Xanthogen Disulfide-Grafted Activated Carbon: An Efficient and Affordable Adsorbent for Mercury Removal from Water

In this study a novel and highly efficient adsorbent for mercury removal has been developed. The synthesized adsorbent, referred to as XAT@AC, is prepared using a simple and cost-effective method by grafting xanthogen disulfide (XAT) moieties onto the framework of activated carbon (AC). The XAT@AC was charqacterized using various techniques such as energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), Zeta potential, and N₂ adsorption–desorption analysis to investigate its properties. Next the resulting XAT@AC adsorbent was utilized to remove mercury from aqueous solutions and examined multiple parameters, including the amount of adsorbent, mercury concentration, co-ion interference, and pH, to optimize its effectiveness and understand the removal process. Both the Langmuir isotherm and pseudo-second-order kinetic models provided an adequate description of the adsorption process. The maximum adsorption capacities at pH = 6 obtained from the Langmuir fitting and experimental results reached up to 404.8 and 347.7 mg/g, respectively, surpassing the majority of adsorptive materials. The interference of co-existing cations and anions in the adsorption process was also investigated and it was found that the adsorbent exhibits excellent selectivity towards mercury. However, the presence of lead and cadmium ions significantly disrupts this feature. The grafted XAT@AC demonstrated a maximum adsorption efficiency of 76% with an insignificant adsorbent dosage of 0.2 g/L, and it exhibited excellent reusability and recycling performance, maintaining its adsorption capability after five cycles. Overall, this newly designed adsorbent holds great promise as a superior alternative to traditional activated carbon for mercury remediation.