| The dyes pollution to aquatic environments and food have caused serious concerns for harmful impacts on the existence and health of mankind. Therefore, purification of organic dye wastewater and monitoring of trace disable dyes in food are both necessary. Due to the high efficiency, simple operation and low cost, adsorption is the most popular treatment technology of dye wastewater. Because of the fast reaction rate, short time, high mineralization and degradable property of opaque and bio-refractory organic pollutants, MICD has become the emerging dye wastewater treatment technology. In order to reduce the sample matrix interference, and improve the detection sensitivity, SPE of disable dyes in food was mainly used for separation, purification and concentration of sample. However, traditional adsorbent/catalyst/extractant was limited to its difficult recovery. In order to solve the problem, spinel bimetal oxide AB2O4 (A= Cu, Ca or Ni; B=Fe or Co) magnetic functional materials were constructed for the adsorption/MICD/SPE technology.The main research contents and results of this paper are as follows:1. Spinel CaFe2O4 MNPs magnetic functional materials were prepared. The morphology, particle size, structure, specific surface area and magnetic property of synthesized CaFe2O4 MNPs were characterized by TEM, XRD, BET, FTIR and VSM, respectively. It could be employed to selectively adsorb CR from the ternary mixture system(CR-MO-RhB). CaFe2O4 MNPs showed the high adsorption selectivity for CR with removal efficiency of 96.1%, and still maintain high adsorption efficiency for CR after five regeneration-removal cycles. The influence factors of adsorption selectivity were examined. It revealed selective adsorption mechanism of CaFe2O4 MNPs for CR in the ternary mixture system. The adsorption isotherms, kinetic and thermodynamic behavior of CaFe2O4 MNPs for CR were also systematically discussed. The sorption behavior could be well interpreted by Langmuir model. Sorption kinetics data followed the pseudo-second-order model. The thermodynamic parameters revealed the spontaneous (ΔG0<0) and exothermic (ΔH0<0) nature of the sorption process and reduced degree of chaos(ΔS0<0).2. Spinel 3D hierarchical dandelion-like magnetic microspheres (3D NiCo2O4-S) as adsorbent were constructed, and were used to selectively adsorb six kinds of organic dyes. The morphology, particle size, structure, surface property, specific surface area, pore size distributions and magnetic property of synthesized 3D NiCo2O4-S were characterized by SEM, XRD, TG, FTIR, BET and VSM, respectively. The adsorption selectivity of 3D NiCo204-S was evaluated.3D NiCo2O4-S exhibited the high adsorption performance for anionic CR, MB and AF, and almost no adsorption for cationic RhB, CV and MeB.3D NiCo2O4-S could be rapidly separated and recycled by a magnet, and still maintain high adsorption efficiency for CR after five regeneration-removal cycles. Electrostatic interactions between the positive charge of the adsorbent and anionic CR enhanced the adsorption. On the contrary, electrostatic repulsion for cationic dyes reduced the adsorption. The effect of solution pH, ionic strengths and interfering ions on selective adsorption for CR were examined. The adsorption isotherms, kinetic and thermodynamic behavior of 3D NiCo2O4-S for CR were also systematically discussed. The results showed that pH 4-7 did benefit to the adsorption. PO43-、HPO42- and CO32- caused a remarkably decrease in the adsorption of CR. The sorption behavior could be well interpreted by Langmuir model. Sorption kinetics data followed the pseudo-second-order model. The thermodynamic parameters revealed the spontaneous (ΔG0<0) and endothermic (ΔH0>0) nature of the sorption process and increased degree of chaos(ΔS0>0).3. Four different morphology of NiCo2O4 magnetic functional materials, including OD NiCo2O4 nanoparticles, 1D NiCo2O4 nanorods,2D NiCo2O4 nanoplates and 3D NiCo2O4-S, were constructed. The morphology, particle size and specific surface area of materials were characterized by SEM and BET. The prepared NiCo2O4 magnetic materials combined with MW were used to synergistically degrade organic dye CR. The influence of the morphology of catalyst on degradation efficiency was investigated. Compared with