Molecular Simulations of the Effect of Hydrated Montmorillonite on the Viscosity of Polyacrylamide under Confined Shear

Our researches are based on the fact that the systems composed of polyacrylamide and montmorillonite under a kind of shear state often appear in some important practical processes like drilling well etc. The viscosity of polyacrylamide is usually the most important one among the characteristics to decide if the practical processes succeed or not. Therefore, we studied the effect of hydrated montmorillonite on the viscosities of polyacrylamide with temperature and shear rate varying under confined shear by molecular simulation method. Adopting the condition of confined shear in the research could make our simulations and the practical processes as similar as possible. First, the model of one polyacrylamide polymer chain with 20 monomers linearly linking surrounded by water molecules between two of montmorillonite layers was constructed. Then canonical ensemble （NVT） MD simulations were carried out for the built model at different temperatures and shear rates. From the gained simulation results, we calculated the polymer＇s structural property-radius of gyration, which was directly related to the viscosity property of polyacrylamide polymer. It was found that the viscosity of the polyacrylamide polymer between hydrated clay layers decreased with the temperature increasing from 298 to 343 K under the condition of confined shear. The variation trend of viscosity from simulation results was also confirmed by our experiments. Besides, the viscosity of the polyacrylamide between hydrated clay layers decreased with the shear rate increasing within the range of higher shear rates.

STUDY OF COMPOSITE BY MELTING INTERCALATION OF POLYACRYLAMIDE IN MONTMORILLONITE

The synthesis of polyacrylamide (PAM)-montmorillinote composite by direct melting intercalation of polymer powders is studied using XRD, IR and DSC. The results show that melt PAM can intercalate into montmorillonite layer. The layered distance(d//0//0//1) of montmorillonite increases, and the melt absorption peak of PAM in layer has eliminated. (Author abstract) 8 Refs.

Preparation and Performance of Organically Modified Montmorillonite Composite Separation Membrane

A new composite separation membrane was developed by using organically modified montmorillonite(OMMT)as an additive.The effects of OMMT on the modification and properties of PVDF composite membranes were investigated.It is found that different kinds and amounts of OMMT into the casting solution can obviously change the pure water flux,separation performance and hydrophilicity of composite membrane in varying degrees.When the TA/PDA-MMT was 0.5 wt%,the pure water flux of the membrane reached the maximum,which was 584.7 L/(m^(2)·h),about 6 times that of the original membrane.The OMMT/PVDF composite membrane had good hydrophilicity and stability in the treatment of oily wastewater.The development of novel OMMT/PVDF composite membrane will provide a new idea for solving the problem of oily wastewater treatment.

Layer-by-layer fabrication of montmorillonite coating immobilizing Cu_(2)O nanoparticles for continuously catalyzing glycerol to dihydroxyacetone

Microreactors are increasingly used for green and safe chemical processes owing to their benefits of superior mass and heat transfer,increased yield,safety,and simplicity of control.However,immobilizing catalysts in microreactors remains challenging.In this investigation,a technique for creating Cu_(2)O/montmorillonite catalyst coating,using electrostatic attraction for layer-by-layer self-assembly,was proposed.The montmorillonite film's morphology and thickness could be efficiently regulated by adjusting the degree of exfoliation and surface charge of montmorillonite,alongside layer-by-layer coating times.The Cu_(2)O nanoparticles were immobilized using the flow deposition approach.The resulting Cu_(2)O@montmorillonite-film-coated capillary microreactor successfully transformed glycerol into dihydroxyacetone.The conversion of glycerol and product selectivity could be controlled by adjusting the molar ratio of reactants,temperature,residence time,and Cu_(2)O loading.The maximum glycerol conversion observed was 47.6%,with a 27%selectivity toward dihydroxyacetone.The study presents a technique for immobilizing montmorillonite-based catalyst coatings in capillary tubing,which can serve as a foundation for the future application of microreactors in glycerol conversion.

