Removal of Hardness Utilizing Charred Byproducts of Coconut, Peanut, and Vegetable Matter as Natural Sorbents

This study investigates the use of biomass-derived charcoal as a low-cost and sustainable adsorbent for hardness removal from groundwater. Charred sorbents were prepared from coconut shells, peanut shells, and vegetable residues and evaluated in both batch and continuous column systems. The initial hardness concentration of groundwater was 1,200 mg/L as CaCO3. The effects of key operational parameters, including sorbent dosage (1.0, 2.0, 3.0, 4.0, and 5.0 g), solution pH (5, 7, and 9), contact time (5.0, 10.0, 20.0, 40.0, and 60.0 minutes), and flow rate (50, 100, and 200 mL/min), were systematically examined. The results showed that hardness removal efficiency increased with increasing sorbent dosage and contact time, while it decreased with increasing flow rate. Among the tested materials, vegetable-derived charcoal exhibited the highest performance, achieving a maximum removal efficiency of 43.6%. The adsorption process was significantly influenced by solution pH, with optimal removal observed at pH 9.0. Column experiments further demonstrated that lower flow rates enhanced removal efficiency because of increased contact time within the packed-bed system. These findings indicate that agricultural-waste-derived charcoal is a promising alternative adsorbent for hardness removal. The proposed approach supports biomass valorization and offers a practical solution for sustainable water treatment in alignment with circular bioeconomy principles.