Application of a stabilized bioproduct, ceria–biochar ( <scp>CeO</scp> ₂ / <scp>BC</scp> ), for economic nitrate removal from drinking water

Abstract Nitrate contamination in drinking water is a pervasive global issue. Biochar has been widely investigated for nitrate removal, and modification with cerium oxide can enhance its performance. Biochar was pretreated with KOH, H 2 O 2 , HCl, or left untreated, and ceria–biochar (CeO 2 /BC) composites were fabricated accordingly. The synthesized materials were characterized using scanning electron microscopy (SEM), X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy, and zeta potential measurements. The highest nitrate removal (78%) was achieved using a ceria–biochar composite (HCB), which exhibited a specific surface area of 131.23 m 2 g −1 and a near‐neutral zeta potential at approximately pH 5. Nitrate adsorption was pH dependent, with maximum removal at pH 5. Nitrate concentrations of 10 to 90 mg L −1 were adsorbed within 0–360 min at pH 7, reaching equilibrium in 120 min. Kinetic analysis indicated pseudo‐second‐order chemisorption. Practical applicability was confirmed using real drinking water samples from Andhra Pradesh, India, where nitrate levels exceeded safe limits. The HCB composite outperformed other adsorbents, demonstrating potential as a cost‐effective and durable solution. This study advances environmentally friendly strategies for mitigating nitrate pollution and improving drinking water quality globally.