Yajie Zhu

Simultaneous adsorption of Cd(2+) and BPA on amphoteric surfactant activated montmorillonite

The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd(2+) from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd(2+)/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd(2+) adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd(2+) and BPA with an equilibrium time of 24 h. The Cd(2+) and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd(2+) in aqueous solution was slightly enhanced after modification, indicating that Cd(2+) adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction.

Highly enhanced adsorption for the removal of Hg(II) from aqueous solution by Mercaptoethylamine/Mercaptopropyltrimethoxysilane functionalized vermiculites

Vermiculites modified with Mercaptoethylamine (MEA) and 3-Mercaptopropyltrimethoxysilane (MPTMS) were used as effective adsorbents for the removal of Hg(II) from aqueous solution. The physicochemical characteristics of the pristine and functionalized vermiculites were analyzed by XRD, BET, FTIR, SEM, TEM and Zeta potentials, confirming that the vermiculite was successfully functionalized by the organic ligands containing the thiol (SH) metal-chelating groups. Batch adsorption experiments demonstrated that the factors such as initial pH, contact time, temperature, coexisting cations and initial Hg(II) concentration could significantly influence the adsorption behaviors typically for VER and MEA-VER, whereas the adsorption capacity of MPTMS-VER showed negligible dependence on such factors. The maximum adsorption capacity of Hg(II) ions was greatly improved after functionalization, which was in the order of MPTMS-VER>MEA-VER>VER (286.29 μg g(-1), 176.33 μg g(-1), 99.95 μg g(-1), respectively). The adsorption isotherm could be well described with Langmuir model and the kinetic studies indicated that the adsorption process fitted well with the pseudo-second-order model. The calculated thermodynamic parameters suggested that the adsorption process was feasible and spontaneous. The adsorption mechanism of Hg(II) on thiol groups was studied through XPS analysis. Considering the favorable adsorption capacities, thiol-functionalized vermiculites show a promising application in the removal of Hg(II) from wastewater.

Synthesis and catalytic properties of La or Ce doped hydroxy-FeAl intercalated montmorillonite used as heterogeneous photo Fenton catalysts under sunlight irradiation

A series of La and Ce doped hydroxyl FeAl intercalated montmorillonite (FeAl-Mt) were prepared by a co-intercalation method for catalytic oxidation of Reactive Blue 19 (RB19) by a heterogeneous photo Fenton process under natural sunlight irradiation. The physicochemical properties of the obtained catalysts were deciphered by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) and UV-vis diffuse reflectance spectroscopy (DRS). The results showed that Ce or La doped FeAl Keggin polyoxocations were intercalated into the gallery of montmorillonite and the physicochemical properties of intercalated FeAl Keggin polyoxocations were mildly changed after Ce or La doping, resulting in defects and lattice vacancies. The doping of Ce or La could effectively improve the catalytic performance of FeAl-Mt measured by heterogeneous photo Fenton degradation of RB19 catalyzed by the obtained products. The synergistic effect between the doped element and FeAl intercalated montmorillonite played a crucial role in the enhancement of heterogeneous catalytic activity under natural sunlight irradiation.

3D hierarchical honeycomb structured MWCNTs coupled with CoMnAl–LDO: fabrication and application for ultrafast catalytic degradation of bisphenol A

3D hierarchical honeycomb nano-structured o-MWCNTs coupled with CoMnAl-layer double oxides have been successfully fabricated and characterized as a heterogeneous catalyst for bisphenol A (BPA) degradation using potassium monopersulfate (PMS) as oxidant. The role of MWCNTs was investigated and discussed in terms of surface morphology, structure, composition and catalytic activity of the as-prepared nanohybrid by investigation of SEM, TEM, XRD, XPS, and Raman measurements, etc. The results showed that catalytic performance of the CNTs–LDO can be significantly enhanced with the increase of o-MWCNTs content in the hybrids, and MWCNTs provided orientation/confinement for nanohybrid formation and the defects generated by calcination might increase PMS activation for the production of sulfate radicals.

