Studies on the adsorption of aqueous cadmium and the treatment of mine tailings using anionic Type-C starch

Abstract

Adsorption-based water treatment technology is a sustainable strategy for health and environmental wellness, as well as mineral recovery and resource conservation. Extended studies on the Cd2+ adsorption characteristics of the cross-linked/phosphorylated carboxymethyl starch (SCCS) derivatives produced by treating a Type-C starch with anionic precursors, including sodium trimetaphosphate (STMP) and sodium monochloroacetate (SMCA) were carried out. The optimum product was subjected to surface area studies using the Brunauer–Emmett–Teller (BET) method, and then Fourier transformed infrared (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) before and after adsorption of Cd2+. The BET results showed that the derivative is mesoporous (pore size: 3.5–6.4 m3/g), while the FTIR results indicated that the adsorption of Cd2+ can be attributed to interactions with the hydroxyl, carbonyl, and phosphoryl functional groups on the SCCS platform. Adsorption equilibrium, kinetics, isotherms, thermodynamics, and recovery/regeneration were extensively studied using various models and experimental conditions. The results showed that Cd2+ was efficiently adsorbed (≈ 99%) at equilibrium, and the data fitness for multiple models indicated that the adsorption process is based on a combination of physisorption and chemisorption processes that are thermodynamically feasible and reversible for economic utilization of the adsorbent. The adsorbent was used in the treatment of mine tailing, and the result showed that the removal of minerals from the tailings was very efficient (≈ 100%).