Effect of Polycarboxylic Acid Used as High-Performance Dispersant on Low-Rank Coal-Water Slurry

A new polycarboxylic (PC) acid was prepared from copolymerization of 2-methyl-1-butylene alcohol polyoxyethylene ether (HPEG), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and used as a high-performance dispersant in low-rank coal-water slurry (CWS). The optimized conditions are as follows: the reaction temperature is 80°C, the mole ratio of HPEG, AA, and AMPS is 1:3:0.3, and the inherent viscosity of PC polymer is 49.26 ml/g. The molecule structure of PC polymer was characterized by means of FTIR. Moreover, the apparent viscosity, static stability, and rheological property of CWS with the concentration of 63.0 and 65.0 wt% were all determined by adding PC hyper-dispersant or naphthalene sulfonate-formaldehyde (NSF) condensate dispersant at 0.5 wt% dosage. The result shows that PC dispersant has better properties than commercial NSF product in low-rank CWS. The effect was well rationalized by a combination of electrostatic repulsion force, wetting property, and steric hindrance provided by PC polymer.     

Effect of thickener structure on paper-coating color properties

Physical and chemical properties of clay-based paper-coating colors have been characterized. The “surface potential” (zeta potential) of kaolin particles used in paper-coating formulations was determined as functions of pH and sodium polyacrylate (used as a dispersant) concentration. The optimal pH and dispersant concentration have been established. The effect of adsorption of two different thickeners on the kaolinite particle potential was also investigated. The rheological properties of coating colors, thickened with an associative polymer and a commonly used thickener, have been compared. The rheological behavior of all the coating colors studied was found to be similar, except for the magnitude of the elastic modulus, which was considerably larger for the more hydrophobic thickener. The water-retention properties of the colors could be qualitatively correlated with the molecular structure of the thickeners. An interaction mechanism (e.g. formation of hydrophobic micellar domains) between kaolinite particles and the associative polymer has been proposed. Received: 10 August 2000/Accepted: 2 January 2001     

Physical Chemistry or Biological Interfaces A. Baszkin & W. Norde,editors. Marcel Dekker,Inc. New York, 1999, hardbound,pp. ix + 836; $225

The size distribution and morphology of microcrystalline cellulose (MCC) particles and the effect of pH on the rheological properties of their dilute aqueous dispersion were studied. The 0.3 wt% aqueous dispersion of fine particles (89 nm) also showed solid‐like dynamic viscoelastic behavior at low pHs (below pH 3), in contrast to liquid‐like behavior at high pHs. These findings suggest that at lower pHs the electrostatic repulsion force between MCC particles decreases to induce the aggregation of particles into a three‐dimensional network structure. The minimum empty space in the network structure is expected to be 450 nm or more.     

Rheology Behaviors of C22-Tailed Carboxylbetaine in High-Salinity Solution

Viscoelastic wormlike micelles have attracted special interests over the past decade due to their unique rheological response. Few efforts were however devoted to the rheological properties of worms in high-salinity solution. Here, worm-containing viscoelastic fluid is designed from single N-erucamidopropyl-N,N-dimethyl carboxybetaine (EMAB), using brine water (total dissolved solids: 32,868 mg L^?1; [Ca²⁺] + [Mg²⁺]: 873 mg L^?1) as solvent. Upon increasing concentration, EMAB brine solution shows remarkable macroscopic viscoelasticity above a low overlapping concentration (0.04 wt%) without adding special hydrotropes, implying a giant 3D network-like entanglement formation. Such a viscoelastic network aggregates exhibit thermo-induced thickening behavior in a comparable temperature range due to the hydrogen bond interaction, and excellent thermal stability. The apparent viscosity at 170 s^?1 can keep above 50 mPa · s at 130°C for 2 hours. These preliminary results will give EMAB a rich prospective for use as rheological modifier, especially for using in some extremely environment such high temperature, high salinity, and high shear.     

Characterization of concentrated colloidal ceramics suspension: a new approach

The dispersion behavior of a concentrated ceramic suspension (Al(2)O(3)) has been investigated in terms of capillary suction time (CST) with varying solids concentration both in the absence as well as in the presence of dispersant (APC). The CST value is found to be the lowest at the pH(iep) whereas it increases as the pH is changed either to the acid side or alkaline side due to the repulsive forces acting among the neighboring particles keeping them in more dispersed state. It has been further observed that the CST value increases with increasing concentration of solids in the suspension. The dispersability of the suspension has been quantified in terms of dispersion ratio (DR). The higher the dispersion ratio of a particular system above unity, the better is the dispersability and vice versa. Further, quantification of dispersion stability by the CST technique is found to be useful and practical for optimization of different parameters concerning suspension stability. A correlation is found among the CST, zeta potential, colloidal stability, and maximum solids loading. It has been finally concluded that the CST method could be potentially employed as a quantitative and diagnostic technique for characterizing concentrated ceramic suspension.     

