Surface charge and rheological properties of raw porcelain gres suspension with acrylic copolymers bearing carboxylic groups

The continuous demand of porcelain gres as a raw material for many ceramic applications is requiring a particular attention to the green body properties. The fluidity of these suspensions must be appropriate and their solid content must be as high as possible in order to minimize the drying cost. To circumvent this problem, incorporation of polyelectrolytes to get a high state of dispersion could be a solution. In this contribution, the effect of copolymers bearing carboxylate during the preparation of aqueous porcelain gres suspensions was investigated using adsorption isotherms, electrokinetic properties and rheology. The trends by the adsorption isotherms suggest the formation of a monolayer according to the Langmuir model. Moreover, the density of charge of the surface of porcelain gres particle was found to depend on the quantity of adsorbed carboxylic groups. The ability of the acrylic copolymer to stabilize porcelain gres suspension was found to be greatly affected by the content of carboxylic groups contained in the macromolecular chain. Moreover, we analyzed the relation between polymer adsorption and flow properties of concentrated suspension.     

Effects of Solvent Mixtures on Dispersion of Lanthanum-Modified Lead Zirconate Titanate Tape Casting Slurries

The effects of xylenes/ethanol solvent mixtures on lanthanum-modified lead zirconate titanate (PLZT) nonaqueous suspensions were investigated by measuring sediment height, viscosity, and adsorption of dispersant. Well-dispersed colloidal suspensions were obtained in xylene-rich solvents with a minimum amount of menhaden fish oil as a dispersant. It was also shown that adsorption of dispersant on particle surfaces strongly depends on selection of solvent(s). The ratio of solvent mixture affects PLZT solids content of unfired tapes, in which using insufficient as well as excess dispersant could decrease the packing density of particles. Solubility of other organic additives, such as binder, was also considered when selecting a xylene/ethanol ratio.     

以甘蔗渣为原料制备水溶性分散剂的研究

以甘蔗渣、发烟硫酸为原料合成了纤维素硫酸钠和木质素磺酸钠为主的水溶性分散剂 ,同时测定了其表面活性。     

The adsorption of PAHs, BTEX, and heavy metals on surfactant-modified desulfurization sorbents in a dry scrubber

The injection of dry Ca-based sorbents for removing acid gases had been investigated previously. However, the utilization of Ca-based sorbents for adsorbing other air pollutants was rarely examined. The objective of this study was to investigate the reduction of organic compounds polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) and heavy metals by using the desulfurization sorbents in a dry scrubber integrated with a fabric filter. Four surfactants, calcium lignosulfonate, sodium lignosulfonate, alkyl naphthalene sodium sulfonate and β-naphthalene sodium sulfonate condensates, were used as additives to modify the surface characteristics of desulfurization sorbent calcium hydroxide (Ca(OH)₂). Modifying the desulfurization sorbents with surfactants showed different effects on removal of PAHs, BTEX, and heavy metals, and exploited the potential of Ca-based sorbents for adsorbing air pollutants other than SO₂.     

Effects of chemicals and blending petroleum coke on the properties of low-rank Indonesian coal water mixtures

In this study, the effects of different chemical additives including dispersant and stabilizer on the solid loading, viscosity, rheological behaviour and static stability of coal water mixtures have been investigated. In the experiments, naphthalene sulfonate formaldehyde condensate (NSF) was selected as dispersant and carboxymethyl cellulose sodium salt (CMC-Na) and nano-stabilizer were employed as stabilizers. An Indonesian low-rank coal, taken from Berau, East Kalimantan, was used for the study. To obtain high-loaded slurry, Liaohe petroleum coke was used to blend with Indonesian coal sample. The results of the experiments showed that adding chemical additives and blending Liaohe petroleum coke can effectively improve the slurryability of Indonesian low-rank coal.     

