机械力化学活化HPW-TiO_2/膨润土光催化降解甲基橙

采用溶胶-凝胶法制备了磷钨酸(HPW)改性TiO_2,并固载于膨润土上,再经机械力化学活化,得到机械力化学活化HPW-TiO_2/膨润土(MCA-HPW-TiO_2/膨润土)复合光催化剂。采用XRD,SEM,EDS技术对复合光催化剂进行了表征,并将其用于甲基橙的紫外光催化降解。表征结果显示:活性组分TiO_2和HPW成功固载于膨润土上;在机械力化学活化作用下,膨润土层间结构遭到破坏,TiO_2的XRD特征峰形呈弥散状态。实验结果表明:机械力化学活化作用对HPW-TiO_2/膨润土的光催化性能提升效果显著;在酸性及近中性条件下MCA-HPWTiO_2/膨润土均具有较高的催化活性;在溶液p H 6.2、初始甲基橙质量浓度10 mg/L、反应时间180 min、MCAHPW-TiO_2/膨润土投加量1 g/L的条件下,甲基橙去除率达88.27%;该光催化降解过程符合一级动力学模型。

贝利特的机械力化学活化

将１３５０℃下合成的贝利特置于振动磨中粉磨１～７０ｈ后，研究了贝利特在粉磨过程中所发生的机械力化学变化，如粒度分布、晶体结构、晶格应变、粉体表面特性及早期水化活性等。结果表明，粉磨作用可降低贝利特粉体粒度，并使贝利特晶胞参数发生变化；同时使贝利特晶体结晶度下降，贝利特晶格应变及早期水化活性增加，大大提高了贝利特浆体强度；随着粉磨时间延长，贝利特表面伦敦色散分量及极性分量不断提高。当粉磨时间超过３０ｈ时，贝利特表面能反而降低，并使贝利特粉体粒度增大。

部分水解聚丙烯酰胺的固相力化学活化

利用磨盘型力化学反应器对部分水解聚丙烯酰胺(HPAM)进行固相力化学碾磨。随着碾磨次数的增加,特性黏度先降低,后上升,表明在碾磨过程中HPAM主链断裂,产生大分子自由基,继而发生重新聚合;平均粒径由碾磨10次的0.822μm减小到碾磨30次的0.436μm,说明碾磨后HPAM活性增强;碾磨前起始分解温度为233.9℃,碾磨10次、30次后分别为233.1℃和232.4℃,碾磨前熔融温度为209.4℃,碾磨10次、30次后分别为206.7℃和205.4℃,说明固相力化学作用使HPAM的热稳定性降低。

HPAM/St的固相力化学合成及产物表征

利用磨盘型力化学反应器对部分水解聚丙烯酰胺(HPAM)和疏水单体苯乙烯进行固相力化学共碾磨。产物红外谱图分析表明,接枝产物既有HPAM的结构,同时含有苯环,说明两者发生聚合。差示扫描量热结果显示,未碾磨的HPAM的熔融温度为209.4℃,碾磨10次后下降为206.7℃,而碾磨10次的共聚产物为256.2℃,说明发生共聚反应后使聚合物的热稳定性明显改善。热重分析表明,未碾磨的HPAM的Ti为233.9℃,碾磨10次后Ti降低为233.1℃,碾磨10次的共聚产物的Ti没有降低反而升高为281.6℃,提高了47.5℃,进一步说明聚合物的热稳定性提高。

高KH熟料的特性及高游离氧化钙水泥的机械力化学改性研究

通过实验室试验研究了石灰饱和系数(KH)对水泥熟料的显微特征、粉磨特性及物理性能的影响 ,并就机械力化学活化对高游离氧化钙水泥的改性和混合材效应的影响等进行了探讨。研究表明 ,低温烧成的特种高钙熟料具有高强、早强及易磨性好等优异性能 ,通过机械力化学活化可有效地提高高游离氧化钙水泥的强度和改善安定性 ,大幅度地提高混合材的利用率。

不同活化程度胶粉对SBS改性沥青性能影响研究

研究了不同活化程度胶粉的微观结构,探索了不同活化程度胶粉应用于SBS改性沥青的可行性及物理/流变性能变化。结果表明,活化处理后的胶粉分子链结构保持完整,产生了羟基、羧基官能团;表面棱角减少、孔洞增多且趋于形成整体。随着活化程度加深,活化胶粉可溶物含量增加,甲苯可溶物Mn降低、PDI变大;甲苯不溶物含量及交联密度降低;SBS改性沥青的储存稳定性及低温性能增强,且不影响高温性能和施工和易性;改性沥青的高温抗车辙能力逐渐下降,抗疲劳开裂及低温抗开裂性能增强且优于SBS改性沥青。增加极高活化程度胶粉用量,改性沥青的高温抗车辙性能逐步提升,抗疲劳开裂及低温抗开裂性能显著提升且明显优于SBS改性沥青;耐热氧-紫外老化能力显著增强。

