Degradation kinetics and mechanisms of phenolin photo－Fenton process

Phenol degradation in photochemically enhanced Fenton process was investigated in this work. UV-VIS spectra of phenol degradation showed the difference between photo-Fenton process and UV/H2O2, which is a typical hydroxyl radical process. A possible pathway diagram for phenol degradation in photo-Fenton process was proposed, and a mathematical model for chemical oxygen demand (COD) removal was developed. Operating parameters such as dosage of H2O2 and ferrous ions, pH, suitable carrier gas were found to impact the removal of COD significantly. The results and analysis of kinetic parameters calculated from the kinetic model showed that complex degradation of phenol was the main pathway for removal of COD: while hydroxyl radicals acted weakly in the photo-Fenton degradation of phenol.     

Morphological and mineralogical characterizations of oolitic iron ore in the Exi region, China

The morphological and mineralogical characterizations of a Chinese oolitic iron ore (Exi deposit) were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy in this work. It is shown that the Exi ore is mainly composed of hematite, quartz, apatite, and chlorite. The hematite is present as the oolitic layers and in the spaces between the aggregated ooids; quartz exists as granular particles in the spaces and as nucleuses in ooids; the harmful mineral, apatite, is associated with hematite as the oolitic layers, fine dissemination, granular particles in the spaces, and nucleuses in ooids. From the viewpoint of mineral beneficiation, it is hard to separate apatite and chlorite but easy to separate quartz from hematite in the Exi iron ore in recovering the iron values.     

A NEW PROCESS OF COMBINATION OF INORGANIC PARTICLES WITH CELLULOSIC FABRICS

Instead of finishing the fabrics with inorganic particles by a binder, in this study the fine aluminium oxide powder were added during the polymerization system of a monomer with functional hydroxyl groups HPMA. The hot alkaline testing showed that the Al_2O_3 particles had reacted with the polymer latex. The absorbability and wash durability of the fabric treated with such a latex with Al_2O_3 were measured.     

Catalytic oxidation of phenol in wastewater-A new application of the amorphous Fe78Si9B13 alloy

The amorphous Fe78Si9B13 alloy was used as a heterogeneous Fenton catalyst in the process of phenol degradation.The influences of main operating parameters such as reaction temperature,catalyst amount,hydrogen peroxide dosage and initial pH of solution on phenol degradation rate were investigated.The maximum mineralization of phenol was achieved at 60°C,6 g/L Fe78Si9B13, 0.31 mol/L hydrogen peroxide,with an initial pH of 2.5.More than 99%of phenol was completely removed under the optimum conditions within 10 min for a solution containing 1000 mg/L of phenol.Batch experiments for solutions containing phenol con- centrations ranging from 50 to 2000 mg/L were investigated under the above conditions and the same excellent degradation rate was obtained.The Fe78Si9B13 showed better catalytic activity than iron powder and Fe 2+ .Addition of n-butannol(hydroxyl radical scavenger)decreased the degradation rate of phenol,which demonstrates that hydroxyl radicals were mainly responsible for the removal of phenol.We demonstrated that phenol may be degraded by hydroxyl radicals decomposed by hydrogen peroxide on the surface of Fe78Si9B13 and illustrated the reaction mechanism for this process.This amorphous alloy exhibited high stability in recycling experiments and showed excellent reuse performance even after continuous operations of 8 cycles.     

Microstructure simulation of rapidly solidified ASP30 high-speed steel particles by gas atomization

In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element (CAFE) model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions (UDFs) to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also investigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy (SEM). The experimental results showed that four major types of microstructures were formed: dendritic, equiaxed, mixed, and multi-droplet microstructures. The simulated results and the available experimental data are in good agreement.     

