Activated carbon (AC) is often regarded as the most-used adsorbent in water treatment. Its wide use is due to the material’s extensive internal pore network that provides a high specific surface area and adsorption capacity. With pore sizes ranging from under 2 nm to over 50 nm, AC adsorbs contaminants of diverse molecular sizes. However, once saturated, the media must be regenerated or replaced. This requirement poses a significant logistical barrier for remote communities, where the cost and difficulty of transporting fresh AC often limits its use.
This presentation covers a potential sustainable solution: manufacturing AC from white spruce wood, a common waste material in remote Canadian regions. The study evaluates the feasibility of phosphoric acid activation and investigates how three distinct wood pre-treatments (torrefaction, hydrothermal and alkaline) influence the resulting surface area, pore size distribution, and adsorption capacity. To understand the mechanism by which porosity is introduced in the resultant AC, the physical, chemical, and crystalline properties of the wood were characterized both before and after pre-treatment. These findings were further supported by analyzing off-gases produced during the carbonization process.
The results indicate that all three pre-treatments yielded AC with higher surface areas and adsorption capacities (Iodine Numbers) competitive with commercially produced AC. These improvements were broadly driven by the removal and decomposition of amorphous biopolymers, which increased volatilization during carbonization, leading to larger average pore diameters.
Most notably, the study hypothesizes that differences in pore size distribution are primarily governed by the mean size of cellulose crystallites in the wood. A shift in the dominant pore-development mechanism was observed based on this crystalline property: larger crystallites tend to facilitate the formation of larger pores. This effect was most significant in alkaline pre-treated samples, which showed the g