高活性超细粉煤灰的制备及其生产应用

提高粉煤灰水化反应活性主要有三种技术途径:物理磨细方法、化学激发方法以及物理方法与化学激发方法组合。水泥工厂通常是采用物理方法磨细,即机械力化学活化方法对原状粉煤灰进行超细粉磨。粉煤灰的平均粒径(中位径)D50与特征粒径X’越小,水化反应速度与水化反应活性越高。我公司采用Φ4.2m×13m管磨机制备的高活性超细粉煤灰,28d活性指数达到91.1%,比原状粉煤灰活性指数72.3%提高了18.8%,应用于水泥生产及混凝土配制,取得了显著的降本增效效果。

高硅型铁尾矿对混凝土碳化及抗硫酸盐腐蚀性能的影响

将某高硅型铁尾矿进行机械力化学活化,将其作为辅助胶凝材料部分取代水泥制备混凝土,取代量(质量分数)分别为10%,20%,30%及40%,开展高硅型铁尾矿对混凝土碳化及抗硫酸盐腐蚀性能影响的试验研究.结果表明,掺加尾矿的混凝土抗碳化性能低于基准混凝土,随着取代量的增加,混凝土抗碳化性能呈下降趋势,但能满足混凝土结构工程的实际要求;随着取代量的增加,混凝土抗硫酸盐腐蚀性能呈上升趋势,取代量为20%,30%及40%时,混凝土抗硫酸盐腐蚀性能优于基准混凝土.经过机械力化学活化,某高硅型铁尾矿作为混凝土辅助胶凝材料部分取代水泥制备混凝土,就混凝土抗碳化性能及抗硫酸盐腐蚀性能而言是可行的.

Leaching kinetics of gold bearing pyrite in H_2SO_4-Fe_2(SO_4)_3 system

Gold bearing pyrite leaching was conducted in H2SO4-Fe2（SO4）3 system at different reaction temperatures,with different ferric ion concentrations,sulfuric acid concentrations and stirring speeds.The leaching kinetics and mechanism were studied.When the temperature ranged between 30-75 °C,the pyrite leaching was mainly controlled by chemical reaction with positive correlation to the ferric ion concentration.The activation energy obtained from Arrhenius empirical formula is 51.39 k J/mol.The EDS and XPS analyses suggest that the oxidation of sulfur within pyrite is through a series of intermediate stages,and eventually is oxidized to sulphate accompanied with the formation of element sulfur.This indicates a thiosulfate oxidation pathway of the gold bearing pyrite oxidation in H2SO4-Fe2（SO4）3 system.

Photocatalytic activity of Fe-doped diopside

UV-visible light induced photocatalytic degradation of methylene blue (MB) over Fe-doped diopside was investigated. The structure, composition, morphology and absorption property of UV-visible light of as-prepared samples were characterized using XRD, SEM, FTIR and UV-vis DRS. The experimental results show that doping Fe3+ induced the formation of some new species in diopside, and promoted light adsorption property of diopside in UV-visible region. Photochemical reactivity of Fe-doped diopside obviously depended on the content of doping Fe3+. The diopside with 1.848% Fe3+ exhibited the superior photocatalytic activity with 95% degradation of MB under UV-visible light for 3 h. The photocatalytic degradation kinetics of MB over all samples showed the first-order reaction nature.

Isothermal kinetics of mechanochemically and thermally synthesized Ag from Ag_2O

The kinetics of isothermal reduction of Ag2O with graphite under argon atmosphere for a non-activated sample and mechanically activated sample was investigated.It is found that Johnson-Mehl-Avrami model appropriately explained the thermal and mechanochemical synthesis of Ag from Ag2O＋ghraphite mixture.The process kinetics was investigated using the same approach for milled and unmilled samples.The results show that the Avrami exponent of mechanochemical reduction is higher than that of high temperature thermal reduction.Also,the mechanisms of nuclei growth in thermal and mechanochemical reduction are diffusion controlled and interface controlled,respectively.

Comparative kinetic analysis of conventional and ultrasound-assisted leaching of scheelite by sodium carbonate

For further comprehending the mechanism of the intensification of ultrasound for extraction,the difference of leaching kinetics between the ultrasound-assisted and conventional sodium carbonate leaching of scheelite was studied,and the corresponding kinetic equations were established.The results indicate that the obtained apparent activation energy with or without ultrasound is same 72 kJ/mol,and both reactions are controlled by surface chemical reaction.By comparing the leaching kinetics of scheelite by Na2CO3,NaOH and Na3PO4 reactants with or without ultrasound,a general conclusion for scheelite hydrometallurgy is obtained.For the process with the formation of compact product layer,the intensification of the tungsten extraction with ultrasound mainly reflects in the stripping and elimination of product layer,corresponding to the transformation of kinetic controlling step from diffusion controlling step and reduction of apparent activation energy.For the one without compact product layer or with a loose and porous product layer,the intensification mainly embodies in the increase of frequency factor,and the controlling step and apparent activation energy of the reaction always remain constant.

