TWI635900B - Method for preparing arsenic and fluoride adsorbent by using the sludge of water treatment as raw material - Google Patents

Abstract

The invention is a method for preparing arsenic and fluorine adsorbents and an application thereof. The raw material used is sludge rich in aluminum and iron produced in the process of purifying water. The sludge is first washed by dilute acid, and the heavy metal oxide therein is dissolved and removed. Secondly, the aluminum and iron compounds in the sludge are dissolved into aluminum/iron ions by strong acid under microwave heating. After the acidified sludge is dehydrated, the filtrate is adjusted with a base to adjust the pH to form aluminum hydroxide and iron hydroxide precipitate. Finally, the dried aluminum and iron hydroxide precipitates are heated and activated to become an adsorbent for arsenic and fluorine. The adsorbent may be in the form of powder or granules, and the powder may be added to the clay to form a ceramic filter; the granular material may be used as a filler in other filter cavities, or may be directly put into water to apply fluorine. Adsorption.

Description

Method for using purified water sludge as raw material as arsenic and fluorine adsorbent

The invention is part of water purification technology and resource reuse. The adsorbent which can remove arsenic and fluorine in water is prepared by using the sludge generated in the water treatment process.

Arsenic is ubiquitous in the environment and is a substance that is toxic to humans. Although it is only a small amount of food, it is also a danger of acute death. Drinking arsenic-containing water for a long time may cause obstruction of peripheral blood vessels, necrosis of peripheral tissues of the extremities, and lesions commonly known as blackfoot disease, leading to the fate of amputation. In addition, arsenic also causes many different diseases and cancers. The International Agency for Research on Cancer (IARC) has classified arsenic as a first-class carcinogen, and the US Environmental Protection Agency has classified it as a Class A carcinogen. In many areas where there is no supply of tap water, people avoid sinking groundwater that is easily contaminated, and use groundwater as drinking water. Although groundwater can avoid the threat of diseases such as gastrointestinal diseases caused by contamination of surface water, it also exposes drinkers to the risk of arsenic-containing groundwater poisoning. In South Asia and East Asia, many examples of diseases caused by drinking arsenic-containing groundwater have been found. These areas include Bangladesh, India, Myanmar, and China, and even in places such as Taiwan and the United States, where groundwater contains high levels of arsenic. . In Bangladesh, for example, more than 30% of the country (140 Groundwater wells in 10,000 places contain relatively high concentrations of arsenic. In order to ensure the safety of drinking water, the concentration limit of arsenic in drinking water in the world is set at 10~70μg/L. In Bangladesh and India, where arsenic pollution is most severe, the government limits the arsenic content to no more than 50 μg/L. In 2001, the US EPA reduced the limit of arsenic in tap water from 50 to 10 μg/L. The current drinking water standards of the European Union and the World Health Organization WHO recommend that the arsenic content of drinking water should not exceed 10 μg / L. The current standard in Taiwan has also been reduced from 50 to 10 μg/L. In addition, fluorine is often added to tap water to prevent dental caries. However, more than a certain concentration of fluorine is easily combined with calcium, and excessive fluoride in drinking water has an undue influence on teeth and bones. The amount of fluorine in groundwater may be as high as 10 mg/L. The World Health Organization recommends that the fluoride content of drinking water should not exceed 1.5 mg/L. Activated alumina is currently the most effective and widely used method for reducing the amount of fluorine in drinking water. Activated alumina also has excellent adsorption capacity for arsenic.

Many feasible solutions have been proposed for the removal of arsenic, including: (1) coagulation precipitation - adding appropriate amounts of coagulants (such as iron salts, aluminum salts, lime, soda) and coagulants (such as polymer). It is removed by compressing the electric double layer to form a rubber feather, sweeping and coprecipitation. (2) Adsorption - adsorption of pollutants by a large surface area, such as activated carbon, activated alumina, manganese dioxide, etc., adsorption and removal of arsenic in water. (3) Ion Exchange - Charged arsenic is ion-exchanged into the resin by an ion exchange resin. (4) Reverse osmosis - pressurization causes smaller water molecules to pass through the filter membrane, leaving a larger particle size material. (5) Activated sludge adsorption-adsorption of arsenic by the extracellular polysaccharide mixture of activated sludge gelatin produced by biological treatment.

