Adsorption Kinetics Studies for Groundwater Remediation: A Study on Environmental and Economic Sustainability

This study investigates the potential of neem seed waste as an adsorbent for reducing total dissolved solids (TDS), hardness, calcium, and magnesium concentration in groundwater. Groundwater samples were collected from various locations within Quaid-e-Awam University of Engineering, Science and Technology (QUEST) and Nawabshah city. The objective of this research is to optimize the use of neem seed powder for removal of TDS, hardness, calcium, and magnesium concentration and physicochemical parameters from groundwater samples. Different dosages (0.5, 1.0 1.5, 2.0, 2.5, 5.0, and 10.0 g) and retention speed (0, 50, 100, 125, 150, 175, 200) were tested to optimize the treatment process. At a neem seed powder dosage of 2.0 g, a notable reduction in TDS was observed, with values of 48% for S1, 45% for S2, 52% for S3, and 58% for S4, respectively. Additionally, under a retention speed of 150 rpm, a significant decrease in TDS concentrations was recorded, with reductions of 72%, 65%, 79%, and 62% for S1, S2, S3, and S4, respectively. These results underscore the adsorbent's efficiency. Characterization techniques such as FESEM and FTIR were employed to understand the adsorption mechanism. The neem seed powder exhibited a considerable surface area of 55.30 m²/g according to BET analysis. Kinetic adsorption analysis showed a good fit with the pseudo-second-order (PSO) model with R² values 0.9978, 0.9946, 0.9967, and 0.9954 for TDS, Hardness, Calcium, and Magnesium. A higher R-squared value indicates that the PSO model aligns more closely with the data compared to the pseudo-first-order (PFO) model. The adsorbent molecules undergo a chemical reaction between surface molecules and adsorbate. This indicates chemisorption of adsorbs molecule. The study concludes that neem seed powder is a viable option for TDS removal due to its cost-effectiveness and availability compared to other materials like sodium zeolite and kaolin. Future research could explore the applicability of neem seed powder for removing other contaminants in groundwater or provides valuable insights into utilizing agricultural waste for groundwater treatment, offering a sustainable solution to water quality challenges.