Enhanced adsorption treatment of landfill leachate using coal-based activated carbon modified by nitric acid

The coal based powder activated carbon was modified by nitric acid, the adsorption properties of activated carbon under different modification conditions was investigated the modified activated carbon obtained under the optimal modification conditions was used for the advanced treatment of landfill leachate to investigated the pollutants removal efficiency with varying different parameters such as input dosage and absorption time.The ratio of mesoporous aperture diameter and absorption properties of activated carbon attained the highest after modification 2 h with the concentration of nitric acid 15% and the temperature of modification 60 ℃.The removal rates of COD, NH₃-N, TN and Cr⁶⁺ were 79.0%, 43.3%, 52.6% and 100%, respectively, when the dosage of modified activated carbon was 4 g/150 mg/L, the adsorption time was 12 h, and the solution pH of 7.And after modification, the removal rate of COD and TN increased by 10.1% and 17.3% compared with previous activated carbon.It was found that the reaction of adsorption and degradation of COD in 12 h was more consistent with zero order reaction when analyzing the kinetics of COD adsorption and degradation.In addition, the nonlinear fitting of degradation process indicates that the degradation process can be simulated and predicted by Logistic function model.A better regenerative result was achieved by using ultrasonic method with the options of pH was 4.5 and ultrasonic time more than 2 h.Taking UV₂₅₄ as reference value, the regenerative post-treatment rate was reduced by 12% compared with the initial using which indicated that the nitric acid modified coal-based activated carbon has good regenerative capacity and could be reused.