Synergetic effect of functionalized carbon nanotubes on ZnCr–mixed metal oxides for enhanced solar light-driven photocatalytic performance

In this work, ZnCr–mixed metal oxides (MMO) hybridized with functionalized carbon nanotubes (A-CNTs) have been successfully fabricated via vacuum calcination of the layered double hydroxide precursors. The structural and morphological characterization of the samples was investigated by multiple techniques such as XRD, SEM, TEM, XPS, BET, Raman and UV-vis DRS. The results showed that A-CNTs were well incorporated into the MMO nanoparticles to form a nanohybrid structure dependent upon intimate interfacial contact. As compared to pristine MMO, the obtained MMO–CNTs nanohybrids exhibited significantly enhanced photocatalytic performance for bisphenol A (BPA) degradation under simulative solar light irradiation, providing powerful evidence for the superiority of the hybridization with A-CNTs. The key role of A-CNTs played in enhancing the photocatalytic activity of the nanohybrids was probably ascribed to the larger surface area, higher visible light absorption and the more efficient restriction of charge carriers recombination.

Preparation and characterization of ZnTiO3–TiO2/pillared montmorillonite composite catalyst for enhanced photocatalytic activity

Abstract ZnTiO3–TiO2/organic pillared montmorillonite (pMt) composite catalyst was successfully prepared in this paper by immobilizing ZnTiO3–TiO2 onto pMt. The composition and texture of the prepared composite catalyst were characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive spectrometry, ultraviolet–visible light (UV–Vis) diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity was tested via photocatalytic degradation of methyl blue (MB) under both visible irradiation and UV light. The results indicated that the ZnTiO3–TiO2/pMt composite catalyst had an apparent absorption at the area of visible irradiation, and exhibited a higher efficiency of photocatalytic degredation of MB under visible irradiation. This was due to the heterostructure of ZnTiO3–TiO2, and the mesoporous structure and specific surface area of the ZnTiO3–TiO2/pMt composite. In addition, the results of the radical scavenging experiments showed that the holes and superoxide radicals are responsible for the degradation of MB under visible irradiation.

The role of oxygen vacancy over ZnCr-layered double oxide in enhancing solar light-driven photocatalytic degradation of bisphenol A

Environmental context An important goal in attempts to degrade environmental organic pollutants is the development of a photocatalyst that is responsive to visible light. We report a facile method for preparing a zinc-based photocatalyst with oxygen vacancies that efficiently degrades bisphenol A under solar light irradiation. The study will stimulate further investigations into the efficacy of other metal oxide nanostructures for the photocatalytic degradation of organic pollutants. Abstract Two ZnCr-layered double oxides (ZnCr-LDO) were fabricated via different thermal treatment of the ZnCr-layered double hydroxide (ZnCr-LDH) precursor. ZnCr-V-700 and ZnCr-A-700 were obtained at 700 °C under vacuum and air, respectively. As X-ray diffraction revealed, both ZnCr-V-700 and ZnCr-A-700 were made up of ZnO and ZnCr2O4 spinel, and ZnCr-V-700 displayed a lower crystallinity and many uniform particles with oxygen vacancies. Scanning electron microscopy and transmission electron microscopy revealed that the particle size of ZnCr-V-700 was ~30 nm and its disordered crystallinity suggested the existence of oxygen vacancies. Notably, the ZnCr-LDO materials showed remarkably enhanced photocatalytic activity compared to the ZnCr-LDH precursor. ZnCr-V-700 was the most active material and more than 90 % of BPA was degraded after irradiation for 200 min with high mineralisation (up to 37 %). The results of Brunauer–Emmett–Teller surface area analysis, X-ray photoelectron spectroscopy, Raman and UV-vis spectroscopy and electron paramagnetic resonance spectroscopy showed that oxygen vacancies incorporated into ZnCr-V-700 played a key role in improving the photocatalytic performance by enhancing interfacial charge transfer and restricting the charge recombination. In addition, the uniform particle size, larger surface area and the coexistence of ZnO and ZnCr2O4 also played a synergistic role. In conclusion, this work not only provides a facile and low-cost method to prepare photocatalysts for treatment of wastewater containing BPA, but also supplies a new idea for improving the performance of photocatalysts.