Effects of Nickel Nitrate Modification on the Characteristics of Cashew Nutshell-Derived Biochar

Abstract:

This study investigates the effects of nickel nitrate modification on the physicochemical, structural, and thermal characteristics of cashew nutshell (CNS)-derived biochar. Biochar is an emerging eco-friendly material used in adsorption, catalysis, bio-composites, and bioenergy. It can be further functionalized to enhance its properties for specific applications. In this study, biochar was prepared via slow pyrolysis at 500 °C with a heating rate of 5 °C min^-1 under argon flow and a residence time of 1 h. The biochar was then loaded with nickel nitrate (0–15 wt% Ni) via wet impregnation and re-pyrolyzed under the same conditions with a residence time of 2 h. The obtained samples were characterized using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area and pore size analysis. The catalytic activity of the samples was evaluated for syngas production. XRD identified Ni° and NiO crystalline phases within the biochar matrix. XRF analysis indicated that the synthesized samples contained 0.03–10.69 wt% Ni. These results indicate successful Ni loading. Nickel doping altered the chemical composition of inherent oxides, improved thermal stability through strong metal-support interactions, and increased porosity. Among the samples, the 10 wt% Ni (NiBC-2) showed an optimal balance of pore accessibility, nickel dispersion, metal-support interactions, a stable carbon structure, and catalytic activity. Notably, Ni addition increased the specific surface area from 8.09 m²/g (BC) to 13.12 m²/g (NiBC-3), producing nickel crystallites ranging from 17.13 to 21.47 nm. These findings demonstrate that CNS biochar is a promising support material for catalytic applications.

• Periodical: International Journal of Engineering Research in Africa (Volume 79)
• Pages: 1-19
• DOI: https://doi.org/10.4028/p-fs02Dd
• Online since: June 2026
• Authors: Rodgers Tumwine*, Hiram Ndiritu, Fredrick Njunguna
• Keywords: Biochar, Cashew Nutshells, Characteristics, Nickel-Modified Biochar, Pyrolysis

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