For areas that do not have the financial capacity to build a water system, some simple and cheap treatments have also been proposed. Among them, activated alumina has a large specific surface area and exhibits excellent adsorption capacity. It has been proven to have good arsenic and fluorine adsorption capacity, and the removal of arsenic from groundwater containing arsenic can reach 95% (for example, from 500μg/L). Dropped to 25μg/L). Alumina (Al ₂ O ₃ ) can be obtained by heating and dehydrating aluminum hydroxide (Al(OH) ₃ ), and aluminum hydroxide starts dehydrating at a temperature of about 150 ° C to form alumina. Alumina is divided into three types according to its three-dimensional structure: α, β, γ and δ, each with different activities, among which α and γ are the main species. The activity of gamma alumina is the highest, and the formation temperature is low. As the temperature increases, the stereostructure of alumina changes, the activity is also reduced, and the temperature rises to 1,200 ° C. Almost all alumina exists in the form of α, α oxidation Aluminum has almost no activity. Therefore, the temperature at which the activated alumina is prepared should be carried out at a relatively low temperature, and the alumina formed at 750 ° C has the closest composition to γ alumina (Catalyst 29, Vol. 10). In addition to activated alumina, iron, iron salts (such as ferric chloride) and iron oxide have good effects on the removal of arsenic (US Pat. No. 7,309,245 B2).

Coagulation is one of the commonly used procedures in water treatment. After the raw water is removed by primary sedimentation, the coagulant is added to make the fine suspended particles flocculate into larger particles to facilitate removal from the water. These fine suspended particles are mainly composed of cerium oxide and organic substances. The particle size is similar to that of clay, and the surface is often negatively charged and easily dispersed in water. Coagulants which are often used to destroy the stability of fine particles in water and are cemented into larger particles include aluminum salts and iron salts. Aluminum salts include aluminum sulfate, aluminum chloride and polyaluminum chloride, and iron salts are commonly used. Iron, iron sulfate, ferrous sulfate and multi-component iron citrate. The amount of coagulant added can be determined by the cup test due to the difference in water quality. The sludge with aluminum salt (or iron salt) as a single additive has an aluminum (iron) content of up to 30% of the dry weight. Different forms of aluminum coagulant are mainly present in the form of aluminum hydroxide (Al(OH) ₃ ) in water, and aluminum hydroxide is heated and dehydrated to form alumina (Al ₂ O ₃ ). As mentioned above, it has Excellent adsorption capacity. After the iron salt is dissociated in water, the main component is iron hydroxide (Fe(OH) ₃ ), which forms iron oxide (Fe ₂ O ₃ ) after heating, and has the same adsorption capacity for arsenic.

The sludge is the waste continuously generated in the process of purifying water. After being recycled, it can reduce the burden on the environment, the cost of transportation and disposal, and even create value through waste recycling. Water treatment sludge has been used in different fields, including concrete additives, sanitary landfill soil, forest land improvement, etc. Because of its similar properties to clay, it is also used in bricks and fireproof materials. Some techniques are used to remove alum (Al ₂ (SO ₄ ) ₃ ) from an aluminum-containing tap water sludge by acidification and addition of sulfate or directly by adding concentrated sulfuric acid, such as US Pat. No. 3,959,133, Japanese Patent No. JP 2012219002A, Chinese Patent CN 105271486A, and the like. In addition, some technologies from the aluminum-rich sludge in the aluminum industry, adding a strong alkali to dissolve aluminum ions, and then neutralizing and recovering the higher purity aluminum hydroxide, such as Japanese patent JP 2010222159A. The Chinese patents CN 102627362A and CN 103833116A/B add alkali to the treatment of acidic aluminum-containing industrial waste liquid to recover aluminum hydroxide.

