Enzymatic degradation of thermoresponsive poly(N‐isopropylacrylamide) grafted to carboxymethylcellulose copolymers

The enzymatic degradation of poly(N‐isopropyl acrylamide) (PNIPAM) grafted to carboxymethylcellulose (CMC) copolymers with a cellulasic preparation (Trichoderma viride) was studied. The enzymatic activity of the cellulasic preparation against CMC and the grafted copolymers was determined by the Petterson–Porath method, while their reduced viscosity variation in the presence of the same preparation was also followed. It has been shown that the enzymatic degradation behavior depends on the copolymer composition and the reaction temperature. Reducing sugars analysis showed that the experimental values for the grafted copolymers were higher than the calculated ones. At 50°C, the enzymatic reaction is completed in about 20 min for the copolymers, whereas for CMC it takes more than 40 min. It can be concluded that their enzymatic degradation is facilitated by the presence of the PNIPAM grafts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1383–1386, 2003     

Fe掺杂A-TiO_2在溴甲酚绿中的可见光催化活性及动力学

以FeCl_3·6H_2O为Fe源,采用水热法制备了Fe掺杂锐钛型TiO_2(A-Ti O2)光催化剂。以溴甲酚绿为降解对象,考察溴甲酚绿的初始浓度、催化剂用量、掺Fe量等因素对自制催化剂可见光催化降解反应的动力学方程的影响。结果表明:在40 W白炽灯照射下,当溴甲酚绿初始浓度为10 mg/L(pH=7)、催化剂的用量为0.6 g/L、掺Fe量为4%(摩尔分数)、室温下反应时间为3 h时,溴甲酚绿的降解率最大为76.05%。溴甲酚绿光催化降解曲线符合一级反应动力学方程,于上述最佳条件下其表观反应速率常数k达到最大值,为0.389 7 h-1。     

Zr掺杂g-C3N4光催化降解有机污染物

以盐酸胍为前驱体，硝酸锆为锆源，通过热聚合法制备了Zr掺杂的Zr/g-C3N4光催化剂。运用XRD、SEM、UV-Vis DRS、PL、XPS、BET等手段对催化剂的结构、形貌、光学性能进行了表征分析。结果表明：Zr掺杂改性的Zr/g-C3N4光催化剂拓宽了可见光的吸收，增大了比表面积，且降低了光生电子-空穴的复合率，具有较好的光催化活性。可见光照射下，在60 min内，5Zr/g-C3N4对罗丹明B（RhB）的光催化降解率达99.29%，光催化降解过程符合一级动力学方程，其速率常数k= 0.08647 min-1，是纯g-C3N4的8.3倍。捕获剂实验发现降解RhB的主要活性物种为超氧自由基，并推测了可能的反应机理。     

纳米TiO2光催化降解有机物的机理及其影响因素的研究

对纳米TiO2光催化降解水中有机物的机理进行了研究，并对溴苯酚降解为目标反应，系统分析了紫外光强度、TiO2浓度、温度、溶液的pH值以及杂质等对光催化降解为溴苯酚程度的影响。优化这些因素可以提高纳米TiO2光催化降解率。     

难降解有机废水的高级氧化技术

介绍了处理难降解有机废水的湿式(催化)氧化、超临界水(催化)氧化、光化学(催化)氧化、化学(催化)氧化、固定化细胞及基因工程等高级氧化处理技术的反应机理、特点及应用,这类处理技术应用于一般生物处理难以奏效的有机工业废水处理。     

