Pyrolysis modification enhanced the efficacy of weathered coal residue in decreasing soil nitrate leaching

Soil nitrate leaching is a critical challenge for global agriculture and environment, requiring cost-effective and sustainable mitigation strategies. In this study, an innovative nitrate adsorbent was developed via pyrolysis modification of waste weathered coal residue (WR) at 600 °C. Batch adsorption experiments showed that the resulting pyrolysis-modified weathered coal residue (PWR) exhibited a maximum nitrate adsorption capacity of 5.69 mg g^-1 at 298 K, representing a 392.98 % increase compared to unmodified WR. The adsorption process was exothermic and spontaneous, dominated by the availability of active surface sites. Characterization results and desorption experiments revealed a mixed adsorption mechanism involving pore filling and hydrogen bonding formed with the oxygen-containing functional groups of PWR. And PWR can still exhibit excellent nitrate fixation performance through the strong interaction of hydrogen bonds, even under conditions of high pH and ionic strength. Soil column leaching experiments validated that PWR application reduced nitrate leaching by 10.45 % and increased soil nitrate retention by 78.62 %, confirming its superior performance in mitigating nitrate loss. This study provides a sustainable solution for mitigating agricultural nitrate pollution and promoting the circular utilization of waste WR, with significant implications for sustainable agriculture and environmental remediation.