Showing papers on "Activated alumina published in 2001"

Sewage sludge-derived materials as efficient adsorbents for removal of hydrogen sulfide.

Abstract: Sewage sludge-derived materials were used as adsorbents of hydrogen sulfide from moist air. The adsorbent obtained by carbonization at 950 °C has a capacity twice of that of coconut shell-based activated carbon. The capacity of the sludge-derived materials increases with increasing carbonization temperature. It is likely that during carbonization at 950 °C a mineral-like phase is formed that consists of such catalytically active metals as iron, zinc, and copper. The results obtained demonstrate that the presence of iron oxide significantly increases the capacity of commercial carbon and activated alumina. The sludge-derived adsorbents are efficient for hydrogen sulfide removal until the pore entrances are blocked with sulfur as the product of oxidation reaction. For materials in which the catalytic effect is predominant, hydrogen sulfide is adsorbed until all pores are filled with sulfur. There is also indication that chemisorption plays a significant role in the removal of hydrogen sulfide from moist air.

Adsorption and removal of antimony from aqueous solution by an activated Alumina

Abstract: The adsorption of Sb(V) ions from aqueous solutions onto commercially available activated alumina (AA) was investigated. AA has a much higher adsorption capacity than presently used adsorbents. Sb(V) ions are likely adsorbed through electrostatic attraction and/or specific adsorption mechanism, while the optimum pH is found in the range of 2.8–4.3. The Sb(V) ions adsorption capacities increase with increasing temperature. The addition of nitrate, acetate, arsenite, chloride, and silicate ions affected Sb(V) ions adsorption only slightly, while the coexisting ascorbate, arsenate, phosphate, sulfate, EDTA, tartrate, and citrate ions substantially depressed Sb(V) ions adsorption.

Activated alumina as an energy source for peptide bond formation: consequences for mineral-mediated prebiotic processes.

Abstract: The catalytic properties of various forms of alumina were tested for alanine dimerization reaction. The catalytic efficiency of alumina depends on the structure, as well as on acid/base properties of the catalyst. The highest yields of Ala2 were achieved on activated alumina with surface of neutral pH (about 3% conversion after 2 weeks). Thermal analysis of Ala + alumina reaction systems shows that the thermal behavior of amino acid changes substantially in contact with the activated surface of the alumina catalyst. The reaction of Ala is detected as being strongly endothermic by differential thermal analysis of pure amino acid (above 250°C). The alanine endothermic reaction is shifted substantially to lower values (below 200°C) and hardly detectable if activated alumina is present. The reaction mechanism of amino acid activation on alumina surface and its significance for mineral-catalyzed prebiotic peptide bond formation are discussed.

Fluoride in drinking water: the problem and its possible solutions

Abstract: Removal of fluoride ions from model solutions of Tallinn drinking water was tested using Aqua Juraperle (calcium carbonate) and activated alumina as filtration media. The experiments with Aqua Juraperle demonstrated that this filter medium does not maintain fluoride ions. Other water constituents, except iron, were not influenced by the filtration either. The total iron content was reduced by 50%. Filtration through activated alumina reduced the fluoride concentration in water. The sorption capacity of alumina was 4.5 g/kg and volumetric capacity 3.95 g/L. Different coagulants and their doses were tested to remove fluoride with coagulation as well. The coagulant consumption for fluoride removal was 80 mg Al 2(SO4)3 per 1 mg F - . The use

Method and materials for purifying hydride gases, inert gases, and non-reactive gases

Abstract: A process for removing trace amounts of moisture and/or one or more impurities from contaminated hydride, inert and non-reactive gases, thus decreasing the concentration of the impurities to parts-per-billion (ppb) or parts-per-trillion (ppt) levels. The gas purifier materials of this invention include thermally activated aluminas, said aluminas including organic alumina materials, modified organic alumina materials, and modified inorganic aluminas. The thermally activated alumina materials of this invention are activated by heating the alumina material at a temperature between about 50° C.–1000° C. in an inert or non-inert atmosphere or in a vacuum and maintaining the activated material in the inert or non-inert atmosphere or in a vacuum atmosphere subsequent to said activation but prior to use.

