超顺磁性氧化石墨烯复合材料固定辣根过氧化物酶催化去除氯酚（英文）

采用超声辅助共沉淀法成功地将磁性Fe3O4纳米颗粒沉积在氧化石墨烯表面,利用透射电镜、磁滞回归曲线和X射线光电子能谱对材料进行了表征.将该材料作为载体固定辣根过氧化物酶,考察了固定化酶催化2-氯酚、4-氯酚和2,4-二氯酚降解反应,研究了溶液p H值、反应温度、反应时间、H2O2和氯酚浓度以及固定化酶用量对酚类物质去除率的影响.基于取代基数量和位置不同,去除率排序为2-氯酚4-氯酚2,4-二氯酚.另外,采用GC-MS研究了降解过程中的氧化产物.固定化酶的生化性质研究表明,固定化酶比游离酶具有更好的储存稳定性、pH稳定性和热稳定性.经过4次循环利用,固定化酶仍保留66%的活性,说明磁性纳米材料可以分离回收并重复利用,在污水处理领域具有应用前景.     

氮掺杂Bi2O3光催化剂可见光催化降解2,4-二氯酚

采用自制的Bi2O3及氮掺杂Bi2O3(N-Bi2O3)光催化剂,以卤钨灯为光源,在可见光下对2,4-二氯酚进行光催化降解.结果表明,N-Bi2O3较Bi2O3具有更高的可见光催化活性.当N-Bi2O3光催化剂投加量为2.0 g/L、2,4-二氯酚初始浓度为20 mg/L和pH =7时,光催化反应320 min,2,4-二氯酚的降解率最高可达到91.5％.2,4-二氯酚的光催化反应初活性与其浓度之间的关系符合Langmuir-Hinshelwood动力学速率模型.对降解过程中总有机碳及Cl-测试结果表明,N-Bi2O3光催化剂能较好地完成对2,4-二氯酚的深度矿化及脱氯.     

纳米Fe0降解2,4-二氯酚的影响因素及其机理

采用化学还原法制备了纳米Fe⁰, 并研究了不同条件下纳米Fe⁰对2,4-二氯酚(2,4-DCP)的降解情况, 探讨了纳米Fe⁰降解2,4-二氯酚的反应途径. 结果表明, 纳米Fe⁰对2,4-二氯酚的去除作用包括吸附、脱氯、开环三种机制. 其中脱氯作用是一种界面反应, 发生在氯酚分子被吸附到Fe原子表面之后. 2,4-二氯酚可以脱去一个氯原子生成2-氯酚或4-氯酚, 也可以脱去两个氯原子生成苯酚. 随着氯酚初始浓度的增大, 其相对去除率略有降低, 但绝对降解量有较大提高. 温度不仅影响脱氯速率, 而且影响氯酚的去除途径. 温度较高时脱氯作用占主导地位, 先脱氯后开环, 温度较低时吸附作用占主导地位, 较易发生先开环后脱氯的情况.     

磁性氧化石墨烯固定化氯过氧化物酶及其在奥酸性蓝45脱色中的应用

以氧化石墨烯和Fe_3O_4为原料制备磁性氧化石墨烯,采用吸附法将氯过氧化物酶固定在磁性氧化石墨烯上,考察了固定化体系缓冲溶液p H值、固定化时间及反应温度对固定效果的影响.以氯过氧化物酶催化氧化奥酸性蓝45染料脱色反应为模型反应,探讨了固定化氯过氧化物酶的操作稳定性.实验结果表明,p H=3.5,反应15 min、反应温度15℃为固定化氯过氧化物酶的最佳催化条件;采用共沉淀法制备载体,加入的NH_4Fe(SO_4)_2·12H_2O与氧化石墨烯(GO)质量比为10.7∶1时,得到的磁性氧化石墨烯(TMGO)的酶固载量大于二者质量比为5.35∶1时得到的磁性氧化石墨烯(FMGO),这可能与FMGO氧化石墨烯表面的Fe_3O_4含量不足有关;与游离酶相比,固定化氯过氧化物酶表现出更好的酸碱稳定性、H_2O_2稳定性、热稳定性和储存稳定性,在35~50℃,聚集或堆积的磁性氧化石墨烯(TMGO)片层打开,导致固定化酶活损失率明显小于游离酶.重复使用5次后,TMGO-氯过氧化物酶(CPO)的相对活性仍然保持在60%以上.     