Thermooxidative degradation of natural rubber/clay composite

The clay is treated with a reducing agent and an acid so as to obtain a clay containing various metal components with a variable‐valence state. Then, the clay is coprecipitated with natural rubber (NR) latex to prepare a vulcanized NR/clay composite. The degradation process of the NR/clay composite under hot air condition was studied dynamically by using a Fourier transform infrared spectrometer attaching an in situ sample cell and was also investigated using the TGA method. The test result obtained from the infrared spectrometry indicated that under low decomposition temperature, the decomposition products of the test samples mainly are ethylene, low molecular olefinic hydrocarbon, and carbonyl compounds. As the decomposition temperature rises, the low molecular olefinic hydrocarbon content decreases, the olefine with longer chain is formed, and a lot of alkane decomposition products are formed at the same time. When the content of the metal components with a variable‐valence state in clay such as Cu, Mn, Co, and Fe increases, the oxidation products containing the carbonyl group, the olefinic hydrocarbon, and CO₂ in the decomposition product of the test sample also increase. The TGA result clearly shows a shoulder peak that appears by the side of the main peak on the DTG curve of NR/clay composite. With the increase in the content of metal components with variable‐valence state in clay, the initial degradation temperature of the test sample (T₀), the degradation peak temperature (T_p1), and the final degradation temperature (T_f1) in first‐stage reaction, as well as the degradation peak temperature (T_p2) and the last final degradation temperature (T_f) in second‐stage reaction of all the test samples more or less shift to the direction of low temperature; besides, the activation energy (E) of the reaction of the test samples more or less decreases. This means that the metal components with variable‐valence state promote the oxidative degradation of the clay–rubber masterbatch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3809–3815, 2006     

Sequence distribution and thermal properties of poly(butylene naphthalate terephthalate)

Poly(butylene naphthalate terephthalate) (PBNT) copolyesters were synthesized from bis(4-hydroxybutyl) terephthalate (BHBT) and bis(4-hydroxybutyl) naphthalate (BHBN) as starting materials. BHBT and BHBN were either homopolymerized or copolymerized at 260∼270 °C in the presence of titanium tetrabutoxide (TBT) as a catalyst to provide PBNT with various compositions. The copolyesters were characterized using inherent viscosity, X-ray, d.s.c., t.g.a. and ¹H NMR. The composition and sequence distribution of the copolyesters was determined from ¹H NMR spectra. The copolyesters exhibited a degree of randomness of about 1, indicating that the reactivity of BHBT and BHBN was almost the same. X-ray and d.s.c. showed PBNT copolyesters to be crystalline polymers. T.g.a. kinetics showed PBNT copolyesters to exhibit higher degradation activation energy, that is, better thermal stability, than PBTs.     

Photocatalytic degradation rate of oxalic acid on the semiconductive layer of n-TiO2 particles in the batch mode plate reactor Part I: Mass transfer limits

Organic compounds dissolved in water can be decomposed on a layer of n-TiO2 particles irradiated by u.v. light, which generates holes and electrons in the TiO2 material. Dissolved oxygen was used as electron scavenger and holes reacted with water to give OH radicals. The rate of degradation of the dissolved organic compounds by OH radicals is limited by the transfer of either oxygen or of theorganic compounds to the surface of n-TiO2 particles. The consequence of these limits is that, in the batch mode reactor with recirculation of the liquid, the dependence of the concentration of an organic compound on time has either a linear or an exponential form. Experiments with decomposition of oxalic acid in aqueous solutions using a plate reactor (60 cm × 120 cm) confirmed the analysis. Equations for evaluation of the mass transfer coefficient of the dissolved species to the surface of the plate reactor with a moving liquid fil m were developed for the case of the thickness of the Nernst diffusion layer being thinner than the thickness of the liquid. The experimentally obtained decomposition rate of oxalic acid was about 60 to 80% of the theoretical decomposition rate limited by oxygen flux through the film of a moving liquid. The present theory neglects the diffusion of oxygen into the porous layer of n-TiO2.     

高效优势降解菌处理樟脑废水

针对樟脑废水,从活性污泥中筛选出降解樟脑废水的高效优势菌,通过分离纯化,优选出3株适应能力强、生长旺盛的菌株,分别为ZH-1、ZH-2、TZH-2。经初步鉴定分别为动胶菌属、假单胞菌属、短杆菌属。试验测定了樟脑混合菌最佳生长条件的优化组合为:葡萄糖质量浓度20 g.L-1,温度30℃,pH值为7,转速为125 r.m in-1,培养时间55 h。并测定了单株菌和混合菌对樟脑废水的降解效果,结果表明混合菌的降解效果最为明显,降解率为75.23%。     

半导体光催化氧化在有机废水处理中的应用与研究进展

简要介绍了半导体光催化氧化降解有机物的作用机理,重点阐述半导体光催化氧化在处理有机废水中的应用,并就该技术之不足对其应用前景和发展方向作了展望。