Showing papers on "Aluminium hydroxide published in 2006"

Arsenate sorption on lithium/ aluminum layered double hydroxide intercalated by chloride and on gibbsite: sorption isotherms, envelopes, and spectroscopic studies.

Abstract: The objective of this study was to provide fundamental knowledge of arsenate sorption on lithium/aluminum layered double hydroxide intercalated by chloride (Li/Al LDH-Cl) and further to reveal the contribution of exposed positive charge surface of Li/Al LDH-Cl created by intercalating LiCl into Al(OH)3 layers to arsenate sorption. Therefore, sorption isotherms, envelopes and extended X-ray absorption fine structure (EXAFS) technique were employed to examine the reaction of arsenate on Li/Al LDH-Cl and on gibbsite. Based on an isotherm study, the sorption maximum of Li/Al LDH-Cl for arsenate was approximately six times higher than that of gibbsite. Sorption envelopes of arsenate on Li/Al LDH-Cl displayed a pH-sensitive behavior from pH 4.0 to 7.0, but it was insensitive to pH above pH 7.0, approaching to the pHpzc of Li/Al LDH-Cl (7.22). This transformation with shifted pHs illustrated that there were two types of reaction sites within Li/Al LDH-Cl that participate in arsenate sorption; one is pH-sensitive...

Combining kinetic investigation with surface spectroscopic examination to study the role of aromatic carboxyl groups in NOM adsorption by aluminum hydroxide

Abstract: The adsorption of a series of aromatic carboxylic acids, with different numbers and positions of carboxyl groups in the phenyl ring, on aluminum hydroxide was investigated with ATR-FTIR and kinetic analyses to verify the role of aromatic carboxyl groups in the surface complexation of NOM with aluminum hydroxide. It was revealed that the formation of outer-sphere complexes dominated the adsorption of most of the aromatic carboxylates over the pH range examined in this study. Inner-sphere complexes were only detected at some pH levels for some aromatic carboxylates adsorption. The aromatic carboxylates were most likely to be adsorbed onto the first surface layer of hydroxyl groups and water molecules without forming coordinative bonds with the aluminum hydroxide surfaces, but strong hydrogen bonds were formed in this process. The adsorption data fitted the pseudo-second-order kinetic model very well. The activation energies of adsorption calculated from the rate constants of pseudo-second-order kinetics agreed with the ATR-FTIR analysis that the aromatic carboxylates, except pyromellitate, were adsorbed predominantly as outer-sphere complexes on aluminum hydroxide at pH 7. This study revealed that phenolic groups may be more significant than carboxylic groups for the chemical adsorption of NOM onto minerals. The presence of additional carboxylic groups enhanced the adsorption considerably, while the enhancement was limited when there were three or four carboxylic groups on the phenyl ring. The adsorption of aromatic carboxylates was affected by the positions and pKa values of the donor groups and the solution pH.

Environment-friendly type charcoal composite material and its preparation method

Abstract: The invention provides an environment-friendly type composite charcoal material, wherein the its components comprises (by weight portion): resin 10-50%, fabric 1-20%, charcoal powder 40-80%, quartz or crystal powder 05-2%, aluminium hydroxide 1-10%

Process for extracting aluminium hydroxide from flyash

Abstract: A process for extracting aluminum oxide from powdered coal ash includes such steps as grinding, calcining, mixing with H2SO4 solution, heating while reaction for extracting aluminum oxide, boiling in water, concentrating, cooling while educing out aluminum sulfate crystals, heating for dewatering, heating for decomposing to obtain gamma-Al2O3, and further preparing metallurgy-class aluminum oxide

Li-based conversion coatings on aluminium: An electrochemical study of coating formation and growth

Abstract: The formation of inorganic conversions coatings on aluminium, without the aid of external polarisation have been studied involving lithium ions in the presence and absence of carbonate in alkaline solutions. Evidence of coating growth produced by open circuit measurements, cyclic voltammetry and electrochemical impedance spectroscopy points towards the formation of a lithium aluminate as pore filler in a matrix of previously produced aluminium hydroxide. Concentration of lithium and solution pH conditioned lithium availability for incorporation into the film. Coatings were found to be more stable in the absence of carbonate as suggested by the lower current densities displayed after lithium incorporation and associated overall higher resistance for the system.

