Low-cost biochar adsorbents were prepared from pineapple peel waste (PPW) via hydrothermal carbonization (HTC) for CO 2 capture. The effects of hydrothermal carbonization temperature, retention time, and heating rate were studied. The hydrochar samples were further carbonized to produce pineapple peel biochar adsorbents. The effects of CO 2 concentration in the feed, adsorption temperature, and feed flow rate on adsorption capacity were investigated in a fixed-bed column adsorption system. The experimental data were analyzed using pseudo-first-order and pseudo-second-order kinetics, and the Avrami equation. The CO 2 adsorption capacity of this system was improved with increasing CO 2 feed concentration and decreased with rising temperature and feed flow rate. The Avrami kinetics model was best fitted to the experimental data. The CO 2 adsorption performance of PPW biochar (PPW-BC) in a fixed-bed column was successfully predicted by the Thomas and Yoon-Nelson models. The prepared PPW-BC adsorbents could be a viable option for CO 2 capture because they were synthesized from a low-cost biomass source and are environmentally benign.

Axle Wood Carbon (AWC) was used to study the removal of Methyl Blue (MB) from its aqueous solution in a fixed-bed column adsorption system. The adsorbent (AWC) was characterized using SEM and pH PZC . SEM revealed the surface morphology and from the pH PZC determination, it was found that at pH of 8.21 the adsorbent has a net surface charge of zero. The column adsorption parameters were optimized and the maximum percentage removal was achieved by setting the level of process variables at 100 mg/L initial MB dye concentration, 28cm bed height, and 3mL/min flow rate. The fixed-bed adsorption system was found to perform well with lower initial dye concentration, higher adsorbent bed height, and lower feed flow rate. The breakthrough curve obtained from the adsorption process was fitted into Adams-Bohart and Yoon-Nelson models. Yoon-Nelson model showed the time required to achieve 50% adsorbate breakthrough, (τ) agreed closely with the experimental data (τ50% exp.) whose value is 298. While Adams-Borhat model, gave 35.7885 as the volumetric sorption capacity of the bed (N 0 ). This implies that the column has reached first saturation level. As such AWC is effective for the removal of MB and the selected kinetic models can be used to explain the column behaviours for the removal of MB and also to predict the large scale industrial application of the process.

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