Reactive Dye Removal Using Inorganic-Organic Composite Material: Kinetics, Mechanism, and Optimization

An inorganic-organic composite material (MCPAM) consisting of magnesium chloride and polyacrylamide, was applied to remove reactive dye (Cibacron Red FN-R) from aqueous solution through coagulation-flocculation process. MCPAM with the ratio of 90% MgCl2/10% PAM was the best ratio in removing reactive dye. Kinetics of reactive dye removal was investigated using pseudo-kinetics model and it fits pseudo-second-order reaction model. The mechanism of reactive dye removal was investigated through physicochemical properties of supernatant, flocs, and sludge. The change of conductivity and pH denotes the interactions between reactive dye and MCPAM. The chemical structure, settling, and microstructure of sludge indicate the formation of sludge during coagulation-flocculation process. The settled sludge volume and sludge volume index (SVI) that of MCPAM was lower than that of MgCl2. The flocs formed using MCPAM was also relatively compact and larger in size compared to that of MgCl2. The reactive dye removal was optimized through central composite design whereby color removal (%) and chemical oxygen demand (COD) reduction (%) were optimized by five operating factors, namely, concentration of dye, pH, dosage of MCPAM, agitation speed, and agitation time. The optimal values reported for color removal (%) and COD reduction (%) were of 97-98% and 60-81%, respectively.