Vertically aligned montmorillonite aerogel-encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

The conversion and storage of photothermal energy using phase change materials(PCMs)represent an optimal approach for harnessing clean and sustainable solar energy.Herein,we encapsulated polyethylene glycol(PEG)in montmorillonite aerogels(3D-Mt)through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs.When used as a support matrix,3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG.Simultaneously,3D-Mt/PEG demonstrates outstanding shape retention,increased thermal energy storage density,and commendable thermal and chemical stability.The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating-cooling cycles.Furthermore,the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels,facilitating efficient phonon transfer.This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction.This study addresses the shortcomings of PCMs,including the issues of leakage and inadequate flame retardancy.It achieves the development and design of 3D-Mt/PEG with ultrahigh strength,superior flame retardancy,and directional heat transfer.Therefore,this work offers a design strategy for the preparation of high-performance composite PCMs.The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.

Oxidation of Partially Hydrolyzed Polyacrylamide from Polymer Flooding Processes Using Fenton Reagents

The degradation of partially hydrolyzed polyacrylamide(HPAM) found in alkaline/surfactant/polymer flooding sewage was investigated using Fenton-type reagents. Different Fenton reagent treatments for HPAM degradation were compared. The effects of pH, hydrogen peroxide(H_(2)O_(2)), ferrous ion(Fe^(2+)), and tartaric ion(C_(4)H_(4)O_(6)^(2-)) concentrations were studied. The degradation reaction occurred within a wide range of pH(3–9). The HPAM degradation performance of photo-Fenton processes using solar light and UV were compared with that of the Fenton process. The degradation rate was found to be strongly dependent on the H_(2)O_(2)/Fe^(2+)/C_(4)H_(4)O_(6)^(2-)molar ratio. The HPAM degradation efficiency was 90%, and the chemical oxygen demand removal efficiency was 85%. HPAM could be degraded into a compound with a lower molecular weight, but it was difficult to achieve complete mineralization to CO_(2). The presence of intermediate products hindered further oxidation in the Fenton process.

A review of complications of polyacrylamide hydrogel injection

Once a popular injectable filler,polyacrylamide hydrogel(PAAG)has been banned in China since 2006 due to its unclear safety and long-term complications.However,it is still being used worldwide because of its huge commercial profit,leading to emerging complications and an urgent need for standardized clinical management.This review aimed to assess the properties,safety,and complications of PAAG and treatment strategies for its removal.

Hydration Characteristics and Mechanical Properties of Cement-Based Materials Modified by Calcined Zeolite and Montmorillonite

Montmorillonite and clinoptilolite zeolite were used as representative materials to prepare calcined clay-cement binary cementitious materials in order to study the effect of calcination treatment on the activation of clay minerals and the activity difference between layered and framed clays in this research.The influence of different calcined clay content(2%,4%,6%,8%,10%)on the fluidity,compressive strength,microstructure,phase change,and hydration heat of cement-based materials were analyzed.The calcined clay improves the fluidity of cement-based materials as compared with the uncalcined group.The addition of calcined montmorillonite(CMT)improves the development of mechanical strength,and the optimal compressive strength reaches 85 MPa at 28 days with 8%CMT.However,the activity of calcined clinoptilolite zeolite(CZL)is weak with few reaction sites,which slightly reduced the mechanical strength as compared to the blank sample.The addition of CMT changes the microscopic morphology of hydration products such as C-S-H and C-A-H,leading to the formation and transformation of ettringite in the early stage.It promotes the gradual polymerization of Si-O bonds into Si-O-Si bonds simultaneously,which accelerates the early hydration process.However,CZL acts mainly as a filling function in the cementitious system.In brief,CMT as an admixture can improve the mechanical properties of cement,but CZL has little effect.This work provides a guideline for the applications of calcined clay in cement,considering the influence of clay type on workability and mechanical strength.

