Adsorption of NH4+-N and E. coli onto Mg2+-modified zeolites

Abstract

Mg2+-modified zeolites (MMZs) were used for the adsorption of NH4+-N and Esherichia coli at different concentrations for a batch experiment. The adsorption characteristics (i.e. kinetics, isotherms, and mechanisms) of NH4+-N and E. coli on natural zeolites and MMZs were studied. Simple kinetic models, including pseudo-first-order kinetic models and pseudo-second-order kinetic models, were used to model the adsorption mechanism. Adsorption of NH4+-N and E. coli followed a pseudo-second-order kinetic model with the pseudo-second-order kinetic constants (k(2)) increasing with an initial increase in NH4+-N and E. coli concentrations. An intraparticle diffusion model was also used to investigate the mechanism of adsorption. From the intraparticle diffusion model results, NH4+-N and E. coli adsorption onto natural zeolites and MMZs could be described via film diffusion followed by particle diffusion. Furthermore, film diffusion was the rate-determining step in NH4+-N adsorption and particle diffusion was the rate-determining step in E. coli adsorption on natural zeolites and MMZs in this study. The maximum adsorption of NH4+-N and E. coli onto MMZs was 7.759 and 0.175 mg/g, respectively. Greater E. coli adsorption onto MMZs was due to the unique surface properties of the material compared with natural zeolites. Electrostatic interactions and hydrophobic attractions simultaneously affected the adsorption of E. coli onto MMZ in this study. Therefore, MMZ can be an efficient adsorbent material for the simultaneous removal of NH4+-N and E. coli from carcass leachates.