Dispersion of TiN in aqueous media

The dispersion of TiN powders in aqueous media was studied through XPS, zeta potential, adsorption, sedimentation, and rheology measurements. XPS showed that there are TiO2, TiN, and TiOxNy sites on the TiN particle surface. In the absence of dispersant, the isoelectric point (pH(IEP)) of the TiN particles was at pH 2.2. Based on the surface properties of TiN particles, a cationic polymer, polyethylene imine (PEI), was selected as a dispersant. In the presence of PEI, the pH(IEP) shifted from pH 2.2 to pH 11.10. It was evidenced that TiN slurries could be stabilized around pH 9.50 with 1-2 wt% PEI as dispersant. Subsequently, TiN slurries with solid content as high as 57 vol% were developed and exhibited dilatant rheological behavior at high shear rate. The results showed that PEI is an effective dispersant for TiN in aqueous media.     

Influence of Polycarboxylate Dispersants with Different Molecular Structures on the Performance of Coal Water Slurry

Polycarboxylate dispersants have variable structures and can be designed according to practical needs. Further study on the influence of molecular structures on the performance of coal-water slurry (CWS) has vital significance. A variety of polycarboxylate dispersants was designed and synthesized with different monomers. The performance of each dispersant for the low-rank China CWS (i.e., Shenfu coal) was evaluated. Results showed that sodium p-styrene sulfonate (SSS) was the most efficient monomer with better adsorption performance on the surface of coal particles and lower apparent viscosity (i.e., mole ratio of SSS and acrylic acid (AA) sodium 65:35, CWS concentration 63 wt%, dispersant dosage 0.5 wt%). Polyethylene glycol acrylate (PA) was also effective. In addition, 5 wt% cationic monomer methyl acryloyl oxygen ethyl trimethyl ammonium chloride (DMC) was introduced into the structure. The polycarboxylate dispersant with optimal molecular structure was applied in Shenfu coal. The performance of water slurry could meet the national standards well (i.e., apparent viscosity 920 mPa · s), displaying good rheological property and stability.     

Rheological characteristics of municipal thickened excess activated sludge (TEAS): impacts of pH,temperature, solid concentration and polymer dose

Rheological characterization of sludge is known to be an essential tool to optimize flow, mixing and other process parameters in wastewater treatment plants. This study deals with the characterization of thickened excess activated sludge in comparison to raw primary sludge and excess activated sludge. The effects of key parameters (total solid concentration, temperature, and pH) on the rheology and flow behavior of thickened excess activated sludge were studied. The rheological investigations were carried out for total solid concentration range of 0.9–3.7 %w/w, temperature range of 23–55 °C, and pH range of 3.6–10.0. Different rheological model equations were fitted to the experimental data. The model equations with better fitting were used to calculate the yield stress, apparent, zero-rate, infinite-rate viscosities, flow consistency index, and flow index. The decrease in concentration from 3.7 to 3.1 %w/w resulted in a drastic reduction of yield stress from 27.6 to 11.0 Pa, while a further reduction of yield stress to 1.3 Pa was observed as solid concentration was reduced to 1.3 %w/w. The viscosity at higher shear rate (>600 s^?1) decreased from 0.05 Pa·s down to 0.008 Pa·s when the total solid concentration was reduced from 3.7 to 0.9 %. Yield stress decreased from 20.1 Pa down to 8.3 Pa for the Bingham plastic model when the temperature was raised from 25 to 55 °C. Activation energy and viscosity also showed decreasing trends with increasing temperature. Yield stress of thickened excess activated sludge increased from a value of 6.0 Pa to 8.3 Pa when the pH was increased from 3.6 to 10.0. The effect of polymer dose on the rheological behavior of the thickening of excess activated sludge was also investigated, and the optimum polymer dosage for enhanced thickener performance was determined to be 1.3 kg/ton DS.     