Improving physical properties of poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels via the Hofmeister effect

Hydrogel is a kind of three-dimensional crosslinked polymer material with high moisture content.However,due to the network defects of polymer gels,traditional hydrogels are usually brittle and fragile,which limits their practical applications.Herein,we present a Hofmeister effect-aided facile strategy to prepare high-performance poly(vinyl alcohol)/montmorillonite nanocomposite hydrogels.Layered montmorillonite nanosheets can not only serve as crosslinking agents to enhance the mechanical properties of the hydrogel but also promote the ion conduction.More importantly,based on the Hofmeister effect,the presence of(NH_(4))_(2)SO_(4)can endow nanocomposite hydrogels with excellent mechanical properties by affecting PVA chains'aggregation state and crystallinity.As a result,the as-prepared nanocomposite hydrogels possess unique physical properties,including robust mechanical and electrical properties.The as-prepared hydrogels can be further assembled into a high-performance flexible sensor,which can sensitively detect large-scale and small-scale human activities.The simple design concept of this work is believed to provide a new prospect for developing robust nanocomposite hydrogels and flexible devices in the future.

Synthesis and Flocculation of Polyacrylamide with Low Water Absorption for Non-dispersible Underwater Concrete

The polyacrylamide which is directly added into concrete shows strong water absorption property.Thus the construction of underwater constructure would demand high amount of water,resulting in poor workability of concrete and strength shrinkage after hardening.Herein,a kind of anionic polyacrylamide(APAM)grafted with water reducing functional group(-COOH)was synthesized at low temperatures by partial factor design and response surface design.The structure and morphology of APAM were characterized by UV,FTIR and SEM methods.The experimental results show that the molecular weight of the synthesized APAM could reach 11 million,under the condition that the temperature was 35℃,the pH value was 8,the monomer concentration was 27wt%,the initiator dosage was 0.6wt%,and the monomer ratio(n(AM):n(AA))was 3.When the APAM was applied into the underwater slurry,it presented good flocculation and low water demand.When the dosage was 1%of the mass of the cement,the water demand increased by 12%,which could meet the self-leveling and anti-dispersity of the underwater slurry at the same time.This technology provides technical guidance for the large-scale industrial production of polyacrylamide for underwater concrete construction while achieving environmental protection during production.

Study on the Effects of Polyacrylamide on Phosphorus Adsorption and Desorption Characteristics of Soil Aggregates

[Objective]The research aimed to provide scientific reference for reasonable utilization of polyacrylamide(PAM).[Method]After PAM treatment,the soil aggregates were classified through dry sieve analysis and the adsorption capacity and desorption capacity of all soil aggregates to phosphorus at different phosphorus concentrations were analyzed.[Result] The phosphorus adsorption and desorption of soil sample treated by PAM declined. The amount of phosphorus adsorption increased with the increase of phosphorus concentration and this increase was fast in low phosphorus concentration area but slow in high phosphorus concentration area.At different phosphorus concentrations,adsorption showed a へ shape changing trend.The phosphorus adsorption was related to phosphorus concentration and the 2-3 mm aggregate had the highest desorption rate while 0.1-0.25 mm aggregate and 0.45-1 mm aggregate had lowest desorption rate.[Conclusion]The PAM treatment generated significant influence on phosphorus adsorption and analytic features of aggregate in all size fractions.

Improvement of Polyacrylamide Gel Electrophorus in Phytophthora infeatans SSR Marker

[Objective] The paper was to improve polyacrylamide gel electrophorus in Phytophthora infeatans SSR Marker.[Method] With the disease sample of P.infeatans collected from Guyuan in Ningxia Province in 2009 as test material,its DNA was extracted and amplified with PCR,and its products were carried out polyacrylamide gel electrophoresis.[Result] 12% polyacrylamide gel electrophoresis was used to detect primers D13,G11 and PI02,and 8% polyacrylamide gel electrophoresis was used to detect primers PI4B,PI63,SSR4,SSR8 and SSR11,then 0.1% silver nitrate was used to stain,and an ideal electrophoresis and staining effect was obtained.[Conclusion] The electrophoresis and staining method suitable for P.infeatans SSR Marker established in the study had the characteristics of high sensitivity,simple operation and clear bands,which was an effective,simple and quick detection method.

