Performance and mechanism of zeolite derived from coal gasification coarse slag for adsorbing Ni(II) from wastewater

The heavy metal Ni2+ in water, posing a serious threat to humans and other organisms through food accumulation, can be removed using high-performance zeolites. The study successfully prepared a highly efficient Yzeolite adsorbent from coal gasification coarse slag (CGCS) via alkali melt-seed induced hydrothermal synthesis, with an average pore diameter of 8.3 nm. The comprehensive characterization and adsorption experiments were conducted on the synthesized Y-zeolite to investigate diverse factors' influence on performance. The removal efficiency of Ni2+ reached 98.325 % within 20 min and then stabilized at 99.760 % at a dosage of 1 g L- 1, pH maintained at 7.0, and an initial concentration of Ni2+ at 100 mg L- 1. The adsorption process conforms to the Pseudo-second-order kinetic model and Langmuir adsorption isotherm model, with the adsorption capacity of 98.943 mg g- 1 and the theoretical maximum adsorption capacity of 515.500 mg g- 1. The adsorption mechanism was analyzed by SEM-EDS and FTIR, based on the ion exchange interaction between Ni2+ and T-O groups. Furthermore, DFT calculations were employed to prove the most stable site for Ni2+ adsorption on Y-zeolite. The successful adsorption of Ni2+ on suitable sites located in six-membered rings of SuCage-6mr and Cage-6mr. In conclusion, Y-zeolite showed great potential as an efficient adsorbent for Ni2+ removal, promoting the comprehensive utilization of solid waste and creating a mutually beneficial outcome.