Synthesis of an absorption material based on oil shale semi-coke: Discussion to adsorption mechanism and corresponding site energy distribution analysis

Oil shale semi-coke (SC) is an industrial solid wastes, which is urgently needed to be transformed into high value-added products. In this work, a new adsorbent AFSC with high adsorption property for Congo red (CR) (793.62 mg/g) better than SC (46.45 mg/g) were synthesized by hydrothermal reaction of pretreated SC with oxalic acid (OA) and Fe(III). The microscopic structure, chemical composition and adsorption performance of the adsorbent were studied, and the reaction parameters for synthesizing an efficient adsorbent were optimized. The results indicate that AFSC are mainly composed of quartz and humboldtine, the specific surface area of that obviously raised, and the surface negative charge decreased, which developed the adsorption properties of the adsorbent. The adsorption behavior and mechanism are further studied. Site energy distribution (SED) theory suggested that more high-energy sites was generated on AFSC, which resulted in a higher adsorption amount of AFSC for CR. This work provides a better way for the effective application of SC waste. • A new and efficient adsorbent AFSC was prepared with semi-coke as the precursor. • The adsorption of AFSC to CR is significant higher than other Semi-coke adsorbent. • Site energy distribution theory confirms there are more high-energy sites on AFSC.