In this work, the effects of some experimental parameters (supporting electrolyte, current density, and initial pH) on the anodic dissolution of aluminum and on the electrocoagulation of tannic acid aqueous solutions as well as real industrial wastewaters containing tannic acid were investigated. Experimental results indicated that both chemical and electrochemical dissolution play an important role in the formation of hydroxo-aluminum species. The chemical dissolution of aluminum is strongly influenced by the solution pH. Corrosion studies have demonstrated that the presence of chloride ions in water accelerates dissolution of aluminum by pitting corrosion while phosphate ions inhibit the corrosion of aluminum by formation of a thick passive layer of aluminum hydroxide/phosphate on the aluminum surface. The results obtained can be used to better understand the mechanism of the electrocoagulation process due to the importance of the anode surface electrodissolution in the treatment process. Electrocoagulation using aluminum electrodes achieved high removal efficiency of chemical oxygen demand (≥80%) from aqueous solutions containing 0.51 g•L -1 tannic acid. The primary mechanism implicated in eliminating tannic acid from water by electrocoagulation using Al electrodes involves the adsorption of tannic acid molecules on the aluminum hydroxide surface. Also, results of the treatment of real wastewater obtained from the pulp and paper industry with an initial chemical oxygen demand (COD) concentration of 1450 mg•L -1 have shown that more than 60% of COD can be removed by electrocoagulation using Al electrodes under optimized experimental conditions. The specific energy required for the electrochemical process with Al electrodes was estimated to range from 1 to 2 kWh•m -3.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering