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

In this study, the characteristics and mechanism of NH4+-N adsorption by nitrifying sludge (NS) waterborne polyurethane (WPU) immobilized pellets were investigated. The NH4+-N adsorption by WPU immobilized pellets at different initial NH4+-N concentrations, and the influences of temperature, pH, salinity on NH4+-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 NH4+-N adsorption capacity of the nitrifying sludge WPU was higher than that of the pellets without sludge (CK), and it increased with increasing initial NH4+-N concentrations. The optimal pH for NH4+-N adsorption was 7.0; High temperature and high salinity had an inhibitory effect on the NH4+-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.