| Fluorescent whitening agent-VBL(FWA-VBL) wastewater often contains a variety of organic compounds and intermediates. These organic pollutants have complex componets, make them reduce light penetration, and usually can not be degradabed. Hereby, the impacts of FWA-VBL on the environment have been paid much attention, and the treatment of effluents containing FWA-VBL has to be enforced before they are discharged into the environment. In this paper, we prepared TiO2@yeast microspheres adsorbent using TiO2 particles as the guest particles and yeast as the host cores. The obtained TiO2@yeast microspheres adsorbents not only have excellent adsorption properties for FWA-VBL wastewater treatment but also exhibit desired regeneration capacity.(1) TiO2@yeast microspheres with a unique raspberry-like structure were prepared through electrostatic-interaction-driven self-assembly heterocoagulation. The obtained products were characterized by FE-SEM, FT-IR, XRD and UV-vis, respectively. FE-SEM ascertains that the resulting samples retain ellipsoid shape, with the uniform size(length 2.6±0.5 μm, width 2.0±0.3 μm)and good dispersity. FT-IR elucidates the possible formation mechanisms of TiO2@yeast microspheres. XRD pattern shows that the main crystal structure of as-synthesized TiO2@yeast microsphere is consisted of anatase and rutile. UV-vis proves that the samples have a desired responding to UV light.(2) The obtained TiO2@yeast microspheres were subsequently used as adsorbents for removal of anionic FWA-VBL from aqueous solutions. The adsorption characteristics were determined by investigating factors such as pH, initial concentration and adsorbent dose, respectively. The results show that FWA-VBL could be adsorbed effectively under acidic conditions, the amount of FWA-VBL adsorbed by TiO2@yeast microspheres increased rapidly with increased initial FWA-VBL concentration; the amount of FWA-VBL adsorbed decreased obviously with increased amount of TiO2@yeast microspheres. On the basis of single factor experiment, the effect of three parameters on batch adsorption of FWA-VBL by TiO2@yeast microspheres was evaluated using an optimal experimental design based on Box-Behnken Response Surface method. The factors included pH,initial dye concentration and adsorbent dosage. The results show that the effect relationship of each factor is pH>initial concentration>adsorbent dosage. The adsorption equilibrium data were best represented by the Langmuir isotherm model, and the maximum adsorption capacity of the sorbent was 167.50 mg/g at the temperature of 323.15 K. The adsorption kinetic was found to follow the pseudo-second-order kinetic model. Thermodynamic parameters indicate that the adsorption is a spontaneous and endothermic process.(3) FWA-VBL from aqueous solution was also investigated using fixed-bed adsorption column by TiO2@yeast microspheres. The effects of pH, bed height, inlet concentration and feed flow rate on the breakthrough characteristics of the adsorption system were determined. The results showed that the highest bed capacity of 223.80 mg/g was obtained under the condition of pH 2.0, 80 mg/L inlet dye concentration, 1.0 cm bed height and 5 m L/min flow rate. The adsorption data were fitted to three well-established fixed-bed adsorption models, namely, BDST model, Thomas model and Yoon-Nelson model. The TiO2@yeast microspheres have desired regeneration ability and could be reused for four times.In addition, on the basis of single factor experiment, the effect of four parameters on fixed bed adsorption of FWA-VBL by TiO2@yeast microspheres was evaluated using an optimal experimental design based on Box-Behnken Response Surface method. The factors included pH,initial dye concentration, bed depths and flow rate.The results show that the effect relationship of each factor is pH>initial concentration> bed depths>flow rate.(4) The special strawberry structure of TiO2@yeast microspheres has good regeneration properties. The TiO2 adhered to the surface of yeast can degrade dye molecules adsorbed to the yeast by ultraviolet radiation.Meanwhile, H2O2 can be used as oxidizing chemical to make a better effect of photo-catalytic TiO2, and thereby enhance the effect of regeneration TiO2@ yeast microspheres and recycling rate. |
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