efficiency of powdery activated carbon in ammonia-nitrogen removal from aqueous environments (response surface methodology)

background & aims of the study: nitrogenous compounds could directly create many problems for human's health and the environment. thus, removal of nitrogenous compounds is necessary. among the most important problems, decreasing dissolved oxygen, toxicity for aquatics, eutrophication, converting aerobic medium into anaerobic one and corrosion could be noted. the aim of this study was determination of powdered activated carbon absorption efficiency in ammonia-nitrogen removal from aqueous environments. materials & methods: this study was conducted as an experimental laboratory scale. in discontinuous system, the effect of parameters including absorbent dose (0.5-1.5 gr), initial n- ammonia concentration (100-200 mg/l), ph (3-9) and contact time (2-120 min) on system efficiency evaluated through response surface methodology (rsm). the results were fitted into freundlich and langmuir absorption isotherm and then absorption by the activated carbon absorbent compared by these models and absorption were analyzed. also, first order, semi-second order and particulate infiltration reaction kinetics were evaluated. results: n- ammonia removal efficiency had a direct relationship with absorbent dose, ph, contact time and reverse relation with initial n-ammonia concentration. study the isotherms and kinetics process showed that activated carbon followed freundlich isotherm as well as semi-second order kinetics. results from central composition design (ccd) model showed that the studied system efficiency fitted to linear equation and results from model predictions had a great agreement with experimental data (r2=0. 98). conclusion: according to appropriate removal efficiency, powdered activated carbon could be utilized as an efficient and inexpensive absorbent for ammonium absorbance. decreasing the system efficiency by increasing pollutant concentration must be considered.