Application of alkali modified coal gasification slag absorbent for treating lead-contaminated water: Isotherm, kinetic, and mechanism adsorption

Gasification slag landfill has caused serious environmental pollution in coal chemical sector. Therefore, the utilization of coal gasification slag as a precursor for adsorbent production represents a significant avenue for the sustainable management of this industrial by-product. However, there are few researches on the systematic alkali modification of gasification slag. In this study, an optimized alkali modification process employing a 3 mol/L NaOH solution, a liquid-to-solid ratio of 10:1, conducted at 100 °C for a duration of 10 h, resulted in the production of a high-performance adsorbent, i.e., alkali modified coal gasification slag (CGS-OH). Besides, The formation of an axial crystal structure zeolite crystal on the adsorbent surface. Under optimal adsorption conditions with a pH of 6, an adsorbent dosage of 3 g/L, and a temperature of 25 °C, CGS-OH exhibits the optimal adsorption performance for removal of Pb 2 + , characterized by a high removal rate of 95.77 % and substantial equilibrium adsorption capacity of 47.5 mg/g. Herein, the adsorption kinetics of the above process are well described by the pseudo-second-order kinetic model ( R 2 = 0.9981), indicating that the adsorption process is predominantly governed by a chemical adsorption mechanism, primarily involving electrostatic attraction and ion exchange at the adsorbent's surface. This research underscores the potential of CGS-OH as a cost-effective and high-performance adsorbent for Pb 2+ removal, offering significant implications for industrial wastewater treatment and environmental remediation strategies. It also provides a feasible path for the high-value utilization of industrial by-products in coal chemical sector.