This study evaluates the influence of hydrothermal carbonization (HTC) or slow pyrolysis (SP) process conditions on the physicochemical properties of precursor biochars and activated carbon (AC). The AC is achieved through a direct or a two-step method with subsequent chemical activation using KOH. A theory is developed on the biochar propensity to be chemically activated based on the lignocellulosic structure composition. X-ray photoelectron spectroscopy elemental analysis shows that the O/C ratio decreases after chemical activation for HTC biochar but remains the same for SP biochar. X-ray powder diffraction indicates that the SP biochar and all ACs have broad amorphous carbon peaks, whereas corn stover and the HTC biochar have distinct cellulosic crystalline peaks. Vanillin adsorbent experiments were performed on various ACs with up to 98% reduction shown. The best adsorbent for vanillin was the AC produced directly from corn stover, followed by AC HTC and then AC SP.

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To remove Ni(II) ions from an aqueous solution, researchers used red mud modi ed by chitosan (RM/CS) material as a new adsorbent. According to the ndings, the surface area of red mud is nearly doubled after being treated with chitosan, from 68.6 m 2 /g to 105.7 m 2 /g. The effects of pH solution, contact time, and material dosage on the Ni(II) uptake were examined. In comparison with the pseudo-rst-order and pseudo-second-order models, the intra-diffusion model was the most suitable kinetic model for the Ni(II) removal. Besides, the three-parameter Sips model was used to predict the Ni(II) adsorption of RM/CS from aqueous solution. Furthermore, the Langmuir maximum Ni(II) uptake capacity of this material was 31.66 mg/g at 323K, which was higher than red mud and several other natural materials. Notably, thermodynamic investigations demonstrated that Ni(II) adsorption on RM/CS is both exothermic and physic.

To remove Ni(II) ions from an aqueous solution, researchers used red mud modified by chitosan (RM/CS) material as a new adsorbent. According to the findings, the surface area of red mud is nearly doubled after being treated with chitosan, from 68.6 m2/g to 105.7 m2/g. The effects of pH solution, contact time, and material dosage on the Ni(II) uptake were examined. In comparison with the pseudo-first-order and pseudo-second-order models, the intra-diffusion model was the most suitable kinetic model for the Ni(II) removal. Besides, the three-parameter Sips model was used to predict the Ni(II) adsorption of RM/CS from aqueous solution. Furthermore, the Langmuir maximum Ni(II) uptake capacity of this material was 31.66 mg/g at 323K, which was higher than red mud and several other natural materials. Notably, thermodynamic investigations demonstrated that Ni(II) adsorption on RM/CS is both exothermic and physic.

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