DOI: https://doi.org/10.55373/mjchem.v28i4.1

Keywords: Raw duck eggshells, nitrate, isotherm, kinetic models, groundwater

Abstract

Nitrate is an essential element for plant and animal growth. However, excess nitrate in groundwater may impact the environment and human health. Even though a variety of treatments for nitrate are available, there is still a need to verify the theoretical and experimental data using kinetic and isotherm models. This study aimed to investigate the performance of raw duck eggshells in removing nitrate from groundwater. The batch experiment used different adsorbent masses (2, 4, 6, 8, 10 g) in 100 mL aqueous solution for a certain time. The theoretical and experimental data were verified using kinetic (pseudo-first-order and pseudo-second-order) and isotherm (Langmuir and Freundlich) model studies. The equilibrium nitrate adsorption time obtained was 1440 min and the highest nitrate removal efficiency was 49.3 % for a 10 g mass of adsorbent with an adsorption capacity of 0.0365 mg/g. The kinetic verification model for pseudo-second-order fit well and had a correlation coefficient, R² of 0.9998, which showed that chemical sorption occurred within the adsorption process. The Langmuir isotherm model was the best fit, with an R² value of 0.5210. This indicated single layer adsorption on specific surface sites of adsorbent. Contour prediction was developed to simplify the estimation of removal efficiency with different initial concentrations using the required adsorbent mass. The results highlight the potential of raw duck eggshells in removing nitrate from water, and is an eco-friendly method for future water treatment.