In many low-developing areas or remote areas, due to the construction of the tap water system Whole people often use simple porous pottery to filter and purify water. A certain proportion of wood chips, rice husks, broken wheat straw, broken corn stover, etc. are mixed in the nearby clay to increase the porosity of the pottery. The pottery made in the kiln can filter out impurities and bacteria in the water, greatly reducing the threat of gastrointestinal diseases. However, these filters have a very limited effect on arsenic and fluorine removal in water. The present invention is based on the fact that the tap water sludge contains a high amount of aluminum hydroxide and iron hydroxide, and is purified and activated to be an adsorbent capable of removing both arsenic and fluorine.

The raw water is subjected to pretreatment such as sand removal and sedimentation, and after removing sediment and impurities, an appropriate amount of coagulant is added to further remove fine particles suspended in the water. The type of coagulant and the amount of dosing vary depending on the pH and the quality of the water. A cup test can be performed to determine the most suitable dosing method. Generally, the coagulant dosage of low-concentration raw water (<10 NTU) is between several mg/L and 20 mg/L. If necessary, a coagulant such as polymer can be added to help clear water quality and sedimentation of sludge. The formed sludge needs to be separated from the water by proper solid-liquid separation. The method of solid-liquid separation of sludge includes gravity sedimentation, filtration and pressurized floating, etc., and is generally most commonly achieved by means of gravity precipitation. The moisture content of the sludge after solid-liquid separation is still quite high above 95%. At this time, the content of sludge cake, besides water, is mainly impurities derived from raw water such as cerium oxide, organic matter, etc., and added Coagulants, coagulants, even heavy metals. In the sludge with aluminum salt or iron salt as coagulant, most of aluminum and iron are stored in the form of aluminum and iron hydroxide with relatively low solubility. At the same time, the concentration of dissolved aluminum and iron species is quite small.

Aluminum hydroxide is one of the raw materials for producing activated alumina. However, since the above-mentioned various substances are contained in the purified water sludge, further removal is required to obtain aluminum hydroxide of high purity. Among them, heavy metals tend to form insoluble hydroxide precipitates in general water bodies, which are easily dissolved in solutions with low pH, while aluminum and iron hydroxides require lower pH to dissolve them. Therefore, by controlling the pH of the sludge, the heavy metal can be dissolved and removed with the filtrate. Acids that can be used include hydrochloric acid, sulfuric acid, sodium sulfate, sodium hydrogen sulfate, oxalic acid, and citric acid. The sludge after coagulation and sedimentation in the water purification plant is washed with an acidic solution in an acid washing concentration tank. At this time, the pH of the liquid should not be too low, so as to avoid the dissolution of aluminum and iron in the sludge, pH control Between 4 and 5. In order to obtain more aluminum, the pH is preferably 4.5, and the pickling and concentration time is not less than 3 hours. After the panning, the concentrated sludge is further dissolved in the next stage of aluminum (and iron), and the pickling waste liquid is discharged after being treated. The pickling and concentrating tank can be continuous or batch; the stirring method can be mechanical stirring, liquid stirring or gas stirring; the concentration method can be gravity type, filter type or centrifugal type concentration.

Both aluminum and iron hydroxide are soluble in acid. Compared with other metal hydroxides, the pH of dissolved aluminum hydroxide and iron hydroxide is relatively low. When the pH is lower than 3, most of the aluminum hydroxide can be dissolved into The aqueous solution of aluminum ions, so the pH of this stage can be controlled between 0 and 3, preferably pH 1.5. The acid used is predominantly hydrochloric acid to avoid the formation of other aluminum compounds. The concentrated sludge mixed with the acid is heated by microwave irradiation to increase the temperature of the aluminum, and the temperature at which the heating reaches can be 50 to 100 ° C, and the contact time with the acid should be 10 minutes or more. Microwave frequency for heating The rate can be 2,450 MHz or 915 MHz. The acidified and heated sludge enters the dehydration process, and the filtrate rich in aluminum and iron ions is separated from the sludge, and the filtrate is collected for subsequent treatment. The remaining sludge contains a large amount of impurities and needs to be separately recycled or discarded. .

