Artificially modified adsorbing materials mainly aim to remedy the disadvantages of natural materials as much as possible. Using clay materials such as rectorite, sodium bentonite and metakaolinite (solid waste material) as base materials, hydrothermally modified and unmodified materials were compared. CM-HT and CM (adsorbing materials) were prepared and used to adsorb and purify wastewater containing malachite green (MG) dye, and the two materials were characterized through methods such as BET, FT-IR, SEM and XRD. Results: (1) The optimal conditions for hydrothermal modification of CM-HT were a temperature of 150 °C, a time of 2 h, and a liquid/solid ratio 1:20. (2) Hydrothermal modification greatly increased the adsorptive effect. The measured maximum adsorption capacity of CM-HT for MG reached 290.45 mg/g (56.92% higher than that of CM). The theoretical maximum capacity was 625.15 mg/g (186.15% higher than that of CM). (3) Because Al-OH and Si-O-Al groups were reserved in unmodified clay mineral adsorbing materials with good adsorbing activity, after hydrothermal modification, the crystal structure of the clay became loosened along the direction of the c axis, and the interlayer space increased to partially exchange interlayer metal cations connected to the bottom oxygen, giving CM-HT higher electronegativity and creating more crystal defects and chemically active adsorbing sites for high-performance adsorption. (4) Chemical adsorption was the primary way by which CM-HT adsorbed cationic dye, while physical adsorption caused by developed pore canal was secondary. The adsorption reaction occurred spontaneously.

Polycarboxylic superplasticizers (PCEs) exhibit numerous advantages as concrete additives, effectively improving the stability and strength of concrete. However, competitive adsorption of PCEs occurs in the presence of clay, which may affect the cement dispersion and water-reducing performance. Extensive research has been conducted on the physical and mechanical properties of PCEs; however, the effect of the diverse structures of PCEs on the competitive adsorption on clay and cement hydration products has been rarely studied. This study employs Ca-montmorillonite (CaMMT) as a clay representative, by constructing adsorption models of PCEs on CaMMT and cement hydration products. A comparison of the adsorption energies considering different side-chain lengths of PCEs is included. Typically, the adsorption energy on CaMMT is lower than that on hydration products, leading PCEs to preferentially adsorb on the clay, thereby reducing its effective dosage in the cement particles. The challenge of PCE adsorption on CaMMT increases with the polymerization degree, and methylallyl polyoxyethylene ether (HPEG) exhibits lower adsorption energies on CaMMT. The density of states (DOS) analysis indicated the highest peak values of allyl polyethylene ether (APEG) as well as the peak area at n (polymerization degree) = 1. The total number of transferred electrons for APEG was 0.648, surpassing those of other PCEs. The interaction mechanism of PCEs with clay and hydration products is further elucidated through electronic gain/loss analysis, also providing a basis for the theoretical analysis on how to reduce the adsorption of PCEs on clay and the structural design of mud-resistant PCEs.

Coal-series kaolin is an associated mineral resource in coal mining process, often contains organic components and other discoloring impurities, which may lower the quality and limit the industrial application. However, the occurrence, stability of organic component and how they affect the surface physical and chemical properties of coal-series kaolin is known little. In this article, several representative organic components have been enrolled for analyzing the interactions with different minerals of the coal-series kaolin. Results shows that the unsaturated double bonds may be easier to adsorb with kaolinite, and the energy on C₂₀H₄₀ is the least among all the compositions. Among the different crystal planes of kaolinite, the (001) surface may possess higher adsorption characteristic on the organic molecules, which may be consistent with the crystal face index of the kaolinite. While the adsorption energy between the organic molecules and the impurities in coal-series kaolin was positive all the time, suggesting that the organic matter could only adsorb with kaolinite compared with the impurities such as pyrite, quartz and anatase. Calculations of state density also showed that the displacement of the energy band for kaolinite may shift to the lower state after adsorbed with different organic matter, also a rearrangement and significant increase of peak values for the state density may occur after adsorption. This study aims to provide a theoretical basis for the occurrence state and stability differences of different organic matters on the coal-series kaolin, also further solve the long-term problems of restricting the whiteness and comprehensive utilization of coal-series kaolin resources.

Chitosan has significant advantages due to its good biocompatibility and biodegradability. However, the original chitosan often has problems such as limited adsorption capacity and poor selectivity. Therefore, modifying chitosan to improve its adsorption performance has become an important research direction. This study adopted molecular dynamics simulations to explore the factors influencing the physical modification of chitosan and further conducted adsorption experiments with three different dyes. The results indicated that when combined with different clays, the interaction between chitosan and montmorillonite was more likely to occur, making it a suitable adsorbent for physical modification. As the molecular weight (MW) of chitosan increased, the 0.99004), while lower temperature was more conducive to the adsorption process. The results would help determine the optimum synthetic conditions for chitosan-based composite materials and make positive contributions to the green development of agriculture.