Stability of titania nano-particles in different alcohols

The alcoholic suspensions of titania nano-particles were prepared using the methanol, ethanol, isopropanol and butanol as the solvents as well as triethanolamine (TEA) as an dispersant. The colloidal stability of suspensions, both in the absence as well as presence of TEA, was studied by measuring the zeta potential, sedimentation, pH and electrical conductivity of suspensions, dispersant adsorption and particles size distribution. Results showed that in the absence of TEA, the stability of the suspensions increases with the molecular size of alcohol (from methanol to butanol), while the zeta potential decreases. It was also observed that with the addition of TEA up to the optimum dosage (4 mL/L and 1.33 mL/L for isopropanolic and butanolic suspensions, respectively), the stability of isopropanolic and butanolic suspensions increases; however, its addition into the methanolic and ethanolic suspensions, even at very low concentrations in the order of 0.1 mL/L, results in the quick settling of the particles in the suspension. It was found that the mechanism of TEA action as a dispersant, in the isopropanolic and butanolic suspensions, is its protonation and then adsorption on the titania nano-particles, which yields an electrostatic and some steric stabilization mechanisms.     

改性聚环氧琥珀酸对纳米碳酸钙分散性的研究

为避免纳米碳酸钙在水中团聚,采用可生物降解的改性聚环氧琥珀酸作为分散剂。由于改性聚环氧琥珀酸结构单元中有强极性磺酸基团,增强了分散液粒子之间的静电斥力。与聚环氧琥珀酸相比,改性聚环氧琥珀酸作分散剂时纳米碳酸钙悬浊液的稳定性更好,分散液粒子的粒径更小,流动性更好。将三聚磷酸钠作协同分散剂与其配合使用后,可显著提高改性聚环氧琥珀酸对纳米碳酸钙的分散效果。     

Effects of sewage sludge on rheological characteristics of coal-water slurry

The coal-sludge slurry (CSS) containing coal, sewage sludge and water was prepared to study the effects of sewage sludge on rheological characteristics of the CSS. The yield stress, thixotropy and rheological type of CSS were investigated and compared with those of coal-water slurry (CWS). The results showed that the yield stress of CSS appears at the shear rate range from 0.05 to 0.14 s⁻¹. For CSS with the naphthalene sulfonate sodium formaldehyde condensate as dispersant and the sludge/coal mass ratio of 10:100, the yield stress can reach to 22.9 Pa. The thixotropy was quantitatively described by the thixotropy loop area, and sewage sludge can obviously improve the CWS thixotropy. The non-Newtonian behavior of CSS was characterized by a progressive decrease in viscosity with increasing shear rate at the shear rate range from 5 to 180 s⁻¹. By the analysis of FTIR, SEM and optical microscope, hydrophilic functional groups and colloidal structure of sewage sludge play the key roles on the different rheological characteristics of CSS and CWS.     

分散剂对二氧化钛分散性能的影响

用沉淀法来研究超细二氧化钛在水中的分散情况，对比了自制产品丙烯酸-2-丙烯酰胺-2-甲基丙磺酸共聚物（AMAMPS）钠盐和国外分散剂产品YUS-WG5（聚羧酸酯）在不同分散剂用量、不同溶液的pH值时对水相中二氧化钛分散情况的影响，实验证明两者的分散性能相当，可以替代国外产品进行使用。     

Rheology of Concentrated Suspensions Containing Weakly Attractive Alumina Nanoparticles

The use of nanoparticles for the fabrication of new functional ceramics and composites often requires the preparation of concentrated fluid suspensions. However, suspensions containing nanoparticles are limited in solids content because of the excluded volume formed by the dispersant adlayer around the particles. We investigated the effect of the adlayer thickness on the rheological behavior of suspensions containing model alumina nanoparticles, using dispersant molecules with deliberately tailored chain length. The apparent viscosity and yield stress of the particle suspensions were markedly decreased by increasing the dispersant length, mainly due to a reduction of the attractive forces among particles. Fluid suspensions with solids content up to 35 vol% were prepared in toluene using a dispersant length of 2.5 nm. Our experimental results and viscosity predictions based on a hard sphere model indicate that fluid suspensions with up to 43 vol% of 65 nm alumina particles could be prepared using an optimum dispersant length of about 3.6 nm.     