The obtained filtrate is introduced into a reaction tank, and an alkaline solution is added to the reaction tank. When the pH is raised to 5-7 (pH 6 is a preferred control point), the hydrated ions of aluminum and iron gradually form a solubility. Quite a low aluminum hydroxide and iron hydroxide precipitate. The precipitate particles at this stage are minute. In order to obtain a solid material smoothly, an appropriate amount of a coagulant such as polyacrylamide (PAM), active citric acid, bone glue, or the like may be added, and sufficient mixing is sufficiently performed to promote the reaction. After that, through further solid-liquid separation and dehydration treatment, the aluminum hydroxide/iron product is recovered, and the water content is reduced to 85% or less for subsequent processing. The method of dehydration may be a method of filtering dehydration, pressure filtration dehydration, centrifugal dehydration, vacuum dehydration, and spiral extrusion dehydration. The filter can be refluxed to the pickling concentration tank as washing water or discharged after treatment.

The dehydrated aluminum-iron sludge cake needs to be further dried to lose the water therein, and the agglomerated sludge cake is broken up and ground to facilitate the subsequent sludge activation process. The purpose of drying is to remove as much free water as possible from the sludge, which can be achieved by air drying or heating. The drying temperature can be between 20 and 200 ° C. The usual method is heating and drying, and the temperature is 105 ° C. The process of grinding the sludge cake can be carried out simultaneously in the drying, or after drying. The method can be carried out by mashing or mechanical grinding, and the dried sludge after grinding removes larger particles, and the particle size is not A large excess of 0.5mm is preferred. Since the purpose of this stage is to remove free water from the sludge, the hydroxide in the sludge Aluminum and ferric hydroxide have not yet been converted to alumina and iron oxide, and the color of the dried sludge is gray to light gray like cement.

In the next step, the dried sludge powder can be heated and activated, or it can be mixed into clay to make a ceramic filter. In the process of activation, temperature plays an important role. Insufficient temperature can not convert the hydroxide in the sludge into oxide. Too high temperature will cause the oxide to crystallize and lose its activity. The temperature can be 300~1,000. °C, the most suitable temperature is 750 °C. The activated sludge powder contains red iron and has a reddish brown color. The powder was directly subjected to the adsorption experiment of arsenic. A sufficient amount of activated adsorbent was added to the water sample containing 500 μg/L of arsenic. After stirring for 1 minute, it was allowed to stand for 2 hours to precipitate the adsorbent, and the supernatant was taken for analysis. The content was reduced to 20 μg / L. The activated adsorbent can provide different applications and will be described later. If the dry sludge powder is added to the clay to make a ceramic filter, it is necessary to add appropriate amount of wood chips, rice straw chips, crushed wheat straw, crushed corn stover, grass ash and other fluffing agents to improve the porosity and water repellency of the pottery. Depending on the nature of the clay and additives used, the additive ratio is generally about 20-50% of the weight of the clay. Excessive additives will reduce the strength of the ceramic. The dry sludge powder has fine particles and is similar to clay, and its addition amount is about 20 to 70% of clay. The clay, sludge and fluffing agent should be thoroughly mixed before the embryo is made to avoid the gap after the firing, resulting in uneven filtration. Such ceramic filters can be in the form of basins, hemispheres, candles or tubes. If the firing temperature of the ceramic filter is too high, the activity of the alumina is lowered, and if the temperature is insufficient, the strength of the filter is lowered. The firing temperature is 600 to 1,000 ° C, and 800 ° C is most suitable. In this condition The finished ceramic filter was tested with a water sample containing 500 μg/L of arsenic, and the filtrate was collected for analysis, and the content of arsenic was reduced to 20 μg/L. The adsorption capacity of activated alumina for fluorine has been widely used, and it can easily lower the fluorine below the drinking standard. The presence of chromium and cadmium was not detected in the collected filtered water, and the concentration of lead was 0.1 mg/L, which was below the drinking water standard.

