Heavy Metal Removal from Produced Water Using Waste Materials: A Comparative Study

Produced water, a typical byproduct of oil and gas extraction, is considered a significant environmental and health problem due to its heavy metals content. The objective of this study is to evaluate and compare the efficiency of seven low-cost, waste-derived adsorbents in removing Cr3+, Cu2+, Fe2+, Zn2+, and Pb2+ from simulated produced water. The sorbents include gypsum, neem leaves, mandarin peels, pistachio shells, date seed powder, date seed ash, and activated carbon from date seeds. Adsorption experiments were performed using 2.5 and 5 g/L of the adsorbent. SEM and EDX analyses were used to confirm morphological changes and metal deposition after adsorption. Results showed that date seed ash exhibited the highest efficiency (85–100% across all metals), followed by activated carbon (25–98%), with strong Fe and Cu removal but a lower Pb uptake. Neem leaves, mandarin peels, and date seed powder showed moderate efficiencies (30–97%), while gypsum and pistachio shells were the least effective (0–81%). Lignocellulosic peels also showed good results due to the abundance of –OH and –COOH functional groups. Gypsum performed poorly across most metals. Integrating these waste-based adsorbents into secondary or tertiary treatment stages is an economical and sustainable solution for oil wastewater treatment. The results revealed the potential for valorizing agro-industrial and construction waste for circular economic applications in heavy metal pollution control.