Dispersion of TiO2 nanopowders to obtain homogeneous nanostructured granules by spray-drying

This work deals with the dispersion and stabilisation of nanosized TiO₂ particles in an aqueous medium as a first step in the preparation of spray-dried nanostructured powders.A colloidal route leading to the production of titania nanostructured feedstocks to obtain nanostructured powders was developed. The process was based on the production of homogeneous and concentrated TiO₂ nanosuspensions dispersed in deionised water with a suitable control of pH and the use of an appropriate anionic dispersant. Concentrated suspensions could be obtained by mixing with an ultrasounds probe at different times depending on the dispersing conditions.Homogeneous suspensions prepared were then reconstituted by spray drying into free-flowing powders with an adequate granule size distribution for diverse purposes, such as atmospheric plasma spraying coatings.     

稳定的BaTiO3陶瓷浆料的制备

本文采用胶体"静电位阻稳定机制",以磷酸酯作为分散剂,以沉降高度作为衡量浆料稳定性的参数,研究了BaTiO3粉末的悬浮流变特性及分散剂磷酸酯加入量对BaTiO3浆料稳定性的影响.在最佳pH值和分散剂加入量条件下,制备了高固相含量(50vol%)、稳定性和分散性好的BaTiO3浆料.     

Dispersion and rheological properties of concentrated silicon aqueous suspension

This work focuses on the optimization of the rheological properties of silicon suspensions by changing the concentration of a dispersant and the pH value of the dispersing medium. The zeta potential and rheological properties of silicon suspensions as a function of tetramethyl ammonium hydroxide (TMAH) concentration were carried out. The results show that the isoelectric point of the silicon particles was at pH 1.6. A silicon suspension with 46 vol.% particles displayed a minimum viscosity at pH 9.6. The results also show that TMAH is an efficient dispersant by enhancing the absolute value of the zeta potential of silicon particles. The optimum dosage of the dispersant was 0.4 wt.% of silicon particles.     

Removal of colloidal particles utilizing gelation reaction of sodium alginate

A novel technique utilizing the gelation reaction of natural polymers has been proposed for the separation of solid from liquid in difficult-to-filter colloidal suspensions. This technique is especially effective in the treatment of colloidal muddy water of high solid concentration, which is often produced as a byproduct of certain construction processes. Colloidal suspensions are mixed with a sodium alginate solution, and this mixture is added to a calcium chloride solution, resulting in the entrapping of colloidal particles by the calcium alginate gel. Gel suspensions are then drained gravitationally, followed by mechanical expression of gel particles. Fundamental aspects of this process are investigated by using sodium bentonite as an experimental material. The alginate-bentonite mixture is added dropwise to the calcium solution. Decreasing the droplet size of the mixture expedites gelation since the diffusion of calcium ions into droplets determines the rate of gelation reactions. Reducing the alginate content expedites expression of the gel since alginate content is inversely proportional to the rate of expression.     

萘磺酸盐甲醛缩合物在灭幼脲界面的吸附特性研究

利用残余质量浓度法、ζ电位测定和IR法研究了萘磺酸盐甲醛缩合物分散剂在灭幼脲颗粒界面的吸附量、吸附状态、ζ电位、吸附作用力等性能。分析认为,萘磺酸盐甲醛缩合物分散剂在灭幼脲颗粒界面吸附后具有静电排斥和空间位阻双重作用,这对维持灭幼脲水悬浮剂的分散稳定性具有重要意义。     

Development of a dispersion process for carbon nanotubes in ceramic matrix by heterocoagulation

The surface properties of carbon nanotubes have been changed by heat treatment with ammonia to yield a basic surface or with N₂ to yield an acidic surface without destroying the integrity of the nanotubes. The dispersion state of CNTs could be much improved by the adsorption of a cationic dispersant of poly(ethylenimine) (PEI) or an ionic dispersant of sodium dodecyl sulfate (SDS). Through the electrostatic interaction between components, CNTs could be successfully coated with particles of titania or alumina by colloidal heterocoagulation. A titania coating on 1.5wt% CNTs, shows the same photocatalytic properties in phenol degradation and has advantages in separation and reuse.     

