Feasibility study of Aesculus turbinata fruit shell-derived biochar for ammonia removal in wastewater and its subsequent use as nitrogen fertilizer.

In the face of increasing nitrogen demand for crop cultivation driven by population growth, this study presents a sustainable solution to address both the heightened demand and the energy-intensive process of nitrogen removal from wastewater. Our approach involves the removal of nitrogen from wastewater and its subsequent return to the soil as a fertilizer. Using biochar derived from Aesculus turbinata fruit shells (ATFS), a by-product of post-medical use, we investigated the effect of pyrolysis temperature on the NH 4 –N adsorption capacity of ATFS biochar (ATFS-BC). Notably, the ATFS-BC pyrolyzed at 300 °C (ATFS-BC300) exhibited the highest NH 4 –N adsorption capacity of 15.61 mg/g. The superior performance of ATFS-BC300 was attributed to its higher number of oxygen functional groups and more negatively charged surface, which contributed to the enhanced NH 4 –N adsorption. The removal of NH 4 –N by ATFS-BC300 involved both physical diffusion and chemisorption, with NH 4 –N forming a robust multilayer adsorption on the biochar. Alkaline conditions favored NH 4 –N adsorption by ATFS-BC300; however, the presence of trivalent and divalent ions hindered this process. Rice plants were cultivated to assess the potential of NH 4 –N adsorbed ATFS-BC300 (NH 4 -ATFS-BC300) as a nitrogen fertilizer. Remarkably, medium doses of NH 4 -ATFS-BC300 (594.5 kg/ha) exhibited key agronomic traits similar to those of the commercial nitrogen fertilizer in rice seedlings. Furthermore, high doses of NH 4 -ATFS-BC300 demonstrated superior agronomic traits compared to the commercial fertilizer. This study establishes the viability of utilizing ATFS-BC300 as a dual-purpose solution for wastewater treatment and nitrogen fertilizer supply, presenting a promising avenue for addressing environmental challenges. [Display omitted] • Biochar from Aesculus turbinata fruit shells (ATFS) is a valuable resource. • ATFS was used as an adsorbent for NH 4 –N removal in wastewater. • ATFS pyrolyzed at 300 °C showed the highest NH 4 –N adsorption. • The NH 4 –N adsorbed ATFS-BC was a beneficial nitrogen fertilizer for rice growth. [ABSTRACT FROM AUTHOR]