ties, and the parameter indicating its nature is pH, namely pH of the zero charge, which is 8.2. In the medium characterized by the pH below 8.2, the adsorbent material exhibits anion-exchange properties, and at the pH above 8.2 – it becomes a cation-exchanger. For example, the mechanism of arsenate ions removal from aqueous solutions of this adsorbent is close to the removing of arse- nates on weakly basic anion exchangers [Hering et al. 2004; Mc Neill, Edwards 1995]. Activated alumina is much less likely to be used for water treatment than activated charcoal; however, it is used to remove inorganic contaminants such as fluorides, arsenic, selenium, and silicates. The European Commission has granted activated alu- mina oxide as an absorbent material for the re- moval of fluoride ions from water. In addition, adsorption on activated alumina oxide has been proposed by the EPA (Environmental Protection Agency) as an effective and inexpensive technol- ogy to remove arsenic and selenium from drink- ing water, considered among the best available BAT techniques [Davis, Misra 1997; Singh, Pant 2004; EPA 2007; Lin, Wu 2001].
Analyzing the changes in the pH of the treat- ed water in the entire technological system (table 1), it was observed that pH increases in the water after purification on Al 2 O 3 . The largest increase in pH occurred in a series of research at the speed of filtration equal to 5 m/h. In this test series, the pH has increased by 0.70. In the case of other two se- ries, in which the water was purified at 10 and 15 m/h the increase in pH of the water adsorption on Al 2 O 3 was much smaller and amounted 0.2 units. The reason for pH increase of purified water after step associated with the activated alumina is an amphoteric nature of the material. When water contacts Al 2 O 3 on the surface are formed hydrox- ides, that raise the pH of water flowing through the adsorbent bed. The highest increase in pH is when using a speed equal to 5 m/h, due to the lon- ger contact time of the water with Al 2 O 3 granules forming the adsorbent bed.
dialysis or electrodialysis  and adsorption [19-24]. The adsorption of chromium (VI) onto different types of adsorbents, such as activated carbon, activated alumina, peat, leaf mould and wheat bran, has been studied and showed a good affinity with chromium and high amount of removal [19-23]. The Donnan dialysis is a useful membrane process used to recover valuable ions and remove undesirable ones from some waste effluents [24-32]. The theory and principles behind the Donnan dialysis process are recently reviewed by Luo et al. . A number of fundamental and experimental studies have been conducted including treatment of alkali, alkali earths, transition and rare metals [34-39].
In 1978 Sorg and Logsdon  first started to study the arsenic removal technologies, like coagulation, lime softening, ion exchange, adsorption, reverse osmosis and electrodialysis. Jekel  continues their work by testing oxidation processes and activated alumina. Kartinen and Martin  found good results on arsenic removal by using green sand and they also systematically arrange different treatment technologies into catego- ries. UV rays and ozone were introduced for arsenic removal by Kuhl- meier and Sherwood in 1996 . Rott and Friedle  demonstrated in 1999 how to remove arsenic by adsorption onto fresh Fe(OH) 3 precipi- tatation if the water contains iron and manganese. There are a number of technologies used for removing arsenic . It is very important to establish the form in which arsenic is present in water, because the
capacity of the medium ranges between 1400 – 1800 mg/kg, depending on the grade used (ND, 2006). The ability to remove fluoride also depends on the raw water quality and characteristics such as hardness can alter the effectiveness of the treatment process. After removing a certain amount of fluoride from the drinking water, the material becomes saturated with adsorbed fluoride and the capacity to remove fluoride further is reduced. The adsorbed fluoride must then be washed off chemically (using hypochlorite acid, sulphuric acid, alum or sodium hydroxide), in a process known as regeneration. The used activated alumina can be reused after regeneration up to 10 – 12 times (ND, 2006). It should be noted that using sodium hydroxide to regenerate the activated alumina requires neutralization to remove any residual sodium hydroxide from the bed, as the treatment process is pH dependent. As the alkalinity of the raw water increases, the efficiency of the activated alumina decreases. The main disadvantages of activated alumina as a defluoridation technique are the cost of regeneration and operational and maintenance issues (Ganeshi et al, 2003). The fluoride-rich effluent from the cleaning process must also be disposed of carefully to avoid contamination (UNICEF, updated. In their study of Chari K.V., Rao R.J. 5 they found that activated alumina As an excellent adsorbent for removal of fluoride from water of various composition and lowering the fluoride level to <1 mg/lit, which is in accordance with maximum admissible concentration level for drinking water, is readily achieved by activated alumina. The removal of fluoride from Industrial waste more than 96%.The possible removal of fluoride by impregnated alumina can be explained by ion exchange method and hydroxide group on the surface material. It is observed that to reduce the fluoride concentration to low level, activated alumina is the most popular and effective because of ease of application and low cost.
