This work presents the preparation of nickel catalysts supported on taro peel-derived activated biochar (AB) for p-nitrophenol (PNP) reduction using NaBH 4 . Taro peel-derived biochar was produced via pyrolysis under nitrogen at 350 °C for 35 min and 600 °C for 65 min. The biochar was then activated with 0.60 M citric acid to produce AB. Nickel was loaded onto the AB via wet impregnation, followed by calcination at 700 °C. Characterization using XRD, BET, FTIR, SEM, EDS, HR-TEM showed that citric acid activation introduced functional groups and slightly increased the biochar surface area (from 2.9 to 11.7 m 2 g -1 ). Subsequent Ni loading followed by high-temperature calcination further enhanced the surface area to 439.4 m 2 g -1 (sample M2) and sharply increased micropore volume. Systematic investigation identified that under the suitable reaction conditions (catalyst dosage of 0.50 g L -1 , a 1:200 molar ratio of 10 ppm PNP to NaBH 4 ), the M2 catalyst achieved an apparent rate constant of 0.600 min -1 following pseudo-first-order kinetics. Control experiments confirmed that the PNP removal was predominantly driven by catalytic reduction rather than physical adsorption. This study demonstrates that citric acid-activated agro-waste biochar is an effective support for Ni catalysts applied in the treatment of nitroaromatic pollutants. • Citric acid activation slightly increases taro peel-derived biochar surface area, from 2.9 m 2 g -1 for the biochar to 11.7 m 2 g -1 for activated biochar • Loading Ni onto the citric acid-activated biochar, followed by high-temperature calcination, caused a sharp increase in specific surface area, from 11.7 to 439.4 m 2 g -1 , and promoted the formation of micropores • An appropriate Ni loading markedly improves catalytic performance for efficient p-nitrophenol reduction • Efficient Ni-based catalyst (sample M2) shows fast kinetics (k = 0.60 min -1 ) following pseudo-first-order kinetics (R 2 = 0.9688) and maintains activity after six cycles
Vuong et al. (Fri,) studied this question.