Low-cost coal-based adsorbents for the removal of high concentrated ammonia nitrogen from real coking wastewater: Aiming at industrial application

Background: The removal of high-concentrated ammonia nitrogen (AN) from the real coking wastewater (CW) is a tough nut to crack for coking industry. Coal-gangue, a solid waste, troubles the world, too. From the perspective of treat waste with waste, a promising coal-gangue-based adsorbent BY-N1, was developed to treat high-concentrated real CW and show excellent regenerability and removal rate (RR). This work hopefully broadens a new horizon for the development of waste-based adsorbent for removing AN in industrial application. Methods: BY-N1 was prepared from coal-gangue by simple solvent treatment and calcination. The effects of the adsorbent dosage, pH, initial concentration and reusability were investigated. Based on the adsorption isotherms, kinetics and thermodynamics, the adsorption mechanism was proposed. Significant findings: BY-N1 exhibits the potential in industry application, with the best ammonia nitrogen removal rate (ANRR) of 40.53 % for the complex real CW (about 3000 mg/L) in 20 mins and promising regenerability. Chemical adsorption dominant the adsorption process, the quasi-second-order model and Freundlich isotherm fit the adsorption process better, the maximum saturated adsorption capacity of BY-N1 is 240 mg g-1. This is a spontaneous and endothermic process by thermodynamic analysis, which involves the crucial contribution of complexation, hydrogen bonding interaction, electrostatic adsorption and Vander Waals force.