Removal of synthetic reactive dyes from textile wastewater by Sorel's cement

Removal of some reactive dyes (RY-145, RR-194 and RB-B) from textile wastewater effluents using Sorel's cement is described. Parameters affecting dye uptake including contact time, reagent dosage and pH are examined and optimized. Dye adsorption equilibrium data are fitted well to the Langmiur isotherm rather than Freundlish isotherm. The adsorption isotherm indicates that the adsorption capacities are 107.67, 120.89 and 103.14 mg dye per gram of Sorel's cement for RY-145, RR-194 and RB-B reactive dyes, respectively. The adsorption isotherms, including Langmuir constant ( Q° and b) and Frendlich constant ( K F and n), for the dyes decrease with the increase of temperature. The values of enthalpy change (Δ H) for RY-145, RR-194 and RB-B dyes are −146.96, −49.23 and −264.86 kJ mol −1, respectively, indicating that the removal process is exothermic. The sorption of the dyes is enhanced by increasing the pH, reaching a maximum at pH 6–11. Experimental runs conducted to measure the chemical oxygen demand (COD) of textile wastewater loaded with reactive dyes, reveal ∼96% removal of the COD contents within 30 min under optimized conditions.