The activated adsorbent is added to the clay to prepare a ceramic filter. The process and requirements are the same as the direct addition of the dry sludge to the ceramic. The firing temperature is 600-1,000 ° C, and the optimum temperature is 800 ° C. The activated sludge adsorbent can also be used after granulation, and the granular adsorbent particle size should not be too large, so as to prevent the water flow from flowing rapidly between the particle gaps, and the adsorption effect is reduced, and the particle diameter ranges from 0.5 to 10 mm. The activated sludge after granulation can be directly put into water as an adsorbent, and the stirring time and related adsorption conditions in contact with water vary depending on the water quality, and can be determined by the bottle test. The granular adsorbent can also be used simultaneously with a ceramic filter which can be filled in the space of a ceramic filter (pot, hemispherical, candle or tube) due to the filtration of the ceramic filter. The slow rate provides sufficient contact time for the activated adsorbent to adsorb arsenic and fluorine in the water. In addition, the granular sludge adsorbent can also be filled in a non-ceramic filter container, which is a self-contained water purification unit, which can be used independently or in combination with other processing units. The granular adsorbent has the advantage of convenient replacement after adsorption saturation. Adsorbents adsorbed by arsenic and/or fluorine can be reused for recycling purposes or for final treatment.

P01‧‧‧Pre-treatment

P02‧‧‧Chemical Coagulation Unit

P03‧‧‧ Solid-liquid separation

P04‧‧‧ Pickling Concentration Unit

P05‧‧‧Microwave dissolution

P06‧‧‧ Acidified sludge dewatering

P07‧‧‧Reaction tank

P08‧‧‧Aluminum hydroxide/iron dehydration

P09‧‧‧Dry grinding

P10‧‧‧heat activation

A01‧‧‧Adding ceramic filter made of aluminum hydroxide/iron

A02‧‧‧Particle sorbent

A03‧‧‧Ceramic filter prepared by adding powdered adsorbent

M01‧‧‧ raw water

M02‧‧‧ Waste and waste sand

M03‧‧‧Coagulant

M04‧‧‧Sludge

M05‧‧‧Clean water

M06‧‧‧Diluted acid

M07‧‧‧Concentrated sludge

M08‧‧‧Washing waste

M09‧‧‧ Strong acid

M10‧‧‧ Acidified sludge

M11‧‧‧Aluminum/iron solution

M12‧‧‧Excess sludge cake

M13‧‧‧Alkaline solution

M14‧‧‧Coagulant

M15‧‧‧ hydroxide precipitation solution

M16‧‧‧Aluminum hydroxide/iron cake

M17‧‧‧ dehydrated filtrate

M18‧‧‧Aluminum hydroxide/iron powder

M/19‧‧‧ arsenic/fluorine adsorbent

Figure 1 is a flow chart of a method for preparing an arsenic/fluorine adsorbent

Figure 2 is a schematic view showing an embodiment of preparing an arsenic/fluorine adsorbent

Example 1 Purification of aluminum hydroxide/iron from self-cleaning water sludge

After the raw water (M01) is pretreated (P01), impurities such as waste sand and waste residue (M02) are removed, and a coagulant (M03) such as polyaluminum chloride, aluminum sulfate, or chlorination is added to the chemical coagulation unit (P02). A composite formulation of iron, ferric sulfate, ferrous sulfate, and polybasic iron citrate or a plurality of coagulants, which forms a rubber feather with suspended solids in water, and is subjected to solid-liquid separation (P03) to obtain a sludge (M04). The sludge (M04) is transferred to a pickling and concentrating unit (P04), and dilute acid (M06) is added to control the pH value between 4 and 5, and the mixture is slowly stirred to dissolve the heavy metal hydroxide. The sludge after the panning gradually settles and forms a concentrated sludge (M07), and the sludge residence time in the pickling and concentration process is 6 hours. After that, the concentrated sludge (M07) is removed and the strong acid (M09) is added to control the pH between 1 and 2, and the aluminum ferrite ion is heated and dissolved by the microwave at a frequency of 915 MHz (P05), heated to 95 ° C, and the acidification time is 20 minutes. . The acidified sludge (M10) is dehydrated (P06), and the aluminum/iron solution (M11) dissolved in the acid is filtered out and collected in a reaction tank (P07), and an alkaline solution (M13) is added to adjust the pH. The value is controlled between 5.5 and 6.5, and then a coagulant (M14) such as polyacrylamide (PAM), active citric acid or bone cement is added to form a hydroxide solution (M15) of aluminum and iron. The precipitate solution (M15) is pumped to a dehydrator for dehydration (P08) to remove excess water to produce hydrogen and oxygen. Aluminum/iron mud cake (M16) with a moisture content of less than 80%. Thereafter, the sludge cake (M16) is further heated, dried and ground (P09) to produce a dry aluminum hydroxide/iron powder (M18) having a particle diameter of less than 0.5 mm. Finally, the dried powder (M17) is heated to 750 ° C to activate (P10) to form an adsorbent (M19) capable of adsorbing arsenic and fluorine.

