Granulated activated charcoal, as a traditional adsorption substance, possesses advanced adsorption effect due to its porous structure. However, the granulated activated charcoal produced by ordinary factories often has problems such as uneven pore distribution and mismatch between pore size and target pollutant molecules, which can easily lead to poor performance, resulting in insufficient selectivity for specific pollutants in complex systems. In recent years, researchers have precisely regulated the pore structure of granular activated carbon through physical activation, chemical modification, and template methods, attempting to achieve targeted adsorption of different-sized and polar pollutants by optimizing the proportion and distribution of micropores, mesopores, and macropores. This measure further improves the adaptability of granular activated carbon.
In terms of physical activation regulation, by adjusting the types of activators, activation temperature and time, the pore size distribution of granulated activated charcoal can be effectively changed. For example, using coconut shell as the raw material and activating it at 800-900℃ with CO₂, the proportion of micropores can be increased, significantly enhancing the adsorption capacity for small molecule pollutants; while extending the water vapor activation time to 2-3 hours can promote the formation of mesopores, which is more conducive to the adsorption of dye molecules. The chemical modification principle involves introducing specific functional groups to interact synergistically with the pore structure, further enhancing selectivity. Studies have shown that the surface carboxyl content of activated carbon treated with nitric acid increases, and the proportion of mesopores rises to over 30%, with the adsorption selectivity for molecular substances in water bodies being nearly three times higher than that of unmodified samples.
However, the regulation of pore structure still poses challenges for the improvement of adsorption selectivity. On one hand, most regulation methods result in a decrease in the specific surface area of granular activated carbon. How to maintain a high specific surface area while ensuring the matching of pore diameters is the key to balancing adsorption capacity and selectivity. On the other hand, pollutants in actual water bodies or gases often exist in a mixed state, and single pore structure regulation is difficult to cope with the competition of multiple components for adsorption. It is necessary to combine surface chemical modification, charge regulation, and other multi-dimensional collaborative designs. Future research can focus on dynamic pore structure regulation technologies and pore structure-selective adsorption performance prediction models based on machine learning, providing theoretical guidance and technical support for the precise design of high-selectivity granular activated carbon adsorption materials.