Abstract

Although chromium is used in the form of basic chromium sulfate for processing hides, it has wellknown adverse effects when improperly disposed of in the environment under certain circumstances when Cr(III) can be oxidized to Cr(VI). Tanneries use large amounts of water for processing hides; hence, chromium recovery from tanning wastewater is an environmentally friendly and economically viable alternative, as it can prevent a greater amount of chromium-containing sludge from being disposed of in industrial hazardous waste landfills. Compliance with environmental legislation also poses a challenge to the leather industry, as the parameters for discharging treated wastewater into receiving water bodies are increasingly stringent, which encourages the practice of techniques for recovery and reuse of chemical inputs in the tanning of hides. This study focuses on the removal of the chromium present in tanning wastewater through chemical precipitation and electrocoagulation. In both methods, chromium is separated in the form of an insoluble precipitate either by the addition of alkali or by the oxidation and reduction of metal anodes. Chemical precipitation resulted in 99.74% of removal efficiency, while in electrocoagulation with aluminum, copper and iron electrodes, removal efficiency was 97.76%, 69.91% and 90.27%, respectively.