Adsorption of BiOBr microspheres to rhodamine B and its influence on photocatalytic reaction.

Adsorption and its influence are often neglected during photocatalytic degradation of organic pollutants. To call attention to these issues, a novel bismuth oxybromide (BiOBr) microsphere with hierarchical flower-like structure was fabricated through a facile hydrothermal process using polyvinyl pyrrolidone (PVP) as additive in this work, and then the adsorption of the BiOBr microspheres to RhB and its influence on the photocatalytic degradation of RhB were investigated in detail. Experimental results show that the BiOBr microspheres have a very strong adsorption capacity to RhB. The adsorption behavior follows the Langmuir model and the quasi second order kinetic equation. Tests of the photocatalytic degradation of RhB under visible irradiation verify that the adsorption of the BiOBr microspheres to RhB greatly boosts the degradation of RhB due to the "enriching effect", and a complete degradation of 20 mg L-1 RhB only requires 37 min.

Preparation and Characterization of Temperature/pH Dual-Responsive Gel Spheres for Immobilizing Nitro Bacteria.

The temperature/pH dual-responsive gel spheres were prepared by orthogonal experiments and response surface methodology, and finally, the optimal synthesis conditions were obtained by a composite score, including swelling, mechanical properties, mass transfer properties, and so forth. The results showed that a sodium alginate concentration of 3% (w/v), CaCl2 concentration of 2% (w/v), gelling time of 40 h, drop height of 14 cm, NaCl concentration of 0.6% (w/v), N-isopropylacrylamide concentration of 0.03% (w/v), and acrylic acid concentration of 4.06% (w/v) were optimal synthesis conditions. The environmental change tolerance experiments showed that the nitrogen removal of the dual-response nitrifying gel spheres was better than the domesticated sludge at low temperatures (4 °C) and in alkaline (pH 9 and 10) conditions. The as-obtained gel spheres can respond intelligently to the changes in ambient temperature and pH. It is hoped that this study will provide technical parameters for the development and application of microbial immobilization carriers.