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New high-efficiency silica-aluminum salt defluorination material

The new high-efficiency silicon-aluminum salt fluoride removal material has made several major breakthroughs on the basis of conventional materials, and the fluoride removal capacity has been greatly increased, far exceeding that of conventional materials; the regeneration repeatability is good; at the same time, innovative improvements make the filter material can use multiple regeneration methods at the same time, and can flexibly switch between various regeneration methods according to local conditions.

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New high-efficiency silica-aluminum salt defluorination material
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    The new high-efficiency silicon-aluminum salt fluoride removal material has made several major breakthroughs on the basis of conventional materials, and the fluoride removal capacity has been greatly increased, far exceeding that of conventional materials; the regeneration repeatability is good; at the same time, innovative improvements make the filter material can use multiple regeneration methods at the same time, and can flexibly switch between various regeneration methods according to local conditions. At present, the application of this fluoride removal material in Hebei, Shandong, Shanxi, Anhui, Inner Mongolia and other places has reflected the best fluoride removal effect and achieved good economic and social benefits. At the same time, the products are exported to foreign countries and have been unanimously recognized by foreign counterparts. According to the identification of authoritative departments, the fluoride removal performance of this material is better than that of all conventional materials on the market, and it has reached the domestic and international leading level in terms of effect and cost performance.

    (1) Physical and chemical indicators

    Ingredients: Natural Minerals

    Form: solid particles

    Color: off-white

    Solubility: insoluble in water

    Bulk density: 1.33 g/ml

    Specifications: 0.5mm~ 1.5mm

    (3) Toxicological indicators

    Toxicity: non-toxic

    Skin Contact: Non-irritating to skin

    Eye Contact: Not irritating to eyes

    (4) Surface microscopic morphology

    The electronic scanning electron microscope observation of the silicon-aluminum salt filter material is shown in Figure 2. It can be seen in the figure that the surface of the filter material is relatively smooth, and there are irregular porous structures on the surface, mainly microporous and mesoporous structures, and a few macroporous structures are distributed around. This complex pore-like structure provides conditions for the material to carry out various adsorption methods, and is the structural basis for high fluoride removal capacity. The surface of the zeolite is mainly distributed with a uniform microporous structure, which will produce the characteristics of superporous effect, and the special molecular structure will form a large electrostatic attractive force. Therefore, the fluoride removal of zeolite mainly depends on the large specific surface area of the surface. The surface of activated alumina is mainly a macroporous structure. Since the mass transfer coefficient of fluoride ions in the macropores is very low, its contribution to the fluoride removal ability is small. It can be seen that the surface structure of silica-alumina salts is beneficial to improve the adsorption capacity compared with the two.

    Figure 2 Scanning electron microscope image of silicon-aluminum salt (30000 times magnification)

    (5) Defluorination mechanism

    After the high-fluoride water is contacted with the silica-aluminum salt, the surface of the filter material undergoes dual reactions of adsorption filtration and ion exchange. The fluorine ions in the water are adsorbed on the filter material and the fluorine ions are exchanged with the OH-ions on the surface of the filter material. The purpose of fluoride removal is achieved.

     

    Figure 3 Defluorination mechanism diagram

    (6) Fluoride removal capacity

    The defluorination capacity of silicon-aluminum salt is about 1-4 mg/g, which exceeds the current conventional filter material. The defluorination capacity varies with factors such as the fluorine concentration of the raw water, local water quality and water temperature.

    (7) Performance comparison of common fluoride removal filter media

    Comparison of the volume of fluorine-containing water treated by silica-aluminum salt filter media and conventional filter media under the same conditions. The fluorine-containing water used in the test is groundwater in high-fluoride areas, which can truly reflect the performance of the equipment during actual operation, and avoid the situation that the results of the small test do not match the operation of the on-site equipment. The performance of silica-aluminum salt filter media is significantly better than that of conventional filter media. The volume of fluorine-containing water treated by silica-aluminum salt filter media is 1.57-1.69 times that of activated alumina, and 11.7-12.9 times that of activated zeolite molecular sieve.

