An investigation on the new operational parameter effective in Cr(VI) removal efficiency: A study on electrocoagulation by alternating pulse current

The performance of an electrocoagulation (EC) process with aluminum/iron electrodes for removal of chromium on laboratory scale was studied. The effect of operational parameters such as initial pH, current density (CD), reaction time, initial concentrations (50, 100, 500, 1000 mg/L), solution conductivity, electrical energy consumption (EEC) and type of circuit were studied in an attempt to reach higher Cr(VI) removal efficiency. Alternating pulse current (APC) was used to prevent the passivity or polarization of electrodes. Important operating parameters were optimized to access higher (99%) Cr(VI) removal efficiency as follows: EEC range: 4-58 kWh/m3 wastewater, CD: 56-222 A/m2, operating time: 20-110 min, pH 3-9 (pHoptimum 5), voltage: 15-25 V. NaCl, KCl, PAC (poly aluminum chloride), NaNO3 were used as supporting electrolytes. NaCl as well as KCl handled the EC with the best performance in every aspect; however, PAC and NaNO3 did not have the same results (Applied conductivity is better than literature). The results of this work are comparable with those of recent studies. Equal removal efficiency was obtained in “direct current” (DC) and (APC); however, when “APC” was used, water recovery (0.92 m3/m3 wastewater) was significant and the turbidity was 1 NTU. “APC” amazed our experimental team.