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Reduction of Cr (VI) often happens simultaneously with biosorption, making it difficult to exactly understand its removal mechanism. Quantitative description of Cr (VI) reduction is a key point to identify the two mechanisms. Herein, corn stalk based anion exchanger (CS-AE), capable of removing Cr (VI) rapidly and effectively, was used as model biosorbent to investigate Cr (VI) reduction. Batch experiments confirmed Cr (VI) was mainly removed via ion exchange with chloride ion on CS-AE. X-ray photoelectron spectroscopy (XPS) was employed to characterize Cr-laden CS-AE. Result showed the presence of Cr (III) on CS-AE surface and indicated N-contained group especially quaternary ammonium participated in the reduction reaction as electron donor. The effects of initial concentration, pH and sorbent dose on Cr (VI) reduction were studied by quantifying Cr (III) content both in liquid and solid phase. It was found that Cr (III) formation increased with initial Cr (VI) concentration because high concentrations of Cr (VI) enhanced oxidation-reduction potential (ORP) as well as the reactivity of Cr (VI). Acidic conditions facilitated the reduction reaction to form more Cr (III), and the positive relationship between H + depletion and Cr (III) formation was observed. Increase of sorbent dose also can promote the reduction to some extent. Kinetic study showed that reduction of Cr (VI) could reach near equilibrium in about 20∼30 min under experimental conditions. Rate equations based on the change of Cr (III) amount were proposed to describe the reduction reaction, and better fittings were obtained with zero-order kinetic equation. Moreover, activated energy of Cr (VI) reduction reaction was evaluated as about 36.8 kJ/mol. It was also found that increase of temperature favored the reduction of Cr (VI). [ABSTRACT FROM AUTHOR]

Natural products often contain a large number of structurally similar compounds, however, from which the isolation of monomer compounds is complex and time-consuming. In this study, for the first time, a Zr-based metal-organic framework (MOF), UiO-66, was used for the separation of three isoflavones (genistein (GEN), puerarin (PUE), and daidzein (DDZ)) with similar structures. UiO-66 was demonstrated to have a distinct high adsorption capacity (q e , 105.42 ± 2.36 mg/g) for GEN with high separation factors from PUE (α, 35.52 ± 1.22) and DDZ (α, 7.41 ± 0.76), dramatically increasing the purity of GEN from ∼33–92% after primary separation. According to SEM-EDS and XPS characterizations together with RDF analysis, GEN and PUE were adsorbed on the surface of UiO-66 at the same dominant Zr cluster site (O...Zr), while DDZ was bound onto the inferior site via weak hydrogen bonding (H...O), indicating the separation of GEN from PUE was in a competitive manner, while the separation from DDZ was selective. For these three drugs, their adsorption kinetics and adsorption isotherms conformed Pseudo-second-order kinetic model and Langmuir model, respectively, indicating that the monolayer adsorption of isoflavones on UiO-66 surface was the dominant mechanism. The thermodynamic study demonstrated that both adsorptions of GEN and PUE were spontaneous (Δ G 0 < 0), whereas the DDZ adsorption is non-spontaneous (Δ G 0 > 0). Compared to traditional separation techniques, this study provided a simple and efficient approach to isolate structurally similar compounds from natural products in drug discovery. [Display omitted] • UiO-66 can effectively separate GEN from three structurally similar isoflavones(GEN, PUE, and DDZ). • The adsorption of GEN and PUE on UiO-66 was spontaneous, whereas that of DDZ was non-spontaneous. • GEN was separated from PUE and DDZ in a competitive and selective manner, respectively. • MOF adsorption is a promising approach for effectively separating similar structural natural compounds. [ABSTRACT FROM AUTHOR]