Pulmonary toxicity induced by three forms of titanium dioxide nanoparticles via intra-tracheal instillation in rats

Titanium dioxide (TiO2) nanoparticles are in wide commercial use worldwide. To evaluate if acute pulmonary toxicity can be induced by nano-TiO2 particles, rats were intra-tracheally instilled with 0.5, 5, or 50 mg/kg of 5, 21, and 50 nm TiO2 primary particles. Toxic effects were determined with the coefficients of lung tissues to body weight, histopathology, biochemical parameters of blood, activity of lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and acid phosphatase (ACP) in tissues, and the phagocytotic ability of alveolar macrophages (AMs). All the indicators were observed in sacrificed rats one week post-exposure. There was a significant difference of coefficients of pulmonary tissues between the high-dose group and the low- or moderate-dose groups with an exposure of 5 nm TiO2. At the same time, 5 nm TiO2 primary particles increased the activity of LDH and ALP when exposure dose was >5 mg/kg. A significant difference in LDH and ALP activity was observed between the 50 mg/kg group and 0.5 or 5 mg/kg group with exposure of 5 nm TiO2. Lung tissues showed increased ALP activity only if treated with 5 and 50 mg/kg of 21 nm TiO2 particles. There was no significant difference in LDH and ALP activity in the 50 nm TiO2 group and control group. Histopathologic examination of lung tissues indicated that the pulmonary response to exposure to TiO2 particles in rats manifested as dosedependent inflammatory lesions, which mainly consisted of infiltration of inflammatory cells and interstitial thickening. Analysis of uptake of neutral red dye showed that 50 nm TiO2 particles significantly increased phagocytotic ability of AMs compared with controls (P < 0.05), whereas exposure with 5 nm TiO2 reduced the phagocytotic ability of AMs when the exposure dose was 50 mg/kg. These results suggest that particle size and exposure dose may have important roles in pulmonary toxicity. The toxic effect of TiO2 nanoparticles in lung tissue exhibited a dose–response relationship. After exposure with TiO2 particles of >5.0 mg/kg, 5 and 21 nm TiO2 particles induced standing pulmonary lesions; and 5 nm TiO2 particles may suppress the phagocytotic ability of AMs if exposure dose was ≥50 mg/kg. Pulmonary toxicity caused by 5 nm TiO2 particles was more severe than that caused by 21 and 50 nm TiO2 particles.     

Superior machinability of steel enhanced with BN and MnS particles

The strategy that replacing part of MnS with BN was proposed in order to decrease the sulfur content in sulfur based free-cutting steel. The effects of BN and MnS inclusions on the microstructure and machinability of the steel were systematically investigated. The results show that most of the BN and MnS inclusions exist individually in the steel and only a small amount of them are in a composite state forming either isolated particles or clusters of particles. In the case of multi-phased steel, the theoretical calculation predicts that the volume of large BN particles should be 0.7 times of the volume of large MnS particles. The machinability of this type of BN and MnS alloy steel over a wide range of cutting speeds ranging from a low speed appropriate for drilling to a high speed appropriate for turning is confirmed as being equal to or superior to that of an MnS reference steel, even though the sulfur content in the composite steel is only half that of the MnS steel. The aptitude for cutting effect of 240 ppm nitrogen and 115 ppm boron in the composite steel is demonstrated to be equivalent or even better than 1000 ppm sulfur in MnS free-cutting steel.     

