Heat Activated Zeolite for the Reduction of Ammoniacal Nitrogen, Colour, and COD in Landfill Leachate

Abstract

Landfills are the main option for waste disposal all over the world. Most of the landfill sites across the world are old and are not engineered well to prevent contamination of the underlying soil and groundwater by the toxic leachate. The present study examines the potential use of raw zeolite and heated activated zeolite in the reduction of COD, NH3-N, and colour from leachate. Zeolite was activated using different temperatures at 150 °C, 200 °C, and 250 °C for 3 h. General characterization was conducted for raw zeolite and heat-activated zeolite to investigate the influence of temperature on zeolite properties. Batch experiments were conducted at the optimum dosage of zeolite and pH. Results demonstrated that the optimum dosage of raw zeolite was 10 g with 53.1%, 22.5% and 46% reduction of NH3-N, COD, and colour, respectively. The optimum pH for NH3-N was 7 with a percentage removal of 55.8% while better reduction of COD and colour was obtained at pH 4 with a percentage removal of 24.3% and 73.8%, respectively. Also, the optimum temperature tested was at 150 °C, where the optimum dosage using activated zeolite heated at 150 °C was 10 g, resulted in the maximum reduction of NH3-N, COD, and colour of 45.1%, 11.8% and 43.7%, respectively. The optimum dosage of activated zeolite heated at 200 °C and 250 °C, which was 25 g. This indicates that the use of the activated zeolite heated at 150 °C can achieve the optimum removal at a lower cost which is applicable for a larger scale of wastewater treatment. In addition, it was found that the capacity of the zeolite before and after heat activation was 41.30 cmol/kg and 181.90 cmol/kg, respectively. The adsorption isotherm analysis reveals that both Freundlich and Langmuir isotherms were in agreement with experimental data. However, the Freundlich isotherm model was more favourable than Langmuir isotherm to evaluate the adsorption equilibrium of the three pollutants as verified by the high R2 values.