Magneto-hydrodynamic flow of squeezed fluid with binary chemical reaction and activation energy

The present exploration is conducted to describe the motion of viscous fluid embedded in squeezed channel under the applied magnetics effects.The processes of heat and mass transport incorporate the temperature-dependent binary chemical reaction with modified Arrhenius theory of activation energy function which is not yet disclosed for squeezing flow mechanism.The flow,heat and mass regime are exposed to be governed via dimensionless,highly non-linear,ordinary differential equations (ODEs) under no-slip walls boundary conditions.A well-tempered analytical convergent procedure is adopted for the solutions of boundary value problem.A detailed study is accounted through graphs in the form of flow velocity field,temperature and fluid concentration distributions for various emerging parameters of enormous interest.Skin-friction,Nusselt and Sherwood numbers have been acquired and disclosed through plots.The results indicate that fluid temperature follows an increasing trend with dominant dimensionless reaction rate σ and activation energy parameter E.However,an increment in σ and E parameters is found to decline in fluid concentration.The current study arises numerous engineering and industrial processes including polymer industry,compression and injection shaping,lubrication system,formation of paper sheets,thin fiber,molding of plastic sheets.In the area of chemical engineering,geothermal engineering,cooling of nuclear reacting,nuclear or chemical system,bimolecular reactions,biochemical process and electrically conducting polymeric flows can be controlled by utilizing magnetic fields.Motivated by such applications,the proposed study has been developed.

Antioxidant power of phytochemicals from Psidium guajava leaf

Dried ground leaves of Psidium guajava L. (guava) were extracted by water and aqueous ethyl alcohol 50% (1:10) ratio, and the total phenolic content in the extracts was determined spectrophotometrically according to Folin- Ciocalteu’s phenol method and calculated as gallic acid equivalent (GAE). Remarkably high total phenolic content 575.3 ±15.5 and 511.6±6.2 mg of GAE/g of dried weight material (for ethanol guava leaf extracts and water guava leaf extracts, respectively) were obtained. The antioxidant activity of lyophilized extracts was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydryzyl (DPPH˙) colorimetry with detection scheme at 515 nm. The activity was evalu- ated by the decrease in absorbance as the result of DPPH˙ color change from purple to yellow. The higher the sample concentration used, the stronger was the free radical-scavenging effect. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than the extracts from guava leaf. On the other hand, the commercial guava leaf extracts and ethanol guava leaf extracts showed almost the same antioxidant power whereas water guava leaf extracts showed lower antioxidant activity. The parameter EC50 and the time needed to reach the steady state to EC50 concentration ( TEC50 ) affected the antiradical capacity of the sample. The antioxidant efficiency (AE) has been shown to be a more ade- quate parameter for selecting antioxidants than the widely used EC50. This study revealed that guava leaf extracts comprise effective potential source of natural antioxidants.

Kinetics and Mechanism of Decomposition of Nano-sized Calcium Carbonate under Non-isothermal Condition

Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Redfern's equation was used to determine the apparent activation energy and the pre-exponential factors. The mechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and the kinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonate was different from that of bulk calcite. Nano-sized calcium carbonate began to decompose at 640℃, which was 180℃lower than the reported value for calcite. The experimental results of kinetics were compatible with the mechanism of one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate was estimated to be 151kJ·mol-1 while the literature value for normal calcite was approximately 200kJ·mol-1. The order of magnitude of pre-exponential factors was estimated to be 10~9 s-1.

Use of chemically activated cotton nut shell carbon for the removal of fluoride contaminated drinking water: Kinetics evaluation

Chemically activated cotton nut shell carbons （CTNSCs） were prepared by different chemicals and they were used for the removal of fluoride from aqueous solution. Effects of adsorption time, adsorbent dose, pH of the solution, initial concentration of fluoride, and temperature of the solution were studied with equilibrium, ther- modynamics and kinetics of the adsorption process by various CTNSC adsorbents. It showed that the chemically activated CTNSCs can effectively remove fluoride from the solution. The adsorption equilibrium data correlate well with the Freundlich isotherm model. The adsorption of fluoride by the chemically activated CTNSC is spon- taneous and endothermic in nature. The pseudo first order, pseudo second order and intra particle diffusion kinetic models were applied to test the experimental data. The pseudo second order kinetic model provided a better correlation of the experimental data in comparison with the pseudo-first-order and intra particle diffusion models, A mechanism of fluoride adsorption associating chemisorption and physisorption processes is presented allowing the discussion of the variations in adsorption behavior between these materials in terms of specific surface area and porosity. These data suggest that chemically activated CTNSCs are promising materials for fluoride somtion.