Process for producing phenoxyphosphazene compound, flame- retardant resin composition, and flame-retardant resin molding

Abstract: An improved phenoxyphosphazene compound is produced by treating a phenoxyphosphazene compound with (a) at least one adsorbent selected from activated carbon, silica gel, activated alumina, activated clay, synthetic zeolite and macromolecular adsorbents, (b) at least one reagent selected from metal hydrides, hydrazine, hypochlorites, thiosulfates, dialkyl sulfuric acids, ortho esters, diazoalkanes, lactones, alkanesultones, epoxy compounds and hydrogen peroxide, or (c) both the adsorbent and reagent, thereby reducing the acid value of said phosphazene compound to lower than 0.025 mgKOH/g.

The plasma assisted catalytic treatment of gases

Abstract: A catalytic material for the plasma-assisted treatment of the exhaust gases from internal combustion engines, consisting of an activated alumina, which contains silver or molybdena (MoO3). For silver doped alumina, a preferred silver concentration is between 0.1% and 5% by weight. The preparation and use of silver doped alumina material also is described.

EVALUATION OF THE HEAT OF ADSORPTION OF SOME n-ALKANES ON ALUMINA AND ZEOLITE BY INVERSE GAS CHROMATOGRAPHY

Abstract: The isosteric heat of adsorption of some n-alkanes (n-C5 to n-C8) on some adsorbents(activated alumina, natural zeolite(clinoptilolite) and 13X molecular sieve) were evaluated by inverse gas chromatography using the temperature dependence of adsorption The isosteric heat of adsorption of the probes on alumina and clinoptilolite were determined in the finite concentration region, and those on 13X were determined in the infinite dilution region It was found that the adsorption isotherms for alumina and clinoptilolite conform with the Langmuir equation, and the isosteric heats of adsorption increase linearly with increasing carbon number of the probes for alumina and 13X

The kinetics of the partial dehydration of gibbsite to activated alumina in a reactor for pneumatic transport

Abstract: The dehidration kinetics of gibbsite to activated alumina was investigated at four different temperatures between 883 K and 943 K in a reactor for pneumatic transport in the dilute two phase flow regime. The first order kinetic behavior of this reactionwith respect to the water content of the solid material was proved and an activation energy of 66.5 kJ/mol was calculated. The effect of residence time on the water content is given and compared with theoretical calculations. The water content and other characteristics of the products depend on two main parameters, one is the short residence time and the other is the temperature of the dehydration of gibbsite. The short residence time of the gibbsite particles in a reactor for pneumatic transport prevents crystallization into new phases, as established from XRD analysis data. Reactive amorphous alumina powder, with a specific surface area of 250 m2/g, suitable as a precursor for catalyst supports is obtained.

Redox reactions of arsenic in As-spiked lake water and their effects on As adsorption

Abstract: Removal of inorganic arsenic from As-spiked Lake Washington water by sorption onto activated alumina, iron-oxide-coated sand (IOCS), and an ion exchange resin was studied in laboratory systems. The sorption results could be rationalized only by invoking unanticipated changes in arsenic speciation between As(III) and As(V) in the feed reservoir. The changes in As speciation were subsequently confirmed in independent experiments, and the factors controlling the changes were investigated. Oxidation and reduction reactions sometimes occurred in the same system sequentially over a period of days to weeks, and in other systems both oxidation and reduction seemed to be proceeding simultaneously. Because As(III) has a much lower affinity for the adsorbents than does As(V), arsenic breakthrough was much more rapid when the influent arsenic was in the reduced form. In some cases, the combination of speciation changes in the influent and differential sorption of As(III) and As(V) generated breakthrough curves for total arsenic in which the breakthrough increased and then declined for a period before increasing again. Reduction of As(V) to As(III) was facilitated by filtration of the sample and by incubating the sample in the light, and it was impeded by the addition of PO 4 to solution. Neither filtration nor exposure to light had a discernible effect on the rate of As(III) oxidation. As(III) oxidation was facilitated by autoclaving the sample either before or after the As(III) was added. Although arsenic speciation changes are reproducible and explainable when investigating the behaviour of a given water sample under well controlled laboratory conditions, they are not easily extrapolated to other laboratory systems or field conditions, because they result from chemical and microbially mediated reactions that are strongly interrelated and evolve with time.