介孔SiO2/Fe3O4中空磁性微球的漆酶固定化

以介孔SiO2/Fe3O4磁性中空微球作为载体,采用物理吸附法对漆酶进行固定化,考察了时间、温度和pH值对漆酶固定化效果的影响,并对固定漆酶的活性及稳定性进行了研究.结果表明,介孔SiO2/Fe3O4磁性中空微球吸附漆酶分子后,介孔材料的比表面积与孔体积均减小.在3 h时复合微球对漆酶的吸附达到平衡,复合微球中介孔SiO2对漆酶的有效固定量为689 mg/g,大大高于纯介孔材料MCM-41的漆酶固定量(319 mg/g).在pH=3～6的条件下,复合微球中固定漆酶仍保持70%以上的相对酶活.当温度不高于60℃时,固定漆酶的相对酶活仍保持65%以上.固定漆酶的pH稳定性和热稳定性都明显优于游离漆酶,固定漆酶的米氏常数为1.05 mmol/L,与游离漆酶相比,固定漆酶与底物的亲和力有所降低.当2,4-二氯苯酚的浓度为10 mg/L时,固定漆酶对其去除率在6 h时达到81.6%,表现出很好的催化活性.     

2,4-二氯苯酚的电化学氧化降解反应研究

采用循环伏安法和原位红外光谱技术研究了2,4-二氯苯酚在Pt电极上的电化学氧化降解反应,结合Fukui函数值预测了2,4-二氯苯酚在电化学氧化过程中的反应位点. 结果表明,Pt电极对2,4-二氯苯酚有良好的电催化活性,2,4-二氯苯酚在电极表面反应主要有3个途径：直接通过电化学反应脱去氯离子,生成苯酚;在·OH的进攻下,C—Cl键断裂,4位Cl较2位Cl先脱去,生成苯二酚,并可进一步氧化生成苯醌以及不饱和羧酸;在·OH的进攻下发生苯环开环反应,生成含氯不饱和羧酸. 在1700 mV左右,2,4-二氯苯酚可经电化学氧化生成CO₂.     

磁性固定化酶处理含酚废水的研究

研究了磁性壳聚糖微球(磁性CS-M)及壳聚糖微球(CS-M)固定化辣根过氧化物酶(HRP)对模拟含酚废水的催化效果,探讨了反应时间、酶活力、H2O2浓度及酚浓度对反应的影响。对均相与非均相酶处理酚效果进行比较,显示固定化酶处理含酚废水具有很大的优越性,且磁性酶的效果最佳。     

单宁酸修饰的后交联吸附树脂的制备及对氯酚的吸附性能

采用氯甲基化的低交联苯乙烯-二乙烯苯共聚物,通过交联反应和化学修饰反应制备了单宁酸修饰的后交联吸附树脂TAMR-1和TAMR-2,并对其进行了红外光谱分析、比表面及孔径分析和热重分析。通过静态吸附实验,比较了TAMR-1和TAMR-2对2-氯酚、4-氯酚和2,4-二氯苯酚的吸附去除率。通过小柱吸附-脱附实验,探讨了TAMR-1对3种氯酚的吸附性能。结果表明,与TAMR-2相比,TAMR-1的比表面积较高,氯残留量低,后交联反应与化学修饰反应更完全。TAMR-1和TAMR-2的外推起始分解温度均超过680K。TAMR-1树脂对3种氯酚(C0均为200mg/L)的吸附去除率均超过85%,明显高于TAMR-2树脂,且对2,4-二氯苯酚的吸附量最大。4%的NaOH溶液对吸附氯酚饱和后的TAMR-1树脂具有良好的再生效果。     

硼掺杂金刚石薄膜电极上二氯酚的电化学阻抗谱研究

以2,4-二氯酚(2,4-DCP)和2,6-二氯酚(2,6-DCP)为模型污染物,采用循环伏安法和电化学阻抗谱研究了硼掺杂金刚石(BDD)电极上2种氯酚的电催化氧化过程.结果表明,2,4-DCP和2,6-DCP的氧化电位分别为1.55和1.62 V.等效电路拟合结果表明,当极化电位由开路电位提高至1.5 V时,2种氯酚的电荷转移电阻均有明显下降,反应控制步骤为扩散控制步骤.与2,6-DCP相比,2,4-DCP在BDD电极上更容易发生直接电化学氧化.     

