Utilization of Waste Eggshells as Low-Cost Adsorbents for Heavy Metal Removal in Wastewater Treatment

The rapid industrialization and urbanization across the globe have led to a significant increase in wastewater containing toxic heavy metals, such as Mercury (Hg²⁺), cadmium (Cd²⁺), and chromium (Cr⁶⁺). These contaminants pose serious environmental and public health risks due to their non-biodegradable nature and high toxicity (Fu & Wang, 2011). While conventional methods like chemical precipitation, ion exchange, and membrane filtration are effective, they are often costly and unsustainable for large-scale applications, especially in developing regions (Barakat, 2011). Several studies have demonstrated the potential of calcium-rich agricultural waste for water purification. Eggshells, predominantly composed of CaCO₃ (about 95%), can bind to metal ions through ion exchange and surface adsorption mechanisms (Tsai et al., 2006). Recent research by Shoukat et al. (2022) found that modified eggshells significantly improved lead ion removal, achieving up to 98% removal under optimal conditions. Furthermore, the regeneration and reuse potential of eggshell adsorbents make them a promising alternative in circular economy models (Abbas et al., 2023). In this context, low-cost and environmentally friendly biosorbents are gaining attention. Eggshells, a common food waste, are rich in calcium carbonate (CaCO₃), and their porous structure makes them a potential adsorbent for metal ions (Babalola et al., 2021). This research aims to explore the efficacy of treated eggshell powder as a natural adsorbent for removing heavy metals from wastewater. The problem statement for this work is the current wastewater treatment methods are expensive and often inaccessible in low-income areas. Simultaneously, eggshell waste is abundant and underutilized, contributing to landfill waste. Therefore, there is a compelling need to investigate the dual benefit of reducing waste and addressing water pollution through sustainable materials like eggshells. The main objectives of this work are: (1) To evaluate the adsorption capacity of eggshell powder for selected heavy metals (Hg²⁺, Cd²⁺ and Cr⁶⁺). (2) To characterize the surface morphology and composition of eggshells before and after treatment using FTIR, SEM, and XRD analyses. (3). To assess the effects of pH, contact time, initial metal concentration, and adsorbent dose on the adsorption efficiency. and finally (4) To compare the performance of eggshells with conventional adsorbents. in this work we plan to follow this methodology: (1) Preparation of collected eggshells samples; it will be washed, dried, and ground into fine powder. A portion will be treated thermally or chemically (e.g., with citric acid) to enhance surface reactivity. (2) Characterization by SEM (to observe surface morphology), FTIR (to identify functional groups involved in adsorption.) and XRD (to analyze crystal structure (if possible)). (3) Adsorption Experiments: Batch adsorption tests will be conducted using synthetic wastewater. Variables such as pH (3–9), contact time (0–120 min), and adsorbent dosage (0.5–5 g/L) will be optimized. The main instrument used for this study is spectrophotometer (Based on using EDTA rand/or another reagents) for complex reaction. Regarding the expected outcomes, it will be as follows: (1) Identification of optimal conditions for heavy metal removal using eggshell powder. (2) Development of an effective, low-cost, and eco-friendly adsorbent. and (3) Contribution to sustainable waste management and clean water access. Finally, the significance of this research will contribute to green chemistry by valorizing food waste and addressing environmental pollution simultaneously. It aligns with Sustainable Development Goals (SDGs) 6 (Clean Water and Sanitation) and 12 (Responsible Consumption and Production).