Manganese (Ⅲ) Acetate:A Versatile Reagent in Organic Chemistry

1 Results Free radical reactions have become increasingly important,as well as a very attractive tool,in organic synthesis within the last two decades,due to their powerful,selective,specific,and mild reaction abilities.Mn(OAc)3 mediated oxidative free radical reactions have been extensively developed in the last twenty years[1,6].Numerous regio-,chemo-,and stereoselective synthetic methods have been developed in both inter-and intramolecular reactions,and have detailed the progress of Mn(OAc)3 mediated oxidative free radical reactions. The selective oxidation of enones led to α′-acetoxy-enones by Mn(OAc)3 oxidation.In general,Mn(OAc)3 oxidations are characterized by higher α′-regioselectivity and chemical yields,and milder reaction conditions,in turn tolerating many sensitive functional groups.The use of Mn(OAc)3 in combination with other carboxylic acids or manganese(Ⅱ) carboxylates extends this methodology to the preparation of a variety of α′-acyloxyenones that are otherwise inaccessible in a one-step procedure.We developed a general method for the synthesis of biaryls starting from arylhydrazines and aromatic solvents in the presence of Mn(OAc)3.We showed for the first time that Mn(OAc)3 is a versatile reagent for the generation of aryl radicals from arylhydrazines.In a subsequent work,we extended this method for the synthesis of heterobiaryls,which was able to be achieved in thepresence of heteroaromatic compounds such as furan and thiophene. Another biaryl coupling reaction starting with arylboronic acids,mediated by Mn(OAc)3,was developed.The treatment of arylboronic acids with Mn(OAc)3 in benzene at reflux temperature afforded the corresponding biphenyl in high yields[7].     

Effect and mechanism of siderite on reverse flotation of hematite

The effects of siderite on reverse flotation of hematite were investigated using micro flotation, adsorption tests, and Fourier transform infrared spectroscopy. The flotation results show that interactions between siderite and quartz are the main reasons that siderite significantly influences the floatability. The interactions are attributed to dissolved siderite species and fine siderite particles. The interaction due to the dissolved species is, however, dominant. Derjaguin-Landau-Verwey-Overbeek (DLVO) theoretical calculations reveal that adhesion on quartz increases when the siderite particle size decreases and that fine particles partly influence quartz floatability. Chemical solution calculations indicate that the dissolved species of siderite might convert the surface of active quartz to CaCO₃ precipitates that can be depressed by starch. The theoretical calculations are in good agreement with the results of adsorption tests and FTIR spectroscopy and explain the reasons why siderite significantly influences reverse flotation of hematite.     

Preparation and cellular uptake of PLGA particles loaded with lamivudine

Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles loaded with lamivudine and coated with bovine serum albumin (BSA) were prepared via a double emulsion method. The influences of experiments parameters such as volume of inner aqueous phase, concentration of organic phase and ultrasonication time on the particle size and drug entrapment efficiency were investigated, obtaining PLGA particles with a diameter of ~260 nm and drug entrapment efficiency of ~35%. The particles were observed by scanning electron microscopy and transmittance electron microscopy, showing a core-shell structure. BCA assay found that 58 mg BSA was present on/in 1 g LPB particles. The loaded lamivudine showed a burst release at beginning and sustained release until 24 h in physiological conditions. Low pH could accelerate the release of lamivudine from PLGA particles, making the PLGA particles potential intelligent intracellular drug carriers. The PLGA particles were readily internalized into the human liver cells within a short time and increased gradually with the prolongation of incubation time regardless of the loading of lamivudine. The particles either resided within lysosomes or transferred to cytoplasm, but could not enter into the cell nucleus. The cell viability was not significantly influenced in the presence of the particles regardless of lamivudine encapsulation, suggesting that this kind of particles may be a good candidate for the intracellular anti-hepatitis B drug delivery.     

一种新的羟自由基生成方法及其在亚甲基蓝降解中的应用

对苯二甲酸是一种羟自由基捕获剂,它与羟自由基作用后生成有荧光的羟基对苯二甲酸,通过测定超声前后对苯二甲酸荧光强度的变化间接测定超声所产生的羟自由基的量.对时间、功率、pH等因素进行初步的研究,考察它们对超声产生羟基自由基的影响,发现超声时间越长、超声功率越大,产生的羟自由基的量越多,在超声时间为10min、超声功率为100W时250mL对苯二甲酸溶液中产生羟自由基浓度31.14μmol/L,且羟自由基产生量与时间呈现出一定的量化关系;此外,pH值对羟自由基的产生量影响不大.本方法可检测到超声产生的羟自由基最短时间为2min,最低检出限达到0.063μmol/L,稳定性好、操作简便,测定快速.采用超声处理亚甲基蓝溶液,亚甲基蓝逐渐被降解,进一步证实羟自由基的产生,为超声降解提供理论依据.     

