磷酸根和Nafion修饰TiO_2表面腐植酸调控的可见光催化降解苯酚性能(英文)

光催化水处理技术有望成为一种有效去除水中难降解有机污染物的方法.尽管人们已经研制了大量的新型光催化剂,但在环境应用中纳米TiO_2仍是最受欢迎的催化剂.由于光催化反应在表面发生,反应动力学主要取决于TiO_2的表面性质,因此,表面修饰是调控TiO_2光催化反应的重要手段,其中Nafion和磷酸根表面修饰TiO_2简单可行.Nafion修饰可以通过离子交换吸附富集阳离子底物提高光催化降解效率;而磷酸根修饰则可以增强对弱吸附底物的降解活性.另一方面,水中共存的天然有机物(NOM)例如腐植酸(HA)将抑制TiO_2光催化降解目标污染物的活性,同时又将通过光敏化诱导可见光催化性能.因此,研究如何调控NOM对光催化反应的影响将有助于光催化水处理技术的工程应用.本文以HA作为代表性的NOM,研究了磷酸根和Nafion两种不同修饰方法对HA敏化TiO_2性能的影响规律.可见光降解苯酚的实验结果表明,HA的敏化可以提高TiO_2可见光降解苯酚的效率.磷酸根修饰TiO_2抑制了HA的敏化作用,而Nafion修饰则增强了HA的敏化作用并提高可见光降解苯酚的活性.当HA浓度为20 mg/L时,Nafion修饰TiO_2降解10 mg/L苯酚的反应速率常数由(0.003±0.001)min^(-1)提高至(0.025±0.003)min^(-1).表面修饰引起的反应活性差异不能归因于HA的吸附容量的变化,因为吸附实验表明在光催化反应条件下,两种表面修饰的TiO_2对HA的吸附容量并无显著差异.添加不同的自由基捕获剂发现,HA敏化TiO_2及Nafion修饰TiO_2降解苯酚的主要活性物质为超氧自由基,而磷酸根修饰TiO_2的光催化反应中并没有超氧自由基.通过检测超氧自由基的电子自旋共振信号进一步证实了这一点.测试发现,光催化反应中Nafion修饰TiO_2产生的H_2O2增加,而磷酸根修饰的几乎不产生H_2O2,说明可能发生了四电子的氧还原反应.莫特-肖特基曲线(Mott–Schottky)的测试结果表明,Nafion修饰TiO_2的平带电位从-0.54 V负移到-0.85 V,多数载流子电子的密度提高了62%.电化学阻抗结果显示,Nafion修饰TiO_2具有较小的界面电子迁移阻抗.这些变化有利于提高电子迁移速率,抑制复合并增加超氧自由基的生成,从而提高光催化性能.因此对TiO_2进行恰当的表面修饰,将有助于强化HA的敏化作用,并提高可见光催化降解目标有机污染物的活性.

Physicochemical and Morphological Variation of Bamboo Cell Wall During Hydrothermal Pretreatment

Pretreatment is important for achieving high-value utilization of biomass.This study is conducted to evaluate the destruction of the Moso bamboo cell wall via hydrothermal pretreatment at different temperatures and pH values.Compositional and morphological analyses and subsequent enzymatic hydrolysis of the solid fractions indicate that the destruction of the cell wall,instead of the degradation or removal of hemicellulose and lignin,or the configuration transition of the cellulose crystal structure,is the most critical aspect for improving bioconversion efficiency.Although only an 8%-10%weight loss is incurred and similar crystalline indexes are achieved after mild hydrothermal treatments,the recovery of glucose is doubled,whereas the recovery of xylose from pretreated samples is approximately 35%.

The Effect of Lignification Process on the Bioconversion Efficiency in Moso Bamboo

Recalcitrance of lignocellulosic biomass is closely related to the presence of lignin in secondary cell walls,which has a negative effect on enzyme digestibility,biomass-to-biofuels conversion,and chemical pulping.The lignification process and structural heterogeneity of the cell wall for various parts of moso bamboo were investigated.There were slight differences among three different column parts of moso bamboo in terms of chemical compositions,including cellulose,hemicelluloses,and lignin.However,the detailed analysis of the fractionated lignin indicated that the acid-soluble lignin was first biosynthesized,and the largest molecular weight value was detected from the bottom part of the moso bamboo,as well as the highest syringyl-to-guaiacyl ratio.Although the main b-O-4 aryl ethers and resinol structures were clearly present in all lignin samples examined by NMR analysis,the relatively small lignin biomacromolecule in the top part of the moso bamboo lead to poor thermal stability.For the bioconversion process,no significant difference was found among all the moso bamboo samples,and the relatively higher hydrolysis efficiency was largely dependent on the low crystallinity of cellulose rather than the degree of lignin biosynthesis.

