二氧化钛光催化降解废水中污染物的研究进展

介绍了TiO2光催化氧化法降解废水中污染物的作用机理。根据近年来的研究成果,对TiO2纳米粉体和TiO2薄膜的研制方法进行了归纳。分别介绍了悬浮式光催化反应器和固定式光催化反应器,讨论了它们各自的优点和缺陷。     

Degradation of Atenolol in a Rectangular Staircase Photocatalytic Reactor with Immobilized ZnO

Atenolol (ATL) was removed with a rectangular staircase photocatalytic reactor (RSPR) using immobilized ZnO under solar irradiation. The effects of operational parameters such as flow rate, pH, and initial ATL concentration were examined. The highest degradation was obtained after 240 min photocatalytic reaction. The effects of different scavengers proved that the ATL degradation was mainly due to the direct oxidization with OH^? radicals, whereas, the h⁺ and O₂^?? radicals played a minor role in the degradation process. Five repetitive operations of RSPR allowed for reaching 77 ± 3 % degradation of ATL for each cycle. Kinetic data indicated that the photocatalytic kinetics followed the global matter balance model.     

改性TiO2固相光催化降解聚苯乙烯薄膜的制备及表征

采用聚合物接枝改性TiO2颗粒作为催化剂,制备了一种新型可光催化降解的纳米PS-g-TiO2复合薄膜,并在空气中紫外光照下进行了薄膜的光催化降解实验.利用失重、FTIR和SEM等分别对光照前后纯PS膜及复合薄膜进行分析表征.结果表明改性TiO2颗粒在聚合物中分散良好、催化活性较高,能有效地降解聚苯乙烯薄膜.复合薄膜经紫外光照396 h后,光降解失重率达到31.9%.     

The Usage of Non‐woven Fabric Material as Separation Media in Submerged Membrane Photocatalytic Reactor for Degradation of Organic Pollutants in Water

Abstract

Photodegradation tests with continuous mode were carried out in a photocatalytic reactor containing a submerged flat sheet non‐woven fabric membrane, which was able to retain the photocatalyst. The non‐woven fabric membrane was made of polypropylene with a pore size of 2 µm. In this study, three operational parameters were investigated: light intensity, feed concentration, and feed flow rate. Experimental results showed no significant variation of permeate flux and TMP (transmembrane pressure) during the experimental period. The SS (suspended solid) of the permeate was non‐detectable. These behaviors were due to the formation of a dynamic porous cake layer on the non‐woven fabric membrane surface in our experimental condition. We also found that it was important to control the operation parameter mentioned above as to exactly when we wanted to maintain the steady pollutant concentration in the permeate at very low value.     

BiVO4/MIL-100(Fe)复合材料光催化降解结晶紫

以NH_4VO_3、Bi(NO_3)_3·5H_2O、均苯三酸、Fe(NO_3)_3·9H_2O为主要原料,采用一锅水热法制备了BiVO_4/MIL-100(Fe)复合材料,用XRD、SEM、N_2吸附-脱附、UV-VisDRS及PL对复合材料的结构、形貌、比表面积及光学性能进行了表征。XRD显示具有较大比表面积的复合材料中BiVO_4为单斜相、四方相的混晶结构,其对可见光的吸收强度高于MIL-100(Fe),吸收光后产生的光生电子、空穴的复合率较低。可见光条件下,不同材料对结晶紫的光催化降解实验中,m(BiVO_4)∶m[MIL-100(Fe)]=1∶3配比的BiVO_4/3MIL-100(Fe)的光催化活性最佳。实验结果表明:光照射50 min,30 mg BiVO_4/3MIL-100(Fe)对30 mL质量浓度30 mg/L结晶紫的降解率为98.7%,主要光催化活性基团是h+。此外,日光下该材料对结晶紫、罗丹明B、亚甲基蓝也有较强的光降解能力。     

Fabrication and evaluation of one-component core/shell structured latex adhesives containing poly(styrene) cores and poly(acrylate) shells

A one-component, non-crosslinked, and ambient temperature-cured core/shell (CS) structured waterborne poly(styrene-acrylate) (PStA) latex adhesive was prepared by two-stage seeded emulsion polymerization. The first-stage polymers were non-polar styrene-based copolymers with T_gs ranging from 86 °C to 41 °C and the second-stage polymer was polar acrylate-based copolymer having a T_g of 8 °C. The effect of latex particle morphology and film microstructure on the CS structured PStA latex adhesive was examined by evaluating film thermal properties and mechanical performance. The results have shown that incorporation of soft shell polymers into hard core polymers can improve adhesive properties without compromising film-forming ability. Wood adhesive performances of latex adhesive were measured by shear strength and boiling water resistance of glued wood blocks. The utilization performances of the one-component CS structured PStA latex adhesive were found to largely depend on CS morphological character and the interfacial compatibility between various polymeric constituents, demonstrating that fabrication of CS latex particles provides a promising approach to realize high-performance latex adhesives.     

