Polymerization kinetics and stabilization mechanism of the monodisperse PMMA microspheres

The effects of the concentration of monomer, crosslinking agent, initiator, stabilizer, and the polarity of medium on the polymerization kinetics were investigated. The results show that the rate of polymerization (Rp) and conversion increased with the increase of monomer concentration from 8% to 15% (total mass); the water content in dispersion medium and the initiator 2, 2′ -azobis (isobutyronitrile) (AIBN) concentration increased as well. Rp and conversion decreases with the increase of PVP when it is low, while it increases when it is high. Moreover, PVP plays an important role in microsphere stabilization. The stabilization mechanism was investigated primarily, which involves both adsorbing mechanism and graft mechanism. Within a certain range of crosslinking degree, Rp and conversion increased with the increase of the crosslinker concentration. The effect can be ignored when crosslinker concentration is above 0.3 % (total mass), and the reason was that the monomer can hardly be diffused into the microsphere phase with a certain degree of crosslinking.     

Pilot Study on Drinking Water Advanced Treatment by GAC-MF System

The pilot pedomance of the combined GAC-MF membrane process for drinking water advanced treatment was described. In the process of GAC adsorption, under the conditions of 20min HRT and 6 m/h filtration rate, the removal efficiencies of UV254 and trichloromethane could reach 40% and 50% respectively and the UV254 and trichloromethane in system effluent was less than 0.015cm^-1 and 5 μg/L respectively. Inthe post MF membrane process, MF membrane effectively retained the particles and bacteria in raw water. The effluentturbidity was less than 0.2 NTU and no bacteria were detectedat all in permeate. A computer-controlled system was employedto control this system. The mcmlrane operating parameters of backwash interval, dtration and flux were studied. The backwash interval of 10-min, 20-min and 60-min wasresearched respectively, and the variation of trans-membrane pressure was also analyzed. Comequently short backwash interval was recommended under the same water consume.     

Dynamic Membrane for Cross-flow Micro-filtration in Treating Activated Sludge

Mixed liquid of activated sludge （AS） were micro- filtrated by dynamic membrane （DM） made of 6 000 mesh kaolin. The results illustrated that the permeate quality and flux with DM filtration were superior to that with direct filtration in treating AS. The experiments of membrane washing showed that DM could abate the internal fouling of membranes efficiently, and the permeate flux of renewed membrane reached 90% of that of new membranes. The denser the mixed liquid suspended solids （MLSS） were, the lower the permeate flux was. Increasing of both flow velocity over the membrane surface and trans-membrane pressure （TMP） could lead to some enhancement of permeate flux, while the former approach could be carried out more economically. The feasibility of application of the DM to membrane bioreactor （MBR） has been ascertained.     

Preparation of A-type zeolite membranes on nonporous metal supports by using electrophoretic technique

A-type zeolite membranes were prepared on the nonporous metal supports by using electrophoretic technique. The as-synthesized membranes were characterized by XRD and SEM. The effect of the applied potential on the formation of the A-type zeolite membrane was investigated,and the formation mechanism of zeolite membrane in the electric field was discussed. The results showed that the negative charged zeolite particles could migrate to the anode metal surface homogenously and rapidly under the action of the applied electric field, consequently formed uniform and dense membranes in short time. The applied potential bad great effect on the membrane formation, and more uniform and denser zeolite membranes were prepared on the nonporous metal supports with 1 V potential.     

Applications of membrane distillation technology in energy transformation process-basis and prospect

Membrane distillation technology is a new type of efficient separation technology that combines traditional distillation technology and membrane separation technology. In the study, applications of membrane distillation technology in thermal engineering and refrigerating engineering with typical energy transformation process were presented. Desorption and regeneration process of saline solution by vacuum membrane distillation was proposed on the basis of the concentration and separation properties of membrane distillation. Membrane distillation technology could be used in lithium bromide absorption refrigeration system, energy storage system, and the regeneration process of liquid desiccant solution in temperature-humidity independent control air-conditioning system. The aim of the applications was to use the low-grade energy such as waste heat, solar energy and geothermal energy adequately and to improve the available temperature difference of heat source. According to latent heat transfer and thermal conduction across the membrane in direct contact membrane distillation process, a novel membrane heat exchanger with both heat transfer and mass transfer processes was proposed. The heat exchanger could be used as the solution heat exchanger of lithium bromide absorption refrigeration system and as the special heat exchanger that recovered heat and pure water simultaneously. Some feasible process flows about the applications of membrane distillation technology to energy transformation process were listed and analyzed. Finally, future research emphases were indicated.     

