Versatile dodecyl trimethyl ammonium bromide modified γ-FeOOH for simultaneous removal and determination of As(Ⅴ)

Establishment of a visual assessment platform for total antioxidant capacity of Ganoderma sichuanense based on Arg-CeO2 hydrogel nanozyme utilizing a self-programmed smartphone app and a self-designed 3D-printed device

A multienzyme-like L-argininemodified CeO2 (Arg-CeO2) nanozyme was prepared for accurate total antioxidant capacity (TAC) determination of Ganoderma sichuanense (G. sichuanense). It exhibits oxidase-like and peroxidase-like activities catalyzing the generation of superoxide anion free radicals and hydroxyl radicals, accelerating 3, 3', 5, 5'-tetramethylbenzidine (TMB) chromogenic reaction. Antioxidants can effectively eliminate the generated free radicals, inhibiting the TMB chromogenic reaction. Hence, TAC can be assessed by Arg-CeO2 catalyzed TMB chromogenic reaction using ascorbic acid (AA) as a reference substance. TAC of G. sichuanense extracted using different solvents was determined, indicating the highest TAC observed in the G. sichuanense extracted by the mixture solvent (deionized water/ethanol/ethyl acetate = 1 : 1 : 1). A visual assessment platform based on Arg-CeO2 hydrogel nanozyme utilizing a self-programmed smartphone app and a self-designed 3D printed device is established. TAC using AA as a reference substance (3.33 ~ 83.33 µM) can be detected with a detection limit as low as 0.58 µM. The platform can realize one-step quantitative determination of TAC in G. sichuanense within 40 min. The proposed visual assessment platform presented exhibits promising application prospects in the field of TAC assessment in food.

α-FeOOH-Modified Sn/N-Codoped TiO2 Bifunctional Composites for As(III) Removal through Photocatalytic Oxidation and Simultaneous Adsorption

Photocatalytic oxidation technology is one of the most efficient and green methods to convert highly toxic As(III) into lowly toxic As(V) for arsenic-polluted wastewater. However, the obtained As(V) may be reduced to As(III) again in the environment, causing secondary pollution. In order to resolve these issues, a bifunctional composite consisting of needle-like α-FeOOH-modified Sn/N-codoped TiO2 granules (SNT-FeOOH) has been synthesized. After modifying, the band gap of SNT-FeOOH narrowed from 2.94 eV (SNT) to 2.29 eV. When the composites were applied to As(III) removal, 10 mg of SNT-FeOOH could totally photocatalytically oxidize 40 mL of As(III) solution with a concentration of 10,000 μg/L within 15 min and synchronously achieve complete adsorption of the produced As(V), which is much more efficient than pure Sn/N-codoped TiO2 [21 min for As(III) photocatalytic oxidation and only 20.01% of total arsenic removal efficiency]. Based on the characterizations, α-FeOOH modification plays a significant role in the promoted performances of photocatalytic oxidation and adsorption of SNT-FeOOH, leading to arsenic removal. On one hand, the Fe-O-Ti interfacial chemical interactions formed between α-FeOOH and Sn/N-codoped TiO2 can further boost the separation rate of photogenerated carriers, hence increasing the photocatalytic oxidation efficiency. On the other hand, α-FeOOH surface hydroxyl groups adsorb the generated As(V) by forming Fe-O-As bonds. The SNT-FeOOH bifunctional composites, prepared in this paper, with dual performances of photocatalytic oxidation and adsorption provide a new strategy to achieve arsenic removal from wastewater.

Iron-doped carbon nanotubes with magnetic enhanced Fe(VI) degradation of arsanilic acid and inorganic arsenic: Role of intermediate iron species and electron transfer

Arsanilic acid (p-AsA), a prevalently used feed additive, is frequently detected in environment posing a great threat to humans. Potassium ferrate (Fe(VI)) was an efficient way to tackle arsenic contamination under acid and neutral conditions. However, Fe(VI) showed a noneffective removal of p-AsA under alkaline conditions due to its oxidation capacity attenuation. Herein, a magnetic iron-doped carbon nanotubes (F-CNT) was successfully prepared and further catalyzed Fe(VI) to remove p-AsA and total As species. The Fe(VI)/F-CNT system showed an excellent capability to oxidize p-AsA and adsorb total As species over an environment-related pH range of 6-9. The high-valent iron intermediates Fe(V)/Fe(IV) and the mediated electron-transfer played a significant part in the degradation of p-AsA according to the probes/scavengers experiments and galvanic oxidation process. Moreover, the situ formed iron hydroxide oxide and F-CNT significantly improved the adsorption capacity for total As species. The electron-donating groups (semiquinone and hydroquinone) and high graphitization of F-CNT were responsible for activating Fe(VI) based on the analysis of X-ray photoelectron spectroscopy (XPS). Density functional theory calculations and the detected degradation products both indicated that the amino group and the C-As bond of p-AsA were main reactive sites. Notably, Fe(VI)/F-CNT system was resistant to the interference from Cl-, SO42-, and HCO3-, and could effectively remove p-AsA and total As species even in the presence of complex water matrix. In summary, this work proposed an efficient method to use Fe(VI) for degrading pollutants under alkaline conditions and explore a new technology for livestock wastewater advanced treatment.