聚乳酸及其共聚物的体外降解方法

聚乳酸(PEA)是一类高分子聚酯,凡是能引起酯键断裂的因素都可以使聚乳酸发生降解。本文综述了聚乳酸(PEA)及其共聚物的化学降解、酶降解、超声波降解、辐射降解和微生物降解的体外降解方法及降解机理。     

Enhanced Solid‐Phase Photocatalytic Degradation Activity of a Poly(vinyl chloride)‐TiO2 Nanocomposite Film with Bismuth Oxyiodide

A new type of photodegradable poly(vinyl chloride)‐bismuth oxyiodide/TiO₂ (PVC‐BiOI/TiO₂) nanocomposite film was prepared by embedding a nano‐TiO₂ photocatalyst modified by BiOI into the commercial PVC plastic. The solid‐phase photocatalytic degradation behavior of the as‐prepared film was investigated in ambient air at room temperature under UV light irradiation, with the aid of UV‐Vis spectroscopy, weight loss monitoring, scanning electron microscopy, and FT‐IR spectroscopy. Compared to the PVC‐TiO₂ nanocomposite film, the PVC‐BiOI nanocomposite film and the pure PVC film, the PVC‐BiOI/TiO₂ nanocomposite film exhibited a higher photocatalytic degradation activity. The optimal mass ratio of BiOI to TiO₂ was found to be 0.75 %. The weight loss rate of the PVC‐BiOI/TiO₂ nanocomposite film reached 30.8 % after 336 h of irradiation, which is 1.5 times higher than that of the PVC‐TiO₂ nanocomposite film under identical conditions. The solid‐phase photocatalytic degradation mechanism of the nanocomposite films was briefly discussed.     

Degradation kinetics of poly (vinyl-pyrrolidone) under ultrasonic irradiation

Ultrasonicaton has proved to be a highly advantageous method for depolymerizing macromolecules because it reduces their molecular weight simply by splitting the most susceptible chemical bond without causing any changes in the chemical nature of the polymer. Solution of poly (vinyl-pyrrolidone) in chloroform with different concentrations and different molecular weights at a fined temperature were subjected to ultrasonic degradation. This study confirms the general assumption that the shear forces generated by the rapid motion of the solvent following cavitational collapse are responsible for the breakage of the chemical bonds within the polymer. A method of viscometry was used to study the degradation behavior and kinetic model was developed to estimate the degradation rate constant. The results were indicated that the polymers with height molecular mass degraded faster than the polymers laving low molecular mass thus the rate of ultrasonic degradation increased with increasing molecular weight. It was found that rate constant decreases as the concentration increases. The calculated rate constants correlated in terms of inverse concentration and relative viscosity of PVP solutions. This behavior in the rate of degradation was interpreted in terms of viscosity and concentration of polymer solution. The effect of polymer concentration can be interpreted in terms of the increase in viscosity with concentration, causing the molecules to become less mobile in solution and the velocity gradients around the collapsing bubbles to therefore become smaller and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased. The experimental results show that the viscosity of polymers decreased with ultrasonic irradiation time and approached a limiting value, below which no further degradation took place.     

氢基质生物膜反应器在水处理中的研究进展

介绍了氢基质生物膜反应器(MBfR)的工艺原理和特点,归纳了基于去除多种污染物、膜回收和微生物群落结构的MBfR国内外研究进展。指出了MBfR存在的膜污染、工艺成本、氢气利用率和膜材料成本等实际问题。认为未来应从MBfR的能源需求、有害物种控制、膜污染控制、多物种生物量控制、膜成本及工艺设计做进一步研究。如果这些研究得到进展,MBfR可能在下一代可持续处理系统中发挥关键作用。     

Sn(IV)-Porphyrin-Based Nanostructures Featuring Pd(II)-Mediated Supramolecular Arrays and Their Photocatalytic Degradation of Acid Orange 7 Dye