Efficient removal of arsenic (As) and lead (Pb) from industrial wastewater has long been a critical environmental issue due to their serious risk to human health. Therefore, in this work, a modified banana peel biochar (MBPB) was prepared by mixing calcium nitrate, diammonium hydrogen phosphate, sulfuric acid, ferric nitrate with dehydrated banana peel biochar as adsorbent for As(V) and Pb(II) removal in wastewater, and their absorption mechanism was investigated. SEM-EDS, TEM, FTIR, XRD, XPS, BET, kinetic, and isothermal characteristics of MBPB and pristine banana peel biochar (PBPB) were conducted. The behavior of both metal ions on MBPB and PBPB was well explained by the pseudo-second-order kinetic with Langmuir and Freundlich models. We found that the two biochar's behaviors were mixture processes of monolayer and multilayer adsorption, achieving maximum capacities as determined by the Langmuir model of 39.5 mg g−1 (MBPB-As), 33.2 mg g−1 (MBPB-Pb), 30.8 mg g−1 (PBPB-Pb), and 23.5 mg g−1 (PBPB-As), with maximum efficiencies of 98.7% (MBPB-As) and 90.3% (MBPB-Pb) under optimum conditions. Thermodynamic tests showed that As(V) and Pb(II) removal on MBPB was a spontaneous and endothermic physisorption process. MBPB showed great reusability in As(V) and Pb(II) removal, with removal rates as high as 71.4% and 66.5% after five cycles, respectively. Selective adsorption of As(V) and Pb(II) was also investigated on MBPB, and the removal rate was still high in the mixture of heavy metals. These findings provide a feasible method for the environmental-benign utilization of banana peel as a low-priced adsorbent in wastewater treatment. [Display omitted] • Modified biochar made from banana peel for heavy metals removal was investigated. • Adsorbent was characterized by SEM-EDS, TEM, FTIR, XRD, and XPS techniques. • Modified biochar showed good adsorption performance for As(V) and Pb(II). • Adsorption mechanisms for As(V) and Pb(II) were defined. [ABSTRACT FROM AUTHOR]

Highlights: [•] A pectin-coated liposomal formulations was prepared by forming an ion-complex. [•] The pectin-coated liposome has an excellent stability and mucoadhesiveness properties. [•] The pectin-coated liposome would be a promising drug carrier system for colon cancer. [ABSTRACT FROM AUTHOR]

Sulfidated nanoscale zero-valent iron (S-NZVI) has attracted significant attention in pollutant remediation due to its higher electron selectivity than NZVI. However, the agglomeration behavior of S-NZVI particle limits its practical application. In this study, S-NZVI was synthesized and dispersed in dendritic mesoporous silica nanospheres (S-NZVI/DMSN) to remove tetrabromobisphenol A (TBBPA) in groundwater. The structural characterization and degradation results illustrated that the dendritic pores of DMSN not only improved the dispersion of S-NZVI particles, but also enhanced the accessibility of pollutants to S-NZVI. The specific surface area of the S-NZVI/DMSN reached 136.2 m2 g-1, which was 2.68 times larger than that of S-NZVI (50.8 m2 g-1). At a S/Fe molar ratio of 0.1 and Si/Fe mass ratio of 1.0, the TBBPA degradation efficiency by S-NZVI/DMSN reached 91.4%, which exceeded that of S-NZVI (66.3%), and the degradation rate constants (0.078 L (mg h)-1) was 2.86 times higher than that of S-NZVI (0.027 L (mg h)-1). The S-NZVI/DMSN could remain high TBBPA degradation performance (76.3%) after even five cyclic degradations. Approximately 70.5% of S-NZVI/DMSN and 1% of S-NZVI successfully passed through the sand column. The much better sustained reactivity and transportability of S-NZVI/DMSN indicated that it could penetrate soil aquifers and degrade TBBPA in groundwater. [Display omitted] • S-NZVI dispersed in the pores of dendritic mesoporous silica nanospheres. • The accessibility and reactivity between S-NZVI and pollutants increased. • S-NZVI/DMSN exhibited better TBBPA degradation performance comparing with S-NZVI. • S-NZVI/DMSN demonstrated high sustained reactivity and transportability. [ABSTRACT FROM AUTHOR]