羧基功能化Fe3O4固定化酶反应器的构筑及性能研究

对固定化酶的载体进行功能化修饰,通过改善载体和酶的界面连接可使酶分子在载体表面形成高度有序的二维排列,从而提高酶的催化活性和操作稳定性.用柠檬酸修饰的Fe₃O₄磁性纳米粒子(CA-Fe₃O₄)易于磁性分离且表面富含羧基,可作为一种优良载体通过吸附法固定化氯过氧化物酶(CPO)构筑CPO@CA-Fe₃O₄酶反应器、共固定化CPO和葡萄糖氧化酶(GOx)构筑GOx&CPO@CA-Fe₃O₄级联酶反应器.将酶反应器应用于催化氧化结晶紫染料的脱色时,两种酶反应器均显示出良好的催化活性、对底物的亲和性与专一性、热稳定性,在实际水样中也有良好的应用效果.与CPO@CA-Fe₃O₄相比, GOx&CPO@CA-Fe₃O₄酶反应器因级联反应中H₂O₂的原位产生而表现出更优异的催化性能...     

Photocatalytic degradation of chlorophenols under direct solar radiation in the presence of ZnO catalyst

The photocatalytic degradation of chlorophenols was evaluated under direct solar radiation using commercial ZnO catalyst. Effects of several parameters such as a catalyst loading, pH of solution and initial concentration on the degradation process have been investigated. The photocatalytic degradation efficiency of chlorophenols at the optimum value of the parameters was compared under similar experimental conditions. The results of efficiency and mineralization showed the degradation of 2-chlorophenol and 2,4-dichlorophenol compound with the first order kinetic rate and the rate constant decreases as the initial concentration of the chlorophenols increase. However, the rate constant was strongly affected by type of chlorophenols compound present either 2-chlorophenol or 2,4-dichlorophenol. The highest removal of chlorophenols was obtained after 120 min and the final intermediate compounds of chlorophenols degradation are lower molecular weight compound consisting of acetic acid which was analyzed through the HPLC.     