水煤浆添加剂与煤之间的相互作用规律研究 Ⅰ. 复合煤颗粒间的相互作用对水煤浆流变性的影响

使用12种不同分散剂对14种不同变质程度的煤进行了成浆性实验，分析了182个水煤浆(CWS)样品的流变性。结果表明，低变质程度和高灰煤浆多呈屈服假塑性，煤的性质起主导作用；变质程度高且灰分较低煤浆的流变性，主要依赖于分散剂的结构与性质；分子结构单元立体空间效应大，疏水基团与亲水基团呈立体间隔分布的分散剂，易形成屈服假塑性CWS；分子线度长，亲水基团与疏水基团呈线性间隔分布的分散剂，易形成胀塑性CWS。复合煤粒间的相互作用方式是决定CWS流变特性的关键。     

Aqueous Dispersions of Positively Charged Al/Mg Mixed Metal-Hydroxide Particles:Surface Chemistry and Rheological Properties

The solids concentration, pH and NaCl were found to have a very significant effect on the rheological properties of aqueous dispersions of positively charged Al-Mg mixed metal hydroxide particles (Al-Mg MMH). At low solids concentrations the flow curves of the dispersions at natural pH followed the Newtonian model very well in the observed range of shear rate, while at high solids contents the dispersions developed a yielding type of response, with yield stress increasing rapidly as solids concentration increases. The variation in rheological properties with pH and NaCl contents correlated well with the change in surface properties of Al-Mg MMH particles. Al-Mg MMH dispersions with maximum yield stress occurred near the isoelectric point (IEP) where the Zeta potential (or electrophoretic mobility) is zero. At the IEP, the shear yield stress decreased monotonously in magnitude as a function of the increasing NaCl concentration, which is in contrast to the increment in the yield stress observed below the DEP at NaCl concentrations less than 0.1 mol dm^-3. At low NaCl concentrations, significant shear yield stress differences exist at and below the IEP. By contrast, at high NaCl concentrations, almost identical shear yield stress versus NaCl results are obtained in both cases.     

Effect of Process Variable on the Gelation Time of Sulfonated Polyacrylamide Nanocomposite Hydrogel

Among the methods available to reduce water production during oil recovery, injecting a gelling system composed of a polymer and a crosslinker has been widely used. In this study, a Plackett-Burman design was used for screening a large number of factors such as concentrations of polymer, crosslinker, pH, temperature, and presence or absence of NaCl, CaCl₂, MgCl₂, KCl, thiourea, sodium lactate, and nanoclay on the gelation time of sulfonated polyacrylamide nanocomposite hydrogels by rheological tests. Among these factors, temperature, pH, and CaCl₂ concentration were found to have the greatest effect on the gelation time. The effects of these three factors and their interactions on the gelation time were then determined by using central composite design of response surface method. As a result, the interactions of CaCl₂ concentration with temperature and pH were considerably more than the interactions of pH and temperature on the gelation time. At low pH (3 < pH < 7), the gelation time decreased by decrease of pH while at CaCl₂ concentration of 3750–11250 ppm and at 7 < pH < 11, the gelation time increased with the increase of pH. It was found that temperature was the most effective parameter to control the gelation time.     

In Vitro Skin Permeation Enhancement of KIOM-MA-128 by Monoolein Cubosomes

Monoolein (MO) cubosomes were investigated in terms of in vitro skin permeation enhancer of KIOM-MA-128 (MA-128), a natural product known to be efficacious against atopic dermatitis. First, an aqueous suspension of MA-128 was prepared by homogenizing the powder in Pluronic F-127 (a dispersant) solution in water. The Pluronic F-127 concentration and the pH have no significant effect on the size and the zeta potential of MA-128 particles. The mean diameters and the zeta potentials fell within 1000–1500 nm and ?10 to ?20 mV, respectively. The sedimentation rate of the particles was lower at a higher concentration of the polymeric dispersant, possibly because the polymeric surfactant can act as a spring and push away approaching particles. The size of MO cubosomes was tens to hundreds of nanometers and exhibited black and white stripes. Cumulative amount of MA-128 permeated through hairless mouse skin was obviously higher when the cubosome was included in the MA-128 suspensions. However, the cumulative permeation amount was inversely proportional to the content of cubosomes, when the contents of cubosome in the suspension increased from 0.5% to 2.0% with MA-128 concentrations kept constant (2%).     

