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Taihu Lake, the third largest freshwater lake in China, has experienced rapid salinization in the past decades; however, little is known about the impact of sodium (Na) on ion exchange in the lake environment. To explore the potential effect of increased Na on the migration of base cations (Ca and Mg) and resulting redistribution between the water and sediment, we used the adsorption-exchange experiment, MINTEQ modeling to explore the cation exchange induced by high Na input, and its impact on the redistribution of Ca and Mg in Taihu different media. The results indicated that exchanged quantity of Ca and Mg increased with time, and the exchange process reached 90% during 0-4 h and reached equilibrium after 24 h under 100 mg/L Na (the maximum Na concentration in Taihu sediment pore water). Our MINTEQ modeled result indicated that the exchanged quantity of Ca and Mg increased with the increasing Na concentration, with Ca being preferably exchanged over Mg at the same Na concentration. The MINTEQ model further predicted that, in the Taihu lake environment, the exchange adsorption would reach the equilibrium at the concentration of 6000 mg/L Na, with exchanged Ca 2+ and Mg 2+ accounting for 47% and 55% of the total exchangeable Ca and Mg in the sediment, respectively. Although current Na-induced exchange in the Taihu lake has been far from the equilibrium, the MINTEQ result confirmed the existence of this reaction and predicted the potential redistribution of base cations or Ca/Mg ratio in the lake sediment and water phase with further Na increase. Furthermore, our field observations not only confirmed the existence of Na-induced cation exchange in this lake environment but also were generally in agreement with our experimental and modeled results. The increased salinization-induced ion exchange would alter the re-distribution of base cations and the resulting potential ecosystem consequences should be given close attention in this large freshwater lake., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The challenge towards modern technologies has been enquiring and culminating in the continuously expanding use of rare earth elements (REEs). The non-renewable primary resources of REEs such as bastnasite, monazite, and xenotime, are 78% dominated by China, and their exhaustive exploitation and future availability have raised global concerns. The recycling of end-of-life (EOL) products containing rare earths, waste streams in mining, and metallurgical industry, also referred to as secondary resources - has therefore become an alternative. This, however, requires advanced separation and extraction technologies to achieve high yields from the raw materials and high purities of the recovered REEs. Hydrometallurgy, starting with leaching, and having solvent extraction as the solution purification step, has been employed worldwide for capturing REEs from primary and secondary resources, with high reported recycling efficiencies. Among the frequently used processes, ion exchange (IX) has become one potential method due to its high selectivity, simple use and maintenance, and easy accessibility. This review briefly highlights the updated separation and extraction technologies used to separate REEs from sulfate-based solutions and secondary sources and mostly focuses on ion exchange separation systems. Significant benefits of IX are outlined, and the content of this review emphasizes that IX can still be used as an efficient, economical, and green method for the enhanced extraction of REEs from secondary sources. [Display omitted] • REEs occur in nature as mixtures that are difficult to separate into single element. • Ion exchange is a promising method for the extraction and separation of REEs. • The best recovery of REEs is achieved with chelating resin from sulfate solutions. • Challenges and prospects for separation of REEs from secondary sources are reviewed. [ABSTRACT FROM AUTHOR]

Camphor leaf from a native everygreen tree (Cinnamomum camphora) widely distributed in southwestern part of China is locally available waste in China. A novel biosorbent (SCLP) was prepared by modification camphor leaf with succinic anhydride for Pb (II) removal. SCLP was characterized by Fourier transform infrared spectrum (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Chemical modification reduces negative effects on the treated water, and it introduces carboxyl groups on the surface, improving the sorption capacity. Sorption of Pb (II) ions was evaluated at different SCLP dose, pH, contact time and initial concentration. Sorption equilibrium and kinetics were investigated by sorption isotherms and kinetic models. Sorption of Pb (II) onto SCLP follows pseudo-second order kinetics and Langmuir model. Ion exchange plays an important role for Pb (II) uptake onto SCLP. The removal rate and sorption capacity is up to 99.98% and 185.2 mg g −1 . It is anticipated that camphor leaf would find important application in purification Pb (II) from wastewaters, owing to the advantages of high efficiency, low cost and environmental friendliness. [ABSTRACT FROM AUTHOR]

