CN104556182B - Method for preparing solid high-efficiency flocculant polyaluminum chloride from fly ash - Google Patents

Abstract

The invention discloses a method for developing a solid high-efficiency flocculant polyaluminium chloride by using fly ash as a raw material. The method uses fly ash as a raw material to develop a solid high-efficiency flocculant polymerization through an intermediate product α-Al(OH) ₃ Aluminum chloride thirteen [Al ₁₃ (OH) ₂₄ (H ₂ O) ₂₄ Cl ₁₅ ·13H ₂ O] (abbreviated as P-Al ₁₃ ) crystallization. In the present invention, the aluminum-containing solution obtained by acid leaching the clinker obtained by sodium carbonate and fly ash in the solid phase reaction at high temperature is reacted with sodium hydroxide to obtain α-Al(OH) ₃ intermediate product, and then mixed with it under high temperature and normal pressure conditions After the hydrolysis-polymerization reaction of hydrochloric acid reaches a certain degree of alkalinity, the solid product of P-Al ₁₃ is naturally crystallized, and the remaining mother liquor is combined with the acid leaching solution to realize recycling and reuse, so as to achieve zero emission of aluminum ions. Show through flocculation test: the present invention is a kind of aluminum ion loss rate low, the method that P-Al ₁₃ transformation rate is high, and its gained solid product P-Al ₁₃ flocculation effect is obviously better than Keggin-Al ₁₃ ([AlO ₄ Al ₁₂ ( OH) ₂₄ (H ₂ O) ₁₂ ] ⁷⁺ ), and meet the national standard (GB15892‑2009) premium product specifications.

Description

A method for developing solid-state high-efficiency flocculant polyaluminum chloride with fly ash as raw material

technical field

The invention relates to a comprehensive utilization of fly ash and a preparation method of solid high-purity polyaluminum chloride, in particular to a method for developing a solid high-efficiency flocculant polyaluminum chloride using fly ash as a raw material.

Background technique

Fly ash is a complex multiphase solid waste that remains after coal is burned in a combustion boiler. The main phase composition of fly ash is mullite, and the main chemical composition is SiO ₂ , Al ₂ O ₃ . At present, many experts and scholars at home and abroad are engaged in the comprehensive development and utilization of fly ash, which has realized that fly ash is widely used in building materials, agriculture (planting) breeding, concrete construction, chemical engineering and other fields; while turning waste into treasure, it also produces Good economic benefits, environmental benefits and social benefits. Using fly ash as raw material to prepare high-efficiency flocculant to realize the treatment of sewage and wastewater is one of the methods of high value-added utilization of fly ash. At present, it has been realized to prepare aluminum silicate flocculant, aluminum iron silicate flocculant and polyaluminum ferric chloride flocculant by using fly ash as raw material. However, the use of fly ash to prepare Al ₁₃ , which is considered to be the most effective flocculation form in polyaluminum and has superior water purification performance, has not been reported.

Al ₁₃ is considered to be the smallest and most stable nano-species in polyaluminum chloride solution due to its nano-molecular size and high charge. However, so far, various synthetic preparation methods have been tried in various technical fields at home and abroad, but it is impossible to obtain a high-concentration, high- _Al13 -content polymerized aluminum solution and a high-purity Al13 solid product with industrial application value.

In 2006, Sun Zhong reported in Chinese _{J.Struct.Chem.25} (10):1217-1227 that P-Al ₁₃ (Al ₁₃ (OH) ₂₄ (H ₂ O) ₂₄ Cl ₁₅ · 13H ₂ O), its polycation has 15 positive charges, and the patent application number 200510064782.6 discloses the production of aluminum hydroxide, crystallized aluminum chloride, and water under the condition of an autoclave at 200°C A method to obtain high-purity P-Al ₁₃ , and proved that P-Al ₁₃ has better deturbidity than Keggin-Al ₁₃ at different pH values, a wider range of effective flocculation dosage and adaptable water bodies pH. This shows that P-Al ₁₃ is a high-efficiency flocculant with superior performance and promising prospects, which is of great significance to the development and utilization of Yellow River water, the treatment of various wastewater, and the conservation of groundwater resources.

Contents of the invention

The technical problem to be solved in the present invention is to provide a method for developing a solid high _- efficiency flocculant polyaluminum chloride with fly ash as a raw material. Solid high-efficiency flocculant P-Al ₁₃ with high purity and single form and excellent flocculation performance.

