Activated alumina is a porous material made by heating aluminium hydroxide at high temperatures. This process removes water molecules, creating an intricate network of pores with impressive moisture-absorbing capabilities.
Once a device’s capacity has been identified, maintenance schedules based on gallon treated are suggested to ensure its contaminant removal capacity remains constant.
Water Purification
Granular activated alumina (GAA) is a highly porous form of aluminum oxide commonly used for water purification. It’s often chosen as part of home and commercial water filters to eliminate harmful pollutants like fluoride, arsenic and heavy metals as well as color and odor from drinking water, working by adsorbing these contaminants onto its surface rather than simply filtering them away through screening devices.
Activated alumina has an affinity for hydroxyl groups, making it a suitable material for absorbing contaminants of all sorts. Depending on impurity level, properties, device design and water quality, its efficiency as a filter with granular activated alumina varies; typically up to 1.5% can be absorbed from one cubic foot of activated alumina material.
Alumina desiccants can be created in multiple ways using equipment such as a pin mixer, disc pelletizer or an agglomerator. Alumina granules may be treated with free fatty acids and phospholipids to speed crystallization and improve their oxidative stability for faster crystallization and higher stability resulting in either round, elongated or flaky forms of desiccants.
Granular activated alumina’s highly porous structure and high absorption capacity make it suitable for water treatment applications, including fluoride removal and reduction of humic and fulvic acids from natural mineral waters. Furthermore, activated alumina has received NSF approval, and under optimal conditions of use, aluminium leaching should remain below the maximum limits established in European Directives or California Proposition 65 regulations.
Natural Gas Dehydration
Every gas contains moisture and water vapour that needs to be eliminated during processing and transport. Gas dehydration or drying removes this water vapor in a natural gas to ensure safety and regulatory standards compliance while simultaneously preventing formation of hydrates, increasing pipeline efficiency and process efficiencies, decreasing corrosion risks, protecting water-sensitive catalysts in refinery processes and protecting them.
Activated alumina is an ideal desiccant material due to its high porosity, permeability and resistance to thermal shock. Produced through controlled heating of alumina to dehydrate it and create porous material with an astounding surface area of over 350,000m2/kg, activated alumina has an affinity for gaseous elements such as helium, hydrogen, nitrogen, argon and chlorine that need dehydration while it also has the capability of absorbing organic molecules like kerosene aromatic compounds and essences from being dehydrated by activated alumina.
Granular activated alumina dehydration begins with the preparation of aluminum oxide as raw material through calcination at high temperatures. Once activated, this material is bound together using water into desired shapes such as granules and spheres before being heated again to activate it – this causes further dehydration leading to release of water vapor and loss on ignition of 4-8% which is then bound with other materials to form desiccant units.
Chemical Purification
Activated alumina is used as a desiccant in various industrial applications, including fluoride removal from natural mineral water sources, eliminating color and odor problems and phosphate removal, and in recovering sulfur at oil refineries.
The activated alumina used in these applications is typically granular, meaning it has a large surface area and is easy to handle. It is created by heating hydrated alumina which causes it to expand and rupture its crystal lattice along planes of weakness, producing porous material with well-defined pores of an average pore diameter of 4nm, more resistant than silica gel in terms of attrition resistance.
Granular activated alumina filter media has the power to remove humic and fulvic acids as well as iron, manganese and arsenic from drinking water supplies, while in some instances even fluoride. Unfortunately, many municipal water systems add fluoride as part of their water treatment systems.
Alumina used in these applications typically meets California’s Proposition 65 safety standards. Furthermore, it’s free from aluminum and in line with European purity regulations regarding chemical reagents used in drinking water supplies. At FEECO’s Innovation Center we can test and analyze various forms of alumina both batch and pilot scale in terms of thermal and agglomeration testing capabilities.
Waste Water Treatment
Activated alumina is produced through controlled heating of hydrated aluminum oxide, producing a highly porous and absorptive material with an exceptionally large surface area. These properties make activated alumina an efficient desiccant for use in various applications, including drying moisture from gasses such as acetylene, hydrogen, oxygen and nitrogen; liquids such as lubricants oils solvents etc; as well as waste water treatment where it can remove contaminants such as arsenic and fluoride from drinking water supplies.
FEECO provides custom-sized granular activated alumina manufactured for any application, with tailored adsorption characteristics for improved results such as pores size and surface area. Furthermore, this media produces minimal dust generation – making it perfect for situations in which dust contamination is an issue.
Activated alumina is an economical media for filtering arsenic and fluoride from water as well as copper and lead contaminants, among others. Breakthrough levels for these contaminants are as low as 10,000-20,000 bed volumes with C0 = 100ppb pH 6 or below (listed by EPA as Best Available Technology for these applications) but, similar to other water filter medias, periodic regeneration with caustic and acid is necessary in order to operate at optimal levels.