Field Application of Mulberry Straw Arch in Ecological Bank Revetment

With the growing level of awareness and increasing demand for environmental protection,timber pile revetments with significant ecological effects have experienced increasingly wide application in China.The current timber pile revetment system has two problems:continuous dense piles have high construction costs and require large timber consumptions,while the discrete pile-bamboo fence systems have poor retaining effects.Considering these problems,an original revetment structure form is proposed:a discrete pile-mulberry straw arch structure.To investigate the mechanical properties of the mulberry straw,some mechanical tests are conducted on mulberry straw and its arch structure.It is found that the average compressive strength of mulberry straw is 2.30 MPa,the bending strength is 20.08 MPa and the shear strength is 2.99 MPa;considering the structural characteristics of arches,mulberry straw arches have a high bending strength,which affords immense potential for their application in revetment structures.Furthermore,by doing field study of the discrete timber pile-mulberry straw arch structure for bank revetment,it is found that the arch height of the mulberry straw arch changes 1.4–1.6 cm after 489 d observation.The soil settlement before the straw arch is 0.13–0.18 cm and the settlement of the pile is 0.66–0.72 mm.Compared with bamboo fence structure,the cost of using mulberry straw arch structure as revetment material can save up to 27.07%.Therefore,the discrete timber pile-mulberry straw arch has a rational and stable structure that provides effective support for protecting the riverbank and the toe of gentle slopes and effectively prevents the collapse of bank slopes in the rear.The new revetment structure proposed in this paper has signifi-cant ecological and economic effects,is easy to construct and feasible for standard production,and consequently has great application potential.

Granulomatosis with polyangiitis presented as multiple cutaneous abscesses after hysterectomy

To the Editor:A 62-year-old woman presented to the dermatology department with a 5-month history of multiple painless cutaneous abscesses and ulcers[Figure 1A],occurring 1 month after a transvaginal hysterectomy due to uterine prolapse.Her general condition was good before and after the surgery,with no abnormal physical signs apart from metroptosis.She reported no fever,night sweat,cough,or abdominal pain,but 10 kg weight-loss.She has no history of diabetes,autoimmune diseases,or chronic infectious diseases.There was no similar illness in her family.

Clinical and histopathological predictors of rapid kidney function decline in patients with biopsy-proven diabetic kidney disease

To the Editor:Diabetic kidney disease(DKD)has become the leading cause of end-stage kidney disease(ESKD).According to the Kidney Disease Improving Global Outcomes(KDIGO)guidelines,rapid kidney function decline in DKD is defined as an estimated glomerular filtration rate(eGFR)slope≤−5 mL∙min^(−1)∙1.73 m^(−2)·year^(−1).The prognoses of patients who experience rapid eGFR decline are usually poor.In a multicenter retrospective study,230 of 377(61%)biopsy-proven DKD patients were rapid decliners.[1]It was reported that 32%and 42%of 195 type 2 diabetes(T2D)Pima Indians with normoalbuminuria and microalbuminuria,respectively,had a rapid eGFR decline,indicating that proteinuria alone has difficulty in fully predicting rapid kidney function decline in DKD patients with T2D.[2]Therefore,it is of interest to identify more useful clinicopathological predictors of a rapid kidney function decline in T2D patients.

德国资历框架内容体系的特点及启示

德国资历框架现已进入全面实施与评估阶段,其内容体系建设已较为完善。在德国资历框架建设的过程中逐渐在综合能力描述、职业资格与学历资格等值沟通、对现有教育体系影响边界等方面形成了自身特色。其框架中以综合能力为导向的学习成果描述、职业教育与普通教育等值不同类的论证、对现有教育领域内部资格体系的不可替代性,对德国资历框架确立建设基础、解决建设难点、设立建设边界等具有突出作用,也能为我国综合性资历框架构建提供有益的启示。