阅读说明：本技术 一种高含量锌铁废酸分步沉淀分离的资源化利用方法 (Resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid ) 是由 赵盈男 罗恒 华蔓 杨合雄 宋德生 石肖 于 2021-07-13 设计创作，主要内容包括：本发明公开了一种高含量锌铁废酸分步沉淀分离的资源化利用方法,利用缓慢氧化水解的方法,将废酸中的铁制备成羟基氧化铁,对废酸中的锌铁进行分步沉淀,首先将铁从废酸液中分离出来,然后调节pH沉锌。本发明有效的解决了锌铁分离夹带严重的问题；将分离后的锌铁分别制备成氧化铁红颜料、氢氧化锌锌等产品。与现有的处理热镀锌废液的技术方法相比,本发明的方法工艺简单易于控制,工艺成本低,并且制备出的沉降物(羟基氧化铁)呈结晶态,过滤性能良好；锌夹带少,沉淀渣较少且渣中含铁高,沉铁效果达到100％。经适当处理可制备成价值较高的产品--氧化铁红颜料。从而实现了废弃物资源化、无害化的利用,具有良好的应用前景。(The invention discloses a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid. The invention effectively solves the problem of serious zinc-iron separation entrainment; and respectively preparing the separated zinc and iron into iron oxide red pigment, zinc hydroxide and other products. Compared with the prior art for treating hot galvanizing waste liquid, the method has simple and easily controlled process and low process cost, and the prepared sediment (iron oxyhydroxide) is in a crystalline state and has good filtering performance; less zinc entrainment, less precipitated slag and high iron content in the slag, and the iron precipitation effect reaches 100 percent. The iron oxide red pigment which is a product with higher value can be prepared by proper treatment. Thereby realizing the resource and harmless utilization of the waste and having good application prospect.)

1. A resource utilization method for fractional precipitation separation of high-zinc-iron-content waste acid is characterized by comprising the following steps:

(1) adding iron oxyhydroxide liquid crystal with the volume ratio of 5-50% into the waste acid liquid containing zinc; adding a sodium hydroxide solution at a certain flow rate, stirring, adjusting the pH value of the solution to 2-4.5, then beginning aeration at a certain speed, controlling the water bath to heat to 40-80 ℃, reducing the stirring speed, simultaneously adding alkali to keep the pH value of the solution at 2-4.5, reacting for a period of time, stopping adding the alkali when the pH value is not changed greatly, continuing aeration for a period of time until the pH value is not changed, stopping the reaction, carrying out solid-liquid separation, and washing filter residues to obtain iron oxyhydroxide;

(2) adding alkali liquor into the filtered filtrate while stirring, adjusting pH to 8-10, stirring for a while, and filtering; so as to obtain zinc hydroxide precipitate.

2. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the step (1) also comprises the step of drying the obtained iron oxyhydroxide in an oven, and then calcining the iron oxyhydroxide in a muffle furnace at the temperature of 600-800 ℃ for 3-4 hours to obtain the iron oxide red.

3. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the iron oxyhydroxide seed crystal of the step (1) is prepared by the following method: pouring ferrous solution with certain concentration into a four-neck flask, adding alkali liquor to adjust the pH value to 7, adjusting the water bath temperature to 25-30 ℃, stirring, introducing air for aeration, and controlling the aeration speed; after the pH dropped to 2.5-3.5, no further change and the solution was orange, the seed preparation was complete.

4. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 3, characterized in that: the alkali liquor is sodium hydroxide with the mass fraction of 30%.

5. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the concentration of ferric ions in the waste acid solution containing zinc in the step (1) is 0-1%.

6. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the step (1) comprises the steps of pretreating the zinc-containing waste acid liquid, and then adding the hydroxyl iron oxide liquid crystal, wherein the pretreatment of the zinc-containing waste acid liquid comprises the following steps: evaporating and concentrating the zinc-containing waste acid liquid to obtain high-zinc-containing waste acid liquid and ferrous crystal products, adding iron powder into the high-zinc-containing waste acid liquid to reduce ferric iron in the solution into ferrous iron, and filtering to obtain zinc-containing waste acid filtrate.

7. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the step (1) of adding the sodium hydroxide solution at a certain flow rate and stirring comprises the following steps: adding 5-15% sodium hydroxide solution at 5-20mL/min, and stirring at 350 rpm.

8. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the reduction of the stirring rate in the step (1) comprises reducing the stirring rate to 250 rpm.

9. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the continuous aeration time in the step (1) is 1-1.5 h.

10. The resource utilization method of fractional precipitation separation of high zinc and iron content waste acid according to claim 1, characterized in that: the stirring time in the step (2) is 10-30 min.

Technical Field

The invention relates to the technical field of environmental protection, in particular to a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid.

Background

Hot galvanizing, also called hot dip galvanizing, is the corrosion-resistant surface protection technology for steel with the widest application range and the largest usage amount at present. The total yield of metallic zinc is about 40% for hot galvanizing steel products every year all over the world. With the development of domestic economy, especially the development of automobiles, household appliances and construction industries, the demand of hot-dip galvanized steel sheets is increasing year by year in China. The rapid increase in the yield of hot dip galvanized steel sheets inevitably leads to the generation of a large amount of hot dip galvanizing waste water. The discharge of hot galvanizing waste water is estimated to be more than 1600 million tons in China according to 300 tons/day discharge of hot galvanizing waste water of a production enterprise producing 15 million tons of hot galvanizing steel plates every year.

A large amount of hydrochloric acid is adopted by a common hot galvanizing enterprise to carry out acid cleaning and rust removal on the metal surface, and two iron salts, namely ferric chloride and ferrous iron, are generated when a metal product is subjected to acid cleaning in the hydrochloric acid. Since pickled metals generally rust very little severely, much ferrous iron is produced. The content of hydrochloric acid is continuously reduced along with the proceeding of the pickling process, the content of metal ions in the acid liquor is continuously increased, when the concentration of the pickling liquor is lower than a specified value or the content of the metal ions in the pickling liquor exceeds an allowable limit value, the acid liquor loses the pickling effect, and at the moment, the hydrochloric acid is discarded and replaced by new acid. The zinc ions in the waste acid are generated by the fact that zinc on the hanging tool and the back plating part is dissolved into the pickling solution through the re-pickling. Thus, the main components of the spent acid produced by the pickling process are ferrous ions, zinc ions and small amounts of ferric ions. If the hot galvanizing waste water is not discharged through proper treatment, the ecological balance can be seriously damaged, and the production and life of local residents are seriously influenced.

The invention patent (CN103755080A) discloses a method for treating hot galvanizing pickling waste liquid by adopting an electrolytic method. The method respectively recycles the chlorine and the sodium hydroxide solution generated by electrolysis for the production of the plating assistant bath solution and the neutralization treatment of the waste acid solution, realizes the recycling of the zinc plating waste acid solution and reduces the wastewater discharge of the hot galvanizing process. The method has higher cost and does not fundamentally solve the problem of zinc and iron treatment in hot galvanizing waste acid.

The invention patent (94112437.1) discloses a method for treating galvanized waste water and recovering precipitate, which utilizes an aqueous solution containing caustic alkali, urea, hexamethylenetetramine, phosphoric acid or salt, bone glue and other substances to add a certain dosage into the galvanized waste water, and achieves the effective treatment of the galvanized waste water and the recovery of zinc oxide by adjusting the pH value of the waste water. This method consumes a large amount of chemical reagents and introduces more impurity ions.

The invention discloses a method for recovering zinc salt in chloride galvanizing wastewater in Chinese patent 200810060227.X, which mainly comprises the following steps: adjusting the pH value of the wastewater to 8-9, adding a sodium sulfide solution, stirring to generate a precipitate, standing, and separating and filter-pressing the precipitate after a period of time. The method needs to add a large amount of alkali liquor to adjust the pH at the early stage, and has higher cost.

The invention patent (200810117788.9) discloses a method for treating cold rolling electrogalvanizing waste water. The industrial slaked lime is added into the wastewater for neutralization, the pH value is controlled within the range of 8.5-9, and after precipitates are filtered, the standard discharge of the wastewater is realized. The pH value of the waste liquid treated by the method can meet the requirement, but a large amount of lime is consumed, and a large amount of sludge with the water content of 99 percent is generated and needs to be dried. And the sludge contains a large amount of metal salts, which causes secondary pollution, and most importantly, useful metal resources in the waste acid liquor cannot be recycled. Resulting in resource waste. Moreover, the ferric hydroxide can be used as a flocculating agent, and the traditional method can cause zinc to be adsorbed and carried by the ferric hydroxide and cannot achieve the effect of zinc-iron separation at all.

