Malachite green dye removal from aqueous solution using fly ash based zeolites /

Abstract

Industries where colors and dyes are being widely used have a liquid colored waste that is directly sent to water streams without implementing any type of operation that can decrease its colored load. Such wastewaters have adverse effects on human being and also disturb agricultural ecosystem through blocking the photosynthesis process. Malachite green dye (MG) has several uses in industries as well as antifungal agent for aquatic system. The intended research utilized the waste of boilers and coal power plant i.e. coal fly ash (CFA) to treat such wastewater contaminated with MG dye through batch adsorption process. CFA was successfully modified to Na-zeolite and Li-zeolite through fusion treatment followed by hydrothermal treatment and characterized using thermal gravimetric analysis (TGA), X-ray diffractometer (XRD) analysis and SEM analysis. Parametric studies were performed by varying adsorbent amount, contact time, initial conc. of dye solution and temperature to estimate the effect on percent removal of MG dye. Kinetic studies were performed using pseudo-first order, pseudo-second order, intra-particle diffusion and elovich model. Elovich model was the best fitted model and the adsorption process was controlled by a diffusion layer inside the particles. Adsorption isotherm was also analyzed by applying Langmuir isotherms model and Freundlich isotherm model. Freundlich isotherms model well explained the adsorption system that was backed-up by elovich model explaining the adsorption was happening in multi-layers. Thermodynamic parameters were also taken in consideration and evaluated that covers Gibbs free energy (ΔG0), enthalpy change (ΔH0) and entropy change (ΔS0).