Absorbent mixtures optimisation for COD and Ammonia Nitrogen reduction in stabilised leachate

This paper describes the optimisation of mixed media for Chemical Oxygen Demand (COD) and Ammonia Nitrogen (NH3-N) removal from stabilised leachate by feldspar (FE), zeolite (ZE), activated carbon (AC), and cockle shells (CS) mixtures using D-optimal mixture design. Linear equations characterised the optimal mixture. The optimum mitigation of COD and NH3-N in landfill leachate was favourable at 12.5 mg/L, 9.72 mg/L, 6 mg/L, and 11.79 mg/L of adsorbent mixed dosage for FE, ZE, AC, and CS, respectively, with the desirability value of 0.886. The predicted R-squared values for NH3-N (0.9839) and COD (0.8972) were in close agreement with the adjusted R-squared values of 0.9940 and 0.9900 for COD and NH3-N, respectively, which validates the obtained regression models. The Lack of Fit F-values of 0.6015 (COD) and 0.4565 (NH3-N) are insignificant, indicating that the models accurately predict the removal. The Fourier transform infrared spectroscopy (FTIR) revealed that the predominant hydroxyl group consisted of –OH at spectra 3306.18 and 3338.74. The study also revealed that the D-optimal mixture design has extremely high application potential as it produces a good mixture design based on the remediation of contaminants from stabilised leachate.