Green Synthesis of Flowers-Like Nanostructured Calcium Silicates: Kinetics and Adsorption Isotherms of Malachite Green Dye Removal from Polluted Water

Microwaves assisted synthesis of flowers-like nanostructured calcium silicates from marble sawing powder and silica fume wastes has been successfully done in a very short reaction time, energy saving and cost effective approach. XRD analysis of the synthesized powder showed that wollastonite; CaSiO 3 is the predominant phase. Cotton-like structures which composed mainly of coalescenced tiny cubes in the range of less than 1000 nm in size have been obtained as observed from FESEM images. The maximum monolayer adsorption capacity, q max at 30 °C of Malachite green was found to be 17.12 mg/g. Different parameters affect the adsorption process as; pH, sorbent dose, dye concentration and temperature was experimented. The kinetics studies indicated that the adsorption kinetics of MG dye on calcium silicate followed the pseudo- first order reaction. The experimental results also showed that the Malachite green adsorption is fitted better to Freundlich isotherm model. The dye adsorption process was spontaneous, exothermic reaction as indicated from thermodynamic studies. Diffusion model reveal that intra-particle diffusion mechanism was not the sole rate-limiting step in this adsorption.