Reduction of hexavalent chromium from electroplating wastewater to trivalent chromium.

• Main Authors: Burdeos, Redelynn R., Lee, Blesmarie G., Santiago, Michelle I.
• Format: text
• Language: English
• Published: Animo Repository 2000
• Subjects: Electroplating > Waste disposal > Environmental aspects; Biochemical and Biomolecular Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/10230
• Institution: De La Salle University

Electroplating wastewater contains hexavalent chromium of significant concentration and must not be disposed directly into bodies of water without treatment and meeting the necessary effluent quality standards set by the Department of Environment and Natural Resources (DENR). For Class C fresh water classification, the maximum tolerable amount of hexavalent chromium is 0.5 mg/L. Hexavalent chromium is a toxic chemical and is found to cause lung cancer. The main objective of this study was to economize a treatment process by physical and chemical methods applicable for small-scale electroplating industries (80L per day of wastewater). Sedimentation and filtration methods were used for the physical treatment while the chemical method involved the reduction-oxidation reaction. The treatment scheme of the hexavalent chromium in the wastewater was operated by batch and involved three stages. The first stage was involved the techniques of sedimentation, filtration and dilution techniques. The second stage was the addition of sodium metabisulfite (190.12 g/gmol) which was used as the reducing agent. In this stage, the hexavalent chromium was converted into trivalent chromium. The final stage consisted of addition of calcium hydroxide (74.08 g/gmol) at different pH values ranging from pH 9.2 to aid in the precipitation of the chrone hydroxide. The efficiency of the treatment scheme was determined by the % reduction of the hexavalent chromium by obtaining the analysis of the hexavalent chromium using the colorimetric method. The treatment scheme showed to be effective as indicated by 99.99% reduction of hexavalent chromium.