Preparation of an Adsorbent Derived from Canola Hull by Slow Pyrolysis for Effective Carbon Dioxide Adsorption

Abstract

Canola hull was proposed as a valuable precursor for activated carbon production, due to its abundance, low cost, and economic viability. This study aimed to develop a waste-based biosorbent from canola hulls by slow pyrolysis for effective CO2 capture. The biochar was synthesized from the canola hull using a fixed-bed tubular reactor through slow pyrolysis at various temperatures. The optimum biochar was activated using KOH as a chemical activating agent at different impregnation ratios. The biochar and activated carbon were characterized by elemental analysis, thermogravimetric analysis, surface textural analysis and FT-IR analysis. All the activated carbon samples with impregnation ratios of 0, 0.2, and 0.4 were screened at a total inlet mass flow rate of 100 mL/min (15% CO2 + 85% N2). Activated carbon prepared with an impregnation ratio of 0.4 (0.4AC) with a specific surface area of 1112 m2/g exhibited the highest adsorption capacity of CO2 (2.9 mmol/g) at 25°C under ambient pressure when the feed gas was 15% CO2). 0.4AC was chosen for further study at different feed compositions. The breakthrough curves were analyzed for the compositions 5%, 15% and 25% CO2 in feed, and the effects of adsorption parameters were discussed. The maximum CO2 uptake of the canola hull based activated carbon (0.4AC) is 13.0 mmol/g at ambient pressure and 25°C, with 100% CO2 inlet. Adsorption isotherm and kinetic were studied on the 0.4AC adsorbent. The canola hull based adsorbent with desirable physiochemical and surface textural properties can work as an effective adsorbent for CO2 capture.