To solve the problem of potential food safety hazards and environmental hazards associated with artificial sweeteners as emerging pollutants, an eco-friendly aerogel (PSPI-GO) consisting of polyethyleneimine-modified soy protein isolate (PSPI) and graphene oxide (GO) was constructed to efficiently eliminate saccharin (SAC), a typical artificial sweetener in water. The equilibrium adsorption capacity of PSPI-GO for SAC was 293 mg/g, which removed 91% of SAC. PSPI-GO exhibited a highly porous structure and excellent renewability. Multiple quantum chemical theory calculations including electrostatic potential (ESP), frontier molecular orbital (FMO), independent gradient model based on Hirshfeld partition (IGMH), and Hirshfeld surface analysis (HSA) further elucidated that electrostatic attraction, hydrogen bonding, and inter-molecular interactions dominate the adsorption process. This work achieved high-value utilization of SPI while providing a new strategy for efficient removal of SAC. The research strategy integrating analysis of macroscopic mass transfer mechanisms and visualization of the adsorption mechanism provides a new perspective for in-depth understanding of inter-molecular adsorption behavior.

Alkaline degradation products of hexose (HADP) were prepared as a representative colorant in remelt syrup to evaluate their adsorption performance onto a decolorizing resin. Four novel phenomenological adsorption mass transfer models, namely, external mass transfer resistance (EMTR), internal mass transfer resistance (IMTR), combined EMTR-IMTR, and adsorption on active sites (AAS), were used to decipher the mass transfer mechanisms for the resin adsorption of HADP. At the initial colorant concentrations of 60, 90, and 120 mg/L, the equilibrium adsorption capacities of the resin for HADP were 190, 270, and 326 mg/g, and the corresponding decolorization rates were 95%, 90%, and 82%, respectively. EMTR combined with IMTR was the rate-limiting step for HADP adsorption onto the resin, and AAS could not be neglected. The dynamic characteristics of HADP adsorption through the liquid film around the resin and the pores inside the resin could be described well using the combined EMTR-IMTR model. The AAS model could accurately calculate the physisorption and chemisorption rates during the whole adsorption process. These models can help provide new insights into the mass transfer behaviors of the adsorption system.

Decolorization of remelt syrup is the most critical step in sugar refining. Currently, benzene-based anionadsorption resins are commonly used in remelt syrup decolorization, but their slow release of monomers may endanger food safety. In this study, a green and environmentally friendly rosin-derived macroporous anion-adsorbing resin was synthesized and used to efficiently capture the caramels in remelt syrup. The results showed that the equilibrium adsorption capacity of the resin for caramels was 86 mg/g, and the corresponding decolorization efficiency was as high as 90%. Following five cycles of repeated use, the decolorization efficiency decreased by only 5%, indicating excellent reusability. The focus was on the multidimensional visualization of the micro-mechanism of the interaction in the adsorption of caramels by the rosin-based resin at the molecular, atomic, and electronic levels on the basis of quantum chemical theoretical calculations (including electrostatic potential, electrostatic potential interaction, average local ionization energy, frontier molecular orbitals, independent gradient model, and Hirshfeld surface analyses). The results indicated that the adsorption occurred with positive-negative potential neutralization and interpenetration. The interaction mechanism was primarily mediated by the electrophilic reaction between carboxylate and protonated tertiary amine groups, followed by weak hydrogen bonding, with the resin acting as a hydrogen bond donor. The combined use of multiple quantum chemical theory calculations to visualize the micro-mechanism of the adsorption interaction can provide novel insights into exploring the adsorption behavior and mechanism at a deeper level, which has a theoretical contribution and practical value.

In this study, a quaternary ammonium-modified chitosan aerogel (QCSA) was developed for the decolorization of remelt syrup. Caramel pigments (a representative pigment from remelt syrup) were used as the adsorption model substrate to study the adsorption performance of QCSA. A novel Wen Li-Wei Wei adsorption mass transfer mixed (LWAM) phenomenological mathematical model was used to analyze the mass transfer mechanism of QCSA adsorption of caramel pigments. Density functional theory (DFT) was used to investigate the microscopic interaction mechanism of QCSA adsorption of caramel pigments. The results showed that the equilibrium adsorption capacity of QCSA for caramel pigments at initial concentrations of 60, 80, and 100 mg/L were 198, 263, and 308 mg/g and the corresponding decolorization rates were 99.8%, 98.2%, and 92.4%, respectively. Analysis using the LWAM phenomenological mathematical model showed that the adsorption rate-limiting steps were jointly determined by external diffusion, internal diffusion, and site binding. The DFT analysis showed that the adsorption mechanism of caramels by QCSA was dominated by electrostatic interactions. Weak interactions, such as hydrogen bonds, occurred between the oxygen atoms of –COO^–/–COOH (caramel pigment) and the hydrogen atoms of –OH/–NH₃⁺ (protonated QCSA), with caramel pigment molecules serving as hydrogen bond acceptors. Among them, O···H H-bonds played a significant role, accounting for 37.88% of the total H-bond superficial area. In summary, the LWAM phenomenological mathematical model can accurately calculate the capture amounts of liquid films, pore channels, and sites at any time during the adsorption process, thereby providing a new perspective for elucidating the underlying mass transfer mechanism. DFT analysis facilitates the understanding of intermolecular interactions in adsorption systems at the atomic level, offering theoretical support for optimizing adsorbent design.