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In this study, we report an efficient, stable, and renewable N, P co-doped coffee biochar-based catalyst loaded with highly dispersed Ni-N x species (Ni/NPCB-600), and it was successfully applied to the aqueous-phase chemoselective reduction or reductive amination of diverse nitroarenes (Yield up to >91%). Experimental and characterization studies revealed that N, P co-doping have a synergistic effect on improving the catalytic performance of Ni/NPCB-600. The textural properties of Ni/NPCB-600 are enhanced after doping of P, which can facilitate mass transfer and expose more accessible active sites in the reaction. The doping of N could induce the formation of Ni-N x sites and enhance the basicity of the Ni/NPCB-600 catalyst, which can promote the adsorption and activation of formic acid and nitroarenes, respectively. This is the first example of N, P co-doped coffee biochar-based catalyst for nitroarenes reduction or reductive amination, and reveals its potential industrial application prospects. [Display omitted] • Ni-N x supported on N, P co-doped coffee biochar was fabricated for the first time. • N, P co-doping could promote the catalytic performance of Ni/NPCB-600. • Using formic acid as a green and renewable source of hydrogen. • Ni/NPCB-600 exhibits good applicability to various nitroarenes. • High activity and chemoselective retained over 10 recycles. [ABSTRACT FROM AUTHOR]

Pyrolysis of calcium-rich feedstock (e.g., poultry manure) generates semi-crystalline and crystalline phosphorus (P) species, compromising its short-term availability to plants. However, enriching poultry manure with magnesium (Mg) before pyrolysis may improve the ability of biochar to supply P. This study investigated how increasing the Mg/Ca ratio and pyrolysis temperature of poultry manure affected its P availability and speciation. Mg enrichment by ∼2.1% increased P availability (extracted using 2% citric and formic acid) by 20% in Mg-biochar at pyrolysis temperatures up to 600 °C. Linear combination fitting of P K-edge XANES of biochar, and Mg/Ca stoichiometry, indicate that P species, mainly Ca–P and Mg–P, are altered after pyrolysis. At 300 °C, adding Mg as magnesium hydroxide [Mg(OH) 2 ] created MgNH 4 PO 4 (18%) and Mg 3 (PO 4) 2.8H 2 O (23%) in the biochar, while without addition of Mg Ca 3 (PO 4) 2 (11%) predominated, both differing only for pyrophosphate, 33 and 16%, respectively. Similarly, the P L 2,3 edge XANES data of biochar made with Mg were indicative of either MgHPO 4.3H 2 O or Mg 3 (PO 4) 2.8H 2 O, in comparison to CaHPO 4.2H 2 O or Ca 3 (PO 4) 2 without Mg. More importantly, hydroxyapatite [Ca 5 (PO 4) 3 (OH)] was not identified with Mg additions, while it was abundant in biochars produced without Mg both at 600 (12%) and 700 °C (32%). The presence of Mg formed Mg–P minerals that could enhance P mobility in soil more than Ca–P, and may have resulted in greater P availability in Mg-enriched biochars. Thus, a relatively low Mg enrichment can be an approach for designing and optimize biochar as a P fertilizer from P-rich excreta, with the potential to improve P availability and contribute to the sustainable use of organic residues. [Display omitted] • Phosphorus bioavailability increases in Mg-enriched biochar up to high pyrolysis temperatures. • OH− anions provided with Mg(OH) 2 could be a mechanism by which Mg-doped biochars have higher P availability. • Adding Mg to poultry manure decreased the formation of Ca–P minerals in low temperatures. [ABSTRACT FROM AUTHOR]

The in-field burning of sugarcane leaf residues presents a major environmental and health burden in Thailand. In this study, sugarcane leaves were converted into a biochar-based slow release phosphorus (P) fertilizer via pyrolysis at 600 °C, and the influence of pre- and post-pyrolysis treatment on the P loading and release was investigated. The sugarcane leaves were pre-treated with an alkaline (diammonium phosphate, DAP) or an acidic P source (phosphoric acid, PA), with or without addition of MgO. Additionally, the biochar was post-treated with DAP to increase the P loading. Extraction of P in DI water and 2% formic acid were used as indicators for potential slow release. The microporous biochars had a specific surface area of 69–333 m2 g−1 and pre-treatment resulted in a P content of 34–82 g kg−1. When MgO was included in the pre-treatment, XRD analysis confirmed formation of crystalline Mg 2 P 2 O 7 , irrespective of the P source. This Mg 2 P 2 O 7 was responsible for slow P release in DI water over 240 h via a dissolution-controlled process. Post-treatment with DAP increased the P loading to 156 g kg−1 in the form of water-soluble monoammonium phosphate (MAP), which did not contribute to slow release. The tunable P release via combinations of pre- and post-pyrolysis treatment makes these engineered biochars attractive as P sources for crops and presents an attractive solution to mitigate in-field sugarcane residue burning. [Display omitted] • P-loaded biochar was prepared by co-pyrolysis of sugarcane leaves with P + MgO. • Addition of MgO in pre-pyrolysis treatment results in slow release of P. • The slow P release is controlled by dissolution of Mg 2 P 2 O 7. • Post-treatment with DAP increases water-soluble P but not slow-release P. [ABSTRACT FROM AUTHOR]