Recovery Properties of Polysulfone Hollow Fiber Chelating Membrane Modified with Thiourea for Mercury （ Ⅱ ）

The adsorption isotherms of the polysulfone hollow fiber chelating membrane modified with thionrea as chelating groups for Hg^2＋ were determined. The effects of mobile phase conditions and the operating parameters on removal performance of the chelating membrane for Hg^2＋ were also investigated. The recovery of Hg^2＋ decreased at low pH and the optimum range of pH was from 6 to 7. The feed concentration effected on recovery of Hg^2＋ at the specified loading amount of Hg^2＋. The Hg^2＋ could be removed from different concentration feed solution by chelating membrane. The increase of feed flow rate led to slight decrease of recovery of Hg^2＋ at the specified loading amount of Hg^2＋. The chelating membrane could be operated at height feed flow rate and a large-scale removal of H^2＋ could be realized. With the increase of load amount, Hg^2＋ recovery decreased, but the saturation degree of chelating membrane increased. According to required recovery of H^2＋ and the saturation degree of chelating membrane, the optimum loading amount of Hg^2＋ should be selected in the actual removal of H^2＋.     

Microwave Irradiation Graft Copolymerization of Butylmethacrylate (BMA) onto Wool Fabrics

Butylmethacrylate(BMA) was grafted onto woolen fabrics by microwave Irradiation In the presence of catalyst ((NH4) 4S2O8) .Various parameters of graft- copolyme-rlzation reaction, namely time of reaction, microwave intensity, catalyst and monomer concentration, were optimized . The graft - copolymerization was also compared with conventional heating graft- copolymerization at the same condition, it showed microwave irradiation could Improve the reactivity of the monomer. The moisture regain decreased as graft add - on increased, the strength of the grafted fabric decreased as graft add - on increased , but the strain increased hi some degree. The infrared spectrum showed an additional peak at 1700 cm-1, confirming ester carbonyl groups of the monomer.     

Effects of coagulation on submerged ultrafiltration membrane fouling caused by particles and natural organic matter （NOM）

Natural organic matter (NOM) and particles in source water are responsible for the majority of ultrafiltration (UF) membrane fouling that occurs during drinking water treatment. This study was conducted to (1) understand the UF membrane fouling phenomena caused by NOM and turbidity-causing particles and (2) investigate the effect of coagulation pretreatment on the alleviation of membrane fouling. In this study, kaolinite and humic acid (HA) were used to simulate the particles and NOM present in source water. The results revealed that the particles contributed to reversible fouling due to cake layer formation on the membrane surface, but that could be effectively reduced by increasing the frequency of physical backwashing. The results of the molecular weight (MW) distribution measurements, resin fractionation, SEM and FTIR analyses showed that HA primarily contributed to irreversible fouling. Taken together, the results of this study imply that the particles and NOM compounds present in source water may have different fouling behavior, and that particles may mitigate the irreversible fouling caused by HA. The addition of coagulant can lead to a higher rate of removal of large-sized hydrophobic compounds. Coagulation pretreatment can improve membrane performance and postpone membrane fouling development effectively, as well as retard the implementation of membrane chemical cleaning.     