Yanpu reports that when J.Carrillo-Abad and the like adopt a single-chamber electrolytic cell to treat hot galvanizing pickling wastewater, Zn is redissolved after electrolysis for a certain timeElectrolytically generated Cl using Anion Exchange Membranes (AEM)₂The positive electrode is not reached and re-dissolution of Zn is prevented. However, due to Cl₂In the presence of, Fe²⁺Will react with Zn²⁺Co-depositing on the cathode, resulting in a significant reduction in the purity of the zinc. In order to prevent co-deposition of iron, AEM is replaced by Cation Exchange Membrane (CEM), acid washing wastewater is in the positive part, and the NAFION-117 membrane (CEM) allows Zn²⁺Preferentially passes through to the negative electrode, and Fe is in the positive electrode²⁺Is oxidized into Fe³⁺But not pass through. But due to Fe³⁺And the existence of the water-soluble organic wastewater can cause irreversible pollution to the membrane, shorten the service life of the membrane and increase the comprehensive treatment cost of the wastewater.

Disclosure of Invention

The invention aims to provide a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid, which has the advantages of simple treatment process, easy control and low cost.

In order to solve the technical problems, the invention adopts the following technical scheme:

a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid comprises the following steps:

(1) adding iron oxyhydroxide liquid crystal with the volume ratio of 5-20% into the waste acid liquid containing zinc; adding a sodium hydroxide solution at a certain flow rate, stirring, adjusting the pH value of the solution to 2-4.5, then beginning aeration at a certain speed, controlling the water bath to heat to 40-80 ℃, reducing the stirring speed, simultaneously adding alkali to keep the pH value of the solution at 2-4.5, reacting for a period of time, continuing aeration for a period of time after the pH value is not changed greatly, stopping the reaction, separating solid from liquid, and washing filter residues to obtain iron oxyhydroxide;

(2) adding liquid caustic soda into the filtered filtrate while stirring, adjusting the pH to 8-10, continuously stirring for a period of time, and filtering; so as to obtain zinc hydroxide precipitate.

Preferably, the step (1) further comprises drying the obtained iron oxyhydroxide in an oven, and then calcining the iron oxyhydroxide in a muffle furnace at the temperature of 600-800 ℃ for 3-4 hours to obtain the iron oxide red.

Preferably, the iron oxyhydroxide seed crystal of step (1) is prepared by the following method: pouring ferrous solution with certain concentration into a four-neck flask, adding alkali liquor to adjust the pH value to 7, adjusting the water bath temperature to 25-30 ℃, stirring, introducing air for aeration, and controlling the aeration speed; after the pH dropped to 2.5-3.5, no further change and the solution was orange, the seed preparation was complete.

Preferably, the alkali liquor is sodium hydroxide with the mass fraction of 30%.

Preferably, the concentration of ferric ions in the waste acid solution containing zinc in the step (1) is 0-1%.

Preferably, the step (1) comprises pretreating the zinc-containing waste acid liquor and then adding the ferric hydroxide crystal liquid, wherein the pretreatment of the zinc-containing waste acid liquor comprises the following steps: evaporating and concentrating to obtain a high-zinc-content waste acid liquid and a ferrous crystal product, adding iron powder into the high-zinc-content waste acid liquid to reduce ferric iron in the solution into ferrous iron, and filtering to obtain a zinc-containing waste acid filtrate.

Preferably, the step (1) "adding the sodium hydroxide solution at a certain flow rate, and stirring" includes: adding 5-15% sodium hydroxide solution at 5-20mL/min, and stirring at 350 rpm. The reduction of the stirring rate in the step (1) comprises reducing the stirring rate to 250 rpm. The continuous aeration time in the step (1) is 1-1.5 h.

Preferably, the stirring time in the step (2) is 10-30 min.

The method of the invention fully utilizes the characteristics of the contents of all components in the waste acid liquid containing zinc: the method comprises the steps of preparing iron in the waste acid solution into iron oxyhydroxide by using a slow oxidation hydrolysis method, performing fractional precipitation on zinc and iron in the waste acid solution, firstly separating the iron from the waste acid solution, and then adjusting the pH value to precipitate the zinc, wherein the method effectively solves the problem of serious zinc and iron separation entrainment; the separated zinc and iron can be respectively prepared into products such as iron oxide red pigment, zinc chloride and the like.

