ELECTRODE MATERIALS FOR ELECTROCOAGULATION OF CARWASH WASTEWATER
DOI:
https://doi.org/10.51699/sep72q80Keywords:
sacrificial anodes, metal electrodes, cathode influence, surfactant removal, water reuse, SDG 6Abstract
Carwash wastewater (CWW) is generated in large volumes, typically 150–600 L per vehicle, and carries high, variable loads of surfactants, oil and grease, suspended solids and turbidity (often exceeding 10³ NTU), together with dissolved salts and traces of heavy metals, making its treatment and reuse a priority for water conservation. Electrocoagulation (EC), in which coagulants are generated in situ by anodic dissolution while cathodically evolved hydrogen drives flotation, is a compact, low-reagent option well suited to such decentralized sources. However, comparisons of electrode materials remain scattered across dissimilar effluents, and the roles of the cathode and of the metallurgical composition of iron are seldom treated systematically. This review critically consolidates the metals reported as EC anodes, namely Al (Al), iron (Fe), zinc, magnesium, copper, stainless steel, titanium and graphite, together with the influence of cathode material and key operating factors, in order to justify electrode selection for CWW. Across the literature, EC typically removes 75–98% of chemical oxygen demand and 80–99% of turbidity, with Al and Fe dominating practice owing to their low cost, availability, non-toxicity and high ionic valence. Al generally affords superior turbidity, color and surfactant removal at lower energy but higher sludge and a risk of residual metal, whereas Fe is often faster and cheaper yet imparts residual color. Other metals are effective only for specific pollutants. The cathode is shown to govern flotation, pH evolution and passivation, and the carbon and impurity content of iron electrodes is identified as an under-explored factor. Al and Fe, alone or as Al/Fe hybrids, emerge as the pragmatic choice for CWW treatment and reuse in line with Sustainable Development Goal 6.
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