Fabrication and Properties of Porous Film/Fabric Composites for Vascular Scaffold Application

A composite vascular scaffold combining textile reinforced structure and biodegradable polymer is introduced, which may possess high porosity and connectivity. Moreover, the porous size could be controlled. The proposed scaffold consists of a warp-knitted poly （ethylene terephthalate ） （PET） fabric with well-defined macropores, which is embedded with a porous biodegradable polymer membrane. The aim of this paper is to study the fabrication and properties of porous polymer membrane through optimizing the parameter of composite methods from freeze drying/particle leaching （ FD/PL ） and gas foaming/particle leaching （ GF/PL ）, subsequently combining with the warp-knitted fabric. Weighing method was utilized to analyze the porosity of the samples and the scanning electron microscope （SEM） images were taken to observe the porous structure of the vascular membrane. In addition, ,the static contact angle （CA） was measured to estimate the hydrophilicity of the samples, and the tensile testing of the composites was performed on the universal mechanical tester. Furthermore, the water permeability of the membrane was also calculated. The results showed that the porosity and pore connectivity of the vascular membrane were diverse, became of solution concentration, particle size, ratio of content, etc. Meanwhile, the stress-strain curves and the bursting strength showed the different mechanical properties among composite scaffolds in different structures.     

Application and Characterization of Cellulose Acetate Membrane Produced from Herbaceous Plant: Solidago Canadensis L.

In this work,the viability of Solidago Canadensis L. for cellulose acetate membrane production was tested. The cellulose was extracted from Solidago Canadensis L. stem by organic solvents,and the cellulose diacetate was obtained by acetylization of cellulose. The properties of the intermediate products of cellulose pulp and cellulose diacetate were characterized by FT-IR and XRD. Compared with commercial cellulose diacetate,the properties of cellulose diacetate were similar to those of the commercial cellulose diacetate. The cellulose acetate membrane with desirable pure water flux and rejection rate was obtained from cellulose diacetate by solution casting. The membrane showed favorable hydrophilic property so that it had good anti-pollution performance. The maximum pure water flux of the membrane was 27. 21 m L /( cm2· h) and the maximum rejection rate was 80. 39%. The results demonstrated that the membrane obtained from herbaceous plant: Solidago Canadensis L. had good performance of ultrafiltration.     

Experimental simulation of model platelet adhesion to a semi-permeable wall exposed to flow disturbance

A sudden tubular expansion with a semipermeable wall was constructed from a tubular dialysis membrane to investigate the effects of rdtration flow and flow disturbance on particle deposition. The expansion was perfused with a dilute, neutrally buoyant suspension of 1.10μm diameter polystyrene latex spheres (as models of platelets) in Tris buffer solution containing 10% Dextran T70 and 2% bovine serum albumin. The results showed that adhesion of particles correlated positively with the filtration rate and inversely with the wall shear rate. In the vortex flow region distal to the expansion, particle adhesion was significantly elevated with a maximum at the reattachment point where the wall shear rate was the lowest and particles were constantly carried toward the vessel wall along the curved streamlines. In conclusion, rdtration flow has a profound impact on the interaction of blood cells such as platelets with blood vessel walls, and the disturbed flow with a low wall shear rate can enhance the deposits of platelet thrombi to the vessel wall.     

Study on the Preparation of Allyl-modified Starch in Isopropyl/Water Medium for Warp Sizing

A new method for the pretreatment of starch by etherification was developed to eliminate the problems of lower grafting efficiency associated with the preparation of starch graft copolymers as warp sizing agents. The etherification of starch with allyl chloride was investigated in order to effectively enhance the reaction efficiency. The tecimological variables of the reaction considered for evaluating the etherification included sodium hydroxide amount, water content in water-isopropyl alcohol medium, allyl chloride concentration, reaction temperature and reaction time. The experimental result demonstrated that the variables considered showed evident effect on the reaction efficiency. For the etherification, a condition of 20% for the water content, 1.5：1 for the molar ratio of sodium hydroxide to allyl chloride, and at 30℃ under 24 h reaction is sufficient to retain the reaction efficiency above 50%. Furthermore, a contrast test demonstrated that the graft efficiency can be increased with the etherification pretreatment.     

