A novel Zirconium-modified Coal Gasification Coarse Slag for phosphate adsorption

The excess phosphate in water leads to eutrophication, and hence finding cost effective adsorbing material for removing phosphorus from water is of great significance. Meanwhile, Coal Gasification Coarse Slag (CGCS) as a general solid waste, poses a potential threat to the environment. To solve these problems, herein, a novel low cost and high-efficiency adsorbing material was synthesized from CGCS by a facile method. The (CGCS)/ZrOCl₂⋅8H₂O mass ratio of 5:4 (denoted as CGCS-Zr4) was selected from a series of adsorbents with different mass ratios for subsequent sorption researches. The performance for phosphorus removal and related adsorption mechanism were investigated. The results showed CGCS-Zr4 had good adsorption property within a broad pH range. The Langmuir isothermal model, the pseudo-second-order kinetic and intra-particle diffusion model described the experiment data well, indicating that 1) the reaction process was monolayer and chemical adsorption; 2) rate determining step were both boundary layer effect and intraparticle diffusion. The adsorption mechanism of phosphorus on CGCS-Zr3 could be mainly achieved by electrostatic attractions and coordination reactions, forming inner-sphere phosphate complexes. The experiment results suggest that using Coal Gasification Slag (CGS) for removing phosphate could be a promising method in the wastewater treatment and resource utilization of solid waste.