Surfactants for CNTs dispersion in zirconia-based ceramic matrix by sol–gel method

Zirconium oxide is a ceramic material widely studied due to its mechanical and electrical properties that can be improved with the use of carbon nanotubes (CNTs) as reinforcement. The synthesis of CNT/zirconia composites by sol–gel method is still very scarce, due to the hydrophobic nature of the CNTs, being their dispersion in aqueous medium an intrinsic difficulty to the synthesis. In this work, we present a sol–gel synthesis for MWCNTs/zirconia composites, where two kinds of surfactants, sodium and ammonium stearates dissolved in water (1 g/100 mL), were used as dispersant agents for multiwall carbon nanotubes (MWCNTs). They are cheap and easy to prepare, and were very effective in dispersing the MWCNTs. Different quantities of MWCNTs (up to 5 wt%) were added in the solution of stearate/water and this solution with the highly dispersed MWCNTs was added to the zirconia sol–gel, producing composites of MWCNTs/zirconia with different concentrations of MWCNTs. All the powders were heat treated at 300 and 500 °C and the powder characterization was performed by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR). The composite MWCNTs/zirconia remained amorphous at 300 °C and presented a tetragonal phase at 500 °C with an average grain size of about 20 ± 3 nm, determined by the Scherrer equation from the XRD patterns. For these crystalline samples, TEM images suggest a more effective interaction between MWCNTs with ZrO₂ matrix, where it can be observed that the carbon nanotubes are fully coated by the matrix.     

Polyphosphate interaction with aluminium-doped titania pigment particles

The interaction of a widely used Calgon™ polyphosphate dispersing reagent with aluminium-doped titania pigment particles has been investigated using electrokinetic and rheological studies combined with adsorption isotherms. The influence of pH, aluminium dopant concentration and polyphosphate concentration is reported. Polyphosphate adsorption density and affinity with the titania pigment surface is highest under acidic solution conditions. This however, does not necessarily transfer to enhanced dispersion properties at low pH values. At pH 9, the polyphosphate adsorption density correlates directly with a reduction in pigment particle interactions making polyphosphate an effective titania pigment dispersant under alkaline conditions. Conversely, at pH 4, polyphosphate adsorption densities less than 0.1 mg m⁻² have no effect on the colloidal stability of the titania particles and their Newtonian flow behaviour. At adsorption densities of 0.1 mg m⁻², approaching the iep (near 0.2 mg m⁻²), the suspension aggregates. It is not until the polyphosphate adsorption density is greater than 0.3 mg m⁻² that the titania pigment suspension begins to restabilise. It is proposed that chemisorption dominates polyphosphate adsorption at pH 9 whilst at pH 4 a combination of chemisorption and electrostatic adsorption occurs. Stabilisation by the polyphosphate present at the pigment surface depends on both electrostatic and steric effects. At high pH, both are effective but at low pH, electrostatic stabilisation is partly neutralised and higher adsorption densities are required for effective stabilisation.     

The effect of particle size on hydrolysis reaction rates and rheological properties in cellulosic slurries

The effect of varying initial particle sizes on enzymatic hydrolysis rates and rheological properties of sawdust slurries is investigated. Slurries with four particle size ranges (33 microm < x < or = 75 microm, 150 microm < x < or = 180 microm, 295 microm < x < or = 425 microm, and 590 microm < x < or = 850 microm) were subjected to enzymatic hydrolysis using an enzyme dosage of 15 filter paper units per gram of cellulose at 50 degrees C and 250 rpm in shaker flasks. At lower initial particle sizes, higher enzymatic reaction rates and conversions of cellulose to glucose were observed. After 72 h 50 and 55% more glucose was produced from the smallest size particles than the largest size ones, for initial solids concentration of 10 and 13% (w/w), respectively. The effect of initial particle size on viscosity over a range of shear was also investigated. For equivalent initial solids concentration, smaller particle sizes result in lower viscosities such that at a concentration of 10% (w/w), the viscosity decreased from 3000 cP for 150 microm < x < or = 180 microm particle size slurries to 61.4 cP for 33 microm < x < or = 75 microm particle size slurries. Results indicate particle size reduction may provide a means for reducing the long residence time required for the enzymatic hydrolysis step in the conversion of biomass to ethanol. Furthermore, the corresponding reduction in viscosity may allow for higher solids loading and reduced reactor sizes during large-scale processing.     