Optimization of SSR-PCR Non-denatured Polyacrylamide Gel Electrophoresis Conditions in Kernelled Apricot

[Objective] The aim was to optimize the SSR-PCR non-denatured polyacrylamide gel electrophoresis conditions in kernelled apricot.[Method]25 accessions of kernelled apricot and three accessions of edible apricot were selected as experimental materials to screen the repeatable SSR loci with high polymorphism by the use of SSR markers combined with non-denatured polyacrylamide gel electrophoresis.And the effect of different factors on electrophoresis conditions was compared to explore the optimal SSR-PCR non-denatured polyacrylamide gel electrophoresis conditions in kernelled apricot.[Result]The optimal non-denatured polyacrylamide gel electrophoresis conditions for SSR-PCR were established as follows：polyacrylamide gel concentration 6%,the ratio of acrylamide to bisacrylamide 29∶1,electrophoresis at 1 000 V for 2-3 h,and staining for 15 min within 0.1% AgNO3.[Conclusion]The optimum electrophoresis system has provided some technical foundations to further study the phylogenetic relationship of kernelled apricots by SSR markers.

Study on the Mechanism of Innovative Montmorillonite for Diarrhea Treatment

[Objective] This study aimed to investigate the mechanism of innovative montmorillonite for diarrhea treatment. [Method] Thirty healthy weanling piglets （Duroc x Landrace x Yorkshire） were randomly divided into five groups and fed with basal diet, basal diet ＋ 1 g/kg innovative montmorillonite, basal diet ＋ 3 g/kg innovative montmorillonite, basal diet ＋ 5 g/kg innovative montmorillonite and basal diet ＋ 3 g/kg Bacillus subtilis microecologic agent, respectively. After four weeks, blood samples were collected via precaval vein, to detect the content of TFF3, NO and SOD in serum by ELISA kits. [Result] Compared with blank control group, the content of TFF3, NO and SOD in high-dose innovative montmorillonite group was extremely significantly increased, extremely significantly reduced and significantly in- creased, respectively; the content of TFF3 and NO in middle-dose innovative mont- morillonite group was significantly increased and significantly reduced, respectively. [Conclusion] Innovative montmorillonite may exert beneficial therapeutic actions on diarrhea by increasing TFF3 and SOD levels and decreasing NO level.

EXPERIMENTAL CHARACTERIZATION OF FLUOROCARBON-MODIFIED POLYACRYLAMIDE/SURFACTANT AQUEOUS SOLUTIONS

The interaction between surfactants and fluorocarbon-modified polyacrylamide (FC-PAM) in aqueous solutionswas evaluated by rheological means and fluorescence spectroscopy and was found to be strong regardless of the surfactant'snature. Two representative surfactants, anionic sodium dodecyl sulfate (SDS) and nonionic Triton X-100, were used. The origin of the interaction and its dependence on the surfactant concentration were discussed.

Preparation of Organic Montmorillonite and Mechanical Properties of Montmorillonite/Unsaturated Polyester Composites

The synthesis process of organic montmorillonite was designed and some kinds of montmorillonitel unsaturated polyester composites using different interlayer spacing montmorillonite were prepared.The interlayer spacing of montmorillonite was investigated by XRD and was increased to 3.98nm.The relationship between the four influential factors and the interayer spacing were regressively analyzed and the mathematical model was established.and the result shows when the content of organic reagent was less than 70%,the relationship between the interlayer spacing and the content was linear as follotes;interlayer spacing=1.771＋2.828× concentration,the effect of the other factors was not significant.Additionally,the testing of mechanical properties of the composites showed the impact strength was improved by 217%.and the bending strength was improved by 355%,when using the montmorillonite（MMT）of the largest interlayer spacing（3.98nm）.The results of ESEM shows the interface is bonded well when the composite specimen contains the 3.98nm MMT.

