Degradation of chlortetracycline hydrochloride by peroxymonosulfate activation on natural manganese sand through response surface methodology

This work studies the degradation of chlortetracycline hydrochloride (CTC) by activated peroxymonosulfate (PMS) with natural manganese sand (NMS). Meanwhile, the NMS was characterized and analyzed by isothermal nitrogen adsorption (BET), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscope (SEM). It can be induced that NMS material may contain C, O, Al, Si, Fe, Mn, and K, and the proportion of each is 6%, 9%, 13%, 34%, 27%, 5%, and 6%. Critical parameters, including initial pH value, catalyst dosage, and PMS amount, were optimized through response surface methodology. One of the essential significances of response surface methodology (RSM) is the establishment and optimization of the mathematical model to reduce the complexity of the experimental process. It can provide the degree of mutual influence between various factors and optimize the response based on the investigated factors. Results indicated that 81.65% of CTC could be degraded under the optimized conditions of PMS amount 2.02 g/L, the NMS dosage 0.29 g/L and pH 3.87. Also, it shows that NMS is the most powerful of each factor on the degradation efficiency. We proposed the degradation pathways of CTC from the liquid chromatograph-mass spectrometer (LC-MS) results. Therefore, NMS could be applied as an efficient activator of peroxymonosulfate to purify the water and wastewater.

Adsorption of organic and inorganic arsenic from aqueous solution: Optimization, characterization and performance of Fe-Mn-Zr ternary magnetic sorbent

Arsenic is a highly toxic pollutant and exists in inorganic and organic forms in groundwater and industrial wastewater. It is of great importance to reduce the arsenic content to lower levels in the water (e.g., <10 ppb for drinking) in order to minimize risk to humans. In this study, a Fe-Mn-Zr ternary magnetic sorbent was fabricated via precipitation for removal of inorganic and organic arsenate. The synthesis of sorbent was optimized by Taguchi method, which leads to an adsorbent with higher adsorption capacity. The adsorption of As(V) was pH dependent; the optimal removal was achieved at pH 2 and 5 for inorganic and organic As(V), respectively. Contact time of 25 h was sufficient for complete adsorption of both inorganic and organic As(V). The adsorption isotherm study revealed that the adsorbent performed better in sequestration of inorganic As(V) than that of organic As(V); both adsorption followed the Langmuir isotherm with maximum adsorption capacities of 81.3 and 16.98 mg g^-1 for inorganic and organic As(V), respectively. The existence of anions in the water had more profound effect on the adsorption of organic As(V) than the inorganic As(V). The co-existing silicate and phosphate ions caused significantly negative impacts on the adsorption of both As(V). Furthermore, the existence of humic acid caused the deterioration of inorganic As(V) removal but showed insignificant impact on the organic As(V) adsorption. The mechanism study demonstrated that ion exchange and complexation played key roles in arsenic removal. This study provides a promising magnetic adsorptive material for simultaneous removal of inorganic and organic As(V).

Polymeric template assisted synthesis of monodisperse-porous manganese oxide microspheres: a new nanozyme with oxidase-like activity allowing biomolecule determination via bimodal sensing

New template assisted synthesis of monodisperse-porous MnO₂ microspheres and their usage as a nanozyme in the first bimodal sensing of ascorbic acid.

Towards magnetic responsive chalcogenides for efficient separation in water treatment: facile synthesis of magnetically layered chalcogenide Fe3O4/KMS-1 composite adsorbents and their zinc removal application in water

A novel easily separated magnetic chalcogenide based composite, Fe₃O₄/KMS-1, was successfully synthesized under vigorous stirring of a mixture in ethanol solution.

Magnetic core–shell-structured Fe3O4@CeO2 as an efficient catalyst for catalytic wet peroxide oxidation of benzoic acid

A magnetic core–shell-structured Fe₃O₄@CeO₂ catalyst was prepared by a simple solvothermal method and applied in the solid state for catalytic wet peroxide oxidation (CWPO) of benzoic acid. The obtained catalyst was characterized by N₂ adsorption–desorption, X-ray diffraction (XRD), magnetic measurements, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The experimental results showed that Fe₃O₄@CeO₂ possessed superior catalytic efficiency for CWPO of benzoic acid than that of Fe₃O₄. The high catalytic activity was caused by a synergistic effect between Fe₃O₄ and CeO₂, which assisted the decomposition of H₂O₂ into hydroxyl radicals (·OH). Fe₃O₄@CeO₂ exhibited low Fe leaching of 4.2 mg L⁻¹, which approximately accounted for barely 0.76% of the total Fe amount in the catalyst. The effects of radical scavengers indicated that benzoic acid was degraded mainly by ·OH attack, which occurred both in the bulk solution and on the Fe₃O₄@CeO₂ surface. In the stability tests, there was loss of merely 4% in the benzoic acid removal rate after six cycles of reaction, and the saturation magnetization of Fe₃O₄@CeO₂ hardly changed, which suggested that the Fe₃O₄@CeO₂ catalyst was fairly effective in reutilization and stability.

Benzoic acid was degraded mainly by ·OH generated by the reaction of Fe²⁺ and Ce³⁺ species with H₂O₂.

Yolk–shell structured CoFe2O4 microspheres as novel catalysts for peroxymonosulfate activation for efficient degradation of butyl paraben

Three-dimensional yolk–shell structured CoFe₂O₄ microspheres were successfully fabricated to activate peroxymonosulfate (PMS) for efficiently catalytic degradation of butyl paraben (BPB) in wastewater.

Insights into the degradation of 2,4-dichlorophenol in aqueous solution by α-MnO2 nanowire activated persulfate: catalytic performance and kinetic modeling

α-MnO₂ nanowires were synthesized through a hydrothermal method. Sulfate and hydroxyl radicals were produced in α-MnO₂-activated persulfate system to degrade 2,4-dichlorophenol.

Granulous KMS-1/PAN composite for Cs+ removal

A novel KMS-1/PAN composite was successfully fabricated simply by combining KMS-1 with PAN. The KMS-1/PAN combines the efficient, rapid adsorption of Cs⁺ by KMS-1 with granulation for easy separation after adsorption.