Study on the adsorption of ammonia nitrogen in wastewater by modified walnut shell

A low-cost adsorbent had been prepared by carbonizing walnut shells using zinc chloride as an activating agent and study had been made to explore the possibility of the absorbent for liquid phase adsorptive removal of ammonia nitrogen (NH3-N). The operation factors, such as carbonization time, pH values of solution, the initial concentration of NH3-N, contact time, temperatures and the dosage of the absorbents, had been explored the effects on the adsorption of NH3-N. The adsorption capacity for NH3-N was 9.79 mg/g at initial pH values between 6.6 and 6.8. It was found that the adsorption process by the adsorbent could be well described by the Langmuir isotherm and the kinetics for NH3-N adsorption followed the pseudo-second-order equation. The thermodynamics study indicated that the adsorption process was a spontaneous endothermic process, and the process was conducted by the cooperation of the physical and chemical adsorption. The SEM images showed reasonable agreement with adsorption measurements.