Inactivation of Giardia by Ozone and Its Disinfect Mechanisms

This study was to investigate the effect of ozone(O3)inactivation on Giardia in water by the fluorescence staining method.In order to elucidate the dominant mechanisms of inactivation,cell surface or inner cell components damage were comparatively examined by scanning electron microscopy(SEM).Results suggested that O3had a stronger effect on inactivating capability.Firstly,when the concentration of O3was above 2.0 mg/L and the contact time was up to 5 min,it showed a significant inactivating effect.Secondly,the effect of turbidity on inactivation was also found to be significant in synthetic water;when turbidity increased,the inactivating effect decreased.Thirdly,the inactivating rates were improved with a temperature increase from 5 to 25℃,but decreased when the temperature were out of this range.The inactivating capability of O3was stronger under acidic conditions than alkalic conditions.Lastly,when the concentration of organic matter in the reactive system was increased,probably due to the competition between Giardia and organics on O3,the inactivating rate was decreased;in addition,the cellular morphology of Giardia varied with different contact times.At contact time of 30 s,cells were rotundity and sphericity;at 60 s they became folded,underwent emboly,and burst;and at 240 s,the cell membrane of Giardia shrinked and collapsed completely.     

Surface Graft Copolymerization of Acrylic Acid onto Corona Treated Cotton Fabric

Acrylic acid was grafted onto the surface of cotton fabric after being short time treated by corona-discharge inair in the presence of initiator.The means of gas-phaseSO_2 derivatization was used along with ESCA to deter-mine corona-discharge-induced-hydroperoxidegroups on the surface.The content of hydroperoxideshows a maxmium value at 15 sec.of corona-dischargetime.Effect of corona treatment time and various con-centration initlator on graft yield was studied.The addit-ion of initiator increases the graft yield.Acceleratedgraft with an increase in the concentration of Mohr's saltshows that peroxide groups on the corona treated cottonfabric initiate graft copolymerization.     

STUDY ON SLOW-RELEASE CHARACTERISTICS OF MICROCAPSULES WITH EMULSION NON-SOLVENT ADDITION METHOD

An O / W emulsion non-solvent addition method was used to prepare ethyleellulose (EC) microcapsules of water soluble pharmaceutical (theophylline). The solvent and non-solvent reagents used in this work were toluene and cyclohexane. The effects of polymer concentration, core wall ratio and particle size on the kinetics as well as the dissolution rate of the drug were investigated. The results show that the dissolution rate increases with the increasing of polymer concentration and core wall ratio. The release of microcapsules prepared with different procedures can be selectively profiled with first order and Higuchi matrix kinetic models.     

Removal of Microcystin-LR in Water by Chlorine Dioxide

Microcystins(MCs)are well known as hepatotoxins produced by blooms of toxic cyanobacteria(blue-green algae) abundant in surface water used as drinking water resource and have drawn attention of environmentalists world over by leading to adverse health effects.A study on efficiency and reaction kinetics of microcystin-LR(MC-LR)degradation by ClO2 was performed. Experimental results indicated that MC-LR was removed by ClO2 effectively and the residual concentration of MC-LR could meet the national guideline(GB5749-2006)(1.0 μg·L-1 ),the efficiency of removal was in positive correlation to ClO2 dosage and reaction time and in negative correlation to initial concentration of MC-LR and pH value, whereas it was affected by temperature slightly.ClO2 dosage was the most important reaction factor on base of the orthogonal test results.The reaction was second order overall and first order with respect to both ClO2 and MC-LR,and had an activation energy of 78.81 kJ · mol-1.The reaction rate constant was 4.74×102 L/(mol·min) at 10 ℃.Therefore, oxidation of ClO2 could be taken as an effective technology for removing MC-LR from drinking water resources in traditional drinking water supplies.     

