Optimized preparation, nitrogen and phosphorus removal capacity of zeolite composite particulate materials

A repair material with simultaneous nitrogen and phosphorus removal capacity was developed in this study to treat water eutrophication. Raw material zeolite was mixed with calcium hydroxide and bentonite after soaking in alkali solution for 24 h. The obtained particulate composite materials were screened for removal of nitrogen and phosphorus, and for mechanical strength. Mixture ratio, calcination temperature, calcination time, heating rate and other processes were adjusted. Optimal conditions for preparation of particulate composite material were found: zeolite, Ca(OH)₂, bentonite mixture ratio 20︰1︰2, calcination temperature 504℃, calcination time 1.2 h, heating rate 5.6℃·min⁻¹. Single-factor experiments and correlation analysis revealed that preparation conditions influenced adsorption and removal rate of phosphate and ammonia nitrogen. Ca(OH)₂ was found to have significant correlation with adsorption of phosphate and ammonia nitrogen. With initial phosphorus and nitrogen concentrations both at 25 mg·L⁻¹, adsorption capacity of the new composite material was 4.39 and 4.01 mg·g⁻¹, respectively. Removal rate was 87.7% and 80.1%, respectively. Loss rate was 11.4%.