Kinetics and isotherm studies for adsorption of arsenic on ferric hydroxide by potentiostatic electrocoagulation

The potentiostatic electrocoagulation (PEC) using iron (CT3 steel) for anode material was applied to removal of arsenic from well water. Some parameters such as potential, electrolysis time, and initial arsenic concentrations were varied for research in this article. The arsenic concentrations before and after PEC processing were analysed by AAS method. The mass of ferric hydroxide was calculated via Faraday's law. The results showed that the residual arsenic concentration in water samples from initial arsenic concentration until 800 ppb is smaller than that of WHO requirement (10 ppb). The adsorption of arsenic on ferric hydroxide fitted well into pseudo second-order kinetic equation, where its equilibrium adsorption capacity was linearly depended on the initial adsorption rate with R-2 of 0.9864. The Langmuir parameters N-max and K-L were 23.58 mg/g and 1060 L/mg with correlation constant (R-2) of 0.827, respectively.