DFT Study of The Interaction Characteristics Between the Organic Matter and Minerals In Coal-Series Kaolin

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.

Adsorption Characteristics of Polymer Solutions on Media Surfaces and Their Main Influencing Factors

In practical applications, the chemical and physical adsorption of a polymer solution greatly affects its action mode and effect. Understanding the adsorption mechanism and its influencing factors can help to optimize the application mode and ensure application efficiency. Three types of polymer solutions—partially hydrolyzed polyacrylamide (HPAM), hydrophobically associating polymer (AP-P4), and dendrimer hydrophobically associating polymer (DHAP), which are viscoelastic liquids—were used as sorbates to study their adsorption by a sorbent such as quartz sand. The effects of the solution concentration, contact time, particle size of quartz sand, solid–liquid ratio, and fluid movement on the adsorption capacity of the polymer solutions were examined. The results showed that HPAM presents a typical Langmuir monolayer adsorption characteristic, and its adsorption capacity (per unit area) is 1.17–1.62 μg/cm2. The association enhances the interactions of the AP-P4 and DHAP solutions, and they present multilayer characteristics of first-order chemical adsorption and secondary physical molecule adsorption. Moreover, the dendrite structure further increases the adsorption thickness of DHAP. Hence, the adsorption thicknesses of AP-P4 and DHAP are four and six times that of HPAM, respectively. The adsorption of the three polymers is consistent with the influence of fluid motion and decreases with increasing fluid velocity. However, the larger the thickness of the adsorption layer, the clearer the influence of the flow, and the higher the decrease in adsorption capacity. Optimizing the injection rate is an effective method to control the applications of a polymer in porous media.

Adsorption of sulfamethoxazole by wheat straw-derived biochars in seawater

The excessive use of antibiotics in mariculture have resulted in high pollution burdens of antibiotics in marine environment. Biochars, as promising adsorbents, have been widely used in organic pollutant adsorption because of their good adsorption performance and stability. However, adsorption characteristic of antibiotics in seawater by biochar is not well known. Thus, the batch experiment for the adsorption of sulfamethoxazole (SMX) was conducted using wheat straw-derived biochars and graphite (GR) under different initial concentration of SMX and different addition of adsorbent in seawater. The results showed that the wheat straw-derived biochars produced at 700 °C was the optimal adsorbent with the maximum removal rate (R) of 70.3%, the maximum adsorption capacity (Qe) of 1.03 mg g-1 and the maximum adsorption coefficient (Kd) of 0.182 L g-1. The Qe values increased with increasing the initial concentration of SMX, while R and Kd values of SMX decreased. The R values of SMX increased with the increasing dosage of adsorbents, while Qe and Kd values of SMX decreased. These findings will shed new light on the environmentally-friendly and low-cost adsorbent for controlling the antibiotic pollution in marine environment.