纳米BiVO_4的制备表征及光催化性能研究

以十二烷基苯磺酸钠(SDBS)为分散剂,采用水热合成法制备了纳米钒酸铋,采用红外光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见光(UV-Vis)吸收光谱进行了结构表征.通过模型化合物亚甲基蓝的降解脱色实验研究了其光催化活性,考察了亚甲基蓝初始浓度、催化剂加量、pH等因素对降解率影响.结果表明,纳米BiVO4在可见光照射下具有良好的光催化性能,450 W高压汞灯光照2.0 h,可使浓度为10 mg/L亚甲基蓝溶液的降解率达90%.在环境水污染治理中有良好的应用前景.     

Application of poly(vinyl alcohol) with an alkyl end group containing anionic groups to coal–water slurry as a dispersant

Anionic groups were introduced with copolymerization of corresponding vinyl monomers with vinyl acetate into poly(vinyl alcohol) (PVA) with an alkylthio end group. The polymers were investigated as a dispersant for coal-water slurry (CWM). Anionic groups such as sodium sulfonate and sodium carboxylate enhance remarkably the ability of PVA with an alkylthio end group to disperse coal. Sodium polyacrylic acid with an alkyl end group also showed a good ability of dispersing coal. The order of the ability of dispersing coal in these polymeric dispersants along with sodium napthalene sulfonate formaldehyde condensate (NSF) varied by the kind of coal used. In cases of the polymeric dispersants, the fluidity of coal in terms of dependence of viscosity on shear rate also varied, from dilatency to thixotropy, in accordance with coal used. Impurities in coal as well as surface properties of coal particles might play important roles in the properties of CWM. © 1995 John Wiley & Sons, Inc.     

Role of Sodium Hexametaphosphate in the Flotation of Acanthite Fines from Finely Disseminated Ores

Abstract

The improvement of the flotation of acanthite fines from a finely disseminated ore through the addition of sodium hexametaphosphate (SHMP) as the dispersant has been studied in this work. This study was carried out on the silver scavenger concentrate from the Fresnillo concentration plant in Mexico. The experimental results have shown that the dispersion processing by adding SHMP as the dispersant greatly increased the separation efficiency and the flotation rate of acanthite fines from the ore. This increase was much more remarkable for smaller mineral particles. It has been found that the improvement might be attributed to the fact that SHMP increased simultaneously the electric double layer repulsion and steric repulsion between minerals (valuable and gangue) particles in aqueous suspensions upon the adsorption of polymetaphosphate anions on the mineral surfaces, and thus eliminated the hetero-coagulation of the fine mineral particles in the aqueous ore suspension.     

Effect of 2-Phosphonobutane-1,2,4-tricarboxylic Acid Adsorption on the Stability and Rheological Properties of Aqueous Nanosized 3-mol%-Yttria-Stabilized Tetragonal-Zirconia Polycrystal Suspensions

2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) was evaluated as a dispersant for nanosized 3-mol%-Y₂O₃-stabilized tetragonal-ZrO₂ polycrystal (3Y-TZP) suspensions. The adsorption of PBTCA was characterized using the decolorization method of ferric 5-nitrosalicylate complexes. Maximum adsorption of the dispersant on the 3Y-TZP powder was found to occur at pH 3.0. At pH >3.0, the adsorbed amount decreased with increased pH. Semiquantitative analysis using auger electron spectroscopy showed that PBTCA adsorbed irreversibly on the powder. The surface charge of the powder was evaluated by measuring the zeta-potential in dilute powder suspensions. The suspension was most effectively stabilized at high pH by the high charge induced by the adsorption of PBTCA. Rheological properties of the suspension were evaluated as a function of dispersant amount and solids loading. The optimum amount of dispersant increased with increased solids loading for solids loading >20 vol%. A stable suspension of 35 nm 3Y-TZP particles with a solids loading as high as 32 vol% was obtained using PBTCA as dispersant, in contrast to 28 vol% when using ammonium polyacrylate (NH₄PAA). Theoretical calculations of the interaction between 3Y-TZP particles showed that the stabilization of the suspensions was attributed to a combination of the electrostatic repulsion and a steric barrier caused by the adsorbed PBTCA. Induced coupling plasma analysis showed that PBTCA could be completely burned out during sintering, which confirmed its suitability as a dispersant for 3Y-TZP.