The abundance and chemical composition of dissolved organic matter (DOM) in the brine of solar ponds affect the efficiency of mineral extraction and evaporation rates of the brine, and cause undesired odor and color of the products. Here, we report an investigation into the composition and changes of DOM in solar ponds from Salt Lake brine with multiple complementary analysis techniques. The results showed that the DOM derived from Salt Lake brine was primarily composed of carbohydrates, aliphatic and aromatic compounds. The concentrations of dissolved organic carbon in solar ponds increased with exposure time by up to 15−fold (from 23.4 to 330.8 mg/L) upon evaporation/irradiation of Salt Lake brine. Further qualitative analyses suggest that the relative abundance of aliphatic compounds (including functionalized ones) increased from 49.5% to 59.2% in the solar pond process, while the opposite was observed for carboxylic acid moieties, aromatics and carbohydrates, which decreased from 15.7%, 7.1% and 26.1% to 13.4%, 5.3% and 23.0%, respectively. The pyrolysis–gas chromatography–mass spectrometry results reveal that the presence of some sulfur-containing organics implied some anaerobic biotic decay, but microbiological processes were probably subordinate to photo-induced DOM transformations. In the Salt Lake brine, exposure-driven decay decreased the abundance of polysaccharides and increased that of mono- and polyaromatic pyrolysis products. Our results here provide new insights for better understanding the changes of DOM chemical composition in the solar ponds of Salt Lake brine.

In salt lake KCl cold decomposition–direct flotation for K-Na separation, octadecylamine hydrochloride (ODA-H) acts as a collector, reducing product purity and limiting high-end applications of salt lake KCl. To study KCl purification mechanisms and optimize crystal properties, this study investigates ODA-H aqueous systems. By regulating the cooling rate, stirring rate, and ODA-H concentration, the crystallization purification of KCl and precise control of its morphology were achieved, ultimately yielding three typical crystal morphologies: cubic, spherical, and ellipsoidal. Of the three crystal morphologies, spherical crystals have the best flowability but lowest purity. Ellipsoidal crystals have better flowability than cubic ones: their purity exceeds that of cubic crystals before washing but falls below it after washing. Cubic crystals, with poorer flowability, reach the highest purity post-washing. This study provides a theoretical basis for enhancing purity via crystal morphology regulation and industrial-scale purification of salt lake KCl.

Amino-functionalized magnetic particles (Fe₃O₄@SiO₂-NH₂) with core-shell structure were synthesized and evaluated for rapid boron removal from aqueous solution. Results showed that the specific surface area of Fe₃O₄@SiO₂-NH₂ (165.17 m²⋅g^− 1) increased greatly compared to the pure Fe₃O₄ (49.07 m²⋅g^− 1). The adsorption equilibrium was less than 2 h with an adsorption capacity of 29.76 mg⋅g^− 1at pH = 6 of 15°C. The quasi second-order kinetic model described well the boron adsorption process and the Freundlich model was more suitable for characterizing the adsorption isotherms. Furthermore, the negative value of Gibbs free energy indicated that the adsorption was spontaneous and an exothermic process. The zeta potential and XPS analysis before and after adsorption revealed that the main adsorption mechanism was the hydrogen bonding formation between the terminal –NH₂ groups of the adsorbent and the boric acid. In addition, the adsorbent still maintained a high adsorption performance after five adsorption-desorption cycles, which illustrated that the Fe₃O₄@SiO₂-NH₂ may be a potential adsorbent for the environmental boron removal treatment.

In this study, amino-functionalized magnetic particles (iron oxide@SiO₂-NH₂) with core-shell structures were synthesized and evaluated for rapid boron removal from aqueous solutions. The results showed that the specific surface area of the iron oxide@SiO₂-NH₂ (131.24 m²⋅g⁻¹) increased greatly compared to pure iron oxide (30.98 m²⋅g⁻¹). The adsorption equilibrium was less than 2 h, with an adsorption capacity of 29.76 mg⋅g⁻¹ at pH = 6 at 15 °C. The quasi-second-order kinetic model described the boron adsorption process well, and both the Langmuir and Freundlich models were suitable for characterizing the adsorption isotherms. The zeta potential and XPS analysis before and after adsorption revealed that the main adsorption mechanism was the hydrogen bonding formation between the terminal -NH₂ groups of the adsorbent and the boric acid. In addition, the adsorbent still maintained a high adsorption performance after five adsorption–desorption cycles, which illustrated that the iron oxide@SiO₂-NH₂ may be a potential adsorbent for environmental boron removal treatment.