Two robust Sn(IV)-porphyrin-based supramolecular arrays (1 and 2) were synthesized via the reaction of trans-Pd(PhCN)₂Cl₂ with two precursor building blocks (SnP¹ and SnP²). The structural patterns in these architectures vary from 2D to 3D depending on the axial ligation of Sn(IV)-porphyrin units. A discrete 2D tetrameric supramolecule (1) was constructed by coordination of {(trans-dihydroxo)[5,10-bis(4-pyridyl)-15,20-bis(phenyl) porphyrinato]}tin(IV) (SnP¹) with trans-PdCl₂ units. In contrast, the coordination between the {(trans-diisonicotinato)[5,10-bis(4-pyridyl)-15,20-bis(phenyl)porphyrinato]}tin(IV) (SnP²) and trans-PdCl₂ units formed a divergent 3D array (2). Axial ligation of the Sn(IV)-porphyrin building blocks not only alters the supramolecular arrays but also significantly modifies the nanostructures, including porosity, surface area, stability, and morphology. These structural changes consequently affected the photocatalytic degradation efficiency under visible-light irradiation towards acid orange 7 (AO) dye in an aqueous solution. The degradation efficiency of the AO dye in the aqueous solution was observed to be between 86% to 91% within 90 min by these photocatalysts.     

Degradation and geometric isomerization of poly(N-propargylamides)

The stability of several poly(N-propargylamides) was investigated in solution and in solid state on the basis of molecular weight change with time, and further their thermal stability was investigated by TGA. When the stability of poly(N-propargylamides) with varying pendent groups was compared, polymers with pendent groups of moderate size showed the highest stability in solution. Too short and too bulky pendent groups were not favorable for the stability of polymers. When poly(N-propargylheptanamide) (poly(6)) was stored in THF as solution at −20 °C in the absence of oxygen in dark, its degradation rate was the lowest. The degradation rate of poly(6) depended on the solvents used, which may be related to different solubility of oxygen in these solvents. Polymers with high cis contents degraded faster than polymers with low cis contents did. Addition of TEMPO and DPPH into the poly(6)/THF solution more or less depressed the degradation of poly(6). The degradation of polymer main chain in solution was always accompanied by the decrease of cis content, i.e. geometric isomerization from cis- to trans-structure. When the polymers were stored in the solid state at −20 °C, the polymers having alkyl pendent groups with moderate length were more stable than those with bulky pendent groups. Geometric isomerization occurred along with degradation in the solid state as well.     

Influence of a hydrogen-bonding co-monomer on polymer diffusion in poly(butyl acrylate-co-methyl methacrylate) latex films

Small amounts of hydrogen-bonding comonomers such as N-(2-methacryloxyethyl)ethylene urea (MEEU) are often included in latex particle synthesis to promote adhesion of latex films to metals and old surfaces. Little is known about how these monomers affect the latex film formation process. Here we examine the influence of 1-7 wt.% MEEU on butyl acrylate-methyl methacrylate copolymer latex films using fluorescence resonance energy transfer (FRET) measurements, in conjunction with donor- and acceptor-labeled latex particles, to study the rates of polymer diffusion in these films. The presence of MEEU in the copolymer leads to small increases in the polymer glass transition temperature (Tg). It also tends to retard the rate of polymer diffusion. This effect, however, is very sensitive to the humidity of the surrounding atmosphere. It appears that moisture taken up in the film minimizes the influence of MEEU groups on the rate of polymer diffusion.     

On the Degradation and Stabilization of Poly(Methyl Methacrylate) in a Continuous Process

Thermally unstable polymers such as poly(methyl methacrylate) are degraded considerably during industrial processing. This degradation and its reduction to a minimum have been investigated in both lab and continuous pilot‐scale experiments. A three‐step degradation mechanism, starting at 180 °C, was proved by Thermogravimetrical Analysis (TGA) and a kinetic approach to describe it was derived. The knowledge of this degradation behavior was then applied to a pilot‐scale process with a production rate of 10 kg/h and the process yield loss during the devolatilization step was investigated. Using heat stabilizers, the overall process yield could be improved by 10 %, whereas the residual organic volatiles concentration (VOC) was drastically reduced to values below 1000 ppm. In order to preserve the molecular weight of the final product these stabilizers were added into the process, separately, at the end of the polymerization reaction but before the devolatilization step.     