NiCo204-P, NiCo2O4-R and NiCo2O4-N,3D NiCo2O4-S exhibited the highest catalytic activity. This may be attributed to its unique hierarchical structure, which allows multiple absorption and scattering of MW. Various parameters affecting degradation efficiency of 3D NiCo2O4-S for CR were examined. The optimum conditions were followed:solution pH 4.0～7.0,0.2 g L-1 of catalyst dosage,700 W of MW power, irradiation for 10 min. Co-existing ions discussed could inhibit the degradation of CR to some extent. The inhibition degree could be ranked in the following order:PO43-> CO32-> SO42-> NO3-≌CH3COO-=Cl-. The intermediates and final products were analyzed by UV-vis, HPLC and IC. The results showed that CR was ultimately mineralized into inorganic ions such as NO3-, SO42-, CO2 and H2O, and no intermediates was generated. The reaction kinetics of MW/NiCo2O4 for CR degradation was also systematically discussed. The catalytic kinetic data followed the pseudo-second-order model. The rate constant k value of 3D NiCo2O4-S was 2.39,5.31 and 8.95 times higher than that of NiCo2O4-R, NiCo2O4-P and NiCo2O4-N, respectively. The types and contribution of various active species (·OH, h+ and ·O2-) and their possible generation process were evaluated by capture experiments, the band gap model, as well as Mott-Schottky analysis. The ·OH and direct h+ were considered to be the active species participated in this degradation process.3D NiCo2O4-S can be rapidly magnetically separated and recovered by a magnet from the solution, which broke the bottleneck of difficulty recovery.3D NiCo2O4-S still maintain high degradation efficiency for CR after five regeneration-catalysis cycles.4. Spinel submicron level CuFe2O4 magnetic functional materials were prepared. The morphology, particle size, structure, specific surface area, pore size distributions and magnetic property of synthesized CuFe2O4 were characterized by SEM, AFM, XRD, TG, BET and VSM. The prepared CuFe2O4 combined with MW were used to synergistically degrade organic dye MG. Various parameters affecting degradation efficiency of CuFe2O4 for CR and the reaction kinetics were examined. The optimum conditions were followed: solution pH 4.0～10,4.0 g L-1 of catalyst dosage,600 W of MW power, irradiation for 2 min. The catalytic kinetic data followed the pseudo-second-order model. The intermediates and final products were analyzed by UV-vis, FTIR and IC. The results showed that MG was ultimately mineralized into inorganic ions such as NO3-, NO2-,CO2 and H2O, and no intermediates was generated. The types of various active species were evaluated by radical capture experiments as well as photoluminescence spectra analysis. The direct h+, ·O2- and ·OH were considered to be the active species participated in this degradation process. The microwave-induced catalytic mechanism of synthesized CuFe2O4 for CR was revealed. CuFe2O4 can be rapidly magnetically separated and recovered by a magnet from the solution, and still maintain high degradation efficiency for MG after five regeneration-catalysis cycles.5. Spinel 3D hierarchical hollow CuFe2O4 magnetic microspheres (3D SH-CuFe2O4) were constructed by a simple template-free and self-assembly method. The morphology, particle size, structure, specific surface area and magnetic property of synthesized 3D SH-CuFe2O4 were characterized by SEM, XRD, BET and VSM. The formation mechanism of 3D SH-CuFe2O4 was verified. The prepared 3D SH-CuFe2O4 as MSPE adsorbent could be successfully employed to extract and separate four Sudan dyes (Sudan Ⅰ, Ⅱ, Ⅲ and Ⅳ) with a high extraction efficiency. Extraction/elution conditions were optimized. A method for the simultaneous determination of four disable Sudan dyes in preserved beancurd based on MSPE coupled with HPLC-DAD was developed. The analytical performances of the proposed method was systematically evaluated. Good linearities were observed in the range of 5～4000 ng g-1. The detection limits were obtained in the range of 0.56～0.60 ng g-1. The recoveries of analytes obtained were in the range of 91.1%～99.3%.3D SH-CuFe2O4 can be rapidly magnetically separated and recovered by a magnet from the solution, and still maintain high extraction efficiency after seven regeneration-extraction cycles. |
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