Application of response surface methodology (RSM) for optimization of ammoniacal nitrogen removal from semi-aerobic landfill leachate using ion exchange resin

Disposal of untreated landfill leachate can be a source of hazard to receiving waters. Hence, treatment of landfill leachate is considered environmentally essential. In this study, optimization of ammoniacal nitrogen (NH3–N) removal from Malaysian semi-aerobic landfill stabilized leachate using synthetic cation ion exchange resin was investigated. An ideal experimental design was carried out based on Central Composite Design (CCD) with response surface methodology (RSM). This RSM was used to evaluate the effects of process variables and their interaction towards the attainment of their optimum conditions. Equilibrium isotherms in this study were analyzed using the Langmuir and Freundlich. Kinetic data were obtained and analyzed using pseudo-first-order and pseudo-second-order equations. Based on statistical analysis, the NH3–N removal model proved to be highly significant with very low probability values (< 0.0001). The optimum conditions obtained were 24.6 cm3 resin dosage, 6.00 min contact time, and 147.0 rpm shaking speed. This resulted in 94.2% removal of NH3–N as obtained from the predicted model, which fitted well with the laboratory results (i.e., 92%). The adsorption isotherm data were fitted well to the Langmuir isotherm, and the monolayer adsorption capacity was found as12.56 mg/g.