In order to solve the problems of the technologies described above, the present invention proposes the following scheme: a method for developing a solid high-efficiency flocculant polyaluminum chloride with fly ash as a raw material, characterized in that, using fly ash as a raw material, through the intermediate product α-Al ( OH) ₃ to develop Al ₁₃ (OH) ₂₄ (H ₂ O) ₂₄ Cl ₁₅ 13H ₂ O (abbreviated as P-Al ₁₃ ), including the following five steps:

①High-temperature melting reaction: Grind and mix fly ash and sodium carbonate at a mass ratio of 0.8-2.0:1, roast and react in a muffle furnace at 750-950°C for 30-150 minutes, cool the clinker to room temperature and grind it thoroughly spare;

②Acid leaching reaction: add 3-12mol/L hydrochloric acid to the above clinker, and add 4-20mL hydrochloric acid for each gram of clinker. After fully stirring, let it stand at room temperature for 5-30 minutes and then filter to obtain the acid leaching solution. ;

③ Preparation of α-Al(OH) ₃ : Take the above acid immersion solution, add dropwise a sodium hydroxide solution with a concentration greater than 4mol/L at 70°C to 90°C to pH = 7.5 to 8.5, obtain a precipitate, and filter to obtain a filter cake It is α-Al(OH) ₃ , which is washed and dried several times, and then finely ground for later use;

④ Preparation of P-Al ₁₃ : React α-Al(OH) ₃ with 8-12mol/L hydrochloric acid under reflux conditions, the reaction temperature is 110-120°C, and the hydrolysis-polymerization reaction occurs under normal pressure for 6-10 hours. Obtain the stock solution so that the aluminum hydroxyaluminum specific alkalization degree is 0.4-1.3. After hot filtration, the filtrate is transferred to the crystallization equipment, evaporated and crystallized at room temperature to 50°C, and Al ₁₃ (OH) ₂₄ (H ₂ O) ₂₄ Cl is to be precipitated ₁₅ ·13H ₂ O crystal or powder is separated, the solid product is washed, and the product is dried at room temperature to 50°C to obtain a solid high-efficiency flocculant Al ₁₃ (OH) ₂₄ (H ₂ O) ₂₄ Cl ₁₅ ·13H ₂ O, The filtrate can be recycled;

⑤ Recycling of mother liquor: All the mother liquor obtained in step ④ is incorporated into the pickling solution obtained in step ② for recycling, which can achieve the purpose of maximizing the conversion rate of aluminum ions and zero discharge.

The experimental principle of this method:

1. Solid phase melting reaction:

The main crystalline phase of fly ash is mullite, and the amorphous phase is aluminosilicate glass. Mullite is insoluble in acid and alkali at room temperature. But under heated conditions, it can react with alkaline substances. In this experiment, sodium carbonate was used as a flux. Under high temperature conditions, fly ash reacted with sodium carbonate to form nepheline.

Al ₆ Si ₂ O ₁₃ +Na ₂ CO ₃ ＝2NaAlSiO ₄ +2Al ₂ O ₃ +CO ₂

At the same time, the Al ₂ O ₃ formed by the reaction and the silicate glass phase in the fly ash will also react with Na ₂ CO ₃ :

Al ₂ O ₃ +2SiO ₂ +Na ₂ CO ₃ ＝2NaAlSiO ₄ +CO ₂

2. Acid leaching reaction:

Nepheline is an acid-soluble substance, which can be decomposed by acid to produce silica gel and Al ³⁺ ; to achieve effective separation of silicon and aluminum.

NaAlSiO ₄ +4H ⁺ ＝Al ³⁺ +Na ⁺ +H ₂ O+H ₂ SiO ₃

3. Preparation of α-Al(OH) ₃ : The reaction of sodium hydroxide solution and aluminum chloride solution can obtain various forms of aluminum hydroxide, but by controlling the temperature and pH, a single form of α-Al(OH) ₃ can be obtained. form.

4. Preparation of P-Al ₁₃ :

When α-Al(OH) ₃ undergoes hydrolysis-polymerization reaction with hydrochloric acid at a certain temperature and reaches a certain degree of alkalization, various forms of polyaluminum including P-Al ₁₃ can be obtained in the solution. When the corresponding degree of saturation is reached After that, P-Al ₁₃ hydrochloride can naturally precipitate and crystallize.

5. Mother liquor circulation:

Since the reaction for preparing P-Al ₁₃ does not introduce any other ions, the remaining mother liquor can be combined with the acid leaching liquor for recycling to achieve the goal of zero discharge.

