Activated alumina is used for a wide range of adsorbent and catalyst applications including the adsorption of catalysts in polyethylene production, in hydrogen peroxide production, as a selective adsorbent for many chemicals including arsenic, fluoride, in sulfur removal from fluid streams (Claus Catalyst process)
Activated alumina is also widely used to remove fluoride from drinking water. In the US, there are widespread programs to fluoridate drinking water. A study from the Harvard school of Public Health found exposure to high levels of fluoride as a child correlated with lower IQ.[1]
Activated alumina filters can easily reduce fluoride levels from 10 ppm to less than 1 ppm. The amount of fluoride leached from the water being filtered depends on how long the water is actually touching the alumina filter media. Basically, the more alumina in the filter, the less fluoride will be in the final, filtered water. Lower temperature water, and lower pH water (acidic water) are filtered more effectively too. Ideal pH for treatment is 5.5, which allows for up to a 95% removal rate.
As per researches conducted by V.K.Chhabra, Chief Chemist (retd.) P.H.E.D. Rajasthan, activated alumina, when used as a fluoride filter, under field conditions can best be regenerated by a solution of lye (sodium hydroxide; NaOH), sulfuric acid (H2SO4).
The fluoride uptake capacity (FUC) of activated alumina can be up to 5000 mg/kg. The FUC using V.K. Chhabra's method can be determined as follows:
Fluoride solution: Dissolve 22.1 g anhydrous NaF in distilled water and dilute to 1,000 mL. 1 mL = 10 mg fluoride. 10 mL/L = 100 mg/L fluoride.
To one litre of simulated distilled water containing 100 mg/L of fluoride, agitate at 100 rpm using the jar test machine. Add 10 g of the AA under test. After one hour, switch off the machine and take out the solution. After 5 minutes, carefully decant the supernatant solution and determine the fluoride. Calculate the difference between the original and treated water fluoride concentration. Multiply the difference by 100 to give the fluoride uptake capacity of AA in mg/kg.
The feed solution is simply pumped through the bed, to yield an effluent containing less than 0.1 ppm fluoride
Once saturated, the alumina bed can be regenerated by following simple steps:
Because of its high adsorption capacity, a unit will be operative for a longer time before change out, this mean savings on handing costs too.
| Physical State: | The material shall be in the white spherical balls, free from visible impurities. |
|---|---|
| Size: | 2 – 4 MM |
| Pore Volume: | 0.4 – 0.5 ml./gm. |
| Surface Area | 350 – 450 m2/gm. |
| Service flow: | 9ltr/m/ft2 |
| Moisture Content | 2% max. |
| Abrasion | >0.4% wt. |
| Bed Crushing Strength | 90% |
| Water Adsorption Capacity | 16% min. (At 60% RH & 30°C) |
| Loss on Ignition | 5% - 8% |
| Attrition Loss | 0.5% max |
| Fluoride Uptake Capacity | 2.0 mg/g (This data may different according to water pressure) |
| AL2O3 | 35% - 40% max. |
|---|---|
| Fe2O3 | 0.89% |
| SiO2 | 22.50% |
| Na2O | 1.80% |
| Water Soluble Chlorides (As CI) | 0.70% max. |
| Water Soluble Sulphates (As SO4) | 0.70% max. |
| MgO | 0.65% |
| CaO | 3.50% |
| PH | 8.10% |