Showing papers on "Activated alumina published in 1993"

Hcl adsorbent and method for making and using same

Abstract: An HCL adsorbent, and method of making and using the adsorbent, the adsorbent comprising an activated alumina pro-moted with an alkali metal in an amount such that if calculated as alkali metal oxide, the adsorbent contains at least about 5 % by weight alkali metal oxide.

A multilayer model for adsorption of water on activated alumina in relation to adsorption potential

Abstract: Adsorption of water vapor on activated alumina was examined by a gravimetric method. The experimental results are described by a Freundlich-type polynomial with respect to the adsorption potential. In order to characterize the adsorption, a multilayer of water is assumed here on the alumina surface. Considering the hydrogen-bonding, several types of formation are modeled on structural hydroxyl groups supposed as the surface sites. In the modeling, two kinds of rules are observed in the relationship between the accumulating layers; structural ratios of molecules and allotment ratios of the potentials. In accordance with these rules, an attempt is made to derive an expression for the multilayer adsorption in a model by applying a Freundlich-type equation to the surface monolayer adsorption. The derivation gives a polynomial similar to the empirical expression. It is found from comparison of the parameters of both equations that the model multilayer is consistent in the examined adsorption system.

Comparative study of adsorption capacity of various adsorbents for treating dye wastewaters

Abstract: The objective of this laboratory study was to determine the effect of dosage, contact time and type of adsorbents on the color and COD (chemical oxygen demand) removal for dye wastewaters. The adsorption parameters for Langmuir and Freundlich isotherms and mass transfer coefficients from bulk solution to particle surfaces for disperse dye were also determined. The adsorbents used in this study included powdered activated carbon (PAC), granular activated carbon (GAC), activated alumina, molecular sieves, diatomite, and sawdust. For an initial dye concentration of 150 ppm and adsorbent dosage of 15 g/1 and a contact time of 2 hours, the COD removal efficiency was 98%, 60–65%, and 24–30%, for PAC, activated alumina, and molecular sieves, respectively. The order of adsorbent efficiency was found to be: PAC > activated alumina > molecular sieves > GAC > diatomite. The adsorption capacity of diatomite and GAC was very poor. The color removal (color difference or AE∗ab) varied from 45 to 55 for most adsorbents s...

Method for purification of acetonitrile

Abstract: Acetonitrile is purified by treatment with ozone. After ozone treatment is ended, acetonitrile is passed through packed columns of molecular sieve, activated alumina and charcoal or graphitized carbon; the process results in virtually pure acetonitrile obtained at an efficiency unachievable by prior art processes.

Adsorption of Water Vapour on Activated Alumina

Abstract: Results of a detailed experimental study of the adsorption of water vapour on activated alumina are reported. The overall equilibrium isotherms are difficult to correlate since they represent the sum of water held in several different ways. Decomposition of the isotherms into their constituent components leads to a simple and coherent interpretation. It is shown that sorption kinetics are controlled by pore diffusion with some contribution from surface flow at higher loadings.

Liquid-phase adsorption of bulk ethanol-water mixtures by alumina

Abstract: Separation of ethanol-water liquid mixtures can be carried out by selective adsorption of water on activated alumina. The moderate selectivity and heat of adsorption of water on the alumina permits easier and less energy intensive desorption of the adsorbed water. Experimental binary surface excess isotherms, liquid-phase adsorption kinetics and column dynamics for the adsorption of bulk water-ethanol mixtures on Alcoa H152 alumina reported. Model analyses of the data are carried out to quantify the selectivity of adsorption, adsorptive mass-transfer coefficients and the properties of the mass-transfer zones in adsorption columns.

Deacidification of vegetable oils

Abstract: A chromatographic process for deacidification of vegetable oils at ambient temperature. According to the process, which can be retrofitted into deacidification operations using miscella refining or solvent extraction, crude vegetable oil is dissolved in a solvent such as isopropyl alcohol and passed through a column of activated alumina (aluminum oxide) at room temperature. The process, which eliminates physical contact between both oil and an alkaline reagent and oil and water, simplifies subsequent bleaching processes by also removing some color pigments. The spent alumina can be reactivated by washing it with a dilute solution of sodium hydroxide or potassium hydroxide.

Catalyst for purifying exhaust gas and purification system with the same used therefor

Abstract: PURPOSE:To exhibit high catalytic performance without using rhodium by carrying a mixture of both a catalytic active component consisting of at least one kind of metallic oxide selected from the group consisting of iron or the like, palladium and alkaline earth metallic oxide and also activated alumina on a monolithic structural body. CONSTITUTION:A mixture of both a catalytic active component consisting of 0.1-20g at least one kind of metallic oxide selected from the group consisting of iron, cobalt and nickel, 0.5-30g palladium, 0.1-50g alkaline earth metal oxide, 10-150g cerium oxide and 0.1-50g zirconium oxide for 1l of a catalyst and 10-300g activated alumina is carried on a carrier having a monolithic structure. Thereby three components of CO, HC and NOx are simultaneously removed at an extremely small amount without using rhodium.