Sintering dust from the steelmaking industry is a hazardous waste that is rich in valuable metals. The purpose with the present study has been to design an efficient process for the preparation of K 2 SO 4 and NH 4 Cl fertilizers by using sintering dust as raw material. The K, S, and Cl in the sintering dust were selectively and efficiently leached using water. The leaching of Ca impurities was then greatly reduced and the appearance of Zn and Mg was avoided. The Cl− ions in the leachate were, thereafter, adsorbed by a 201 × 7 resin to form a K 2 SO 4 solution. Finally, the loaded Cl− on the resin was desorbed to form a NH 4 Cl solution, and the resin was regenerated and recycled. The purified solutions were crystallized to prepare K 2 SO 4 (s) and NH 4 Cl(s) products, which met the national standard of China for superior potassium sulfate and ammonium chloride, to be used for agricultural use. The recoveries of K, Cl, and S from the sintering dust were 80.78%, 92.63%, and 93.92%, respectively. Notably, the Mn content in the leaching residue increased from 9.08% to 14.19%. This could be used for the conversion of Mn impurities into recyclable manganese-rich raw materials. This green process enables an effective extraction of important impurities in hazardous sintering dust, thereby providing a new potassium source for potash fertilizer manufacturing with notable economic and environmental benefits. K 2 SO 4 and NH 4 Cl prepared from recycling of sintering dust: From hazardous solid waste to fertilizers. [Display omitted] • A novel process was proposed to prepare fertilizers using sintering dust. • The high selective recovery of K, S, and Cl can be achieved by water leaching. • The separation of K, S, and Cl is achieved by ion exchange using the 201 × 7 resin. • K, Cl, and S in the leachate have been used to prepare two high-quality fertilizers. • The leaching residue can be converted into recyclable manganese-rich raw materials. [ABSTRACT FROM AUTHOR]

Groundwater is an important water source for agricultural irrigation in Penyang County. Some traditional methods such as irrigation coefficient, sodium adsorption ratio, total alkalinity, total salinity and total dissolved solids were employed to assess groundwater quality in this area. In addition, an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment. The origin of major ions and groundwater hydrogeochemical evolution was also discussed. Groundwater in Penyang County contains relative concentrations of dominant constituents in the following order: Na > Ca > Mg > K for cations and HCO > SO > Cl > CO for anions. Groundwater quality is largely excellent and/or good, suggesting general suitability for agricultural use. Calcite and dolomite are found saturated in groundwater and thus tend to precipitate out, while halite, fluorite and gypsum are unsaturated and will dissolve into groundwater during flow. Groundwater in the study area is weathering-dominated, and mineral weathering (carbonate and silicate minerals) and ion exchange are the most important factors controlling groundwater chemistry. [ABSTRACT FROM AUTHOR]

Abstract: The uptake of Cs(I) on Beishan soil (BS) was strongly dependent on ionic strength and hardly dependent on pH over the observed pH range (6–13). The foreign cations competed with Cs(I) in the following order: K+>Mg2+>Ca2+≈Na+>Li+. The uptake of Cs(I) was a pseudo-second-order process and the activation energy, E a , was about 2.16kJ/mol. EDS analysis suggested that the most of Cs(I) was converged on the basal plane, and a small fraction bound on the frayed sorption site. All the results suggested that ion exchange was the main approach for Cs(I) uptake on BS. [Copyright &y& Elsevier]

Mine water poses severe threats to the quality of the water supply and ecological environment of the Shendong mining areas owing to its excessive fluoride (F-) content. However, the geochemical behaviours and enrichment mechanisms responsible for F⁻ enrichment during mining activities are not fully understood. In total, 18 Yanan groundwater and 45 mine water samples were collected to analyse the spatial distribution, hydrogeochemical behaviours, and formation mechanisms related to elevated F- levels by analysing the stable isotopes and water-rock interactions. In this study, F- concentrations in mine water samples varied from 0.16 to 12.75 mg/L, with a mean value of 6.10 mg/L, and 77.78% of the mine water samples had a concentration that exceeded China's national standards (1.00 mg/L) for drinking water. The F- concentration was markedly high in the mine water samples, with the mean F- concentration being 1.58 times of that in the Yanan groundwater samples. The results of stable isotopes (18O H2O , D, 34S SO4 , and 18O SO4) and water-rock interaction analyses suggested that cation exchange and competitive effects were the dominant factors responsible for elevated F- concentration in mine water during mining activities. Thus, the weathering of F-bearing minerals, agriculture, and domestic activities do not play a significant role in the secondary enrichment of F- concentration. • The abundance and spatial distribution of F- in the mine water of the Shendong mining area were determined. • The hydrogeochemical behaviours and formation mechanisms that further elevate F- levels in mine water during mining activities were evaluated. • The hydrogeochemical processes of mine water at high F- concentration using stable isotopes (34S SO4 , 18O SO4 ,18O H2O , and D) analyzed. [ABSTRACT FROM AUTHOR]