adsorbents such as activated carbons, activated alumina was investigated by Roostaei et al. . Seco et al.  studied the adsorption of heavy metal ions Cu, Cd, Zn and Ni onto activated carbon and reported that adsorption of Cu ions is less sensitive to the presence of other metal ions, when compared to Ni, Cd and Zn. Silica gel, prepared by the reaction between sodium silicate and acetic acid is an amorphous, inert, non-toxic, polar and dimensionally stable form of silica. Due to large number of reactive sites silica gel has a good adsorption capacity for metal ions and phenol. Idris and Saed  investigated the possible utilization of silica gel sludge for the removal of phenol from aqueous solutions and observed that the adsorption capacity increased with decrease in pH. Activated alumina is a granular and highly porous form of alumina available in powder, pellet, or granule form and is prepared by treating aluminium ore so that it becomes porous and highly adsorptive for use in adsorption process. The adsorption of phenol onto activated alumina was investigated by Hassan and Hammad  and it was found that with the increase in the applied voltage, the phenol removal rate increased, while pH increased. The adsorption of heavy metal ions at trace concentrations was successfully studied by Akill et al. and Ceryera et al. onto surface of activated alumina [99, 100]. Therefore, adsorption of heavy metals and phenol on conventional adsorbents such as activated carbon, silica gel and activated alumina etc. have been used widely in many applications as an effective adsorbent, however, the high cost of the activation process limits their use in wastewater treatment applications . The limitations on the use of these conventional adsorbents has lead to research need to find improved alternative non-conventional low-cost adsorbents which will meet several requirements such as regeneration capability, easy availability, cost effectiveness etc and will prove efficient substitutes for pollution control on a large scale.
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ABSTRACT: We have undertaken a study to artificially reduce carbon dioxide using different catalysts in a gasoline passenger caras our continued effort to control carbon dioxide in the atmosphere. Carbon dioxide absorption/adsorption efficiencyfrom the exhaust gas stream using different catalysts such as activated charcoal, activated alumina, ZSM-5 zeolite and activated ZSM-5 zeolite shows a clear trend and dependency on the mass flow rate and surface properties of catalysts. The CO 2 absorption efficiency of these catalysts aremeasured at two different
Kodama et al.(2005) carried out experiments on desiccant cooling process where regeneration was done at low temperature i.e. 60 degree centigrade and heat was obtained from low grade energy such as waste heat or solar heat. Various solid desiccants like silica gel, activated alumina, activated charcoal and zeolite can be regenerated at low temperature by using solar energy which can be easily collected by simple flat plate and evacuated tube solar air collector.
pores configuration at the surface of the porous alumina films is low because the pores develop randomly at the initial stage of the anodization. With the growth of self- organized pores, a densely packed hexagonal pore structure is established gradually. An explosion of porous alumina research was ignited once the capability of producing a nanohole array with excellent regularity was established by Masuda et al. . Highly ordered anodic alumina films have been mostly achieved by the two-step anodizing the aluminum after electropolishing in perchloric acid–alcohol solution. The highly ordered anodic alumina films play important roles in many fields such as photonic crystals and magnetic interaction [10–14]. Recently, another anodic porous photoelectric material, the porous TiO 2 , acquired
pores, reducing the surface area and total pore volume of the catalyst (Table 1). After placing nickel and copper nanoparticles on alumina, density of moderate and weak acids increased significantly . This is due to replacement of nickel and copper with bronsted strong acid sites. Whereas nickel and copper created weak and moderate acid sites, leading to an increase in weak and moderate acid sites after modification with this metals. In addition, it is mutually observed that amount of strong acid site is reduced. Weak and moderate acid sites are more suitable for SO 2 reduction with methane, while their
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High purity of Alumina ceramics can provide such good resistance to chemical attack that can resist hydrofluoric acid and molten alkalis and alkali vapors. The chemical inertness of these same bodies make them ideal for making valves and seals exposed to severe corrosive and abrasive conditions. Alumina ceramics also resist the effects of radiation that can destroy other materials. Alumina ceramic can have very high dielectric strength, high resistivity and low dielectric loss.