Leaching of arsenic from coal fly ashes 2. Arsenic pre‐leaching with sodium gluconate solution

Abstract: The present study deals with the development of an efficient and reliable process for safe disposal of coal fly ash to remove arsenic that has been found to be the most easily leachable and hazardous heavy metal in coal fly ash. Pre‐leaching of fly ash prior to disposal by a natural chelating agent, sodium gluconate (SG), was proposed and studied. Several operational factors influencing arsenic leachability, such as concentration of SG solution, liquid to solid ratio, pH, length of leaching time and leaching temperature were examined. Arsenic was found to leach out substantially with SG, but almost no further release was observed from the ash pre‐leached by SG. After the pre‐leaching treatment, the desirable high buffering capacity of the ash was well sustained. SG solution was effectively regenerated by activated alumina adsorption so that it could be successfully reused for multiple leaching/adsorption cycles.

Porous alumina-based cathode for organic light-emitting devices

Abstract: We propose a new cathode for organic light-emitting devices based on anodic porous alumina films. For this purpose usual and modified porous alumina and structured aluminum with removed porous alumina layer can be used. The usage of porous alumina cathode results in more inhomogeneous electric field and, as a consequence, more intensive auto electron emission and cathode efficiency. Owing to extended surface this matrix also gives the possibility to reach higher luminophor concentration without noticeable luminescence quenching. Organic electroluminescent devices of this type are easily produced and can be more efficient and stable as compared with usual layered structures. An intensive secondary electron emission is observed after irradiating of activated alumina matrix by an electron beam. We developed one of the proposed porous alumina cathode based organic electroluminescence structure doped with amorphous naphthalimide derivative. A bright electroluminescence of naphthalimide in such a structure was observed for the first time. The ways of the further development of this structure are pointed out.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Phosphorus-containing activated alumina

Abstract: PROBLEM TO BE SOLVED: To provide a phosphorus-containing activated alumina excellent in hydrothermal stability, less prone to generate a phase transition to boehmite type alumina hydrate caused by a hydrothermal treatment, also less prone to generate the phase transition to α-alumina by the hydrothermal treatment and showing less reduction of its specific surface area SOLUTION: This phosphorus-containing activated alumina is characterized by exhibiting <=20% phase transition rate to the boehmite type alumina hydrate caused by the hydrothermal treatment

Template synthesis and characterisation of nanoporous alumina with narrow pore size distribution from inorganic salts

Abstract: Publisher Summary This chapter describes the template synthesis and characterization of nanoporous alumina with narrow pore-size distribution from inorganic salts. A polyethylene oxide (PEO) surfactant and an aqueous solution of inorganic aluminum salt are used to prepare activated aluminas with narrow pore size distributions (PSD). The condensation of the aluminum hydrolysate species around the micelles of the surfactant is induced by urea. Mesoporous structure of alumina formed as the surfactant is removed. The function of the PEO surfactant depends on synthesis route. Highly porous alumina is obtained by another process, from the same PEO surfactant and an inorganic salt of aluminum. The proposed synthesis approach is of importance to the preparation of activated alumina with various pore structures in industrial practice.

Adsorption and removal of antimony from aqueous solution by an activated alumina: 2. Adsorption rate and column operation with adsorption and desorption cycles

Abstract: Adsorption rates of Sb(V) ions on an activated alumina (AA) were analyzed by batchwise experiments, while the continuous adsorption, desorption, regeneration of AA, and multiple reuse cycles were studied by flow column tests. The adsorption rates increased quickly with the increases of shaking speed and operation temperature. The adsorbed Sb(V) ions were desorbed easily by a 50 mM NaOH solution, and a 41–90 times concentrated Sb(V) solution was yielded correspondingly. AA was effectively regenerated by desorption operation and ca. 93% of the initial adsorption capacity was retained after six times adsorption/desorption cycles.

