Electrocoagulation removal of anthraquinone dye Alizarin Red S from aqueous solution using aluminum electrodes: kinetics, isothermal and thermodynamics studies

Electrocoagulation (EC) was used for the removal of anthraquinone dye, Alizarin Red S (ARS) from aqueous solution. The process was carried out in a batch electrochemical cell with Al electrodes in a monopolar connection. The effects of some important parameters such as current density, pH, temperature and initial dye concentration, on the process were investigated. Equilibrium was attained after 10 minutes at 30 °C. Pseudo-first order, pseudo-second order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetics of the electrocoagulation process; pseudo-first order and Avrami models best fitted the data. Experimental data were analyzed using six isotherm models: Langmuir, Freudlinch, Redlich–Peterson, Temkin, Dubinin–Radushkevich and Sips isotherms and it was found that the data fitted well with Dubinin–Radushkevich and Sips isotherm model. The study showed that the process depended on the current density, temperature, pH and initial dye concentration. The calculated thermodynamics parameters (ΔGo, ΔHo and ΔSo) indicated that the process is spontaneous and endothermic in nature