To study the effect of H₂O₂ on the content and properties of humic acids (HAs) in lignites, the experimental conditions including oxidation time, H₂O₂ concentration, and the solid–liquid ratio were investigated. Under the optimum oxidation conditions, the contents of HAs of YL and HB lignite were 45.4 and 40.9%, respectively. The HAs extracted from oxidized and raw lignites were characterized and compared. The results showed that the HAs extracted from oxidized lignites contain more total acidic groups, carboxyl groups, and aliphatic carbon than that in HAs extracted from raw lignites, and their hydrophilic–hydrophobic index value is higher and thermooxidative stability is better than those in HAs extracted from raw lignites. In addition, the composition of polycyclic aromatic hydrocarbons and fluorophore types in HAs extracted from oxidized lignites are similar to the HAs extracted from raw lignites. The results indicated that the oxidation operation can increase the content of HAs in lignites, and simultaneously increase the content of oxygen-containing functional groups and biological activity of HAs, which provided a reference for the subsequent application of HAs.

Descriptors are quantitative or qualitative measures that capture key properties of a system. In catalysis, they are essential for understanding the relationship between a material’s structure and its function, facilitating the design and optimization of new catalytic materials and processes. Since the introduction of energy descriptors in the 1970s, various approaches, ranging from electronic properties to data-driven techniques, have been developed to construct these descriptors. This review first categorizes the different types of descriptors, including energy, electronic, and data-driven approaches. It then explores their applications in active site design and finally concludes with a discussion on the challenges and opportunities in advancing catalytic site design.