The high-temperature melting reaction described in this method refers to: adopting the high-temperature solid-phase sintering method of sodium carbonate and fly ash, intending to react mullite, the main phase in fly ash, with sodium carbonate at high temperature to form easy Acid-soluble nepheline clinker; acid leaching reaction refers to: impregnating the above-mentioned clinker with hydrochloric acid to effectively separate silicon and aluminum to obtain an aluminum chloride solution with iron ions as the main impurity ion; α-Al(OH) The preparation of ₃ refers to: adjusting the pH of the pickling solution with sodium hydroxide under constant temperature conditions to obtain α-Al(OH) ₃ ; the preparation of P-Al ₁₃ refers to: using α-Al(OH) ₃ as The raw material undergoes hydrolysis-polymerization reaction with hydrochloric acid under high temperature and normal pressure conditions to obtain a stock solution. After standing at room temperature, P-Al ₁₃ hydrochloride will naturally precipitate and crystallize, and the product will be obtained after filtration; mother liquor recycling refers to: P-Al 13 The mother liquor obtained in the preparation step of ₁₃ is all incorporated into the acid leaching solution obtained by the acid leaching reaction for recycling, which can realize the purpose of maximizing the conversion rate of aluminum ions and zero discharge.

The mass ratio of fly ash and sodium carbonate described in this method, and the determination of calcination temperature and time are to ensure that the main phase mullite in the fly ash reacts completely with sodium carbonate, and on the premise of not causing energy waste .

The amount of acid used for leaching the clinker with hydrochloric acid described in the method is based on the maximum leaching rate of aluminum in the fly ash and the minimum loss rate; excess hydrochloric acid can be recycled and reused.

The preparation temperature of α-Al(OH) ₃ described in the method is 70-90° C., and the pH value is adjusted at 7.5-8.5.

The α-Al(OH) ₃ described in this method does not necessarily need to be a freshly prepared compound.

The method described in the method uses α-Al(OH) ₃ as a raw material to undergo a hydrolysis-polymerization reaction with hydrochloric acid in a temperature range of 110-120° C. under normal pressure for 6-10 hours to obtain a stock solution.

The amount of α-Al(OH) ₃ and hydrochloric acid described in this method needs to ensure that the alkalization degree (hydrazine ratio) of the stock solution for the final reaction is 0.4 to 1.3.

The obtained α-Al(OH) ₃ aluminum form described in this method can realize the reaction with hydrochloric acid under normal pressure conditions and reach the alkalization degree for preparing P-Al ₁₃ .

The reaction solution of α-Al(OH) ₃ and hydrochloric acid described in this method can naturally precipitate P-Al ₁₃ crystals at room temperature, and directly obtain a solid high-efficiency flocculant after filtration without any other solidification device and process.

The raw materials required for the preparation of P-Al ₁₃ described in this method are only α-Al(OH) ₃ and hydrochloric acid, no other catalyst or reagent is required, that is, no other any other substances other than Al(III) are introduced in the preparation process. Impurity ions.

The remaining mother liquor after the precipitation and crystallization of P- _Al13 hydrochloride described in the method can be recycled, and is a method for preparing P- _Al13 with low aluminum ion loss rate, high conversion rate and zero discharge. Advantages of the present invention:

The present invention has the following outstanding advantages:

1. This method converts fly ash into a solid high-efficiency flocculant, providing a way to realize high value-added comprehensive utilization of fly ash.

2. The method is easy to operate, has few influencing parameters, and guarantees product quality.

3. This method explores a method for rapidly preparing α-Al(OH) ₃ by adjusting temperature and pH value.

4. The method can realize the preparation of P-Al ₁₃ by using aluminum hydroxide as a raw material under normal pressure conditions.

5. In this method, P-Al ₁₃ is naturally precipitated and crystallized by adjusting the degree of supersaturation to obtain a solid high-efficiency flocculant without any other solidification device and process.

6. No impurity ions other than Al(III) are introduced during the preparation of P-Al ₁₃ by this method.

7. The product obtained by this method has an effective flocculation component P-Al ₁₃ content of more than 93%, excellent water solubility, no water insoluble matter, and the obtained product meets the national standard (GB15892-2009) premium product specification.

8. This method is a method for preparing P-Al ₁₃ with low aluminum ion loss rate, high conversion rate and zero emission.