Polyethoxylation and polypropoxylation reactions：Kinetics,mass transfer and industrial reactor design

Ethoxylation and propoxylation reactions are performed in the industry to produce mainly non-ionic surfactants and ethylene oxide(EO)–propylene oxide(PO) copolymers.Both the reactions occur in gas–liquid reactors by feeding gaseous EO,PO or both into the reactor containing a solution of an alkaline catalyst(KOH or Na OH).Non-ionic surfactants are produced by using liquid starters like fatty alcohols,fatty acids or alkyl-phenols,while when the scope is to prepare EO–PO copolymers the starter can be a mono-or multi-functional alcohol of low molecular weight.Both reactions are strongly exothermic,and EO and PO,in some conditions,can give place to runaway and also to explosive side reactions.Therefore,the choice of a suitable reactor is a key factor for operating in safe conditions.A correct reactor design requires:(i) the knowledge of the kinetic laws governing the rates of the occurring reactions;(ii) the role of mass and heat transfer in affecting the reaction rate;(iii) the solubility of EO and PO in the reacting mixture with the non-ideality of the reacting solutions considered;(iv) the density of the reacting mixture.All these aspects have been studied by our research group for different starters of industrial interest,and the data collected by using semibatch well stirred laboratory reactors have been employed for the simulation of industrial reactors,in particular Gas–Liquid Spray Tower Loop Reactors.

Steam reforming of methane over Ni catalysts prepared from hydrotalcite-type precursors: Catalytic activity and reaction kinetics

Ni/Mg–Al catalysts derived from hydrotalcite-type precursors were prepared by a co-precipitation technique and applied to steam reforming of methane. By comparison with Ni/γ-Al2O3 and Ni/α-Al2O3 catalysts prepared by incipient wetness impregnation, the Ni/Mg–Al catalyst presented much higher activity as a result of higher specific surface area and better Ni dispersion. The Ni/Mg–Al catalyst with a Ni/Mg/Al molar ratio of 0.5:2.5:1 exhibited the highest activity for steam methane reforming and was selected for kinetic investigation. With external and internal diffusion limitations eliminated, kinetic experiments were carried out at atmospheric pressure and over a temperature range of 823–973 K. The results demonstrated that the overall conversion of CH4 and the conversion of CH4 to CO2were strongly influenced by reaction temperature, residence time of reactants as well as molar ratio of steam to methane. A classical Langmuir–Hinshelwood kinetic model proposed by Xu and Froment(1989)fitted the experimental data with excellent agreement. The estimated adsorption parameters were consistent thermodynamically.

Kinetics of Treated Domestic Sewage Disinfection through Catalytic Oxidation with H2O2

The inactivation of bacterial cells through catalyzed oxidation using hydrogen peroxide as the primary oxidant agent is dependent on a series of factors, such as the concentration of the catalyst, the rate of hydroxyl radical formation in the controlled decomposition of the oxidant agent, and the concentration and toxicity of hydrogen peroxide. The objective of this study was to develop a mathematical model able to predict the kinetics of the inactivation Escherichia coli and total coliforms cells present in treated domestic sewage through catalytic peroxidation. The catalyst used was iron oxide supported on mineral coal （called CP）, and the effects of the operational conditions, including hydrogen peroxide concentration and dosage of catalyst, were evaluated. The results showed that the disinfection kinetics of the treated domestic sewage is dependent on the concentrations of hydrogen peroxide and catalyst dosage. The kinetic model was shown to be able to predict the behavior of the inactivation kinetics of the bacterium Escherichia coli ATCC-25922 when different concentrations of hydrogen peroxide （75 and 100 mg·L^-1） were used, regardless of the catalyst dosage.

INVESTIGATION OF THE INTERACTIONS BETWEEN WATER AND MODIFIED SILICA GEL BY IGC AND TPD

In this work, the thermodynamic parameters for the adsorption of water vapor on untreated silica gel and silica gel treated with hygroscopic salts and silane coupling agent were determined by lnverse Gas Chromatography （IGC） in the infinite dilution region. The desorption activation energies of the water vapor on virgin and modified silica gels were estimated by using the Temperature Programmed Desorption （TPD） technique. The interactions between the water and the virgin and modified silica gels were discussed. Results showed that the thermodynamic parameters and desorption activation energy of water vapour on the silica gels increase with decreasing pore size and increasing the surface hydrophilic properties. The desorption activation energy of virgin and modified silica gels was found to increase with increasing the thermodynamic parameters. The larger the adsorption parameters and the desorption activation energy were, the interactions between water and virgin and modified silica gels were.