Regeneration of As(V)-loaded granular activated carbon through electrocoagulation.

Abstract

As(V)-loaded granular activated carbon was regenerated through electrocoagulation assisted by elution with NaCl. Adsorption of As(V) by activated carbon was highest at pH6, and subsequent desorption in water was highest at pH 11, followed by pH3. Lower initial pH improved arsenic removal during electrocoagulation, NaCl concentration was insignificant, but removal increased with current density. Adding Fe(II) before electrocoagulation led to an improved removal efficiency up to a concentration of 30 mg/L. Regeneration of As(V)-loaded activated carbon increased with current density and time up to a maximum of 85%. An increase in NaCl concentration to 6000 mg/L further improved regeneration to 92%. Regeneration at a lower current density only dropped slightly from 54% to 51% when doubling activated carbon concentration, demonstrating excellent scalability. Repeated adsorption-desorption tests were performed, where 81% and 69% regeneration were obtained after four regenerations with NaCl concentrations of 6000 and 750 mg/L, respectively. NaCl concentration in the tested range did not influence electrocoagulation but improved regeneration through elution. The combination of electrocoagulation and elution facilitated a higher regeneration efficiency, meanwhile removing As(V) from the solution through adsorption on iron hydroxide. PRACTITIONER POINTS: As(V)-loaded activated carbon was regenerated by electrocoagulation with elution. Regeneration increased with regeneration time and current density up to 85%. Addition of 6000 mg/L NaCl further increased regeneration to 93%. Regeneration of 82% was achieved after four regenerations. NaCl did not affect electrocoagulation but improved regeneration through elution.