The invention has simple treatment process, easy control, low cost and high economic value of the product, can realize the aims of recycling and productizing the waste and has good application prospect.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments.

The invention discloses a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid. The invention effectively solves the problem of serious zinc-iron separation entrainment. The separated zinc and iron are respectively prepared into products such as iron oxide red pigment, zinc hydroxide and the like, so that the resource utilization of the zinc and iron containing waste liquid is realized.

The invention relates to a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid, which mainly comprises the following steps:

(1) preparation of iron oxyhydroxide crystals

Pouring ferrous solution with certain concentration into a four-neck flask, adding 30% alkali liquor to adjust the pH value to 7, controlling the water bath temperature to be 25-30 ℃, stirring, introducing air to perform aeration, and controlling the aeration speed; after the pH value is reduced to 2.5-3.5 and is not changed any more and the solution is orange, the preparation of the seed crystal is finished;

(2) preparation of iron oxyhydroxide

And (3) mixing zinc and iron: 4 (adjustable parameters) of the zinc-containing waste liquid is put into a round-bottom flask, and seed crystal liquid with the solution volume ratio of 5-20% is introduced. Then adding 5-15% sodium hydroxide solution at the speed of 10mL/min, stirring at 350rpm, adjusting pH to 2-4.5, aerating at a certain speed, heating in water bath to 40-80 deg.C, and reducing stirring speed to 250rpm, while continuously adding alkali to maintain pH at 2-4.5. Stopping adding alkali when the pH value is constant, continuing aerating for 1-1.5h, and stopping reaction; and (4) carrying out solid-liquid separation, and washing filter residues to obtain the iron oxyhydroxide.

(3) Zinc precipitation method

Adding liquid caustic soda into the filtered filtrate while stirring, adjusting pH to 8-10, continuously stirring for 10-30min, and filtering; so as to obtain zinc hydroxide precipitate.

(4) Preparation of iron oxide red pigments

And (3) putting the washed iron oxyhydroxide into an oven for drying, and then putting the dried iron oxyhydroxide into a muffle furnace for calcining at the temperature of 600-800 ℃ for 3-4 hours to obtain the iron oxide red.

The invention discloses a resource utilization method for fractional precipitation separation of high-content zinc and iron waste acid. The invention effectively solves the problem of serious zinc-iron separation entrainment; and respectively preparing the separated zinc and iron into iron oxide red pigment, zinc hydroxide and other products.

Compared with the prior art for treating hot galvanizing waste liquid, the method has simple and easily controlled process and low process cost, and the prepared sediment (iron oxyhydroxide) is in a crystalline state and has good filtering performance; less zinc entrainment, less precipitated slag and high iron content in the slag, and the iron precipitation effect reaches 100 percent. The iron oxide red pigment which is a product with higher value can be prepared by proper treatment. Thereby realizing the resource and harmless utilization of the waste and having good application prospect.

Example 1

512.65g of filtered zinc-containing waste acid (the components comprise Fe2+ 10.701%, Fe3+ 0.573%, HCl 0.66% and Zn2+ 4.556%) in a 2L four-neck flask, weighing 52.32g of seed crystal suspension, wherein the early stage alkali adding speed is 10mL/min, the stirring speed is 350rpm, after the pH is adjusted to 3.5-4, air is blown in (the aeration speed is 10L/min), the water bath is heated to 65 ℃, the stirring speed is reduced to 250rpm, the pH is controlled to be 3.5-4 by continuously adding alkali, the pH is slowly changed, after the alkali addition is stopped, the air is continuously aerated for about one hour, the pH is basically unchanged, the preliminary oxidation reaction is judged not to be carried out, and the reaction is stopped. Iron oxyhydroxide was formed at this point and the filtrate was iron free (iron was completely precipitated) with a zinc content of about 0.695% on a discus basis.

Example 2

510.38g of filtered zinc-containing waste acid (the components comprise Fe2+ 5.064%, Fe3+ 0.573%, HCl 0.3% and Zn2+ 2.273%) in a 2L four-neck flask in a water bath, 51.08g of seed crystal suspension is weighed, the early stage alkali adding speed is 10mL/min, the stirring speed is 350rpm, after the pH value is adjusted to 3.5-4, air is blown in (the aeration speed is 10L/min), the water bath is heated to 65 ℃, the stirring speed is reduced to 250rpm, the pH value is controlled to 3.5-4 by continuously adding alkali, the pH value is slowly changed, after the alkali adding is stopped, the air is continuously aerated for about one hour, the pH value is basically unchanged, the preliminary oxidation reaction is judged not to be carried out, and the reaction is stopped. Iron oxyhydroxide was formed and the filtrate was iron free (iron was completely precipitated) and the zinc content of the discus base was about 1.2%.