    (8) Technical advantages

    Ø The fluoride removal capacity is high, and the filling amount is much smaller than that of activated alumina and zeolite molecular sieves, which can achieve the same fluoride removal effect and save equipment investment costs.

    Ø The contact time is short, which can greatly reduce the volume of the equipment compared with the traditional filter material.

    Ø High safety, no toxic and harmful substances are dissolved during use.

    Ø The fluoride removal efficiency is high, and the fluoride ions in the water can be completely removed in the early stage of use. Therefore, the method of mixing raw water and treated water can be adopted to further protect the filter material and prolong the service cycle and reduce operating costs.

    Ø The water quality has strong adaptability, and in the case of poor water quality, it can also maintain a high fluoride removal capacity.

    Ø The regeneration cost is low, and a variety of regeneration methods can realize seamless switching, adapting measures to local conditions, flexible and simple.

    At present, the main domestic fluoride reduction methods, advantages and disadvantages are shown in the following table:

    Fluoride removal method

    advantage

    disadvantage

    Anresin ion exchange method

    It is very powerful to remove anions from water

    1. Fluorine removal rate is very low
    2. Expensive, extremely complex to regenerate and difficult to manage

    Activated carbon adsorption method

    Activated carbon has a particularly large specific surface area and a large adsorption capacity

    It cannot be regenerated. After the adsorption is saturated, it can only be discarded. High operating costs are generally unacceptable.

    Activated alumina adsorption method

    Before the 21st century, activated alumina was considered to be a widely used fluoride reduction method

    1. Short continuous running time, it is easy to appear false fatigue
    2. It is necessary to adjust the pH value of the water inlet and outlet with acid and alkali to use it normally.
    3. The filter material is prone to compaction, which makes the water distribution and water collection uneven, which seriously affects the service life
    4. Fear of the coexistence of phosphate in water, because phosphorus and aluminum are combined very firmly and cannot be eluted. Once the surface area of the high-efficiency silicon-aluminum salt natural filter material is occupied by phosphate, the fluoride removal function is completed
    5. The effluent has the possibility of aluminum ions exceeding the standard. Water with a long-term waste aluminum ion content exceeding 0.075mg/L can cause brain aging, cause dementia, stroke, etc
    6. Long regeneration time, complex regeneration, and complex management

    Bone carbon (calcium hydroxyphosphate) adsorption method

    The adsorption of fluorine is very large

    1. High material price
    2. Poor strength, easy to break
    3. The operation is complicated and the management is very difficult, especially when regenerating, the concentration of the regeneration liquid is not well controlled, which will cause material crushing and failure
    4. The effluent has a fishy smell, the taste is very poor, and there is a possibility that ammonia nitrogen exceeds the standard

    High-efficiency silica-aluminum salt natural filter material adsorption method

    1. Has a particularly large specific surface area and a large adsorption capacity
    2. Complete fluoride removal, good effluent quality
    3. The regeneration method is simple and the management is simple
    4. The filter material is easy to never harden
    5. The possibility of no aluminum ions in the effluent exceeding the standard
    6. The filter material has a lifespan of more than 10 years.

    Raw water with coexistence of iron, manganese and fluorine cannot be treated at the same time. If such raw water is treated, iron and manganese should be removed to the sanitary standard GB5749-2006 standard content of domestic wastewater before fluoride removal.

    Electrodialysis

    Complete fluoride removal, good effluent quality, automatic operation, easy management.

    1. High investment,
    2. Operating costs are too high

    Reverse osmosis method

    Fluoride removal is more thorough than electrodialysis, the effluent quality is better, it can be automated and easy to manage.

    1. High investment,
    2. Operating costs are too high
    3. The average water production rate is low. For every ton of water purified, one ton of water needs to be discarded

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