Novel Adsorption and Desorption Chemiluminescence of 10,10′-Disubstituted 9,9′(10H,10′H)-Biacridinylidenes in Alumina Slurries

Abstract: 10,10′-Disubstituted 9,9′(10H,10′H)-biacridinylidene (1) has a novel chemiluminescence (CL) in an alumina slurry. The CL is yellowish green emissions I and II from the excited singlet state of adsorbed 1 onto alumina, 11*(ads), and blue emission III from the excited singlet state of 10-substituted 9(10H)-acridinone (2), 12*. In this study the effects of alumina activity and solvent polarity on the generation of those emitters were investigated and the mechanism was clarified: 1) 11*(ads) is generated by two-step electron transfers, the first electron transfer from 1 to O2 gives 1+•(ads) accompanied by adsorption of 1 and the following electron transfer from –OH and/or –O− on alumina to 1+•(ads) gives 11*(ads), and 2) 12* is generated from the reaction of 12+ and O2−•, both of which are formed during the reaction of emissions I and II. The two key compounds, 12+ and O2−•, were detected spectroscopically. O2−• in a slurry of 1, benzene, and highly activated alumina was found to be extremely stable and to ge...

Desiccant Degradation in Desiccant Cooling Systems: An Experimental Study

Abstract: The authors conducted experiments to quantify the effects of thermal cycling and exposure to contamination on solid desiccant materials that may be used in desiccant cooling systems. The source of contamination was cigarette smoke, which is considered one of the worst pollutants in building cooling applications. The authors exposed five different solid desiccants to ``ambient`` and ``contaminated`` humid air: silica gel, activated alumina, activated carbon, molecular sieves, and lithium chloride. They obtained the moisture capacity of samples as a function of exposure time. Compared to virgin desiccant samples, the capacity loss caused by thermal cycling with humid ambient air was 10 percent to 30 percent for all desiccants. The capacity loss because of combined effect of thermal cycling with ``smoke-filled`` humid air was between 30 percent to 70 percent. The higher losses occurred after four months of experiment time, which is equivalent to four to eight years of field operation. Using a system model and smoke degradation data on silica gel, the authors predicted that, for low-temperature regeneration, the loss in performance of a ventilation-cycle desiccant cooling system would be between 10 percent to 35 percent, in about eight years, with higher value under worst conditions.

Activated alumina powder and its production

Abstract: PURPOSE: To obtain activated alumina powder having high microscopic pore volume and giving a formed article having high mechanical strength by the molding and rehydration treatment by calcining aluminum hydroxide having specific particle size under specific condition. CONSTITUTION: Aluminum hydroxide (e.g. gibbsite) having an average secondary particle diameter of 0.5-10μm and obtained by Bayer process is instantaneously calcined in an air-flow furnace at an ambient temperature of 500-1200°C in a state accompanied by a hot air stream having a linear velocity of 5-50m/sec at a contact time of 0.1-10sec until the ignition loss of the particle reaches 3-10wt.%. The calcination product is separated and recovered from the hot air at ≥200°C using a cyclone, etc. The obtained powder has an average secondary particle diameter of 0.5-10μm and a crystal form essentially consisting of χ and ρ-alumina. It contains g 0.2cm 3 /g of pore having radius of ≤100Å, has a BET surface area of 200-350m 2 /g, gives a rehydrated product consisting essentially of pseudo-boehmite by the rehydration treatment at 80°C for 24hr in the presence of water and exhibits rehydration property and hydraulic property at ≤100°C. COPYRIGHT: (C)1994,JPO

Removing method of phosphate in radioactive organic solvent

Abstract: PURPOSE:To obtain a method for removing phosphate in a radioactive organic solvent in such a manner as not to produce clad. CONSTITUTION:A method for removing phosphate in a radioactive organic solvent used in a spent nuclear fuel recycling extraction process. An adsorbent prepared by mixing at least one kind or more of catalytic carriers such as activated alumina, silica gel and zeolite, in particular, with powder of a metal oxide such as ZnO, ZrO2, CaO or MgO is brought into contact with the phosphate at a temperature of 5 to 60 deg.C and at a liquid passing velocity SV of 0.5 to 4, whereby the phosphate can be removed by adsorption at a very high adsorption rate.