Improved mesoporous catalysts

Abstract: A method of preparing activated alumina catalysts, which have large pore size and greater resistance to the effects of high temperature. The method includes the steps of; forming an aqueous aluminium hydroxide precipitate from mixing an acidic solution and a basic solution; mixing it with a low molecular weight, water dispersable surfactant; forming a homogeneous composite of aluminium hydroxide and surfactant through keeping the aluminium hydroxide and surfactant in a closed environment at approximately 100 °C; and calcining the aluminium hydroxide alumina precipitate and surfactant mixture at greater than 100 °C to eliminate the surfactant and form the activated alumina (AI2O3).An alumina catalyst having a mesoporous structure, formed from nanometer particles of alumina arranged so as to create interstices.

Resin composition for inhibiting generation of chloride and method for inhibiting generation of chloride using the composition

Abstract: PROBLEM TO BE SOLVED: To provide a resin composition, which is able to efficiently inhibit generation of chlorides such as dioxins when combusted along with a chlorine- bearing polymer by adding a reducing agent to a resin base selected from a polyethylene resin, a polypropylene resin, a polystyrene resin and a polyester resin. SOLUTION: The resin composition for inhibiting generation of chlorides by adding 0.01 to 60 wt.% of a reducing agent to one or more resin bases selected from a resin base selected from a polyethylene resin, a polypropylene resin, a polystyrene resin and a polyester resin. An aluminium compound may be used in combination with the reducing agent. The reducing agent preferably includes hypophoshites or phosphites, and the aluminium compound preferably includes one or more members selected from aluminium phosphate, aluminium sulfate, aluminium hydroxide, aluminium oxide and activated alumina. The resin composition is added to a refuse in an amount of 1.0 to 90 wt.% and incinerated to inhibit generation of chlorides.

Method of manufacturing hydrogen peroxide aqueous solution

Abstract: PROBLEM TO BE SOLVED: To provide a method capable of recovering a purified hydrogen peroxide aqueous solution having low impurity (heavy metals, organic materials) content by efficiently removing impurities in a still residue produced by the concentration of a crude hydrogen peroxide aqueous solution. SOLUTION: In a method of manufacturing hydrogen peroxide aqueous solution, which includes a process that the crude hydrogen peroxide aqueous solution is evaporated in an evaporator to take out a mixed vapor of hydrogen peroxide and water from the column top and to discharge an evaporator still residue solution from the bottom and the still residue solution is stripped with steam in a stripping column to recover hydrogen peroxide in the evaporator still residue solution and to discharge a stripping column still residue solution from the bottom part, the evaporator still residue solution is brought into contact with activated alumina to adsorb and remove the impurities in the evaporator still residue solution and the purified hydrogen peroxide aqueous solution is taken out from the bottom part of the stripping column.

Application of activated alumina in the production of hydrogen peroxide by anthraquinone process.

Abstract: The application of activated alumina in the production of hydrogen peroxide by anthraquinone process(including effect of regeneration of degradation products,factors affecting the regenerating ability of alumina,determination method of regenerating activity and method of replacing deactivated alumina) was reported.

Waste as treating method

Abstract: PROBLEM TO BE SOLVED: To provide a treating method unnecessitating an activated alumina manufacturing stage and energy and reducing the cost of a waste gas purifying agent by performing the conversion of aluminum hydroxide to activated alumina by utilizing waste gas heat in a waste gas treating method for removing harmful material, especially acidic material and dioxins, in waste gas by jointly using calcium hydroxide and aluminum hydroxide. SOLUTION: The aluminum hydroxide is blown into a flue during waste gas temperature of 400-800 deg.C, preferably 450-600 deg.C, and the calcium hydroxide is blown at <=300 deg.C.

Development of a portable filter for arsenic removal from drinking water

Abstract: In the present study, different grades of indigenously available activated alumina (AA) were screened for their arsenic removal capacity. For both As(III) and As(V), A1 (Grade 1, 0.3-0.6 mm) activated alumina has shown better removal efficiency. The optimum pH for the adsorption phenomena was around 7.0. Chlorine at a dose of 20 mg/l could completely oxidize As(III) to As(V), which also assured the bacteriological quality of the water. Among various anions studied, sulfate seems to have maximum competition with arsenic for adsorption sites. A portable filter with a flow rate of 6 l/h and a contact time of 5 minutes could effectively be used for the treatment of arsenic contaminated water. The exhausted activated alumina could regenerate with 4% NaOH solution without much reduction in efficiency.