青霉素G酰化酶在含环氧基团的顺磁性聚合物微球上的固定化（英文）

青霉素G酰化酶(PGA)是一种重要的工业生物催化剂,常用于以青霉素G为底物生产7-氨基去乙酰氧基头孢烷酸(7-ADCA)和6-氨基青霉烷酸(6-APA)等半合成β-内酰胺类抗生素.然而,PGA较差的稳定性和可重复使用性能限制了其在工业上的广泛应用.因此,将PGA固定在固体载体上是很有必要的,可以形成一种可重复使用的高性能的多相催化剂.用于生物酶固定化的良好载体应具备以下条件:(1)载体表面具有可用于与生物酶多点结合的高密度的官能团;(2)载体具有较大的比表面积以固定更多的生物酶.通常情况下,可以通过减小载体的粒径来增加其比表面积,然而,小粒径的载体很难从反应混合液中分离出来,造成固定化酶回收使用困难.为了将聚合物微球的优异固定化性能与磁性纳米粒子的独特顺磁性结合起来,我们制备了一种含环氧基团的顺磁性聚合物微球作为PGA的固定化载体.但由于Fe_3O_4纳米颗粒具有较高的表面能,在反相悬浮聚合反应过程中容易团聚成大颗粒,从而导致制备的顺磁性聚合物微球的磁体含量、表面形貌和粒径分布存在差异.此外,Fe_3O_4纳米颗粒与聚合反应单体之间的相容性不好,使得部分磁性颗粒不能很好地包埋于聚合物微球内部,影响固定化酶的活性和操作稳定性.本文以N,N′–亚甲基双丙烯酰胺为交联剂,以甲基丙烯酸缩水甘油酯和烯丙基缩水甘油醚为功能性单体,用反相悬浮聚合方法在SiO_2包覆的Fe_3O_4纳米颗粒表面成功制备出含环氧基团的顺磁性聚合物微球.用SEM,FT-IR,XRD,VSM和低温氮气吸附等手段对含环氧基团的顺磁性聚合物微球进行了表征.研究了SiO_2对Fe_3O_4纳米颗粒的包覆和Fe_3O_4/SiO_2纳米颗粒的数量对于固定化酶的初始活性和操作稳定性的影响.SiO_2在反相悬浮聚合过程中发挥重要作用,用SiO_2对Fe_3O_4纳米颗粒进行亲水性改性,有效改善了Fe_3O_4纳米颗粒与聚合反应单体的相容性,将其引入反相悬浮聚合体系中,可以制备得到球形度好、粒径分布均匀和超顺磁性的含环氧基团的顺磁性聚合物微球,其中当Fe_3O_4/SiO_2纳米颗粒的质量比为7.5%时制备的含环氧基团的顺磁性聚合物微球具有最好的PGA固定化性能.PGA通过其活性非必需侧链基团–氨基与顺磁性聚合物微球表面的环氧基团的共价结合来制备顺磁性固定化酶,该固定化PGA的初始活性为430 U/g(wet),在外加磁场的作用下容易回收使用,重复使用10次后可保留99%的初始活性,具有良好的热稳定性和酸碱稳定性,具有较好的工业应用前景.     

Laccase immobilized on mesoporous SiO<Subscript>2</Subscript> and its use for degradation of chlorophenol pesticides

In this paper, mesoporous silica with large specific surface area was used to immobilize laccase by the glutaraldehyde cross-linking method, and after screening and optimization experiments, the best enzyme immobilization process conditions were found (25°C, pH 5.4, 4% glutaraldehyde and 0.2 g/L laccase, treatment time 6 h). After that, the removal and degradation ratio of 2,4-dichlorophenol (abbreviated as DCP) under different conditions were also studied. After the degradation process was performed for 6 h at 30°C, pH 5.4, and DCP initial concentration of 50 mg/L in the presence of 0.1 g of immobilized laccase, the removal ratio and the degradation ratio were 42.28 and 15.93%, respectively. Compared with free laccase, the reusability of immobilized laccase is significantly improved.     

Spectrometric and 2D NMR Studies on the Complexation of Chlorophenols with Cyclodextrins

The formation and structure of inclusion complexes of - and-cyclodextrins with 2-chlorophenol (2CP), 3-chlorophenol (3CP),4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP), 2,6-dichlorophenol(26DCP) and 3,4-dichlorophenol (34DCP) have been studied by UV-VIS and¹H NMR spectroscopy. Both cyclodextrins were found to form 1:1inclusion complexes. Bindingconstants estimated from titration studies revealed that the stability of the complexes was highly dependent on the structure and polarity of the chlorophenol and on the cyclodextrin used. In general, weaker binding constants were observed for a given chlorophenol with -cyclodextrin than with-cyclodextrin. The weakest binding constants (K_{b < 200} M^-1) were obtained for the ortho-substituted chlorophenols (2CP and 26DCP) and the largest binding constants were obtained between para-chlorophenols (4CP, 24DCP and 34DCP) and-cyclodextrin. 2D-TROESY studies of chlorophenol-cyclodextrincomplexes in D₂O provided insight into the structure of the complexes.     

