operating parameters) has confirmed the predicted models by the experimental design within 95% confidence level (high variance coefficient () value of 0.92) which ensures a satisfactory adjustment of the quadratic model with the experimental data. The results of As(V) removal efficiencies indicate that i, t_EC, d_p and h are significantly affected by process parameters in the EC process. The model predicted at C_f<=9.9 (target) for maximum removal efficiency of As(V) and minimum operating cost at the optimum operating conditions (pH_i = 7.9, i = 0.05 A, t_EC = 1.8 min, d_p = 5 mm, h = 7 cm and Q_air = 6.9 L/min) in the EC process is 80% and 0.0142 $/m³ for initial concentration of 45 . This study clearly shows that the model is suitable for meeting under target value of effluent arsenic concentration (<10 µg/L) with the new EC reactor while keeping the operating cost to minimal.