The investigation of mechanism, kinetic and isotherm of ammonia and humic acid co-adsorption onto natural zeolite

Abstract

This study examined the applicability of the natural zeolite for simultaneous removal of ammonia and humic acid, two of the most encountered concurrent contaminants in the surface waters. The influence of various operating parameters including pH (2–10), concentrations of zeolite (1–10 g/L), initial concentration of ammonia (10–100 mg/L) and/or humic acid (2–20 mg/L), contact time (5–90 min), and temperature (20–50 °C) was investigated on the removal of target contaminants from water through different experimental runs. The results indicated that zeolite had best performance for simultaneous removal of ammonia and humic acid at the pH close to that of natural waters. The adsorption of humic acid was found to be improved in the presence of ammonia. The removal of ammonia and humic acid as single or binary components using natural zeolite was indicated to be a rapid process, following the pseudo-second-order kinetic model. The temperature positively influenced the removal of target contaminant both as single and binary components, although with greater influence for lower concentrations of zeolite. Equilibrium adsorption of ammonia and humic acid onto natural zeolite had best fitness with the Freundlich isotherm at all temperatures ranging from 20 to 50 °C. The maximum experimental adsorption capacities of ammonia and humic acid as binary components were 49.7 and 10.5 mg/g, respectively. It was understood from the results of this study that adsorption onto natural zeolite is an efficient in performance, simple to operate, and economical process and thereby affordable technology for simultaneous removal of ammonia and humic acid from the contaminated water source.