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.

Driven by global resource shortages and carbon neutrality strategies, diatom biorefinery technology has emerged as a key solution to reduce production costs and promote a green economy, thanks to its unique potential for comprehensive resource utilization. Diatoms are rich in high-value substances such as polyunsaturated fatty acids, fucoxanthin, polysaccharides, and phenolic compounds, and their siliceous cell walls hold significant application potential across various industries. However, their industrialization has long been hindered by high production costs, with single-component production models leading to low return on investment—a core bottleneck restricting their development. This review analyzes diatom biorefinery technologies and processes, including co-extraction, sequential extraction, and hierarchical utilization of whole biomass, which significantly enhance resource utilization efficiency and economic benefits. Economic feasibility analyses show that co-producing multiple bioactive substances effectively shares costs, increases profits, and reduces waste treatment expenses, demonstrating promising market prospects. Despite challenges such as upstream process regulation where environmental factors may exert multiple effects on metabolite production, and downstream green chemistry transformation, combining co-production of high-value products with technological innovation can effectively lower costs, achieve efficient resource utilization, and foster sustainable development. Diatom biorefinery processes are poised to achieve larger-scale commercialization, offering new approaches to address global challenges in energy, the environment, and human health.

The abundance and chemical composition of dissolved organic matter (DOM) in the brine of solar ponds influence efficiency of mineral extraction and rates of brine evaporation, and cause undesired odor and color of the products. In this paper, we report an investigation on changes of DOM compositions in solar ponds from salt lake brine through different approaches. The results showed that the DOM was primarily composed of carbohydrates, aliphatic and aromatic compounds. Dissolved organic carbon (DOC) analysis revealed that the concentration of DOC in solar pond increased with exposure time, and up to 15−fold upon evaporation/irradiation of salt lake brine. Analyses with the elemental composition, Fourier transform infrared spectroscopy (FTIR) and cross polarization magic angle spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR) indicated that the relative abundance of aliphatic compounds (including functionalized ones) increased in solar pond process, while an opposite phenomenon was observed for carboxylic acid moieties, aromatics and carbohydrates. Pyrolysis−gas chromatography−mass spectrometry (Py−GC−MS) revealed that most of the DOM in salt lake brine contained methylene chain, terpenoid-like, carbohydrate and/or aromatic structures. The presence of some sulfur-containing organics implied some anaerobic biotic decays, 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. Finally, the implications and guidelines for removing DOM from brine in the process of brine resource exploitation were discussed.