Alumina is the name linked to alum, a compound of Aluminium and Disulphate. Alumina was first extracted from clay using Sulphuric acid in 1754 and the word “Alumina ” was coined in 1761. It is also named as Bauxite, since Alumina was found abundant in the place called Les Baux in Southeast France.
Alumina was first manufactured in 1860 in France using Saint-Claire Deville process. Whereas, the Perfect process for extracting Alumina from Bauxite came from an Austrian and the process was named after him as the “Bayer’s Process”. This process is widely used until today, as the Alumina is in great demand worldwide for material applications.
Alumina exists in several allotropic forms, among them Activated Alumina (Al2O3) or Aluminium oxide which exists in porous form is of great demand because of its porosity. Activated Alumina is obtained after a series of process which includes dissolution of double salt of Aluminium in water at 85degrees Centigrade , recrystallizing it at a pressure of 250psi and a temperature of about 250degrees C. After which it is precipitated and roasted at 850 to 950degrees Centigrade to remove sulfates and finally drying the remaining Alumina yields a high-grade of Alumina called as Activated Alumina.
Metal oxides with the large surface area to Volume ratio are considered as anti-microbial agents. In packaging industries, these anti-microbial agents are of much significance as they stop the growth of microorganisms. Studies revealed that Activated Alumina shows the antimicrobial activity of the microbial forms and is considered as an Anti-microbial agent. Since Activated Alumina has inherent shelf-life; it can be regenerated at a temperature of 110 degrees to 150-degree Centigrade.
Alumina under heat or pressure gets moulded into a solid mass material and is referred to as Alumina Balls. These are white in colour, spherical in shape and they are available in a size ranging from 25mm to70mm. Alumina Balls are specifically robust in nature, therefore not only used in the absorption of moisture but also in the absorption of gases. Accordingly, Alumina balls are not only used as an Adsorbent but also as a catalyst bed support in oil refining and petrochemical, because of its high resistance towards high temperatures and high pressures. Based on the requirement in Industries or Mills and role of Alumina balls, they are Classified into Alumina Grinding Balls and Alumina Supporting Balls.
- Alumina Grinding Balls: These are used in ball mills, sand mills and Industries which manufacture glazed Tiles where Alumina Grinding Balls are used in replacement with natural pebble as grinding media as they are hard due to high density and resist corrosion. Depending on the lining in grinding media they are available in sphere, cylinders or brick forms.
- Alumina Supporting Balls: These are used in Gasification, Petroleum, chemical and Fertilizer Industries, where they support to increase the intensity of the catalyst and also the distribution of gas or liquid in the reacting tower. They are available in Regular as well as in Columnar shape.
ACTIVATED ALUMINA POWDER
Activated Alumina powder can be obtained by calcining the Alumina Precursor powder. It is white in colour and the particle size range from 70 to 290 mesh. It is mostly employed in Chromatography Techniques as they show a characteristic feature of change in pH when slurred with water. The surface area of the Activated Alumina increases along with an increase in the pH value. Chromatography is an analytical technique used for the separation of chemical substances, like Acids, Alkaloids, Steroids, Aldehydes, Ketones, Alcohols and many more. Mostly Activated Alumina Powder with approximately particle size 150 mesh is Preferred for Chromatography. Before performing the Chromatography for separation, the activated Alumina after slurred with water is treated with acid or base to adjust the pH to make it suitable for separation. If the pH of Activated Alumina Slurred is 4.5 then it is called as Acidic Alumina and is used for the separation of strong Acids. If the pH of Activated Alumina Slurred is 10, then it is called as Basic Alumina and is used for the separation of Alcohols, Alkaloids, and Steroids. But if the pH of Activated Alumina Slurred is 7, then it is called as Neutral Alumina and is used for the separation of Aldehydes, Ketones , Esters.
Activated Alumina because of its large surface area to volume ratio, has immense commercial applications in Biomedical as well as in Pharmaceutical field. The large surface area of the Activated alumina plays a major role by altering the biological activity of microorganism, thereby affecting its growth. In Pharmaceutical field, Isolation of Drug requires the elimination of the Pyrogens, originating from the cell walls of Bacteria also called as endotoxins, which is achieved by Activated Alumina. Pyrogen removal or purification of endotoxins from the drugs is enhanced by modifying the activated surface of Alumina to absorb depending on which process it is employed; used as a membrane or used in a Colum Chromatography.
Recovery of Pyrogen free Drug through Chromatography Using Activated Alumina
In Column Chromatography, Activated Alumina is considered as the stationary phase as it enables the least polar compounds to elute first and retains the more polar compound for a longer time. In Column chromatography, there are two methods of packing the column with Activated Alumina. One being the slurry method and the other being the Dry pack method.Dry pack method is employed for microscale separation, whereas Slurry method for Macro scales separation.
Dry pack method: In Dry pack method, Activated Alumina is added to the non-polar solvent, present in the column, such that it floats to the bottom of the Column or Activated Alumina is deposited to an intended height in the Column as it is the stationary phase, then the non-polar solvent is added. After which a thin horizontal band of the drug to be isolated mixed with the polar solvent is added at the top of the column. Then a small layer of sand is added to the top of the column followed by the Solvent eluent. Fractions of the sample containing drug based on TLC results is collected after opening the stopcock, then the solvent in it is evaporated, after which the pure form of the drug is obtained which is then recrystallized.
Slurry Pack Method: In Slurry pack method, Activated Alumina is first mixed with small amount of non-polar solvent in the beaker, then it is poured in the column followed by the addition of the isolating drug and sand. This method gives the best packing if it is evenly distributed.
This Column Chromatography is time-consuming; therefore for a speedy recovery of the Pyrogen free drug, Flash Chromatography method is used in which the rate of the mobile phase is increased by passing 10psi pressure of air or Nitrogen through the fine grade of Activated Alumina.
Role of Activated Alumina in Biopharmaceutical Industries
Pharmaceutical drugs that are semi synthesized and isolated from a living source or Biological source such as microbes are considered as Biopharmaceuticals. They include Vaccines, Antibiotics, Steroids and many more. Secondary metabolites produced by bacteria are considered as Antibiotics, which need to isolate and purify. The Purification of Antibiotics is performed through a series of extraction after which the Antibiotic is finally recovered by Organic Chemical Means such as Column wise purification. In this method, Acidic Alumina placed in the column absorbs the impurities and allows the passage of the Antibiotic through the Column. For Satisfactory purification, Alumina at a ratio of 50:1 based on the solid, present in the feed solution is to be used. Biopharmaceutical drugs have become potent and viable, which is a major concern in the field of Biopharmaceuticals. The inefficiency is attributed due to the ineffective production of the drugs. Therefore, Metal oxides such as Activated Alumina among others are currently the most prominent tool applied for the purification of Biopharmaceuticals. Since the purification process requires de-colourisation of the medical component or drug, Activated Alumina being amphoteric, stable at high temperatures and pressure gives the desired product.
Due to electrostatic forces of the Activated Alumina, Higher molecular weight medical components, such as Vancomycin, Colistin, Gentamicin isolation and purification is been made easy. The macroporous nature of Activated Alumina which acts as a resin which in turn selectively absorbs the effective part of the medical component from the fermented broth thereby enhances the stability of the Product.