Ion exchange is an elegant concept whose simplicity has allowed a wide range of applications in separations (e.g., water treatment, chromatography, radiochemistry, food processing), catalysis and synthesis. The objective of this Perspective is to map its origin and present status, then propose a trajectory into the future. This is addressed with data mined from the open literature as reported in the Web of Science Core Collection (Clarivate Analytics) via a search of the keyword "ion exchange" for the period 1900–1960, then narrowed to 1941–1960, followed by subsequent 20-year periods to the present day. Data are sorted into the top ten WoS Categories, Research Areas, Publication Titles and Countries, then further defined with additional keywords. Interest in ion exchange was found to be constant across the vicennial periods as the number of references kept pace with growth in the chemical (open) literature. The period to 1960 had 1213 references with chemistry the dominant area (60.9%) and engineering at only 4.5% of the papers; resins were the dominant material with membranes a distant second. The period 1961–1980 had 5175 references with chemistry retaining its top ranking but engineering significantly increasing; resins and membranes were the primary materials while separations dominated and catalysis barely registered. There were 21,901 references in 1981–2000 with environmental science appearing as a research area for the first time; resins ended the century as they began – the primary material – but by a small margin over membranes. The 21st century (2001−2020) began with 52,187 references, chemistry held steady compared to the preceding period while engineering and materials science increased significantly and environmental science doubled its percentage, joined by water resources; membranes continued their upward trend, surpassing resins. Output from China increased to outperform the USA. In the last three years of that period, environmental science made a stronger showing and energy fuels replaced biotechnology. In comparing the vicennial periods, the rise of engineering, materials science and ecology combined with water was impressive. In comparing Research Areas in the initial period with those from the latest, it is seen that chemistry fell from 61% to 41% while engineering increased from 4% to 25%. Applications were more likely to involve membranes. Separations remained steady from the initial to the current period while catalysis moved equal to them, Examining the most cited papers in the latest period shows an emphasis on metal-organic frameworks, tailored materials, membranes for energy and environmental applications, and to an array of applications in environmental remediation. Ion exchange is applied as a preparative technique in, for example, batteries, photocatalysts, electrocatalysts, supercapacitors, and perovskite nanocrystals. Ion exchange is thus poised to continue well into the 21st century. It has flourished by its ability to adapt. As the analysis of the literature shows, it will continue to flourish. [Display omitted] • 1941–1960 had 1213 references with chemistry the dominant area (60.9%). • 1961–1980 had 5172 references; chemistry was first but engineering much increased. • 1981–2000: 20846 references; environmental science first appeared as a research area. • 21st century (2001−2021) began with 52,218 references; environmental science doubled • Ion exchange is now a preparative technique and poised to continue flourishing. [ABSTRACT FROM AUTHOR]

Badain Jaran Desert, the coexistence of dunes and lakes, and the presence of the world's tallest dunes, has attracted worldwide attention among hydrologists. Freshwater, brackish, and saline lakes coexistence in the Badain Jaran Desert under extremely arid environmental conditions. This raises the question of why diverse lake water types exist under the same climatic conditions. Answering this question requires the characterization of lake hydrochemistry and the main controlling factors. The purpose of the presented research was to systematically analyzed samples from 80 lakes using statistical analysis, correlation analysis and hydrogeochemical methods to investigate the hydrochemical status and evolution of lakes in the Badain Jaran Desert. The results showed that the lake water in Badain Jaran Desert is generally alkaline, with the average pH and TDS were 9.31 and 165.12 g L−1, respectively. The main cations to be Na+ and K+, whereas the main anions are Cl− and SO42−. HCO3− and CO32− decreased and SO42− and Cl− increased from southeast to northwest, whereas lake hydrochemistry changed from the SO42−-Cl−-HCO3− type to the SO42−-Cl− type and lakes transitioned from freshwater to saline. The freshwater and slightly brackish lakes are mainly distributed in the piedmont area at a high altitude near the Yabulai Moutains, whereas saline lakes are mainly distributed in the desert hinterland at a low altitude, and there is a roughly increasing trend of ions from the Yabulai Mountains. The evaporation-crystallization reactions are the dominant in the study region. Moreover, some saline mineral deposits, are extensive in these regions caused by intense evaporation-crystallization. [ABSTRACT FROM AUTHOR]

