A clean method for controlling pore structure development in potassium activation systems to improve CO adsorption properties of biochar.

The conventional activator KOH poses issues of pollution and equipment corrosion in activated carbon production. This study proposes a low-cost, one-step synthetic method for the cleaner production of biomass-derived carbon. CO adsorbents with high specific surface area (550-1725 m/g) and superior adsorption performance were prepared using a KCl-assisted activation process with three activators (KOH, KHCO, KCO). The results demonstrated that KCl promoted the formation of a molten salt system in all the different activation processes, which improved the activation efficiency through the formation of a liquid-phase environment. The results show that KCl possesses both pore-creating and pore-modulating properties. We investigated the performance of the two properties and analyzed the influencing factors. Specifically, KCl increases the specific surface area and porosity of the material and also selectively increases the ultramicroporous content. The development and regulation of pore structure can be achieved through the selection of activator, temperature, and dosage of KCl. With the addition of KCl, the performance of the adsorbents in all systems improved due to optimized pore structure. Among them, the sample PB700-4 from KCl-assisted KHCO activation exhibited the highest CO adsorption of 4.51 mmol/g at 25 °C and 1 bar. The best sample, PC700-3, from the KCl-assisted KCO activation system had an adsorption capacity of 4.48 mmol/g, which was superior to the best sample, PH800-3 (4.28 mmol/g), obtained from KCl-assisted KOH activation. Given the low corrosiveness and toxicity of KHCO, KCO, and KCl, this study introduces a novel approach for cleaner production of activated carbons and advancements in gas separation technology.