Phosphorus and organic matter removal from synthetic wastewater using alum and aluminum hydroxide

Abstract: At present, chemical processes are widely used to remove phosphorus and organic matter from water or wastewater either as the only advanced treatment method or as a pre-treatment stage to biological treatment, and aluminium salts have been traditionally used as coagulants. In the present study removal of orthophosphate or dissolved organic matter with the use of two aluminium sources: alum [Al2(SO4)3•18H2O] and aluminium hydroxide [Al(OH)3(s)] is examined for the wastewater treatment process. Amorphous aluminium hydroxide was chosen because it is the hydrolyzed (olated) product of alum and an important adsorbent of inorganic and organic substances in soils since bayerite, gibbsite and boehmite contain a large portion of aluminium hydroxides. Laboratory jar test studies were carried out using either an orthophosphate solution (10 mg l -1 ) or a tannic acid solution (50 mgC l -1 ) as simulated wastewater and the effect of parameters such as coagulant dose (up to 15 mg Al l -1 in the case of alum and up to 90 mg Al l -1 in the case of Al(OH)3) and pH (2-12) is investigated. The values of these parameters were based upon measurements on municipal wastewaters from the input of the primary treatment of a wastewater plant in Athens. Orthophosphates have been chosen as a P surrogate as they are the major portion of the total P found in wastewater and tannic acid solution was used as a surrogate for soluble organic matter. It was proven that alum is much more efficient in phosphorus and tannic acid removal than aluminium hydroxide. The optimal pH values are 5-6 in both cases, alum and aluminium hydroxide, although alum is efficient in a wider pH range (4-7) and a mechanism was proposed to interpret these results. In pH values less than 6 the mechanism proposed was chemical bonding between Al species and tannic acid or phosphates creating insoluble complexes while in bigger pH values (6-8) adsorption on solid Al(OH)3. Freundlich isotherm was proven to fit satisfactorily the experimental data for aluminium hydroxide and orthophosphate at 25 0 C suggesting heterogeneous sorption, with KF and N values 49,1 and 0,19 respectively. The findings of this work may not only contribute to a better understanding of the chemistry of chemical wastewater treatment and therefore to an improvement of the process but also on phosphorus and organics fixation in soils that contain a large portion of aluminium hydroxides.

Role of carboxylic and phenolic groups in NOM adsorption on minerals: a review

Abstract: This paper presented the current state of our understanding of the roles of carboxylic and phenolic groups in NOM adsorption and reviewed the contradictory opinions in the literatures. Previous studies carried out by other researchers indicated that aromatic carboxylates were adsorbed onto metal (hydr)oxides via outer-sphere complexes under most conditions and phenolic groups were very crucial for formation of inner-sphere complexes between organic acids and metal (hydr)oxides. Adsorption test with insitu ATR-FTIR spectroscopic investigation were carried out to verify the role of aromatic carboxylic and phenolic groups in the NOM adsorption onto aluminium hydroxide surfaces by using a series of aromatic carboxylic acids and dihydroxybenzoic acids as the surrogate of NOM. Our studies suggested that the formation of outer-sphere complexes dominated the adsorption of most of the aromatic carboxylates over the pH range of 5-9; inner-sphere complexes were only detected at some pH levels for some aromatic carboxylates adsorption; and the aromatic carboxylates were most likely to be adsorbed to the first surface layer of hydroxyl groups and water molecules without forming coordinative bonds with the aluminium hydroxide surfaces but strong hydrogen bonds were formed in this process. Our study also revealed that (1) the presence of phenolic groups can increase the interaction strength of carboxylate groups with aluminium hydroxide; (2) chelate formation involving a carboxylate oxygen atom and ortho-phenolic-oxygen is important for the adsorption of organic matter on aluminium hydroxide at acidic pH; and 3) the phenolic groups adjacent to each other are more important than the carboxylic groups at alkaline pH for organic matter adsorption.

Retarding, corrosion-proof and water type daping slurry prepn. method

Abstract: A water paint with flame-retarding, anticorrosion and damping functions for the structure of vehicle and ship is prepared from mica powder, aluminium hydroxide, styrene-acrylate emulsion, silicic acrylate emulsion, elastic emulsion, flame-retarding agent, emulsifier, propanediol, dimethyl ethanolamine, thickening agent and neutral water through proportional mixing, stirring, regulating pH value, grinding and packing

Influence of aluminium precursor on physico-chemical properties of aluminium hydroxides and oxides

Abstract: The process of hydrolysis of aqueous aluminium sulfate was carried on in ammonia medium at 100°C and for different time intervals (0, 20, 39 or 59 h). The products thus obtained were calcined at 550, 900 or 1200°C for 2 h with the aim to obtain aluminium oxides. The materials were studied with the following methods: thermal analysis, IR spectroscopy, X-ray diffraction, low-temperature nitrogen adsorption, adsorption–desorption of benzene vapours and scanning electron microscopy.

