Efficient cadmium removal from synthetic wastewater using a bipolymeric/Fe3O4 nanocomposite loaded on coal tailings

Recent attempts to produce effective adsorbents for wastewater treatment purposes have led to development of multiphase nanocomposite consisting of a bed, nanoparticle enhancer(s) and one or more polymeric modifiers. However, availability and final price have been always prohibitive factors challenging the wide application of many of multiphase adsorbents. In this research work, a novel bipolymeric/Fe3O4 nanocomposite loaded on coal tailings was synthesized using a two-step procedure and evaluated as a potential low-cost adsorbent for treating synthetic wastewater polluted by heavy metals. Starting material and synthesized quadriphase nanocomposite were characterized using different instrumental analysis techniques. The adsorptive capacity of the nanocomposite was assessed using response surface methodology (RSM) by considering the nanocomposite-to-cadmium ratio (7-233) and initial pH of solution (3-11) as operating factors and cadmium removal as process response. The significance of the effect of operating variables on removal efficiency was assessed and confirmed using analysis of variance (ANOVA) method. The maximum cadmium removal of 99.30% was obtained under optimum conditions including pH of 10 and quadriphase nanocomposite/cadmium ratio of 40 after 2 h of adsorption. Kinetics and multistep adsorption studies showed that an optimum adsorption of 97% could be obtained only after 1.2 min following a first-order single-step process. Isotherm plots revealed that cadmium adsorb as monolayer on the surface of synthesized quadriphase nanocomposite based on Temkin model with the highest correlation coefficient of 97.67% and the least relative error of 16.15%.