9. The flocculation effect of P-Al ₁₃ obtained in the present invention is better than that of Keggin-Al ₁₃ ([AlO ₄ Al ₁₂ (OH) ₂₄ (H ₂ O) ₁₂ ] ⁷⁺ ). The comparative experiments are shown in Table 1. It can be seen from the table that compared with Keggin-Al ₁₃ , P-Al ₁₃ prepared by the present invention has a superior flocculation effect than Keggin-Al ₁₃ regardless of high turbidity stable water samples and low turbidity unstable water samples.

Table 1, P-Al ₁₃ and Keggin-Al ₁₃ ^a flocculation experiment ^b results

Note ^a : Keggin-Al ₁₃ is prepared by slow alkali drop method: under the conditions of constant temperature oil bath 80°C and strong magnetic stirring, NaOH solution is slowly added dropwise to AlCl ₃ solution, and the dropping rate is controlled at about 0.6mL/min. Cool to room temperature after the dropwise addition, and mature for a certain period of time to obtain a polymerized PAC solution containing Keggin-Al ₁₃ , with an Al _b content of about 80%, which is mainly Keggin-Al ₁₃ according to ²⁷ Al-NMR characterization. Note ^b : The flocculation experiment adopts the container test method: the instrument uses JJ-4 six-connected electric stirrer, injects 500mL simulated water sample into the beaker, starts stirring, and puts it into the water sample under rapid stirring (rotation speed: 200r/min). A certain amount of flocculant, continue to stir rapidly for 1min, then change to slow speed (40r/min) stirring for 15min, stop stirring and let it settle for 15min. After the precipitation is completed, the clarified water sample liquid can be drawn from 1cm below the liquid surface, and the remaining turbidity is detected by a 2100N turbidimeter. )

Description of drawings

Figure 1 is a process flow diagram.

Figure 2 is the XRD pattern of the intermediate product α-Al(OH) ₃ .

Figure 3 is the XRD spectrum of the first precipitated P-Al ₁₃ product.

Figure 4 is the XRD pattern of the second precipitated P-Al ₁₃ product.

Figure 5 is the XRD pattern of the third precipitated P-Al ₁₃ product.

Fig. 6 is the XRD pattern of the fourth precipitation of P-Al ₁₃ product.

detailed description

The present invention will be further described through the following examples, but the scope of protection claimed by the present invention is not limited to the scope of protection of the examples.

1. High-temperature melting reaction: Grind and mix the fly ash and sodium carbonate of Hohhot Power Plant in a mortar at a mass ratio of 1.2:1, and roast them in a muffle furnace at 870°C for 80 minutes. After the clinker is cooled to room temperature, it is fully ground for later use. (Fly ash Al ₂ O ₃ content is 49.2%)

2. Acid leaching reaction: Take 75.2g of the above-mentioned clinker in a beaker, add 380mL of concentrated hydrochloric acid and 20mL of distilled water, stir well, let stand at room temperature for 5min, and filter to obtain the acid leaching solution.

3. Preparation of α-Al(OH) ₃ : Take the above acid immersion solution, add dropwise a sodium hydroxide solution with a concentration of 8mol/L at 70°C until pH = 8, obtain a precipitate, and filter the filter cake to obtain α -Al(OH) ₃ , washed and dried for many times, then finely ground for later use. The XRD characterization results of the product are shown in Figure 2.

4. Preparation of P-Al ₁₃ : (1) Take 43g of α-Al(OH) ₃ in a 500mL three-necked flask, add 74mL of concentrated hydrochloric acid and 15mL of distilled water under reflux conditions, react at room temperature for 30min, then raise the temperature to 120°C to continue the reaction After a total reaction of 6 hours, the reaction was stopped, and the stock solution was obtained by filtration while it was hot. The alkalization degree (hydrazine-aluminum ratio) was 1.2. It was transferred to the crystallization equipment and naturally crystallized at room temperature, and Al ₁₃ (OH) ₂₄ (H ₂ O) was to be precipitated. ₂₄ Cl ₁₅ ·13H ₂ O (P-Al ₁₃ ) crystals were isolated. The product was washed with ethanol, air-dried at room temperature, and stored by weighing.

Sampling and analysis results: the total mass of the solid product: 13.51 g, of which the mass content of P-Al ₁₃ is 94.2%, and the conversion rate of aluminum ions: 16.28%. The remaining mother liquor is 140.48g. The XRD characterization results of the product are shown in Figure 3.

