Appearance of activated alumina: activated alumina is white spherical porous particles with uniform particle size, smooth surface, high mechanical strength and strong hygroscopicity. It has strong adsorption to fluorine, and is mainly used for defluoridation of drinking water in areas with high fluorine content.

Activated alumina has selective adsorption capacity for gas, water vapor and moisture of some liquids. After adsorption saturation, it can be revived by heating at about 175-315°C to remove water. Adsorption and resurrection can be performed multiple times. In addition to being used as a desiccant, it can also absorb the vapor of lubricating oil from polluted oxygen, hydrogen, carbon dioxide, natural gas, etc. And can be used as catalyst and catalyst carrier and chromatographic analysis carrier.

Under certain operating conditions and regeneration conditions, the drying depth of activated alumina can be as high as the dew point temperature below -70 degrees. Defluorination agent for transformer oil, deacidification regeneration agent for transformer oil, gas drying in oxygen industry, textile industry, electronics industry, drying of automatic instrument air, desiccant and purification agent in chemical fertilizer, petrochemical drying and other industries (dew point can be adjusted) up to -70 degrees), in the air separation industry pressure swing adsorption dew point up to -60 degrees. It is a high-efficiency desiccant for deep drying of trace water. Ideal for heatless regeneration units.

Related introduction to activated alumina for defluoridation: my country’s “Drinking Water Hygienic Standards” stipulates that the fluoride content should not exceed 1.0mg/L. Raw water with too much fluoride tends to be slightly alkaline, with a pH value often greater than 7.5.

The defluoridation methods are roughly divided into the following categories:

(1) Adsorption filtration method;

(2) Membrane method;

(3) Flocculation and sedimentation method;

(4) Ion exchange method.

The main factors affecting the adsorption performance of activated alumina:

(1) Particle size: The smaller the particle size, the higher the adsorption capacity, but the smaller the particle size, the lower the particle strength, which affects its service life.

(2) PH value of raw water: When the PH value is greater than 5, the lower the PH value, the higher the adsorption capacity of activated alumina.

(3) Initial fluorine concentration of raw water: The higher the initial fluorine concentration, the larger the adsorption capacity.

(4) Raw water alkalinity: If the concentration of bicarbonate in raw water is high, the adsorption capacity will decrease.

(5) Chloride ions and sulfate ions.

(6) The influence of arsenic: activated alumina has adsorption effect on arsenic in water, and the accumulation of arsenic on activated alumina causes a decrease in the adsorption capacity of fluorine ions, and makes it difficult to elute arsenic ions during regeneration.

How to regenerate activated alumina: Sodium hydroxide solution or aluminum sulfate solution can be used as regenerant.

The solution concentration of sodium hydroxide regenerant is 0.75%-1%. The consumption of sodium hydroxide can be calculated based on 8-10g of solid sodium hydroxide required to remove 1g of fluoride. The amount of regeneration solution is 3-6 times the volume of the filter material. . The solution concentration of the aluminum sulfate regenerant is 2-3%, and the consumption of aluminum sulfate can be calculated as 60-80g of solid aluminum sulfate for every 1g of fluoride removal.