Juanjuan Wan,Lijuan Zhang,Bo Yang,Boyu Jia,Jiakuan Yang,Xintai Su
Enzymes have important advantages in sludge dewatering , but their catalytic performance is limited by their poor activity and stability. To address this issue, we develop a series of immobilized enzymes (immobilized acid protease, IE 1; immobilized pectinase, IE 2; immobilized laccase, IE 3) prepared by the electrostatic interaction between the Fe 3 O 4 @SiO 2 -NH 2 as immobilized carrier and the free enzyme, and used for sludge dewatering. As-obtained immobilized enzymes endowed high efficiency and stable sludge dewatering performance in a wide pH range, and had the best dewatering performance when the pH was 5. Specifically, the specific resistance filtration (SRF) performance of the immobilized enzyme at pH 5 was better than that of the control group, and the order was FE 3, 3.84 × 10 13 m kg −1 > FE 1, 2.52 × 10 13 m kg −1 > CL 1, 2.16 × 10 13 m kg −1 > CL 2, 1.34 × 10 13 m kg −1 > FE 2, 2.06 × 10 13 m kg −1 > IE 2, 0.89 × 10 13 m kg −1 > IE 1, 0.82 × 10 13 m kg −1 > IE 3, 0.73 × 10 13 m kg −1 . Such improvement is attributed to two respects: Firstly, the immobilized enzyme has good activity, stability, and abundant functional groups on the surface, which is conducive to the attachment and continuous decomposition of organic matter. Secondly, the solid immobilized carrier can construct the skeleton structure in situ and effectively promote the release of water in sludge. This study provides a feasible way for the practical application of biological enzyme in sludge dewatering.
Kai Zhu,Zhuting Li,Fang Cheng,Chen Wu,Dong Cai,Qiuyu Zhang,Hepeng Zhang
Rapid self-healing of micro-configurations is an effective strategy to enhance the durability of superhydrophobic surfaces, however, this property is challenging to achieve. Here, a durable superhydrophobic coating with a precisely targeted self-healing ability to repair its’ dual structure was developed by spray-coating a polyimine film with a mixture of novel fluorinated epoxy resin and Fe 3 O 4 @SiO 2 –NH 2 nanoparticles . The superhydrophobic surface can heal both the broken morphology and wettability through a short irradiation process on account of its local photothermal conversion ability and dynamic imine bond, and can maintain the static water contact angle at a value higher than 159° even after six damage/healing cycles. Furthermore, superhydrophobic coatings can be controllably degraded in three ways. Additionally, because of the robust epoxy resin protection, the surface can withstand sixteen times the dynamic impact and still maintain a WCA greater than 150°. This preparation strategy may aid the fabrication of durable superhydrophobic surfaces for various practical applications.
Jin Xu,Xuejia Shi,Xiaomeng Zhang,Zhenzhong Wang,Wei Xiao,Linguo Zhao
To efficiently recycle GH78 thermostable rhamnosidase (TpeRha) and easily separate it from the reaction mixture and furtherly improve the enzyme properties, the magnetic particle Fe 3 O 4 -SiO 2 -NH 2 -Cellu-ZIF8 (FSNcZ8) was prepared by modifying Fe 3 O 4 -NH 2 with tetraethyl silicate (TEOS), microcrystalline cellulose and zinc nitrate hexahydrate. FSNcZ8 displayed better magnetic stability and higher-temperature stability than unmodified Fe 3 O 4 -NH 2 (FN), and it was used to adsorb and immobilize TpeRha from Thermotoga petrophilea 13995. As for properties, FSNcZ8-TpeRha showed optimal reaction temperature and pH of 90°C and 5.0, while its highest activity approached 714 U/g. In addition, FSNcZ8-TpeRha had better higher-temperature stability than FN. After incubation at 80°C for 3 h, the residual enzyme activities of FSNcZ8-TpeRha, FN-TpeRha and free enzyme were 93.5%, 63.32%, and 62.77%, respectively. The organic solvent tolerance and the monosaccharides tolerance of FSNcZ8-TpeRha, compared with free TpeRha, were greatly improved. Using naringin (1 mmol/l) as the substrate, the optimal conversion conditions were as follows: FSNcZ8-TpeRha concentration was 6 U/ml; induction temperature was 80°C; the pH was 5.5; induction time was 30 min, and the yield of products was the same as free enzyme. After repeating the reaction 10 times, the conversion of naringin remained above 80%, showing great improvement of the catalytic efficiency and repeated utilization of the immobilized α-L-rhamnosidase.
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