Co-aggregation of Laccase and Nature Egg White: a Simple Method to Prepare Stable and Recyclable Biocatalyst

Cross-linked enzyme aggregates (CLEAs) are a versatile and effective method for enzyme immobilization, which is exquisitely simple and amenable to rapid optimization. In this study, nature egg white, which is low cost, easily available, and nontoxic, was used as protein feeder to replace traditional protein feeder (bovine serum albumin, etc.) in the preparation of laccase CLEAs (CLEAs-egg). The effects of the various parameters—nature of the precipitant, temperature, glutaraldehyde concentration, and cross-linking time—on the activity recovery of the resulting CLEAs were studied. The laccase CLEAs-egg exhibited increased stability compared to the free and the laccase CLEAs without protein feeder. The thermal stability of CLEAs-egg was improved and showed 1.3- and 1.8-fold increase in activity at 40 and 60 °C after 5 h incubation, respectively. The stability of CLEAs-egg against denaturants (urea and GndHCl) and protease (trypsin) was also improved. Laccase CLEAs-egg was also demonstrated to be an active and stable biocatalyst in the removal of chlorophenol. After 30 h, 83.6 and 91.5 % of 4-chlorophenol and 2,4-dichlorophenol can be removed.     

Analysis of phenolic compounds catalyzed by immobilized horseradish peroxidase in silica glass

Horseradish peroxidases are entrapped into tetramethyl orthosilicate derived silicates by a mild sol–gel process. Compared with free enzymes in solution, silica immobilized Horseradish peroxidases are more robust, stable in a long-term and ease of recycle. Therefore, a phenolic compounds analysis method is established on the immobilized enzyme catalyzed oxidation reaction to produce intensely colored products for spectrophotometric analysis. The absorbance of colored product and analyte concentrations is linearly related. The similar methods also employ on analyzing 2-chlorophenol, 3-chlorophenol and 2,4-dichlorophenol. Furthermore, this method permits to reuse immobilized HRP to examine phenolic compounds. The thin silica film is used as an immobilization carrier. It has shorter pathlength for diffusion of analytes, which will lead to faster response times. Decomposition of quinone-imine colored product also has an effect on accuracy and precision of measurement. Decomposition rate constant is 5.549 × 10⁻⁴ min⁻¹. The interference substances have no obvious effect on the analytic results, except for formaldehyde and Pb²⁺. The proposed method can examine a real sample in waste water.     

Photodegradation of chlorophenolic compounds using zinc oxide as photocatalyst: experimental and theoretical studies

Zinc oxide nanoparticles were synthesized via the sol?Cgel method. The structures of the obtained nanoparticles were investigated by X-ray diffraction. The photocatalytic degradation of chlorophenolic compounds, namely 2-chlorophenol (CP), 2,4-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP), was carried out using ZnO nanoparticles under solar intensity of 20?C26?W?m^?2. The photocatalytic degradation efficiency of TCP?<?DCP?<?CP was found. The adsorption energies of the chlorophenolic compounds with ZnO catalyst were calculated from quantum chemical molecular dynamic model and found to increase in the order of TCP?<?DCP?<?CP.     

Immobilization of Horseradish Peroxidase on Nonwoven Polyester Fabric Coated with Chitosan

The immobilization of horseradish peroxidase (HRP) on composite membrane has been investigated. This membrane was prepared by coating nonwoven polyester fabric with chitosan glutamate in the presence of glutraldehyde as a crosslinking agent. The physico-chemical properties of soluble and immobilized HRP were evaluated. The soluble HRP lost 90% of its activity after 4 weeks of storage at 4°C, whereas the immobilized enzyme retained 85% of its original activity at the same time. A reusability study of immobilized HRP showed that the enzyme retained 54% of its activity after 10 cycles of reuse. Soluble and immobilized HRP showed the same pH optima at pH 5.5. The immobilized enzyme had significant stability at different pH values, where it had maximum stability at pH 3.0 and 6.0. The kinetic properties indicated that the immobilized enzyme had more affinity toward substrates than soluble enzyme. The soluble and immobilized enzymes had temperature optima at 30 and 40°C and were stable up to 40 and 50°C, respectively. The stability of HRP against metal ion inactivation was improved after immobilization. Immobilized HRP exhibited high resistance to proteolysis by trypsin. The immobilized HRP was more resistant to inactivation induced by urea, Triton X-100, and organic solvents compared to its soluble counterpart. The immobilized HRP showed very high yield of immobilization and markedly high stabilization against several forms of denaturants that offer potential for several applications.