Synthetic dye production and the consequent generation of dye-rich wastewater are major concerns of water quality in many countries. We developed a sustainable approach with deep eutectic solvent (DES) treatment to enhance the efficiency of mixed cellulose ester (MCE) membrane-based dye removal material. The DES composition and treatment conditions were optimized, and the treated membranes were comprehensively characterized. DES-treated membranes exhibited improved morphology, surface properties, and superior dye adsorption capabilities. Our study revealed that the adsorption process was chemically controlled and driven by electrostatic and hydrogen bond interactions. Thermodynamic analysis confirmed the endothermic and spontaneous nature of the adsorption process. Moreover, the treated membranes exhibited good separation performance for dye/salt mixtures. Additionally, we demonstrated selective adsorption of cationic dyes over anionic dyes using these treated membranes. This selectivity enabled the development of a membrane solid-phase extraction (MSPE) method for quantification of trace amount of dyes. Compared with other methods, DES-treated MCE membranes present a promising solution for efficient dye quantification and removal, offering a green and effective strategy to address water pollution stemming from synthetic dyes. Additionally, this study provides a novel strategy for green chemistry modification of cellulose-based materials.

This article presents a comprehensive overview of recent advancements in natural product extraction, focusing on the evolution from deep eutectic solvents (DESs) to deep eutectic systems (DESys) for extraction. DESs, known for their environmentally friendly properties, have become crucial in extracting various natural products from plants, including micromolecules, lignin, and polysaccharides. Research into the extraction mechanism reveals that target compounds typically form hydrogen bonds with DESs, effectively becoming part of the solvent system. This insight has led to the development of the DESys extraction method, where hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) are directly mixed with the sample to form a DESys containing the target compounds. The shift from DES-based extraction to DESys-based extraction introduces innovative approaches where target compounds are integral to the solvent system, allowing for one-step dissolution and extraction. This methodology eliminates the need for pre-prepared DESs, simplifying processes and enhancing extraction efficiency. Additionally, strategies for DESs recycling and reuse contribute to sustainability efforts, offering cost-effective and environmentally friendly extraction solutions. The expanding applications of DES-based and DESys-based natural product extraction in cosmetics, food, industry, and environmental fields highlight their promising development potential. By delineating the transition from DES-based to DESys-based extraction of natural products, this review offers valuable insights for advancing the practice of green chemical engineering.

In this study, the efficient extraction of lignin from wood meal using a deep eutectic system (DESys) was explored, and the obtained lignin was characterized. The impact of various factors, such as the type of DESys components, extraction time, temperature, water content, and solid-liquid ratio, on the lignin extraction process was systematically investigated. The results indicated that a DESys with a carboxylic acid as the HBD provided the highest lignin extraction efficiency. The obtained lignin was characterized in terms of its molecular weight distribution, elemental composition, functional groups, crystalline structure, and thermal stability. The results showed that the lignin obtained by DESys-based extraction had similar properties to lignin extracted using traditional method. Additionally, the study examined the utilization of the residue left after lignin extraction for the adsorption of cationic pollutants, such as the cationic dye neutral red (NR). The residue was found to contain carboxyl groups, which enabled it to adsorb NR efficiently. The kinetic and thermodynamic models suggested that the adsorption was a chemisorption process. Furthermore, the residue showed selective adsorption for cationic dye over anionic dye. This selectivity was attributed to interactions between the residue's functional groups and the cationic dye molecule. Overall, this study provided a sustainable and comprehensive approach to lignin extraction from lignocellulosic biomass using DESys. It also demonstrated the potential of using the residue from the extraction process for the removal of cationic pollutants from wastewater, showcasing a multi-faceted approach to the valorization of lignocellulosic materials.

A deep eutectic system (DESys) is formed when a hydrogen bond acceptor (HBA) is processed with polysaccharide (hydrogen bond donor, HBD) containing plant substance in water to dissolve, extract, and recover the polysaccharide directly, instead of using a traditional deep eutectic solvent (DES). The extraction efficiency is enhanced by the direct formation of the DESys, in a mechanochemical extraction (MCE) system. Key factors affecting the extraction efficiency were systematically studied and optimized. The effects of the DESys on the structure and physicochemical properties of polysaccharides were studied by several analytical techniques. The findings demonstrated that the direct DESys formation extraction efficiency was superior than that of traditional extraction methods while retaining physicochemical properties of polysaccharides. Moreover, the composition of polysaccharides extracted with this method is different from that obtained by conventional methods. The recovery and purification process of polysaccharides is simplified by eliminating the need for an additional HBD.

To systematically study the influence of host–guest interactions on the analytical performance of direct analysis in real time mass spectrometry (DART-MS), the interactions between cyclodextrins (CDs) and different Sudan dyes were investigated. The results showed that the host–guest interaction between CDs and Sudan dyes did not affect qualitative analysis of the target compounds, but led to a lower signal intensity for Sudan dyes, thus affecting quantitative analysis of the target compounds. The stronger the host–guest interaction, the weaker the signal intensity of target compound on DART-MS. The results also show that both in solution and in solid-phase microextraction (SPME), the addition of organic solvents can weaken the host–guest interaction between CDs and Sudan dyes, thus improving the signal intensity in DART-MS. In SPME, adding organic solvents has a certain practical value and can improve the efficiency of Sudan dye analysis. This study suggests that appropriate sample pretreatment is needed to weaken noncovalent interactions prior to DART-MS analysis to obtain more accurate quantitative results. The data provide some insight into the effects of other noncovalent interactions on the efficiency of DART-MS as an analytical tool, as well as the potential to study intermolecular interactions with DART-MS.