Abstract
The removal of chemical oxygen demand (COD), total organic carbon (TOC), turbidity, and chromium content from tannery wastewater at different stages of the process was experimentally investigated using electrocoagulation (EC) with iron and aluminium electrodes. In the EC of the beamhouse wastewater (S1), the effects of initial pH and current density were analyzed and electrical energy consumption was determined. The COD and TOC in the solution were effectively removed, with an initial pH 7.0, using either metallic electrode. With a current density of 28 mA/cm2 for an electrolysis procedure of 60 minutes, the removal efficiency of COD and TOC was 72% and 57% with aluminium electrodes and 69% and 60% with iron electrodes, respectively. The minimum energy consumption for the highest COD and TOC removal was 0.37 and 0.69 kWh/m3 when employing iron or aluminium electrodes, respectively. At the optimal conditions, removal efficiencies close to 100% for turbidity and chromium content for wastewaters S1-beamhouse, S2-tanning, S3-retanning, and S4-a mixture 1 : 1 : 1 (v/v/v) were achieved. Results show that a pseudosecond-order rate equation provides a good correlation for the removal rate of the parameters. Finally, the results indicate that for tannery wastewater, the EC process does not depend noticeably on the electrode material, but that the stage of the tanning process of wastewater sample has the principal effect on treatment efficiency.
Highlights
Introduction e city of LeonGuanajuato is the first most important tannery industrial area of Mexico having almost 800 companies that provide jobs, economic resources, and a better quality of life to citizens of the city [1]
The ones based on sulfonated naphthalenes and their formaldehyde condensates play a primary role, for volumes and quantity used in the leather tanning industry. e oils cover the greater chemical oxygen demand (COD) equivalents compared to the resins and synthetic tannins [5]
Several publications have shown the efficiency of the treatment of tannery wastewater; most of the papers have focused their interest on the variables that affect the electrocoagulation process studying a single type of sample without an analysis of the wastewater’s origin
Summary
Introduction e city of LeonGuanajuato is the first most important tannery industrial area of Mexico having almost 800 companies that provide jobs, economic resources, and a better quality of life to citizens of the city [1]. It must be noted that these industrial activities use significant quantities of water and produce an average of 35 liters of wastewater per kg of treated hide [2, 3]. This tannery effluent does not meet the environmental regulations for discharge directly into the receiving water [4]. Synthetic tannins, oils, and resins are added to form softer leather at varying doses. The ones based on sulfonated naphthalenes and their formaldehyde condensates play a primary role, for volumes and quantity used in the leather tanning industry. The ones based on sulfonated naphthalenes and their formaldehyde condensates play a primary role, for volumes and quantity used in the leather tanning industry. e oils cover the greater COD equivalents compared to the resins and synthetic tannins [5]
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