From waste to treat waste : exploitation of marble dust as a harmful pollutant to a green adsorbent for dyes and heavy metals from industrial wastewater

The marble dust as a harmful industrial waste of marble fabrication was evaluated as aneconomical and efficient green adsorbent for Acid Red-1 dye and lead ions. The XRD, XRF, particle size, surface area and zeta-potential measurements were used to characterize the marble dust. The removal efficiency was optimized by studying several parameters such as pH, temperature, contact time, adsorbent dose and initial concentration. The optimum removal was achieved at pH 6, 20°C after 60 min in the presence of 2.5g/L marble dust. The rates of adsorption were found to follow the pseudo-second-order model. The results showed better fitting to Freundlich isotherm. The thermodynamic studies revealed that the adsorption process is spontaneous, exothermic and favorable at low temperature. The free energy (∆G°), enthalpy (∆H°), and entropy (∆S°) changes were calculated to predict the nature of adsorption.The removal efficiency was improved by calcination of the marble at 700°C. Application for textilewastewater showed high removal efficiency up to 99.9%of inorganic and organic pollutants. The product of treatment was used in the concrete and bricks manufactured, so there is nogeneration of second-order pollutants.