Using ZrO₂ coated sludge from drinking water treatment plant as a novel adsorbent for nitrate removal from...

This study aimed to produce a novel efficient absorbent using sludge generated from drinking water treatment plants (DWTPs) as a low-cost absorbent and applied to treat nitrate (NO₃^-) from contaminated water. Before the ZrO₂ coating experiment, the drinking water sludge (DWS) from DWTPs was pretreated by thermal treatment (80 °C, 200 °C, and 500 °C). After that, ZrO₂ coated drinking water sludge (DWS@ZrO₂) was produced by a simple precipitated reaction. The synthesized DWS@ZrO₂ was characterized by FTIR, SEM, and EDS with mapping analysis, XRD, and VSM. The results revealed that DWS@ZrO₂ could improve the pore filling in the adsorption experiment. The highest nitrate adsorption capacity was achieved (30.99 mg g^{- 1}) at pH 2 with DWS500@ZrO₂. Adsorption kinetics indicated that pyrolyzed DWS at 500 °C provided the highest nitrate adsorption capacity, followed by 200 °C, and 80 °C. Thermodynamic results showed that the obtained nitrate removal was an endothermic and spontaneous process. The possible nitrate adsorption mechanism of DWS@ZrO₂ could mainly involve pore filling, electrostatic interaction, and ligand exchange. The experimental results suggest that DWS@ZrO₂ is a feasible absorbent with high-efficiency, low-cost, high recyclability, and eco-friendly characteristics for treating nitrate in an aqueous solution.