Effect of Quercetin on Breeding and Apoptosis of Cervical Cancer HeLa Cell and on Growth of Transplanted Tumor in Nude Mice

Effect of quercetin on HeLa cell system of cervical cancer was studied by methods of MTT and Annexin V-FITC/PI. The results show that quercetin has functions of inhibiting breeding of HeLa cells and inducing apoptosis of the cells. The total apoptosis rate is positively proportional to reaction duration and concentration of quercetin used. The maximum apoptosis rate being （88.76±2.35）% was obtained when the concentration was 50.0 μmol/L and the cells were treated with quercetin for 72 hours. Based on establishing a model of tumor of cervical cancer transplanted into nude mice, quercetin of different concentrations was injected into abdominal cavity of nude mice and situation of tumor growth was reviewed. The result showed that with quercetin concent＇ration increasing from 0 to 100.0 μmol/L, the transplantation volume and weight of the tumors decreased from （279.59±70.58） mm^3 and （0.145±0.019） g to （128.72±36.12） mm^3 and （0.089± 0.019） g respectively, while apoptosis rate of the transplanted tumor increased from （9.63±1.85）% to （34,98±0.47）%, which proved that quercetin inhibited increment of volume and weight of transplanted tumor in nude mice bodies.     

Evaluation of virus removal in MBR using coliphages T4

A membrane bioreactor (MBR) with gravity drain was tested for domestic wastewater for 65 days. Resultss howed that the effluent quality was excellent, and met with the reuse water standard of China (GB/T 18920-2002). Virus removal in the membrane separation process was investigated by employing coliphages T4 as a tracer. Two microfiltration membrane modules, with pore sizes of 0.22 and 0.1 μm, were used to investigate their effects on virus rejection at the transmembrane pressure of 8.5 kPa. It was found that 0.1 μm membrane had complete rejection of virus, and 0.22 μm membrane had significant rejection of virus. In the longterm operation of this MBR, no significant difference was observed between both pore sizes because the virus concentrations of the effluent in both cases were in the same order. Effluent virus concentration at steady state of MBR running was less than 2 PFU/mL. The removal ratios of coliphage T4 in MF processes were more than 10^5.5. The membrane surface deposits played an important role in the rejection of virus. The formation of cake clay on the membrane surface was the main cause of high rejection of colipbage T4 with MF of 0.22 μm.     

Studies of the process of moisture exchange across a membrane using irreversible thermodynamics

On the basis of non-equilibrium thermodynamic theory,the coupling phenomena of heat and mass transfer during the process of moisture exchange across a membrane were studied and the relevant physical and mathematical models were established.Formulae for calculating the four characteristic parameters included in the non-equilibrium thermodynamic model were derived,and the dependences of these parameters on the temperatures and concentrations on the two sides of the membrane were analyzed,providing a basis for calculating the heat and mass fluxes.The effects of temperature and concentration differences between the two sides of membrane and the membrane average temperature on the transmembrane mass and heat fluxes were investigated.The results show that for a given membrane average temperature,a larger concentration difference or a smaller temperature difference leads to a higher mass flux.For fixed concentration and temperature differences and with the mass flux predominantly caused by the concentration difference,a higher membrane average temperature yields a higher mass flux.The ratio of the heat of sorption induced by mass flow to total heat relates not only to the temperature and concentration differences between the two sides of membrane but also to the membrane average temperature and the ratio increases when the temperature difference is reduced.     

Preparation and Performance of Collagen Modified Polyester Used as Implantable Artificial Hair

The implantable artificial hair was prepared by grafting collagen on the surface of poly( ethylene terephthalate)( PET) to improve its biocompatibility. Acrylic acid( AAc) was used to modify the surface properties of PET firstly,and then collagen was grafted on the PET-AAc surface. The concentration of collagen solution was discussed to graft more collagen on PET surface. Composites were well characterized by scanning electron microscopy( SEM),Fourier transform infrared spectroscopy( FTIR) and X-ray photoelectron spectroscopy( XPS). SEM indicated that collagen with about 3. 07μm thickness was coated on PET surface when the concentration of collagen solution was 1. 0 mg/m L. FTIR and XPS showed AAc and collagen were both on the surface of PET monofilaments. The optimized concentration of collagen solution was 1. 0 mg/m L,resulting in the most grafting density of 3. 46 μg/cm2. It can be concluded that a large amount of collagen is coated on PET surface.