Search Results (3)

Understanding the differences in the adsorption behaviors of tetrabromobisphenol A (TBBPA) and tetrabromobisphenol S (TBBPS) on soils is critical for assessing their environmental mobility and risks. This study investigated the adsorption characteristics and patterns of TBBPA/S across various soil types. Adsorption kinetics analysis indicated that the adsorption of TBBPA/S on soils followed pseudo-secondary-order kinetics. Isotherm results revealed that the Langmuir model described TBBPA adsorption more accurately, while the Freundlich model was a better fit for TBBPS adsorption, suggesting distinct adsorption mechanisms due to their differing properties. Correlation analysis and principal component analysis (PCA) were performed to identify the key soil physicochemical properties influencing TBBPA/S adsorption. The results showed that TBBPA adsorption was inversely correlated with soil pH and positively correlated with clay content. In contrast, TBBPS adsorption displayed negative correlations with soil pH and sand content, and positive correlations with amorphous iron, amorphous aluminum, and free iron content. Further analysis of different treated soil fractions demonstrated that soil organic matter dominated the adsorption of TBBPA/S, with humic acid playing a more significant role than humin. The adsorption behavior characteristics of TBBPA/S on different soils provide fundamental data for understanding their environmental fate in soil systems. Full article

Alum sludge is an inevitable by-product from the water purification process, which had been applied as substrates in some constructed wetlands with good performance, especially for phosphorus (P) adsorption. The raw alum sludge is similar to a clay lump with an irregular shape, and there is a concern of it leaching into water. For better reuse, herein, some sludge was fired to produce alum sludge ceramsite (ASC) with a uniform spherical shape via a four-step process of kneading the sludge ball, air drying, preheating at 400 °C for 10 min, and firing at 600 °C for 5 min. Meanwhile, an air-dried alum sludge ball (adASB) was manufactured for comparison. The physicochemical properties and P adsorption ability of ceramsite were investigated subsequently. Through XRD and FT-IR tests, there was no obvious difference between ASC and adASB on the phase structure, but there was a certain amount of Al-OH group loss on the surface of ASC. The structure of ASC was still amorphous, similar to adASB, while ASC possessed more micropore structure and a bigger specific surface area than adASB. Adsorption experiments showed the P adsorption behaviors of ASC and adASB were much similar, and their adsorption kinetics were in accordance with the two-step adsorption kinetics rate equation and pseudo-second-order kinetics equation. The maximum adsorption capacities of ASC and adASB fitted by the Langmuir model were 1.66 mg/g and 1.89 mg/g, respectively. It should be pointed out that, compared with other adsorbents, the ASC produced in this study still had a greater ability to adsorb P. Therefore, ASC should have a great application potential for P removal in wastewater treatment in China. Full article

The pseudo-amorphous clay components of some of the pottery sherds that formed a surface in the firing chamber of a Late Byzantine kiln were shown by Fourier Transform Infrared Spectroscopy to have undergone almost complete recrystallization. Powder X-ray diffraction showed that the crystalline montmorillonite component of these sherds increased and kaolinite formed de novo. As this recrystallization process only occurred in the center of the firing chamber, we infer that the recrystallization process was due to repeated exposure of the sherds to high temperatures. The zeolite gonnardite was identified by X-ray diffraction. The chemical compositions of sodium-rich minerals, determined by energy dispersive X-ray spectroscopy (EDS), are consistent with the presence of gonnardite and analcime, and showed that the sodium was partially substituted by calcium and other cations. As these zeolites were also present in sherds from the upper pottery chamber, they did not form only as a result of repeated exposure to high temperatures. The demonstration that the clay mineral component of ceramics can undergo diagenetic recrystallization supports the possibility that provenience studies based on elemental analyses, especially of cooking pots that are repeatedly exposed to high temperatures, may be affected by recrystallization. Full article