Electroflocculation as potential pretreatment in colloid ultrafiltration

Abstract: Electroflocculation (EF) is a coagulation/flocculation process in which active coagulant species are generated in situ by electrolytic oxidation of an appropriate anode material. The effect of colloidal suspension pretreatment by EF on membrane fouling was measured by flux decline at constant pressure. An EF cell was operated in batch mode and comprised two flat sheet electrodes, an aluminium anode and stainless steel cathode, which were immersed in the treated suspension, and connected to an external DC power supply. The cell was run at constant current between 0.06-0.2A. The results show that pre-EF enhances the permeate flux at pH 5 and 6.5, but only marginal improvement is observed at pH 8. At all pH values cake formation on the membrane surface was observed. The differences in membrane behavior can be explained by conventional coagulation theory and transitions between aluminium mononuclear species which affect particle characteristics and consequently cake properties. At pH 6.5, where sweep floc mechanism dominates due to increased precipitation of aluminium hydroxide, increased flux rates were observed. It is evident that EF can serve as an efficient pretreatment to ultrafiltration of colloid particles.

Fire retardant composite material of nano-aluminium hydroxide, clay and ethylene-vinyl acetate copolymer

Abstract: A composite flame-retarding material is proportionally prepared from the surface-modified aluminium hydroxide nanoparticles, organic montmorillonite nanoparticles, zinc borate, ethene-vinyl acetate copolymer, and maleic anhydride grafted ethene-vinyl acetate copolymer. Its advantages are high flame-retarding effect, mechanical performance, flowability and machinability.

Method for preparing large aperture aluminium hydroxide contained titanium and silicon

Abstract: The invention discloses a large aperture aluminum hydroxide containing titanium-silicon composite agent and the relative preparing method. The invention uses ultrasonic to guide the titanium and silicon into aluminum hydroxide, which can confirm the uniform distribution of titanium and silicon on the surface of aluminum hydroxide, fine the grains of aluminum hydroxide containing titanium and silicon, enlarge the surface of specific pore volume and the average pore size. The inventive aluminum hydroxide containing titanium and silicon can be used as catalyst carrier and the hydrogenation catalyst, while it has better physicochemical index and service performance.

Method of preparing phenolic foam insulation material via foaming at normal temp

Abstract: This invention relates to a method to produce phenolic foam heat preserving materials by ordinary-temperature foaming, is which phenol formaldehyde is adopted as raw materials and anhydrous polyethylene oxide sorbitan mono-oleate, aluminium hydroxide, pentane and composite acid curing agent are added. It has the characteristics that auxiliary agents and reinforcing modifiers can be also added in the raw materials; the ingredients added into the phenol formaldehyde raw materials have proportions as follows: 4~8 shares of polyethylene oxide sorbitan mono-oleate, 0.1~20 shares of auxiliary agents, 0.5~25 shares of reinforcing modifiers, 0~80 shares of aluminium hydroxide, 6~20 shares of pentane and 8~20 shares of composite acid curing agent, counting in 100 mass shares of phenol formaldehyde. In this invention, ordinar-temperature preparation of phenolic foam heat preserving materials above 0 deg. C can be realized. The phenolic foam heat preserving materials prepared have excellent properties; they help save energy and can be applied in spot construction, and therefore, they are promising materials.

Paste of remover for removing printing ink

Abstract: An ink erasing paste is prepared from rubbing agent (2-65 Wt%), shaping agent (3-40) and solvent (10-90). Said rubbing agent is the adhesive-type rubbing agent chosen from inorganic adhesive, organic adhesive and their mixture and/or the water-insoluble rubbing agent chosen from aluminium hydroxide, SiO2,calcium pyrophosphate, calcium hydrogen phosphate, calcium carbonate, etc.

Extracting alumina from fly ash by sulfuric acid

Abstract: Hydrated aluminium sulfate(Al_2(SO_4)_3·18H_2O) were prepared by activating,magnetic separation,leaching by sulfuric acid,leaching by hot water,crystallization processes using fly ash and sulfuric acid as raw materials.Metallurgy grade alumina was prepared by calcining aluminium sulfate,γ-Al_2O_3 dissolved by alkali,decomposition of sodium aluminate solution and calcining aluminium hydroxide processes.The whole flow process was confirmed.The extracting efficiency of Al_2O_3 can reach 91.6 percent under the optimum conditions.