Fumaric Acid Production from Alkali-Pretreated Corncob by Fed-Batch Simultaneous Saccharification and Fermentation Combined with Separated Hydrolysis and Fermentation at High Solids Loading

Production of fumaric acid from alkali-pretreated corncob (APC) at high solids loading was investigated using a combination of separated hydrolysis and fermentation (SHF) and fed-batch simultaneous saccharification and fermentation (SSF) by Rhizopus oryzae. Four different fermentation modes were tested to maximize fumaric acid concentration at high solids loading. The highest concentration of 41.32 g/L fumaric acid was obtained from 20 % (w/v) APC at 38 °C in the combined SHF and fed-batch SSF process, compared with 19.13 g/L fumaric acid in batch SSF alone. The results indicated that a combination of SHF and fed-batch SSF significantly improved production of fumaric acid from lignocellulose by R. oryzae than that achieved with batch SSF at high solids loading.     

Evaluation of Dispersant Efficiency for Aqueous Alumina Slurries by Concurrent Techniques

This article reports on results from a comparative study assessing a suitable method for dispersant efficiency evaluation in the case of water‐based suspensions of ultrafine alumina stabilized by a commonly used dispersant, Dolapix CE64. The following measurements were evaluated: zeta potential, specific surface charge, sedimentation behavior, and capillary suction time. The suitability of each of the tested techniques is discussed. A good agreement between the zeta potential and the specific surface charge as a way to determine the optimal dose of dispersant is documented.     

The Effect of Solution pH Value on the Morphology of Ceria–Yttria Co Stabilized Zirconia Particles Prepared Using the Polymerizable Complex Method

Ceria–yttria co stabilized zirconia (CYSZ) was synthesized from solutions through the polymerizable complex method. The only difference in the preparation of the CYSZ samples was the pH of the starting solution, which was set at 1, 7 and 12, respectively. Transmission electron microscopy and scanning electron microscopy analysis revealed that the sample with the pH value of 1 had good homogeneity, low agglomeration, and a quasi-spherical shape with the particle size of 41 nm, while by increasing the pH up to 7 and 12, the particles became more disordered and no more in the range of nano sized materials (≤100 nm). Fourier transform infrared spectroscopy was employed to evaluate the bonding characteristics of the obtained gels at different pH values. thermogravimetric analysis, together with differential thermal analysis, was used to study the differences in the properties of dried gels with temperature. Crystallographic structure of the final product was also studied using X-ray diffraction.     

Dispersion and agglomeration mechanism of flaky graphite particles in aqueous solution

The dispersion and agglomeration behavior of flaky graphite particles in an aqueous solution was studied. The small particles of flaky graphite naturally formed a large and compact agglomeration in an aqueous solution at pH 7.0 and 9.0, respectively. The theoretical calculation result based on typical DLVO theory was opposite the phenomenon observed by optical microscope, indicating that the interaction force between the flaky graphite particles exceeded the van der Waals and electrostatic double-layer forces. When the extended DLVO theory was used, the total interaction energy (U_T = U_A + U_R + U_HI) was negative over most of the distance range, indicating that the agglomeration of the small particles was attributed to the attraction. This result indicated that hydrophobic interactions dominated the dispersion and agglomeration behavior of the hydrophobic flaky graphite particles.     

Influence of cellulose nanofibers on the rheological behavior of silica-based shear-thickening fluid

In this work, the influence of cellulose nanofibers (CNFs) on the rheological behavior of silica-based shear-thickening fluid (STF) is investigated. CNFs of 150–200 nm in diameter were extracted from cotton fibers using a supermasscolloider. CNF-reinforced STF of different concentrations (0.1–0.3 wt.%) was prepared via an ultrasonication technique. The presence of CNFs and their interaction with the silica nanoparticles in the STF were analyzed using SEM and FTIR. The addition of a minute quantity of CNF to the STF (0.3% CNF-reinforced STF) caused a marked increase in the peak viscosity, from 36.8 (unmodified STF) to 139.0 Pa s (0.2% CNF-reinforced STF), and a concomitant decrease in the critical shear rate from 33.45 to 14.8 s^?1 . The presence of a large number of hydroxyl groups on the CNFs enhanced their interaction with the nanoparticles via hydrogen bonding, which induced shear thickening. The mechanism of the interaction between silica nanoparticles and CNF was also demonstrated. Oscillatory dynamic rheological analysis showed that the addition of even a small amount of CNF led to higher elastic behavior in the system at lower shear rates. In contrast, a more viscous nature was demonstrated at higher angular frequencies. As the concentration of  nanofibers in the STFs increased, the crossover point between storage and loss modulus shifted to higher angular frequencies, implying stronger interaction between the constituents of the STF. The dynamic viscosity profile of all samples also exhibited shear-thickening behavior.