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

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 ?, 200 ?, and 500 ?). 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 ? provided the highest nitrate adsorption capacity, followed by 200 ?, and 80 ?. 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.