Method for increasing electric strength of high-voltage insulation in humid environment

Abstract: The proposed method for increasing electric strength of high-voltage insulation in humid environment consists inn applying, to the surface of the insulating element, hydrophobic coating consisting of organic-silicon material with addition of titanium dioxide, which solidifies at a normal temperature. The said material is diluted with organic solvent mixed with low-molecular organic-silicon liquid with addition of aluminium hydroxide.

Preparation method of polymerized aluminium chloride having high aluminium content

Abstract: A process for preparing high-Al aluminium polychloride from aluminium hydroxide includes such steps as mixing aluminium hydroxide with industrial hydrochloric acid, adding the catalyst containing P compound and Al compound, heating to 90-180 deg.C, reacting under 1-8.0 Kg/sq.cm for at least 2 hr, depositing and taking supernatant as product.

Process for producing aluminium hydroxide

Abstract: A process for preparing aluminum hydroxide from sodium aluminate solution by electrolysis includes such steps as adding sodium aluminate slurry into the electrolyzer with anode made of Ti, cathode made of Ni or stainless steel and Na ion membrane, electrolyzing, adding crystal seeds to the solution in anode region to preare aluminum hydroxide, and using the solution in cathode region to extract from ore. The high-purity H2 and O2 can be also generated and used for H-O fuel battery.

Method of preparing ultrafine aluminium hydroxide by coprecipitation sublimation

Abstract: A process for preparing superfine aluminium hydroxide from crystalline or anhydrous AlCl3 by codeposition-sublimation method includes such steps as preparing AlCl3-organic solvent-aqueous solution system, adding ammonia water (or gas), codepositing to obtain deposit containing aluminium hydroxide and ammonium chloride, removing solvent, washing, drying at a temp between boiling point and sublimating temp, and drying at a temp higher than sublimating temp for volatilizing ammonium chloride.

Method for preparing unformed aluminium hydroxide

Abstract: The invention discloses a method for preparing non-shaped aluminum hydroxide, relating to an aluminum hydroxide, especially relating to a method for preparing aluminum hydroxide with high acid dissolubility and low density The method comprises following steps: preparing strong sodium metaaluminate with gibbsite and sodium-hydroxide to control solution caustic ratio; diluting with deioned water and adding hole enlarging agent; adding deioned water into autoclave firstly, got solution of raw material and carbon dioxide flows into autoclave to control glue forming temperature; regulating feeding flow rate and filtering, washing and drying slurry and getting said product The invention employs continous feeding and carbon dioxide of high concentration for glue forming to fasten neutralizing reaction and shorten glue forming time, and thus prevents diaspore generation, saves cooling device, increases device usage or reduces autoclave volumn The product can dissolve into hydrogene nitrate of 20% completely and the bulk density is less than or equal to 04 g/ml

Light noninflammable anti corrosion high strength electric cable bridge trough box

Abstract: A cable crane span channel box of fire proof and anticorrosion type prepares by light material with high intensity is a composite body formed by laying inorganic cement layer and glass fiber layer repeatedly as inorganic cement being prepared from magnesium chloride, magnesium oxide, shale, coal powder, rice husk powder, antimony dioxide, aluminium hydroxide, talcum powder, industrial ammonium chloride, ureas resin and phosphoric acid.