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Manabu Wakuda et al  has experimentally identified material removal response of alumina ceramics to the abrasive particles such as aluminum oxide, silicon carbide, synthetic diamond impact in the AJM process. J.wang et al  has experimentally analyzed performance of multipass AWJ machining. The results obtained were proved that superior performance using multipass over single passes AWJ cutting on alumina material. D.K. Shanmugam et al  has investigated experimentally minimise or eliminate the kerf taper in AWJ cutting of alumina ceramics by using a kerf-taper compensation technique. This technique suggested predicting the kerf taper angle both qualitatively and quantitatively within the tested range of the process parameters.
levels of Er 3+ :Yb 3+ system will be reconstructed when doped with Sm 3+ ions in Alumina-Phospho-Silicates sys- tem. It is well known that the absorption cross-section of Er 3+ and Sm 3+ ions are small, for that Yb 3+ ions was used as a sensitizer to increase the Er 3+ and Sm 3+ ions PL emission and offering good spectral overlap with Er 3+ and Sm 3+ transition, thus allowing efficient Yb 3+ -Er 3+ -Sm 3+ energy transfer with subsequent Er 3+ emission. It has been well addressed that the green emissions at 534 nm have been attributed to the intra-4F-transitions of Er 3+ and Sm 3+ ions and were assigned for both rare earth elements to the ( 2 H 11/2 — 4 I 15/2 ) and 4 G 5/2 — 6 H 5/2 , respective-
The self-dispersed AlOOH nanopowders were prepared by the sol-hydrothermal crystallization and charging composite dispersion method. The nanosized AlOOH were dispersed evenly into the mixed slurry of alumina and ﬂuxing agent by the new batching technology of sol homogeneous dispersion and ball-milling-free for preparation of the ceramic body containing 98.1% alumina. The ceramic ball blank formed by cold isostatic pressing was sintered into ceramic ball at ordinary pressure and the temperature lower than 1500 C for 3 h. Using this method,
Numerous studies were reported in the literature using alumina as catalyst support for the production of biodiesel [12-16]. However, all these catalysts used commercial alumina as support, as such little is known on the catalytic activities of mesoporous alumina synthesized from kaolin, especially one obtained from Kano Nigeria. Utilization of kaolin, which is abundant, inexpensive and non-toxic, as precursor for the synthesis of mesoporous γ-alumina will result in chemical processes that are clean, energy efficient, intrinsically safe and responsive to market needs, this will lead to achievement of the requirements for generation of nearly zero waste chemicals, less energy consumption and use of less hazardous chemicals. In the present work, different amount of sodium hydroxide were supported on mesoporous γ-Al 2 O 3 , the synthesis procedure for the
A detail understanding in fabrication of ceramic product i.e. alumina crucibles through slip casting process will be achieved from the research work. Two types of casting, which are drain casting and solid casting are investigated. Talc powder was added into alumina based material. Microstructure phase analysis, flexural properties, and shrinkage properties are studied.
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Compression strengths of alumina matrix coated with hydroxyapatite are lower than those of pure alumina. The addition of HAp leads to increased strength up to a maximum value of 122 MPa, which demonstrates that sintering of alumina is not complete at 1350℃. Alumina matrix coated with hydroxyapatite tends to exhibit increased compressive strength. The change in compressive strength is related the densification of the alumina matrix coated with hydroxyapatite, which densified with increasing coating time up to a maximum of 407 MPa. A maximum hardness of 504 HV was measured for the alumina matrix coated with hydroxyapatite when sintered at higher temperatures.
Not surprisingly, there appears to be a difference in the distribution of the alpha alumina phase for material produced by different calcination technologies. For the modern gas suspension, fluid flash or circulating fluid bed calciners the alpha alumina seems to be preferentially located at the outer surface of the particles, compared to the rotary kiln calcined aluminas where a more even distribution is observed. This indicates that the high heating rates and short residence times in the modern calciners lead to structural variations not only between particles, but also within them. Another possible consequence of the shell formation is that the particles may crack due to a build-up of internal vapour pressure as the water generated in the phase transition is released from the structure. It is also interesting to speculate on what an alpha alumina shell means for the alumina properties in the smelter. It is probable that particularly the kinetics of HF-scrubbing and the dissolution properties are influenced by these compositional variations.
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In AMZ composites, corundum (alumina), mullite, zirconia (tetragonal and/or monoclinic phase) and minor amount of glassy phase are tailored in a way that improve thermo-mechanical and corrosion resistance properties of composites. Corundum with high refractoriness and hardness, mullite with high creep resistance good thermal shock resistance, and zirconia with high toughness and good corrosion resistance form excellent combined properties to AMZ products [2,3,4]. AMZ refractory composites are produced by different routes such as fused cast and reaction sintering of different raw materials such as zircon (ZrSiO 4 ) and
The increasing demand for ceramic composites as cutting tools for machining steel based alloys in machining industries nowadays, is mainly due to the trend towards high speed machining, dry cutting and the need for tools with complex geometry. Because of these reasons, the ceramic material for examples alumina and zirconia which have well known as hard and brittle materials are being developed as cutting tools to penetrate the tooling market with new features, such as longer tool life, able to cut difficult to machine material such as hardened steel, nickel alloys etc.
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