NH4+-N adsorption behavior of nitrifying sludge immobilized in waterborne polyurethane (WPU) pellets

Abstract In this study, the characteristics and mechanism of NH 4 + -N adsorption by nitrifying sludge (NS) waterborne polyurethane (WPU) immobilized pellets were investigated. The NH 4 + -N adsorption by WPU immobilized pellets at different initial NH 4 + -N concentrations, and the influences of temperature, pH, salinity on NH 4 + -N absorption were respectively studied. Moreover, the adsorption isotherms, kinetics models and intraparticle diffusion model analysis were employed to investigate the adsorption process. The results showed that the NH 4 + -N adsorption capacity of the nitrifying sludge WPU was higher than that of the pellets without sludge (CK), and it increased with increasing initial NH 4 + -N concentrations. The optimal pH for NH 4 + -N adsorption was 7.0; High temperature and high salinity had an inhibitory effect on the NH 4 + -N adsorption. All the equilibrium data conformed to the Langmuir and Freundlich isotherms. The adsorption kinetics followed the pseudo-second-order kinetic model. The adsorption combined surface and internal diffusion.