On the role of acidity in amorphous silica-alumina based catalysts

Abstract: Amorphous silica-alumina (ASA) is widely used as a solid acid catalyst or as a carrier for well-dispersed metal sulfide or metal catalysts. They are often involved in hydrocracking catalyst formulations, especially so when the aim is to produce middle distillates from heavy oil fractions. With increasing demand for diesel and kerosene balanced acidity in these catalysts to combine high conversion with high middle distillates selectivity is crucial. An important advantage of amorphous silica-alumina as an acidic catalyst is its open texture with substantial mesoporosity as compared to zeolites that typically suffer from diffusion limitations when bulky hydrocarbons need to be converted. Strongly acidic supports also cause excessive coke formation and overcracking of the feedstock resulting in lower middle distillate yields. Therefore, the use of ASA as the acidic component in bifunctional hydrocracking has become important. Although moderate acidity is important for ASA supports, accurate control of the acidity is hampered by a lack of understanding about the origin of acid sites in these materials and how they are formed. Regarding the former, the nature of the Bronsted acid sites (BAS) has not been unequivocally established. The more widely shared opinion is that the Bronsted acidity derives from tetrahedral Al3+ in the silica network, as initially proposed by Thomas and Tamele in the late 1940s. This proposal however has remained inconclusive. Alternative explanations for the acidity have been also been proposed. These include Lewis acidic Al ions substituting for protons of surface silanol groups and the higher acidity of silanol groups in the presence of neighbouring aluminium surface atoms The other reason that surface acidity of ASAs is understood to a much lesser extent than that of zeolites relates to the complex surface composition of these mixed oxides. ASAs are made by co-precipitation, co-gelation or grafting processes and in nearly all cases, the resulting materials contain a non-random distribution of aluminium in silica. The present project was thus undertaken with the aim of (i) synthesizing a set of ASA materials by as controlled a method as possible for use in catalytic activity studies and (ii) to learn about the genesis of Bronsted acid sites in ASAs and their strength. The synthesis method chosen was a well-defined variant of grafting, viz., homogeneous deposition-precipitation. The entire process of the deposition of aluminium on silica and subsequent calcination was followed by 27Al NMR spectroscopy . The study showed that the aluminium species in the dried precursors is a function of pH and starting aluminium concentration. At pH of 3 and at low aluminium concentration, the surface mainly consists of tetrahedral and octahedral aluminium species. Under these conditions an increase in pH gives mainly rise to tetrahedral aluminium species on the surface. This is attributed to the further condensation reaction occurring with the surface silanol groups. However, with increasing aluminium concentration, the deposition mechanism involves reaction of aluminium species in solution with species already grafted on the surface. This results in the formation of polymeric aluminium species. In addition, at higher aluminium concentrations some precipitation of aluminium hydroxide also occurs. When the dried precursors are then calcined, redistribution of the grafted aluminium species occurs, mainly with a small fraction of aluminium diffusing into the silica matrix thereby resulting in Bronsted acid sites. The formation of Bronsted acid sites upon calcination was also evidenced by n-alkane hydroconversion activity tests, which requires the presence of strong acid sites. From this systematic study the surface of amorphous silica- alumina could be described as consisting of three different species, namely a pure silica-alumina phase that originates from isolated aluminium grafted onto the silica surface, domains of aluminium oxide and a small fraction of aluminium in the silica network responsible for the strong Bronsted acidity. By following the selective H/D exchange of acidic hydroxyl groups in aluminosilicates by IR spectroscopy clear evidence was provided for the existence in ASAs of BAS comparable in strength to the bridging hydroxyl groups in zeolites. The method is able to distinguish various types and strengths of strong BAS in luminosilicates (zeolites, clays, ASAs) such as enhanced acidic sites in steam calcined faujasite zeolites. By carrying out the H/D exchange under conditions under which zeolites selectively exchange their bridging hydroxyl groups, weak bands were observed at 2630 and 2683 cm-1 in the deuteroxyl region of ASAs. By quantification it follows that the concentration of strong BAS in ASAs is 2-3 orders of magnitude lower than in zeolites. A number of techniques (CO IR, pyridine IR, alkylamine TPD, Cs+ and Cu(EDA)22+ exchange, 1H NMR and m-xylene isomerization) was used to validate the H/D exchange FTIR results and provide further insight into the heterogeneous surface composition of ASA. The results show that the surface contains both Bronsted and Lewis acid sites of varying acidity. The number of strong Bronsted acid sites of zeolitic strength is very low (<10 µmol/g). Careful interpretation of IR spectra of adsorbed CO and pyridine confirmed that the surface contains only very few of such sites. Other methods suitable to estimate strong BAS involve an adaptation of the well-known decomposition of alkylamines and titration of such sites by a base during m-xylene isomerization. These sites originate from Al substitutions in the silica network. Besides, the surface contains between 50-150 µmol/g of a weaker form of BAS, which can be easily quantified by CO IR. Cu(EDA)22+ exchange also appears to probe weak BAS. The structure of these sites remains unresolved, but some of the results suggest that these are related to paired sites, involving the interaction of strong Lewis acid sites with silanol groups. In addition, the surface of ASA contains two forms of Lewis acid sites: (i) a weaker form associated with segregated alumina domains and probably containing five-coordinated Al species that make up the interface between such domains and the ASA phase and (ii) a stronger form which are lower coordinated Al sites grafted to the silica surface.

Method for preparing aluminium hydroxide micropowder

Abstract: The invention relates to a preparation method for micropowder aluminum hydroxide. Wherein, adding aluminum hydroxide as crystal seed into the material of sodium aluminate solution; liquid-solid separating the slurry, clearing and baking the solid; then using gas flow grinder for depolymerisation and stepped treatment to obtain the final product. Compared with prior art, this invention improves product quality and purity obviously, and reduces oil suction quantity and conductivity and sodium oxide content in product greatly.