Organic dye rhodamine B is one of the common organic pollutants in the water and soil environment. This study investigated the feasibility of removing rhodamine B from an aqueous solution through adsorption by kaolin, kaolin-sodium bentonite, and kaolin-organic bentonite. Batch adsorption test results showed that the maximum adsorption quantities of kaolin, kaolin-sodium bentonite, and kaolin-organic bentonite were 7.76 mg/g, 11.26 mg/g, and 12.68 mg/g, respectively, implying that the addition of bentonite to kaolin can effectively improve its adsorption capacity for rhodamine B. Moreover, the Langmuir isotherm model is suitable to describe the adsorption of rhodamine B by kaolin and kaolin-sodium bentonite, while it is preferable to use the Freundlich isotherm model in the case of kaolin-organic bentonite. The adsorption kinetic characteristics of rhodamine B, by these three adsorbents, are suitable to be described with a pseudo-second order kinetic model. Furthermore, the characteristics of the above three adsorbents were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The above results indicated that kaolin and organic bentonite can be used to design efficient adsorbents for organic pollutants similar to rhodamine B.

This study investigated the emission and diffusion of hydrogen sulfide (H₂S), as one of the odorous gases generated from landfills, in a municipal solid waste landfill of a south Chinese city. To this end, the flux of the H₂S emissions in the working area of the landfill and its diffusion in the surrounding area were measured. The diffusion of the H₂S was simulated at different wind speeds, wind directions, bare working areas of the landfill, heights of the landfill, and angles between the wind direction and the long side of the working area. The results indicated that the concentration of the H₂S around the monitoring point ranged from 0 to 60 µg/m³, and the simulated data were consistent with the measured results. At a uniform wind direction, the pollution range of the H₂S was narrow. Furthermore, with an increase in the height of the waste dump, the concentration of the H₂S decreased in the working area but rose in the surrounding area. Notably, when the angle between the long side of the working area and the wind direction was 0°, the H₂S largely spread along the extension cord of the long side of the working area. When the angle increased to 90°, the influence range of the H₂S extended significantly. The working area in the landfill site should be regulated based on the monitored data to reduce the effect of this harmful gas on the living environment, and the health of the landfill staff and nearby residents.

Aged refuse with a landfill age of 1.5 years was collected from a municipal solid waste landfill with high kitchen waste content and mixed with soil as biocover material for landfill. A series of laboratory batch tests was performed to determine the methane oxidation potential and optimal mixing ratio of landfill cover soil modified with aged refuse, and the effects of water content, temperature, CO₂/CH₄, and O₂/CH₄ ratios on its methane oxidation capacity were analyzed. The microbial community analysis of aged refuse showed that the proportions of type I and type II methane-oxidizing bacteria were 56.27% and 43.73%, respectively. Aged refuse could significantly enhance the methane oxidation potential of cover soil, and the optimal mixing ratio was approximately 1:1. The optimal temperature and water content were about 25 °C and 30%, respectively. Under the conditions of an initial methane concentration of 15% and an O₂/CH₄ ratio of 0.8–1.2, the measured methane oxidation rate was negatively correlated with the O₂/CH₄ ratio. The maximum methane oxidation capacity measured in the test reached 308.5 (μg CH₄/g)/h, indicating that the low-age refuse in the landfill with high kitchen waste content is a biocover material with great application potential.

Adding organically modified bentonite into impervious wall materials may improve the adsorption of organic pollutants. In this study, cetyltrimethylammonium bromide organically modified bentonite (CTMAB bentonite) was mixed with sodium bentonite and kaolin to obtain two materials, which were then used as cut-off walls for typical pollutants. Soil column consolidation tests, diffusion tests, and breakdown tests were conducted to study migration of organic pollutants in soil columns. The parameter sensitivity of pollutant transport in the cut-off wall was analysed by numerical simulation. The sodium bentonite mixed with 10% CTMAB bentonite and kaolin-CTMAB bentonite showed the greatest impermeability: with a consolidation pressure of 200 kPa, the permeability coefficients were 1.03 × 10⁻⁸ m/s and 3.49 × 10⁻⁹ m/s, respectively. The quantity of phenol adsorbed on sodium bentonite-CTMAB bentonite increased with increasing water head height. The kaolin-CTMAB bentonite column showed the best rhodamine B adsorption performance, and the adsorption rate reached 98.9% on day 67. The numerical results showed that the permeability coefficient was positively correlated with the diffusion of pollutants in the soil column. The quantity adsorbed on the soil column was positively correlated with the retardation factor, and the extent of pollutant diffusion was negatively correlated with the retardation factor. This study provides a technical means for the optimal design of organic pollutant cut-off walls.