Example 3

500.1g of filtered zinc-containing waste acid (the components comprise Fe2+ 4.24%, Fe3+ 0.15%, HCl 0.13% and Zn2+ 2.9%) in a 2L four-mouth flask in the hot galvanizing industry is weighed, 45g of seed crystal suspension is weighed, the early stage alkali adding speed is 10mL/min, the stirring speed is 350rpm, after the pH is adjusted to 3-3.5, air is blown in (the aeration speed is 10L/min), the temperature of the water bath is increased to 65 ℃, the stirring is reduced to 250rpm, the pH is controlled to 3-3.5 by continuously adding alkali, the pH is slowly changed, after the alkali adding is stopped, the air is continuously aerated for about one hour, the pH is basically unchanged, the preliminary oxidation reaction is judged not to be carried out, and the reaction is stopped. Iron oxyhydroxide was formed at this point and the filtrate was iron free (iron was completely precipitated) with a zinc content of about 2.04% on a discus basis.

Example 4

507.95g of filtered zinc-containing waste acid (the components comprise Fe2+ 5.064%, Fe3+ 0.573%, HCl 0.3% and Zn2+ 2.273%) in a 2L four-neck flask in a water bath pot, 45g of seed crystal suspension is weighed, the early stage alkali adding speed is 7mL/min, the stirring speed is 350rpm, after the pH is adjusted to 3-3.5, air is blown in (the aeration speed is 10L/min), the water bath is heated to 65 ℃, the stirring speed is reduced to 250rpm, the pH is controlled to 3-3.5 by continuously adding alkali, the pH is slowly changed, after the alkali adding is stopped, the air is continuously aerated for about one hour, the pH is basically unchanged, the preliminary oxidation reaction is judged not to be carried out, and the reaction is stopped. Iron oxyhydroxide was formed at this point and the filtrate was iron free (iron was completely precipitated) with a zinc content of about 1.96% on a discus basis.

Example 5

Zinc-iron containing waste sulfuric acid (component composition: F)e2+8.43％，Fe3+0.300％H₂SO₄3.851 percent and Zn2+6.76 percent, 503.45g of filtered zinc-containing waste liquid is weighed into a 2L four-neck flask and placed in a water bath, 45g of seed crystal suspension is weighed, the early stage alkali adding speed is 7mL/min, the stirring speed is 350rpm, after the pH value is adjusted to 3-3.5, air is blown in (the aeration rate is 10L/min), the water bath is heated to 65 ℃, the stirring is reduced to 250rpm, the alkali is continuously added to control the pH value to be 3-3.5, after the pH value is slowly changed, after the alkali adding is stopped, the air is continuously aerated for about one hour, the pH value is basically unchanged, the oxidation reaction is preliminarily judged not to be carried out, and the reaction is stopped. Iron oxyhydroxide was formed at this point and the filtrate was iron free (iron was completely precipitated) with a zinc content of about 0.227% on a discus basis.

Example 6

The zinc-iron containing waste sulfuric acid (composition: Fe2+ 7.587%, Fe3+ 0.546%, H)₂SO₄2.958 percent and Zn2+6.76 percent, weighing 503.70g of filtered zinc-containing waste liquid into a 2L four-mouth flask, placing the flask into a water bath, weighing 45g of seed crystal suspension, heating the water bath to 65 ℃, reducing the stirring speed to 250rpm, continuously adding alkali to control the pH to be 3-3.5, continuing to expose the air for about one hour after the pH is adjusted to 3-3.5, keeping the pH unchanged, preliminarily judging that the oxidation reaction is not carried out, and stopping the reaction, wherein the early-stage alkali adding speed is 7mL/min, the stirring speed is 350rpm, and the aeration rate is 10L/min after the pH is adjusted to 3-3.5. Iron oxyhydroxide was formed at this point and the filtrate was iron free (iron was completely precipitated) with a zinc content of about 0.315% on a discus basis.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.