Fluoride Excess Removal from Brackish Drinking Water in Senegal by Using KSF and K10 Montmorillonite Clays

Fluoride excess in drinking water is noticed in many countries around the world and particularly in Senegal where, in addition to fluoride excess, high levels of salinity are also encountered. In order to reduce fluoride excess in drinking water in the groundnut basin of Senegal, two types of clays namely montmorillonite KSF and montmorillonite K10 as well were used as adsorbent materials. The results show that the pH which was initially alkaline becomes acidic varying from 2.80 to 6.80. The pseudo first-order kinetic model fit well with the adsorption experiments for KSF montmorillonite (r2 = 0.96), while for K10 clay the same model describe the experiments with slight differences (r2 = 0.90). The KSF clay has a better fluoride adsorption capacity compared to that obtained with K10 clay due to the presence of a great level of calcium oxide in the montmorilonite KSF clay.

Drag reduction behavior of hydrolyzed polyacrylamide/xanthan gum mixed polymer solutions

Partially hydrolyzed polyacrylamide（HPAM）as the main component of slickwater fracturing fluid is a shear-sensitive polymer,which suffers from mechanical degradation at turbulent flow rates.Five different concentrations of HPAM as well as mixtures of polyacrylamide/xanthan gum were prepared to investigate the possibility of improving shear stability of HPAM.Drag reduction（DR）measurements were performed in a closed flow loop.For HPAM solutions,the extent of DR increased from 30%to67%with increasing HPAM concentration from 100 to1000 wppm.All the HPAM solutions suffered from mechanical degradation and loss of DR efficiency over the shearing period.Results indicated that the resistance to shear degradation increased with increasing polymer concentration.DR efficiency of 600 wppm xanthan gum（XG）was 38%,indicating that XG was not as good a drag reducer as HPAM.But with only 6%DR decline,XG solution exhibited a better shear stability compared to HPAM solutions.Mixed HPAM/XG solutions initially exhibited greater DR（40%and 55%）compared to XG,but due to shear degradation,DR%dropped for HPAM/XG solutions.Compared to 200 wppm HPAM solution,addition of XG did not improve the drag reduction efficiency of HPAM/XG mixed solutions though XG slightly improved the resistance against mechanical degradation in HPAM/XG mixed polymer solutions.

Cadmium adsorption in montmorillonite as affected by glyphosate

Behaviors of soil heavy metals are often affected by coexisting herbicides due to their physical and chemical interaction. Effect of glyphosate, an herbicide containing -PO 2- 3 and -COOH groups, on cadmium adsorption in montmorillonite was studied in detail. The results showed that the cadmium adsorption quantity in montmorillonite increased with increasing soil solution pH and cadmium concentration as usual, but decreased with glyphosate, which is due to the formation of a low affinity complex of Cd and glyphosate and decreasing solution pH induced by glyphosate addition. When the equilibrium solution pH was below 6.7, glyphosate has little effect on cadmium adsorption, but when the equilibrium solution pH was above 6.7, glyphosate significantly decreased cadmium adsorption quantity in montmorillonite. In addition, the adding order of Cd and glyphosate also influenced Cd adsorption quantity in montmorillonite.

Study on purification technology of polyacrylamide wastewater by non-thermal plasma

In this work, non-thermal plasma has been applied to treat polyacrylamide（PAM） wastewater.We have investigated the influence of the rule of PAM wastewater initial pH, solution concentration and discharge time, discharge voltage on chemical oxygen demand（COD）degradation rate. At the same time, the effect of pH and discharge time on the viscosity removal rate of PAM solution was also studied. Then, the effect of pH on the viscosity removal rate of1.0 gl-1 PAM solution was studied separately. Through orthogonal test, the factors affecting the COD degradation rate of PAM wastewater were determined as follows: discharge time > discharge voltage > solution concentration > wastewater initial pH. The COD highest removal rate of PAM wastewater reached 85.74%, when the optimal conditions are as follows:discharge voltage 40 k V, discharge time 5 h, solution concentration 1.0 gl-1, pH 1.5. This research provides some basic data and new theoretical basis for PAM wastewater purification.