Example 2 Dry aluminum hydroxide/iron powder added to clay to make filter

A ceramic filter (A01) was prepared by mixing dry aluminum hydroxide/iron powder (M18) into clay. The dry sludge powder has fine particles and is similar to clay, and its addition amount is 20 to 70% of clay. In addition, it is necessary to add appropriate amount of wood chips, rice stalks, broken wheat straw, broken corn stover, grass ash and other fluffing agents to improve the porosity and water repellency of the pottery. The amount of addition depends on the clay and additives used, generally The proportion of additives is 20~50% of the weight of the clay. Excessive additives will reduce the strength of the ceramic. Before the embryo is made, the clay, sludge and fluffing agent should be thoroughly mixed to avoid the gap after the firing, resulting in uneven filtration. The ceramic filter has a thickness of 2 to 3 cm and can be in the form of a basin, a hemisphere, a candle or a tube. Temperature plays an important role in the production process. The burning temperature can be 600~1,000 °C. The insufficient temperature can not convert the hydroxide in the sludge into oxide, and the too high temperature will cause the oxide to crystallize and lose. The most suitable temperature for the activity is 800 °C. The activated sludge powder contains red iron and has a reddish brown color. Since the ceramic filter filters the water slowly, it provides sufficient time to contact the activated alumina in the filter to achieve the adsorption effect. These filters have an adsorption capacity of more than 95% in arsenic-containing drinking water at a general concentration (less than 500 μg/L).

Example 3 Activated alumina/iron adsorbent mixed with clay to make filter

The heat-activated adsorbent (M19) was added to the clay to prepare a ceramic filter (A03), and the process and required conditions were the same as those of the above-mentioned Example 2, in which the unactivated dry sludge was directly added to the clay pottery. The activated sludge is added in an amount of 20 to 70% of the clay, the proportion of the fluffing agent is 20 to 50% by weight of the clay, and the firing temperature is 600 to 1,000 ° C, and 800 ° C is most suitable. The thickness of the filter is preferably 1 to 3 cm, and may be in the form of a basin, a hemisphere, a candle or a tube. The prepared filter can absorb more than 95% of the general concentration of arsenic-containing drinking water.

Example 4 The activated aluminum hydroxide/iron adsorbent is made into a granular filling space in the ceramic filter.

After the activated adsorbent (M19) is granulated (A02), the granular adsorbent particle size should not be too large, so as to prevent the water flow from flowing rapidly between the particle gaps, and the adsorption effect is reduced, and the particle size ranges from 0.5. ~10mm. The granular adsorbent can be used simultaneously with the ceramic filter, and the granular adsorbent is filled in the space of the ceramic filter. The filter (A04) can be a pot type, a hemisphere type, a candle type or a tube type. Due to the slow rate of water filtration, arsenic and fluorine have sufficient contact time to contact the granular adsorbent to remove arsenic and fluorine from the water. The granulated adsorbent can be removed from the ceramic filter after being saturated by adsorption, and has the advantage of convenient replacement compared with the second and third embodiments.

Example 5 Activated alumina/iron adsorbent is directly adsorbed into water

The activated adsorbent, whether in powder form (M19) or in pellet form (A02), can be directly introduced into water as an adsorbent. The amount of adsorbent administered and The relevant adsorption conditions such as the mixing time of water contact vary depending on the water quality, and can be determined by the bottle test. Direct adsorption of arsenic in this manner can be reduced to 20 μg/L when the concentration of arsenic in water is 500 μg/L, and the removal effect is over 95%.

