Performance of ball-milling-modified coal gangue on Pb2+, Zn2+, and NH4+-N adsorption

As the numerous industrial solid waste, coal gangue caused serious environmental pollution in China, while the it could be modified and reused as an effective adsorption material in environmental remediation. In the current study, the coal gangue was modified by environmentally friendly ball-milling chemical modification method and used for simultaneous adsorption heavy metal and ammonia in wastewater. Both the initial and modified coal gangue were characterized for structure and composition. Optimization of ball-milling conditions and adsorption parameters was carried out, followed by thermodynamic and kinetic experiments under the defined conditions. The results showed that the adsorption of Pb2+, Zn2+, and NH4+-N accorded with the quasi-second-order kinetic model, with all adsorption isotherms conforming to the Langmuir model. Thermodynamic analysis indicates that the adsorption of Pb2+, Zn2+, and NH4+-N is an exothermic process, and the adsorption reaction can occur independently. Moreover, modified coal gangue exhibited sufficient adsorption sites for the combination of Pb2+, Zn2+, and NH4+-N at low concentrations in adsorption competition experiment, with an adsorption sequence like Pb2+ > Zn2+ > NH4+-N. Our results provide that ball-milling-modified coal gangue can be used as a helpful adsorption material for heavy metal ions and ammonia removal in wastewater treatment.