Adsorption of trimethoprim and sulfamethoxazole using residual carbon from coal gasification slag: Behavior, mechanism and cost-benefit analysis

The search for efficient adsorbents to mitigate the impact of antibiotic pollutants on marine ecosystems, food security and human health is a burgeoning field of research. Further, Trimethoprim (TMP) and sulfamethoxazole (SMX) are widely distributed in the marine environment and are difficult to degrade. In this research, we used gravity separation to enrich the residual carbon from the coal gasification coarse slag and used the resulting carbon-high product (GC) as a low-cost and high-efficiency adsorbent. TMP and SMX were investigated for their adsorption behavior in seawater using GC under varied conditions. The findings indicated that the adsorption capacities of TMP and SMX by GC were 5.0017 mg/g and 5.1391 mg/g, respectively. The equilibrium durations of TMP and SMX by GC were 21 min and 40 min, respectively. Various adsorption models were fitted to the adsorption behavior of two pollutants by GC. The results showed that the adsorption processes of the two pollutants were consistent with the Freundlich equation and the quasi-secondary kinetic model, suggesting that both pollutants were adsorbed on GC surface by both physical and chemical processes. GC more effectively adsorbed TMP than SMX under a competitive adsorption procedure. When we introduced molecular dynamics simulation into this research, the microscopic procedures of GC adsorbing two pollutants were investigated. The energy composition and hydrogen bond types in the adsorption process were quantified. Finally, we summarized the adsorption mechanism of GC adsorbing two pollutants. This work will pave the way for developing effective, low-cost and environmentally friendly novel materials for the adsorption and purification of antibiotic pollutants in the marine environment. This research can produce positive economic and environmental effects in the comprehensive utilization of coal gasification slag.