This study investigates the pyrolysis and adsorption properties of biochar derived from coconut shell (BC-CS), rice husk (BC-RH), and cow manure (BC-CM) under varying thermal treatment conditions. Biochar samples were produced at 800 °C with residence times ranging from 0 to 60 min. Their characteristics were analyzed using their Brunauer–Emmett–Teller (BET) surface area, total pore volume, and pore diameter measurements. BC-CM exhibited the highest BET surface area of 263.3 m²/g and a total pore volume of 0.164 cm³/g, while BC-RH and BC-CS showed maximum BET surface areas of 220.62 m²/g and 197.38 m²/g, respectively. Nitrogen adsorption–desorption isotherms revealed distinct microporous and mesoporous structures, with BC-CM demonstrating superior adsorption capacity across all relative pressures. The adsorption kinetics of methylene blue (MB) were examined at initial concentrations of 1 ppm, 5 ppm, and 10 ppm, with varying biochar doses (0.1 g, 0.3 g, and 0.5 g). The results showed that the adsorption rate constant (k) decreased with higher initial MB concentrations, while the equilibrium adsorption capacity (q_e) increased. BC-CM achieved the highest q_e of 2.18 mg/g at 10 ppm and a 0.5 g dose, followed by BC-RH-800-45 (1.145 mg/g) and BC-CS (0.340 mg/g). The adsorption process was well described by a pseudo-second-order kinetic model, indicating chemisorption as the dominant mechanism. Increasing biochar doses improved MB removal efficiency, highlighting the dose-dependent nature of adsorption. These findings underscore the importance of optimizing pyrolysis parameters to enhance biochar’s adsorption performance and identify key factors influencing its effectiveness in environmental applications.

This study examines the pyrolysis of agricultural residues, namely, coconut shells, rice husks, and cattle manure, in a vertical fixed-bed reactor at varying temperatures from 300 to 800 degrees Celsius for biochar production. The research aimed to evaluate the potential of biochar as biofuels, adsorbents, and soil amendments. Proximate, ultimate, and elemental analyses were conducted to determine their composition and caloric values. Several analytical techniques were used in the physical and chemical characterization of the biochar (SEM, FTIR, BET). The results indicated that the highest S_BET values were achieved under different conditions for each biochar: 89.58 m²/g for BC-CS-700, 202.39 m²/g for BC-RH-600, and 42.45 m²/g for BC-CD-800. Additionally, all three biochars exhibited the highest caloric values at 600 °C. The results showed that 600 °C is the general optimal temperature to produce biochar from an assortment of biomass materials, considering their use for a variety of purposes. BC-CS-800 had the highest elemental carbon content at 93%, accompanied by a relative decrease in oxygen content. The van Krevelen diagram of biochar products shows that biochars derived from coconut shells and rice husks are suitable for use as fuels. Furthermore, FTIR analysis revealed the presence of oxygen-containing functional groups on the biochar surface, enhancing their pollutant adsorption capabilities. This study provides valuable insights into the scalable and environmentally sustainable production of biochar, emphasizing its role in improving soil quality, increasing energy density, and supporting sustainable agricultural practices.

This study explores the potential of reusing eggshell powders as a renewable activating agent for producing porous carbon materials from coffee husk. Carbonization and activation experiments were conducted by heating the samples at a rate of 10 °C/min up to 850 °C under a nitrogen atmosphere. A custom designed double steel-mesh sample holder was used to hold approximately 2.0 g coffee husk on the top, with varying masses of eggshell at the bottom to achieve eggshells to coffee husk mass ratios of 2:1, 4:1, 6:1 and 8:1. The results demonstrated that CO2 released from the thermal decomposition of the eggshell powder significantly enhanced pore development at 850°C. Compared to the pore properties of carbon material produced without eggshell (e.g., BET surface area of 321 m2/g), the activated carbon samples exhibited substantially improved pore properties (e.g., BET surface area in the range of 592 to 715 m2/g). Furthermore, the pore characteristics improved consistently with increasing eggshell content. Observations by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) confirmed the structural and chemical transformations of the resulting carbon materials. Under optimal carbonization-activation conditions, the resulting carbon materials derived from coffee husk exhibited microporous structures and slit-shaped pores, as indicated by the Type І isotherms and H4 hysteresis loops.

Excessive ammonium (NH₄⁺-N) in aquatic environments poses a major ecological challenge, especially in regions that are reliant on intensive agriculture activity. This study developed a simplified waste-based strategy for modifying sugarcane bagasse biochar using a banana peel and banana ash extract to improve ammonium adsorption. Both pre- and post-treatment with acidic and basic extracts were evaluated, and pre-treatment using the basic extract (SC-Pre-B) showed the best performance. Physicochemical characterization indicated that modification enriched the biochar with oxygen-containing functional groups and alkali metal species, and increased the surface negativity (ζ-potential= − 52 mV), despite a reduction in the BET surface area from 123.62 m² g^− 1 to 1.0 m² g^− 1. Batch adsorption experiments showed that SC-Pre-B achieved an experimental maximum adsorption capacity of 17.11 mg g^− 1. The Langmuir-Freundlich model provided the lowest RSS, AIC, and BIC values, although the small difference from the Langmuir model indicated that both models described the adsorption data reasonably well. The pseudo-second-order model best described the overall adsorption kinetics, while the segmented intraparticle diffusion analysis indicated that diffusion contributed to, but did not solely control, adsorption. The improved performance was mainly associated with increased surface negativity, oxygen-containing groups, and exchangeable mineral sites, which suggested that electrostatic attraction and non-specific cation exchange were the primary contributors of NH₄⁺-N uptake, with hydrogen bonding acting as a secondary interaction. SC-Pre-B retained approximately 57% of its initial adsorption capacity after five water regeneration cycles, corresponding to a 43% capacity loss. These results indicated that banana peel-ash modification is a promising waste-based technique that can improve ammonium’s adsorption by biochar; however, further validation using real wastewater, better selectivity testing, and the optimization of the regeneration protocol must be considered before we can confirm practical application. Graphical Abstract

Plant carbon has been used as one of the natural edible colorants, but it must meet the requirements of carbonization conditions and vegetable materials. To evaluate the effects of carbonization conditions on the properties of resulting biochar products from coffee husk, the process parameters were designed by the combinations of heating rate (i.e., 10 and 20°C/min), pyrolysis temperature (i.e., 800 and 850°C) and residence time (i.e., 0, 30 and 60 min) in this work. Based on the thermochemical properties like proximate anal-ysis and thermogravimetric analysis, this lignocellulose-rich biomass is an excellent precursor for producing carbon materials. Although the pore properties of resulting biochar products were not positively related to the carbonization conditions, but the maximal Brunner-Emmett-Teller (BET) surface area of 155.59 m2/g and 354.96 m2/g) were obtained at 850°C for holding 30 min under the heating rates of 10 and 20°C/min, respectively. The data on the observations by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) of coffee husk and resulting biochar were in accordance with the changes on their textures and elemental compositions. Under the proper carbonization conditions, the resulting plant carbon derived from coffee husk had a special feature due to its high values of carbon content (> 90wt%), microporosity (> 70wt%), and BET surface area (> 350 m2/g).