Removal of oxytetracycline (OTC) in a synthetic pharmaceutical wastewater by sequential anaerobic multichamber bed reactor (AMCBR)/completely stirred tank reactor (CSTR) system: biodegradation and inhibition kinetics

BACKGROUND: The antibiotics in industrial and munipical wastewaters could not be removed effectively in conventional anaerobic and aerobic biological treatment plants. Few studies have been performed to investigate the biodegradation and inhibition kinetics of oxytetracycline (OTC) on methanogens and total volatile fatty acids (TVFA). RESULTS: A high rate anaerobic multichamber bed reactor (AMCBR) was effective in removing the molasses‐chemical oxygen demand (COD), and the OTC antibiotic with yields as high as 96% at an influent OTC loading rate of 133.33 gOTC m^?3 day^?1 at a hydraulic retention time (HRT) of 2.25 days. Increasing the OTC loading rates from 22.22 gOTC m^?3 day^?1 to 133.33 gOTC m^?3 day^?1 improved both hydrolysis and specific utilization of molasses‐COD. The inhibition constants of TVFA (K_I?TVFA?meth) and OTC (K_I?OTC?meth) on methanogens decreased at OTC loadings > 133.33 gOTC m^?3 day^?1. The direct effect of OTC loadings > 133.3 gOTC m^?3 day^?1 on acidogens and methanogens was evaluated using the Haldane inhibition kinetic. CONCLUSION: OTC antibiotic was effectively removed in a sequential AMCBR/completely stirred tank reactor (CSTR). The Haldane inhibition constant (K_ID) decreased significantly at high OTC loads indicating the increase in toxicity. Copyright © 2012 Society of Chemical Industry     

Compensation Effect of Benzene Hydrogenation on Pt(111) and Pt(100) Analyzed by the Selective Energy Transfer Model

Kinetic measurements at low temperatures (310–360 K) using gas chromatography (GC) for benzene hydrogenation on Pt(100) and Pt(111) single crystal surfaces have been carried out at Torr pressures. These kinetic measurements demonstrated a linear compensation effect for the production of cyclohexane. A detailed application of the model of selective energy transfer to the experimentally obtained results yields the vibrational frequency of the adsorbate leading to reaction. This frequency is attributed to ring distortion modes. The vibrational frequency of the heat bath, or catalyst, is ascribed to a Pt-H mode. An approximate heat of adsorption of the reacting molecule is also calculated from the model.     

Cr(VI)-乙酸复合体系中硫酸盐掺杂的含钛高炉渣光催化还原Cr(VI)

采用煅烧的硫酸盐掺杂的含钛高炉渣作光催化剂,研究了Cr(VI)-乙酸(AA)复合体系中Cr(VI)的光催化还原效率,考察了初始pH值、Cr(VI)初始浓度、AA/Cr(VI)体积比、协同效率因子、光催化剂使用寿命等因素的影响. 结果表明,增大AA/Cr(VI)比到0.2%,Cr(VI)的还原效率先增大到27.55%随后逐渐降低. 酸性条件下,Cr(VI)单一体系和Cr(VI)-AA复合体系中Cr(VI)的还原率和吸附率都明显提高;相同反应时间下(110 min),初始pH 1.5时,2种体系中Cr(VI)的还原效率分别为76.32%(单一体系)和100%(复合体系). 复合体系中协同效率因子始终大于0. 循环使用5次后催化剂对Cr(VI)的光催化还原率为92.2%. Cr(VI)在Cr(VI)-AA体系中的光催化还原遵循Langmuir-Hinshelwood动力学规律.     

Enrichment of DHA from Tuna Oil in a Packed Bed Reactor via Lipase-Catalyzed Esterification

A packed-bed reactor (length 6.5 cm; id 4.65 mm) has been used to enrich docosahexaenoic acid (DHA) via the lipase-catalyzed esterification of the fatty acid from tuna oil with ethanol. Lipozyme RM IM (from Rhizomucor miehei) was used for the esterification reaction because of its ability to discriminate between different fatty acids, and several reaction parameters, including the temperature, molar ratio of substrates, and water content were explored as a function of residence time. In this way, the optimum conditions for the enrichment process were determined to be a temperature of 20 °C, a molar ratio of 1:5 (i.e., fatty acid to ethanol), and a water content of 1.0 % (based on the total substrate weight). Under these conditions, a residence time of 90 min gave a DHA concentration of 70 wt% and a DHA recovery yield of 87 wt% in the residual fatty acid fraction.     

Degradation of Ba(DPM)2 during storage in a desiccator for extended periods

We have investigated the degradation mechanism of Ba(DPM)₂, which has been stored in a desiccator for extended periods using thermogravimetry, FTIR and mass spectroscopy TG analysis shows that the aged sample loses the initial weight significantly at relatively low temperatures, the rate of weight loss decreases above 380 °C, and large amounts of residue remain at 550 °C FTIR and mass spectroscopy show that Ba(DPM)₂ is easily attacked by CO₂ and H₂O in air, which results in the dissociation of chemical bonds between the Ba ion and the ligand at low temperatures This eventually enhances the oligomerization of Ba(DPM)₂ and the formation of carbonates that exhibit low volatility and unstable thermal properties