自由基与肺癌发病机制

肺癌是严重影响人类健康的疾病,其发病机制目前尚未阐明.自由基医学是近年来兴起的一门交叉学科,本文对自由基在吸烟、职业烟尘微粒、金属离子、石英、石棉等理化因素致肺癌过程中的发病机制进行探讨.     

Studies on kinetics of reactions between phycobiliproteins and hydroxyl radicals by a pulse radiolytic technique

Scavenging of hydroxyl radical (· OH) by phycobiliproteins (C-phycocyanin, Allophycocyanin and R-phycoerythrin) was studied by competitive kinetics methods. Hydroxyl radicals were generated from pulse radiolysis of aqueous systems saturated with nitrous oxide (N₂O). The experimental results indicated that the three types of phycobiliproteins are all strong scavengers of · OH, the rate constants are around (2.8-5.6)×10⁹ L · mol^-1 · s^-1.     

Photochemistry of hypocrellin derivatives under aerobic conditions

Hypocrellins are a novel type of photosensitizers. A series of new hypocrellin B (HB) derivatives have been synthesized to overcome their limitations, i.e. to improve their red absorption and amphiphilicity. The generation of reactive oxygen species (including Superoxide anion radical, hydroxyl radical and singlet oxygen) is investigated in the presence of oxygen. The chemical structures of HB derivatives affect not only the generation efficiencies of Superoxide and hydroxyl radicals, but also quantum yields of singlet oxygen.     

原花青素体外清除自由基活性的研究

从葡萄籽中提取高纯度的原花青素 ,测得其对稳定自由基 1 ,1 -联苯 -β-苦基偕腙肼( DPPH)的半数抑制浓度 ( EC50 )为 44mg/L ;又利用 2 -脱氧 - D-核糖法产生· OH,在原花青素浓度为 1 0 g/L时可清除该体系中 80 %的· OH,表明原花青素是一种天然有效的自由基清除剂     

黄连炮制品清除氧自由基和抗脂质过氧化作用

采用体外氧自由基生成系统和羟自由基诱导的小鼠肝匀浆脂质过氧化反应 ,研究黄连生品、清炒品和酒炙品清除氧自由基能力和抗脂质过氧化作用 ,评价炮制对黄连抗氧化作用的影响 .研究结果表明黄连炮制品可清除次黄嘌呤 黄嘌呤氧化酶系统所产生的超氧阴离子(SAFR)和Fenton反应生成的羟自由基 (HFR) ,并能抑制HFR诱导的小鼠肝脏匀浆脂质过氧化作用 ,各炮制品EC50 之间具有一定显著差异 ,炮制降低了黄连抗氧化能力     

活性炭-纳米二氧化钛电催化氧化降解有机物的基础研究

采用吸附、焙烧法制备了活性炭 -纳米二氧化钛催化剂 ,对偶氮染料甲基橙溶液进行了电催化氧化降解规律的研究。实验结果表明 ,纳米二氧化钛催化剂的催化效果显著 ,该工艺能有效的去除废水中的有机物 ,去除机制主要是电致H2 O2 、·OH对有机物的氧化、降解。以水杨酸为探针性物质 ,推测出电催化氧化过程中羟基自由基·OH的产生。     

活性炭-纳米二氧化钛电解染料废水基础研究

采用吸附、焙烧法制备了活性炭-纳米二氧化钛催化剂,对染料溶液进行了电催化氧化降解规律的研究,通过正交试验比较了各因素对降解效果的影响。结果表明,纳米二氧化钛催化剂的催化效果显著,该工艺能有效去除废水中的有机物,去除机制主要是电致H2O2和羟基自由基(.OH)对有机物的氧化、降解。以水杨酸为探针性物质,推测出电催化氧化过程中羟基自由基的产生。