Preparation of Ag-MnFe204-bentonite Magnetic Composite for Pb（II）/Cd（II） Adsorption Removal and Bacterial Inactivation in Wastewater

An Ag-MnFe2O4-bentonite composite was synthesized by a chemical co-precipitation method and used for adsorption removal of Pb（II）, Cd（II） and disinfection. The result of X-ray diffraction indicate that the diffraction peaks of MnFe2O4 and Ag can be perfectly indexed to the cubic spinel MnFe2O4（JCPDS No.88-1965） and metallic Ag（JCPDS No.41-1402）, respectively. The results of scanning electron microscopy and energy dispersive X-ray spectroscopy manifest the deposition of MnFe2O4 and Ag on the bentonite surface and the presence ofMn, Fe and Ag. The result of X-ray photoelectron spectroscopy displayed that the composition of Ag-MnFe2O4-bentonite was Mn（II）, Fe（III） and metallic Ag. The analysis of Brunauer-Emmett-Teller showed that the specific surface area of Ag-MnFe2O4-bentonite was the largest compared with that of bentonite, MnFe2O4 and MnFe2O4-bentonite. Thermo- dynamic studies revealed that the adsorption of Pb（II） and Cd（II） ions was spontaneous and endothermic. Langmuir model showed an adsorption capacity of 129.87 mg/g for Pb（II） and 48.31 mg/g for Cd（II） ions. The adsorption ki- netics of Pb（II） and Cd（II） ions onto Ag-MnFe2O4-bentonite can be best described by a pseudo-second-order model. The adsorption rate constant of the pseudo-second-order model was 0.0019 g·mg^-1·min^-1 for Pb（II） and 0.0065 g·mg^-1·min^-1 for Cd（II） ions. In addition to the adsorption experiment, the antibacterial properties of Ag-MnFe2O4-bentonite were studied through plate count method. Gram-negative（G-） bacteria Escherichia coli and Gram-positive（G＋） bacteria Lactobacillus plantarum were used to test the antibacterial properties. The results showed that the composite demonstrated excellent antibacterial activity. Thus, Ag-MnFe2O4-bentonite can be em- ployed as an adsorbent as well as an antimicrobial agent.

Activation of Persulfate by Magnetic MnFe2O4-bentonite for Catalytic Degradation of 2,4-Dichlorophenol in Aqueous Solutions

Magnetic MnFe2O4-bentonite was synthesized by chemical co-precipitation method（CCM） and applied as catalyst in heterogeneous activation of persulfate（PS） to oxidize a target pollutant, 2,4-dichlorophenol（2,4-DCP）, in aqueous solutions. The surface morphology and structure of MnFe2On-bentonite were characterized by X-ray diffraction（XRD）, scanning electron microscope（SEM）, energy dispersive X-ray（EDX） and X-ray photoelectron spectroscopy（XPS） analyses.The catalytic activity of MnFe2O4-bentonite for 2,4-DCP degradation was evaluated considering the effects of various process parameters, such as mass ratio of MnFe2O4 to bentonite, concentration of catalyst, PS concentration, and pH. The MnFe2O4-bentonite hybrid exhibited higher catalytic activity than pure MnFe2O4. Treatment with 5 g/L MnFe2O4-bentonite at 30℃ for 240 rain oxidized 92% of 100 mg/L 2,4-DCP（70.2% mineralization）, whereas treatment with pure MnFe2O4 under the same condition oxidized only 70% of the pollutant. This result indicate the erdlanced performance of the activated PS. Moreover, MnFe2O4-bentonite exhibits stable performance with minimal loss in activity after five successive runs. Thus, MnFe2O4-bentonite could be a promising catalyst in oxidative degradation of 2,4-DCE