(2) Merge the remaining mother liquor of (1) into the pickling solution of the second step, add sodium hydroxide dropwise to pH = 8 at 70°C, and obtain α-Al(OH) ₃ solid again, take 43g of α -Al(OH) ₃ Repeat the experimental step (1) to obtain P-Al ₁₃ crystals again.

Sampling and analysis results: the total mass of solid product: 13.49g, wherein the mass content of P-Al ₁₃ is 93.5%, and the total aluminum ion conversion rate combined with the first reaction: 28.58%. The XRD characterization results of the 140.50 g product of the remaining mother liquor are shown in Figure 4.

(3) Merge the remaining mother liquor of (2) into the pickling solution of the second step, add sodium hydroxide dropwise to pH = 8 at 70°C, and obtain α-Al(OH) ₃ solid again, take 43g of α -Al(OH) ₃ Repeat the experimental procedure of step (1) again to obtain P-Al ₁₃ crystals again.

Sampling and analysis results: the total mass of the solid product: 13.52g, of which the mass content of P-Al ₁₃ is 95.7%, and the total aluminum ion conversion rate combined with the previous two reactions: 34.44%. The remaining mother liquor is 140.48g. The XRD characterization results of the product are shown in Figure 5.

(4) Incorporate the remaining mother liquor of (3) into the pickling solution of the second step, and add sodium hydroxide dropwise to pH = 8 at 70°C to obtain α-Al(OH) ₃ solid again, and take 43g of α -Al(OH) ₃ Repeat the experimental procedure of step (1) again to obtain P-Al ₁₃ crystals again.

Sampling and analysis results: the total mass of the solid product: 13.53g, of which the mass content of P-Al ₁₃ is 94.1%, and the total aluminum ion conversion rate combined with the previous three reactions: 40.12%. The remaining mother liquor is 140.47g.

According to the aluminum ion conversion rate of the first four experiments, it can be calculated theoretically: the aluminum ion conversion rate after the fifth mother liquor recycling can reach: 48.07%; the aluminum ion conversion rate after the sixth mother liquor recycling: 50.96%. That is, the more times the mother liquor is circulated, the higher the conversion rate of aluminum ions is, and finally zero emission of aluminum ions can be realized.

Claims (1)

1. a kind of the method for solid-state efficient flocculant aluminium polychlorid is developed it is characterised in that with fine coal for raw material with flyash Ash is raw material, by intermediate product α-Al (OH)₃Develop Al₁₃(OH)₂₄(H₂O)₂₄Cl₁₅·13H₂O, letter is calculated as P-Al₁₃, including Five steps below：

1. high-temperature fusion reaction：Flyash and sodium carbonate are pressed 0.8～2.0: the 1 finely ground mixing of mass ratio, 750 in Muffle furnace Calcination 30～150min at～950 DEG C, is fully ground standby after clinker cooling to room temperature；

2. acid-leaching reaction：In above-mentioned grog, adding the hydrochloric acid of 3～12mol/L, every gram of grog correspondence Jia 4～20mL volume Hydrochloric acid, after being sufficiently stirred for, room temperature is filtrated to get pickle liquor after standing 5～30min；

③α-Al(OH)₃Preparation：Take above-mentioned pickle liquor, Deca concentration is more than the hydrogen-oxygen of 4mol/L under the conditions of 70 DEG C～90 DEG C Change sodium solution to pH=7.5～8.5, be precipitated, filter to obtain filter cake as α-Al (OH)₃, finely ground after repeatedly washing and drying Standby；

④P-Al₁₃Preparation：By α-Al (OH)₃Under reflux conditions with 8～12mol/L hydrochloric acid reaction, reaction temperature 110～ 120 DEG C, condition of normal pressure issues unboiled water solution-polyreaction 6～10 hours, obtains storing solution so as to basicity, and that is, hydroxide aluminium ratio is 0.4～1.3, after filtered while hot, filtrate moves into crystallizer, evaporative crystallization at room temperature～50 DEG C, Al to be separated out₁₃(OH)₂₄ (H₂O)₂₄Cl₁₅·13H₂Separate after O crystal or powder, solid product is scrubbed, at room temperature～50 DEG C, dry product, prepared solid-state Efficient flocculant Al₁₃(OH)₂₄(H₂O)₂₄Cl₁₅·13H₂O, filtrate reusable edible；

5. mother liquid recycling：The mother solution of the 4. step gained is fully incorporated the 2. recycle in the pickle liquor of step gained.