Combination of electrocoagulation and MOF adsorption systems for EBT removal from water

Abstract

ABSTRACT Eriochrome Black T (EBT) is a synthetic and widely used Azo dye in industries and laboratories wastewaters that must be controlled before discharge into receiving waters. A hybrid treatment approach consists of electrocoagulation (EC) and adsorption was adopted to reach the highest level of dye removal. As adsorbent, zeolitic imidazolate framework-67 (ZIF-67) with 1323 cm2 and 0.57 cm3 surface area and pore volume per gram was synthesised at room temperature in an aqueous environment. The EBT removal was higher when aluminium applied as electrode material compared to iron (98.5% versus 93.8%). Dye removal in EC reactor was also quite fast and up to 84.5% of EBT removed in 10 min. The hybrid process, EC and adsorption by ZIF-67, also shows an 85% dye reduction for treating concentrated solutions up to 500 mg EBT/L in half an hour. In the range of 2–12, pH shows a significant influence on the EC process efficiency and maximum dye removal was observed at pH of about 5. Furthermore, the removal strongly improved (from 7.7% to 99.1%) by increasing the potential difference between the electrodes in the range of 2–15 V. The process described by intra-particle diffusion model which shows that the surface diffusion phenomena probably controls the rate of the dye removal process. In conclusion, the proposed EC/adsorption system shows a premium efficacy in treating polluted water by EBT.