Diseño de una planta de recuperación del sulfato de cromo (III) proveniente de las aguas del proceso de curtido de cromo, mediante electrocoagulación y reacción química

Abstract

This research project aimed to recover chromium sulfate from effluents of the chrome tanning industry, for this purpose the effluents were treated with two different methods: electrocoagulation and chemical precipitation- acidification. The physical-chemical characterization of waste effluents tanning results gave as COD values: 10 000 mg/L, BOD5: 11 000 mg/L, Cr+3: 3 200-6 000 mg/L, total solids 10 378 mg / L, pH: 3.5. It was compared with environmental regulations and determined that the COD exceeds 4 000% the value allowed by the standard, BOD5 exceeds 4 400%, pH at 200% and the total solids in 650%, indicating the urgency of treating the effluent before being discharged. In the electrocoagulation process the effluents were treated at different current densities (9, 30, 76 A/m2) and residence times (15, 30, 45 min). Chrome recovery was obtained is 21.9%. It was used Iron electrodes and an electrochemical cell 8 L. Chemical precipitation was evaluated as an alternative process. Sodium hydroxide (NaOH) was used as precipitating agent and it reduced more and 99.3% of the initial concentration of chromium. To pellet the precipitate of chromium hydroxide (Cr(OH)3) for a day, the recovery it is increased to 99.99%. Based on the experimental results the method of chemical precipitation and acidification was chosen as main process. Precipitated chromium was recovered and by acidification with sulfuric acid (H2SO4),it obtained a solution of 6 125 mg/L of chromium sulfate (Cr2(SO4)3) recovered at pH 1. Finally a chromium sulfate (III) recovery plant was designed to a flow of 15 m3 / day, which produces an amount of 243 kg / day. This amount of chromium recovered represents a saving of $ 194 per day for the company.