Claims (12)

A method for using purified water sludge as raw material as arsenic and fluorine adsorbent comprises: (1) adding raw coagulating agent (M03) to the coagulation unit (P02) after pretreatment (P01) of raw water (M01) ) or a composite formulation of a plurality of coagulants (2), the coagulation agent (M03) is added to form a gelatinous treatment water by a solid-liquid separation (P03) to obtain a sludge (M04) (3) the sludge (M04) Move to a pickling and concentrating unit (P04), add dilute acid solution (M06) to adjust the pH value to 4~5, slowly stir and form concentrated sludge (M07) (4) to remove the concentrated sludge ( M07) and add strong acid (M09) to control the pH between 0 and 3, and heat-dissolve aluminum-iron ions by microwave irradiation (P05). (5) The acidified sludge (M10) is dehydrated (P06) and will be dissolved in The acid contains aluminum (iron) solution (M11) filtered out (6) The filtrate (M11) is collected in a reaction tank (P07), an alkaline solution (M13) and a coagulant (M14) are added, the reaction tank (P07) The pH value is maintained between 5 and 7, to produce an aluminum and iron hydroxide precipitate solution (M15) (7), and the precipitate solution (M15) is subjected to another dehydration process (P08) to produce Aluminium iron sludge cake (M16) (8) The sludge cake (M16) is dried and ground (P09) to produce dry hydrogen. Aluminum / iron powder (M18); and (9) The dry powder (M18) activated by heating (P10), produce the adsorbent adsorbing arsenic and fluorine (M19). For example, the composite formulation of the coagulant (M03) and various coagulants in the scope of claim 1 may be a salt containing polyaluminum chloride, aluminum sulfate, ferric chloride, iron sulfate, ferrous sulfate and polybasic iron citrate. Class of compounds. The solid-liquid separation method (P03) as claimed in claim 1 may be gravity separation, filtration separation or pressurized floating separation. For example, the pickling and concentrating tank (P04) of the first application scope can be continuous or batch; the sludge residence time is more than 3 hours; the stirring method can be mechanical stirring, liquid stirring or gas stirring; Gravity, with filter or centrifugal concentrate. The microwave elution (P05) heating according to the first application of the patent scope can reach 50 to 100 ° C, the microwave frequency for heating can be 2,450 MHz or 915 MHz, and the acidification heating time is 10 to 120 minutes. For example, the dewatering method (P06 and P08) of the first application of the patent scope may be a filter type, a pressure filter type, a centrifugal type, a vacuum type or a screw type. The heat activation (P10) temperature range of the first application of the patent scope is 300 to 1,000 °C. The dry aluminum hydroxide/iron powder (M18) as claimed in item 1 of the patent application can be added to the clay and fired into a ceramic filter (A01); or it can be separately activated by heating to form an arsenic/fluorine adsorbent. (M19). The weight ratio of dry aluminum hydroxide/iron powder (M18) to clay added in item 8 of the patent application scope may be 20-70%, and appropriate amount of wood chips, rice straw chips, crushed wheat straw, crushed corn stover, and plant ash are added. The fluffing agent is 20-50% of the weight of the clay, and the firing temperature is 600-1,000 ° C. The arsenic/fluorine adsorbent (M19) as claimed in item 8 of the patent application may be a powder having a particle diameter of less than 0.5 mm or a pellet having a particle diameter of 0.5 to 10 mm (A02). The powdered adsorbent (M19) as claimed in item 10 of the patent application can be added to the clay and fired into another ceramic filter (A03), and the weight ratio of the added amount to the clay can be 20 to 70%. Appropriate amounts of wood chips, rice husks, broken wheat straw, broken corn stover, grass ash and other fluffing agents are 20-50% of the weight of the clay, and the firing temperature can be 600-1,000 ° C. The powdered arsenic/fluorine adsorbent (M19) and the particulate adsorbent (A02) as claimed in claim 10 can be directly put into water to make sufficient contact with water to produce an adsorption effect.