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To evaluate the synergetic adsorption capacity of layered double hydroxide (LDH) and photocatalytic reduction property of TiO2 for aqueous Cr(VI), the Fe3O4-ZnAl-LDH and TiO2 composites (FLT) were prepared via sol-gel method. The removal efficiency of FLT composites for Cr(VI) changed with the mass ratio of Fe3O4-LDH/TiO2, and the optimal ratio was 20% (FLT-2). The adsorption efficiencies of 100 mg FLT-2 were 74% and 64% for 20 and 50 mg/L Cr(VI) solution, and the total removal ratios of Cr(VI) were all over 97% after UV irradiation. The experimental data of adsorption kinetic, adsorption isothermal, and photocatalytic reduction were consistent with the pseudo-second-order, Langmuir, and first-order reaction equations, respectively. From the X–ray photoelectron spectra analysis, FLT composites adsorbed Cr(VI) directly via surface complexation, also reduced aqueous Cr(VI) to Cr(III). The photocurrent and electrochemical impedance spectroscopy of FLT composites indicated the photo-induced electron-hole pairs were separated effectively. The regeneration results show that the FLT composites had good stability and reusability after five consecutive cycles. Therefore, FLT composites are promising materials in the disposal of wastewater containing Cr(VI).

In this work, the magnetic alginate microsphere of Fe3O4/MgAl-LDH (Fe3O4/LDH-AM) was prepared by immobilizing the Fe3O4/LDH with calcium alginate (CA) and was used to remove Cd2+, Pb2+, and Cu2+ from aqueous solutions. The obtained Fe3O4/LDH-AM was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller surface area determination. The results indicated that the surface groups of the alginate and LDH were retained and so was the crystal structure in the alginate microsphere. The adsorption performance of the Fe3O4/LDH-AM for Cd2+, Pb2+, and Cu2+ in aqueous solutions was evaluated by batch and column adsorption experiments. The effects of adsorption conditions, kinetics, isotherms, mechanisms, and potential applications were investigated. The adsorption kinetic data conformed to the pseudo-second-order kinetic equation, and the isotherm data fit well with the Freundlich and Langmuir isotherm models. The adsorption mechanism of Cd2+, Pb2+, and Cu2+ by the Fe3O4/LDH-AM entailed complexation and precipitation. The experimental breakthrough curves were correlated with the Thomas model. Moreover, the Fe3O4/LDH-AM displayed superior regeneration and reusability. These results suggest that the Fe3O4/LDH-AM is an efficient adsorbent for the removal of heavy metals and can be effectively employed in practical applications.

To evaluate the synergetic adsorption capacity of layered double hydroxide (LDH) and photocatalytic reduction property of TiO

In this work, the magnetic alginate microsphere of Fe

Adsorption of cationic methylene blue and anionic orange II onto unmodified and surfactant-modified zeolites was studied using a batch equilibration method. The effects of equilibrium time, solution pH, and sorption temperature were examined. The results suggested that 2% sodium dodecyl benzenesulfonate (SDBS)- and 3% sodium dodecyl sulfate (SDS)-modified zeolites had higher adsorption capacities for methylene blue than the unmodified zeolite, while 2% cetylpyridinium bromide hexadecyl (CPB)- and 2% hexadecylammonium bromide (HDTMA)-modified zeolites were the best adsorbents for orange II. The adsorption conditions were optimized, and the mechanisms of adsorption are briefly discussed.