[Adsorption Characteristics of Arsenic and Cadmium by FeMnNi-LDH Composite Modified by Fulvic Acid and Its Mechanisms]

Toxic As(Ⅲ) and Cd(Ⅱ) ions in water can be transferred and enriched into human bodies through the food chain, causing serious health damage at excessive levels. In this study, fulvic acid (FA) was selected as the modifier of iron-manganese-nickel layered double hydroxide (FeMnNi-LDH), and a stable layered composite (FA@FeMnNi-LDH) was prepared using the co-precipitation method, which could adsorb As(Ⅲ) anions and Cd(Ⅱ) cations simultaneously, especially with the higher adsorption capacity of the cation Cd(Ⅱ). Its structure was characterized by XRD, TEM, FT-IR, and XPS, and the adsorption capacity and mechanisms of As(Ⅲ) and Cd(Ⅱ) in water by the composite were also investigated. The results showed that with typical characteristic peaks of layered double hydroxides, the synthesized composite possessed a stable structure, maximum FA loading capacity, and optimal adsorption performance. The adsorption kinetics of As(Ⅲ) and Cd(Ⅱ) conformed to the pseudo-second-order kinetic model, and the adsorption isotherms well-followed the Langmuir model, with the maximum adsorption capacity at 25℃ being 249.60 mg·g^-1 for As(Ⅲ) and 156.50 mg·g^-1 for Cd(Ⅱ), respectively. The composite exhibited a good adsorption performance on As(Ⅲ) and Cd(Ⅱ) in the range of pH 2-7 and pH 4-7, respectively. The competitive adsorption effect of co-existed anions on As(Ⅲ) showed a sequence of PO₄^3->CO₃^2->NO₃^-, and that of co-existed cations on Cd(Ⅱ) was Pb²⁺>Cu²⁺>K⁺. The adsorption capacity of As(Ⅲ) and Cd(Ⅱ) decreased with the increase in the concentration of competing ions. The main adsorption mechanism for As(Ⅲ) was ion-exchange occurring in the interlayers of LDH, and that for Cd(Ⅱ) was coordination complexation occurring with the loaded FA, respectively. In conclusion, the prepared FA@FeMnNi-LDH composite material posed a good application prospect for adsorption removal of As(Ⅲ) and Cd(Ⅱ) in water and their toxicity control.

Fulvic Acid Attenuates Atopic Dermatitis by Downregulating CCL17/22

The main pathogenic factor in atopic dermatitis (AD) is Th2 inflammation, and levels of serum CCL17 and CCL22 are related to severity in AD patients. Fulvic acid (FA) is a kind of natural humic acid with anti-inflammatory, antibacterial, and immunomodulatory effects. Our experiments demonstrated the therapeutic effect of FA on AD mice and revealed some potential mechanisms. FA was shown to reduce TARC/CCL17 and MDC/CCL22 expression in HaCaT cells stimulated by TNF-α and IFN-γ. The inhibitors showed that FA inhibits CCL17 and CCL22 production by deactivating the p38 MAPK and JNK pathways. After 2,4-dinitrochlorobenzene (DNCB) induction in mice with atopic dermatitis, FA effectively reduced the symptoms and serum levels of CCL17 and CCL22. In conclusion, topical FA attenuated AD via downregulation of CCL17 and CCL22, via inhibition of P38 MAPK and JNK phosphorylation, and FA is a potential therapeutic agent for AD.

[Adsorption of Fulvic Acid on Virgin and Aging Microplastics]

Due to the wide distribution and strong adsorption ability of microplastics (MPs) for organic matter in aquatic environments, the interaction between MPs and natural organic matter (NOM) cannot be ignored. In this study, virgin and aging polyamide 66 (PA66) and polypropylene (PP) MPs were used to adsorb fulvic acid (FA) in order to understand the effect of MPs on NOM. The results indicated that the kinetics experimental data of FA adsorption on virgin and aging MPs well fitted the pseudo-second-order model (R²>0.94), and the adsorption equilibrium was reached at 48 h. Compared to that of PP, the adsorption capacity of FA on PA66 were relatively higher, and the aging process improved the adsorption ability of MPs for FA. Freundlich models were well fitting with the adsorption isotherms experimental data compared to Langmuir models, indicating that the adsorption of FA on the virgin and aging MPs was a multi-layer heterogeneous physical process. The thermodynamics analysis revealed that the adsorption was spontaneous and endothermic. With the increase in pH, the adsorption capacity of FA first decreased and then increased. The desorption experiment indicated that the FA desorbed from the tested MPs in ultrapure water obtained higher desorption rates than that in surface water, and the desorption rates of aging MPs were less than that of the corresponding virgin ones. The aging process had a great influence on the structure of MPs, which resulted in a distinct increase in surface area and roughness of MPs, but slightly affected functional groups. Specific surface area and polarity of MPs were the main influencing factors for the adsorption process, and the main mechanism of FA adsorption on the tested MPs was hydrophobic and π-π interactions.

[Degradation of Pentachlorophenol by Fulvic Acid in a Municipal Solid Waste Landfill]

The structural composition and functional group changes in fulvic acid (FA) at various landfills were studied using ultraviolet and infrared spectroscopy. The electron transfer ability of FA and its ability to degrade pentachlorophenol (PCP) were also studied considering the various landfills. The results showed that the use of MR-1 as an electron donor and the simultaneous addition of fulvic acid in different stages as an electron shuttle can significantly increase the degradation rate of PCP, leading it beyond 80%. Due to the different redox properties of fulvic acid at the different landfill stages, the degradation of PCP has different reduction conversion abilities. Landfill fulvic acid is able to reduce and transform PCP because of its electron transfer ability. These functions are all conducive to promoting PCP reductive dechlorination.