Objective: A new ion exchange column technology was used to establish an efficient and sensitive method for the detection of inorganic arsenic. Methods: Based on the new As Specia Fast Column, the pretreatment methods, liquid phase separation and mass spectrometry determination conditions of inorganic arsenic in rice were optimized. Finally, arsenic compounds were separated by As Specia Fast Column and detected by liquid chromatography inductively coupled plasma mass spectrometry. The external standard method was used for quantitative analysis. The detection limit, precision and accuracy of the method were determined by measuring the content of arsenic compounds in rice samples and rice standard samples. At the same time, three Guangdong rice samples were selected as the experimental samples of this study, and 1 g of each sample was weighed and measured in parallel three times. The method was compared with the method of liquid chromatography-atomic fluorescence spectrometry (LC-AFS) and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) in the national standard. Results: The inorganic arsenic in rice was extracted with 0.5% nitric acid solution at 65 ℃ for 15 h, and the pH was adjusted to alkaline. The mobile phase A (8 mmol/L HNO(3), 50 mmol/L NH(3)·H(2)O) and mobile phase B (40 mmol/L HNO(3), 80 mmol/L NH(3)·H(2)O) were used as the mobile phase gradient elution (93%) . Five arsenic compounds can reach baseline separation under the conditions of RF power of 1 500 W and atomization gas flow of 0.97 L/min. The detection limits ranged from 0.114 to 0.331 μg/L, and the inorganic arsenic content in rice samples ranged from 0.063 to 0.232 mg/kg. The results of determination of arsenic compounds in rice flour reference materials were all within the uncertainty range indicated by the standard. The recoveries were 86.7%~106.7%, and the precision was 1.9%-12.5%. Compared with national standards, the results of determination of arsenate in rice were relatively close (using this method, LC-AFS, LC-ICP-MS to detect the content of arsenate in rice samples 1 was 0.231, 0.226, 0.236 mg/kg, respectively). However, due to insufficient sensitivity, the national standard method is difficult to detect low levels of arsenic compounds (Arsenobetaine was not detected in rice sample 1). The method can detect the content of arsenobetaine in rice sample 1 was 0.023 mg/kg. Conclusion: The established method can meet the requirements of inorganic arsenic determination in rice, and it is more rapid and accurate than the current national standard. It can better monitor and evaluate the content of i-As in rice, and provide accurate data for comprehensively grasping and evaluating the safety of rice consumption of residents.

An improved method, suitable for collecting nitrate from surface waters in the watershed for 15N isotope tracing analysis, was developed on the basis of the anion exchange coupled with diffusion through systematic simulation and comparison experiments. The results showed that the nitrate could be separated and enriched from the waters efficiently by using the improved method. Being simple and practical in operation principle and procedures, cost-economic, and highly efficient in nitrate separation/enrichment, the method met the requirements of delta(15)N mass spectrum analysis and would lay a foundation for the application of 15N isotope tracing approach to the research on non-point source pollution in watershed.

A double chamber bed (DCB) was developed in China in 1980 and has been utilised in more than 500 setups. This paper introduces the structure and operation features of DCB, and also the unique structure of DCB leads to its perfect operation features. It can be also considered as the best option in reconstruction projects which can replace other types of ion exchangers, such as fixed bed, double cell fluidized-bed, multi-bed. Four reconstruction project cases were introduced, which were selected from more than twenty plants designed by us. Through the case study, it is concluded that DCB can not only be used to treat different sources of water (river and well), but can also be used to treat water with the ratio of transient hardness to total cation to be less than 0.5 and the ratio of strong to weak anion to be more than 7.0. These findings enlarge the scope of application of DCB.