Reduction of chromium hexavalent in electroplating industry passivation tank effluent using linz-donawits slag

Hexavalent chromium, Cr(VI), while widely utilised in electroplating industry for its wear and corrosion resistance, is a known carcinogen and mutagen, requiring a strict wastewater treatment. Current Cr(VI) treatment method in the electroplating industry is using Sodium metabisulfite (SMBS) as a reducing agent, capable of completely reduce Cr(VI) at pH 2. However, SMBS application as reducing agent generates large volume of sludge destined for landfill and possess health risks to the facility workers due to the release of hydrogen sulfide (H2S) and sulfur dioxide (SO2) gases. This study explores the utilisation of a steel making industry by-product, Linz- Donawits (LD) slag as a sustainable, low-cost alternative to SMBS. Electroplating passivation tank effluent was first characterised using ICP-MS, revealing Chromium as the highest component at 1614.6 mg/L. On the other hand, LD slag sample composition was characterised using XRF, showed Ferrous (II) oxide (FeO) as the major component (37.2% by mass). Cr(VI) concentration during the experiment was measured using HACH DR900 multiparameter portable calorimeter, aided by ChromaVer® 3 Chromium Reagent.