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What is Activated Alumina?

Activated Alumina is a solid form of aluminum oxide produced by de-hydroxylating aluminium hydroxide to create a porous material and the resultant material being chemically referred to as Al2O3 ,occurring only in gamma meta-stable form,, while the alpha stable form of aluminium oxide does not have the chemical properties of its gamma version. Activated Alumina already made a significant impact on the business markets, creating a $932.4 million Activated Alumina market as of 2020, while the projections for 2027 are reaching $1.2 billion at a CAGR of 3.8% (Global Industry Analysts, 2021).
Activated Alumina was invented as a catalyst to be used in numerous chemical reactions thanks to its significantly high surface area to weight ratio. The use cases of Activated Alumina include dehydration of air, dehydration and purification of hydrogen peroxide, natural gas, adsorption of arsenic, fluoride, and sulfur as well as catalysts in polyethylene production, among others.

What are the Use Cases of Activated Alumina?

activated alumina water filter systemsActivated Alumina can be used in numerous ways, such as creating dryness by adsorbing water from the air or filtering fluoride and other substances that are harmful to human health, such as arsenic and lead, from drinking water. Activated Alumina is also used to clean up toxic waste and rain water spillage from contaminated areas, drying highly humid air and other gases, as well as the dehydration and purification of hydrogen peroxide, natural gas, and gasoline, during their manufacturing stages.
Focusing on the main functions of Activated Alumina, it is seen that the material can be used as an adsorbent, a desiccant, and a catalyst. As an adsorbent, Activated Alumina is considered to be highly effective in gas and liquid applications to remove specific components from their surrounding media, meanwhile offering significant reduction in operational costs.
Activated Alumina Water Filtration System’s adsorbent function is bonding with solid material to create an extremely strong bond that will not be destroyed without a considerable amount of heat being applied to the solution. Activated Alumina’s porous structure consists of tunneled spheres at the microscopic level and therefore, any material that bonds with Activated Alumina is tied with it at the microscopic level, making detachment extremely difficult.
Activated Alumina is an ideal material to deal with any substance that is considered to be a pollutant to the environment or to another medium. Activated Alumina is used in the water filtration & purification, oil & gas as well as polyethylene and hydrogen peroxide manufacturing industries due to the capability of the material to clean up virtually any given material of a specified chemical or material. Generally speaking, Activated Alumina is used as an adsorbent, desiccant, or a catalyst in the mentioned industries, as well as among some others.

1. Water Filters

The most popular uses of Activated Alumina in this sense are water filtration applications where contaminants such as fluoride, arsenic, lead, and sulfur are easily removed from water through the application of Activated Alumina to the specified water solution, with the material being most importantly as a fFluoride aAdsorbent in the world today. For those interested in knowing how do water filters work, in the given process, Activated Alumina granules are located at either the point of entry or the point of use parts of water filtration and treatment devices, allowing the flowing water to go through them, in turn offering a highly efficient process of water purification as contaminants such as arsenic, fluoride, chromium, and selenium are adsorbed by the material. Again, it should be stressed that the chemical bonds that are formed during the process of water filtration are extremely powerful and therefore do not allow any leakage to occur, making Activated Alumina ideal for numerous water filtration system types and purification systems.

2. Catalyst Applications

As a catalyst, Activated Alumina is most popularly used in sulfur recovery efforts at oil and gas refineries, namely as a Claus catalyst, while the material can also be used as an inert carrier or as a substrate for other types of catalysts.

3. Vacuum Systems

Activated Alumina is used in the manufacturing of fore-line traps used in high-vacuum environments, to prevent the oil produced by rotary vane pumps from back-streaming into the system, thanks to its cohesive properties. Similarly, aAs a desiccant, Activated Alumina can be used to adsorb water in the form of humidity from air and keep environments dry, operating similarly to silica gel to dry compressed air as well as other gas and liquid streams. Technically speaking, the material Activated alumina can adsorb up to 20% of its own weight in a water environment with relative humidity of 50%, showing extreme utility in industrial settings where removal of water vapor is a dire necessity. Activated Alumina can slo be reused as the adsorbed water can be desorbed through thermal treatment, adding longevity to its shelf life.

4. Biomaterial

Thanks to its mechanical properties and non-reactivity in biological media, Activated Alumina is also a highly suitable material to protect surfaces against sources of friction in body prostheses, granting the material a media use as well.

5. Defluoridation

Filters made of heavy concentration of Activated alumina have been known to reduce fluoride levels from 10.0 ppm to less than 1.0 ppm, with the contact time between water and the contents of the activated alumina filter determining the given level of reduction, with more contact yielding higher filtration results. The factors that help the given process of filtering include lower water temperature, total alkalinity, Activated Alumina particle size (ideal size being 0.5 to 1 mm), initial concentration of fluoride, and water pH level (acidic water), with the optimal pH level for such filtration being 5.5, resulting in a removal rate of up to 95%.

What is Activated Alumina Agglomeration?

Activated Alumina Agglomeration is the material’s high capability in adsorption and catalysis. Alumina agglomerates, which can be best described as the highly strong and porous particles found within the alumina gel, when used as adsorbents and catalyst carriers, prove to be especially useful for water filtration purposes due to their special crystalline structures and high porosity, while their mechanical strength should always be adjusted in accordance with their exposure to impacts and frictional abrasion.

What is Activated Alumina Calcination?

Activated Alumina calcination is a process where the hydrated alumina is heated to remove the water produced during hydration to become aluminium oxide, Al2O3. AA calcination both strengthens Activated Alumina’s structure and preserves its porosity. As the calcination process strengthens the bonds Activated Alumina creates with other materials, such as contaminants in water, the highly porous structure of Activated Alumina stores such contaminants removed from the watery medium, increasing the efficiency of the water filtration and purification systems consequently.

What is Activated Alumina Testing?

Activated Alumina testing is a procedure applied to evaluate several parameters of the produced material such as particle size, moisture % by mass, bed crushing strength %, packed bulk density (gm/cc), loss on attrition %, pore volume (gm/cc), absorption capacity, individual ball strength (kg), surface area (m2/gm), and loss on ignition (250-1000°C), while a sieve analysis is also carried out to ensure that the material does carry out its function when used in water filtration and purification.

How to Prepare Activated Alumina?

The preparation of Activated Alumina begins with putting 99.9% pure aluminum into a reaction with an aqueous NaOH at room temperature to produce a sodium aluminate solution (NaAlO2), which is then passed through filter paper to be neutralized with H2SO4 at pH levels of 6,7, or 8 to create the white Aluminum Hydroxide Hydrate gel that is chemically denoted as Al(OH)3·XH2O. Following this operation, the gel is dried at 80°C for 6 hours to be stripped of its sulfate ions and then calcined for 3 hours in a furnace at a heating rate of 2°C min-1.

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