Adsorption Studies for the Removal of Nitrate Using Modified Lignite Granular Activated Carbon

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Abstract
The removal of nitrate on ZnCl2 modified lignite granular activated carbon (LGAC) was investigated. The LGAC was modified with varying chemical impregnation ratios (ZnCl2: LGAC) and activation temperatures. Modified LGAC (LGAC5), with a 2:1 chemical impregnation ratio and a 500°C activation temperature had the optimum adsorption capacity for , at a 200 mg/L initial concentration. The initial pH of the testing solutions significantly influenced the adsorption capacity of LGAC5. The contact time studies showed the effectiveness of LGAC5, up to 50 mg/L initial concentration with 30 min of equilibration time. Isotherm studies revealed the highest values of the Langmuir constant (b), confirming strong affinity of LGAC5 for ions. Thermodynamics studies verified the endothermic nature of the adsorption process with randomness at the solid/solution interface. Competitive ion testing demonstrated that interfering anions, such as Cl−, , significantly reduced adsorption on LGAC5.