Reduction of hexavalent chromium to trivalent chromium using green technology: article

Electroplating industry generate harmful anionic heavy metals which is Hexavalent Chromium (Cr⁶⁺) that need to be treated before release it. Exposure of Cr⁶⁺ through inhalation or dermal contact can lead to cancer disease. These Cr⁶⁺ need to reduce first using a reducing agent and then undergo precipitation process for complete removal of (Chromium) Cr component. The common reducing agent is using Sodium Metabisulphite (SMBS). This chemical generated harmful gases which are Hydrogen Sulfide (H₂S) and Sulfur dioxide (SO₂). Other inorganic waste of that can be use as reducing agent is Leeden Gas sludge (LG sludge) that are from acetylene production gas. LG sludge contains high in (Calcium) Ca element and (Ferum) Fe ions that are essential for the reduction of Cr⁶⁺ to (Trivalent Chromium) Cr³⁺. The analysis of LG sludge characterization was done by XRF and XRD instrument with the result of high Ca and Fe ions with (Ca(OH)₂) alkaline properties. The initial concentration of Cr⁶⁺ is 3.25 mg/L using HACH Method 8023 and the initial total Cr concentration is 1124 mg/L was analyzed by ICPAES. The result in the effect of pH variation using LG sludge as a reducing agent was at pH 5.51 that shown 1.25 mg/L which is the lowest Cr⁶⁺ concentration value with 320.2 mV of ORP value. At that pH, the dosage was 1.15 ml with 61.5% reduction that is the highest % reduction. Next, the effect in volume LG sludge variation shown that Cr⁶⁺ was 100% successful reduce at pH 6.04 with volume LG sludge use at 1.8 ml with 264.9 mV of ORP value.