CN115959795A - A method of improving the calcium method to treat sulfate-containing rare earth mining wastewater - Google Patents

Abstract

The invention relates to the field of waste water treatment, in particular to an improved calcium method for treating sulfate-containing rare earth mining waste water. When the existing calcium method treats high-concentration sulfate in water, the concentration of sulfate in the effluent is generally around 1000 mg/L, which is difficult to further reduce, resulting in high treatment costs and serious waste of resources. The method of the present invention is to add calcium dihydrogen phosphate in the rare earth wastewater containing sulfate, add indicator I dropwise, stir at a speed of 300 r/min, react within a preset time, adjust the stirring speed and add calcium oxide in an amount such that The solution can be kept until it changes color, slowly stirred for reaction, left to stand, solid-liquid separation, solid sent to drying treatment, and liquid sent to follow-up reaction treatment. The advantage of the present invention is that under the condition that it is difficult to carry out large-scale technological transformation, the dosing and operation mode and the pH value control mode are changed, which solves the problem that when the calcium method is used to treat high-concentration sulfate radicals in water, the concentration of sulfate radicals in the effluent is generally between 1000 mg/L or so, it is difficult to further reduce the problem.

Description

A method of improving the calcium method to treat sulfate-containing rare earth mining wastewater

technical field

The invention relates to the field of waste water treatment, in particular to an improved calcium method for treating sulfate-containing rare earth mining waste water.

Background technique

With the increasing depletion of rare earth mineral resources and increasingly stringent environmental protection requirements, the country has put forward new requirements for the extraction process of ionic rare earth minerals: to ensure the efficient use of rare earth mineral resources while taking into account environmental protection.

In view of the very limited reserves of ionic rare earths in southern Jiangxi and other regions and their important supporting role in the development of high-tech industries, ionic rare earth resources have been listed as special minerals for protective mining; however, the current in-situ leaching of ionic rare earths The mainstream mining process is "ammonium sulfate leaching-ammonium bicarbonate precipitation". This method improves the shortcomings of the traditional heap leaching method, which is highly polluting and prone to geological disasters. However, a large amount of ammonium salts are introduced into the environment by this process. , The use of ammonium salts has caused environmental problems such as mine tail water, surface water and groundwater near the mining area, excessive ammonia nitrogen, and ammonia nitrogen residues in the soil, which seriously restricts the development of the rare earth industry.

In order to realize resource conservation and effective protection of the environment, relevant mine development companies have carried out scientific research on "green" ionic rare earth extraction processes, and have developed a set of "magnesium sulfate leaching-magnesium oxide enrichment" with independent intellectual property rights. "The mining process system, which breaks the restrictive relationship between rare earth mining and environmental protection. It is possible to change from the source the problem of environmental ammonia nitrogen exceeding the standard caused by the mining of ionic rare earths by the "ammonium sulfate leaching-ammonium bicarbonate precipitation" process. After this process is put into operation, the characteristic pollutants produced are sulfate radical rare earth mining wastewater. At present, the rare earth mining wastewater is selected The ettringite composite salt precipitation method solves the problem that when the calcium method is used to treat high-concentration sulfate radicals in water, the concentration of sulfate radicals in the effluent is generally around 1000 mg/L, which is difficult to further reduce. Mining Water Pollutant Discharge Standard (DB36/1016～2018) requires the first-level standard value, but this method produces ettringite composite salt with large precipitation volume and poor settling performance, which is difficult to filter. Also high. Therefore, based on the existing calcium precipitation method, it is of great practical significance to seek an improved method with low cost, good settling performance and the ability to meet the standard discharge of sulfate radicals in wastewater under the condition that large-scale process transformation is not carried out or it is difficult to carry out in time. .

Contents of the invention

(1) Technical problems to be solved

In order to overcome the shortcomings of the existing calcium method for treating high-concentration sulfate in water, the concentration of sulfate in the effluent is generally about 1000 mg/L, which is difficult to further reduce, the treatment cost is high, and resources are wasted seriously. The present invention provides an improved calcium method. A method for treating sulfate-containing rare earth mining wastewater~.

(2) Technical solution

In order to solve the problems of the technologies described above, the present invention provides such a method of improving the calcium method to process sulfate-containing rare earth mining wastewater, comprising the following steps:

A. Add calcium dihydrogen phosphate to rare earth wastewater containing sulfate, the dosage is 1-6:1 by mass ratio of calcium dihydrogen phosphate to sulfate, add indicator Ⅰ dropwise, stir at a speed of 300 r/min, and carry out within a preset time Reaction, stir and adjust the speed and add calcium oxide, the amount added is enough to make the solution change color and keep, so that the pH value of the solution is ≥ 9.4, slowly stir the reaction, stand still, carry out solid-liquid separation, send the solid to dry treatment, and send the liquid to Subsequent reaction processing;

B. Add flocculant to the separation solution and stir at the same time. The amount added is such that the solution becomes colorless, that is, pH<9.4. Add indicator II dropwise. After the solution changes color, stir, and add flocculant to make the solution lighten, pH≥8. , stirring at a medium speed, stirring at a slow speed, standing still, settling, and centrifuging to remove the flocculation sediment;

C. Add acid to the solution after separating the flocculation precipitate to make the solution colorless, pH<8.0, and it can be discharged.

Preferably, in the step A, the indicator I is 90% ethanol solution of thymolphthalein with a mass concentration of 1‰, and the dosage is 3-10 drops.

Preferably, in step A, the preset reaction time is 1-10 min.

Preferably, in step A, calcium oxide is added at a stirring speed of 150-300 r/min, and the amount is added so that the solution changes from colorless to blue.

Preferably, in step A, the slow stirring after pH adjustment is 20-60 r/min, the reaction time is 60-120 min, and the reaction time is 20-60 min.

Preferably, in step B, the flocculant is polyferric chloride, and the amount is used to change the solution from blue to colorless.

Preferably, in step B, the stirring speed of adding flocculant is 150-300 r/min.

Preferably, in the step B, the indicator II is 90% ethanol solution of thymolphthalein with a mass concentration of 5‰, and the dosage is 3-10 drops, and the solution is bright red.

Preferably, in step B, the solution changes from bright red to light red when the pH is adjusted for the second time.

Preferably, in step B, the time for medium-speed stirring is 1-10 min, and the rotating speed is 80-130 r/min; the time for slow-speed stirring is 5-20 min, and the rotating speed is 20-60 r/min; the standing time is 20-60 minutes.

(3) Beneficial effects

Compared with prior art, the beneficial effect of the present invention is:

Calcium dihydrogen phosphate is added to cooperate with calcium oxide to coagulate and precipitate sulfate radicals to improve the treatment effect of calcium method and realize the treatment of medium and high concentration sulfuric acid wastewater by calcium method. The advantage is that under the condition of no or difficult large-scale process transformation, the dosage, operation mode and pH value control mode can be changed to solve the problem that when the calcium method is used to treat high-concentration sulfate in water, the concentration of sulfate in the effluent is generally 1000 mg/L Left and right, it's hard to lower the puzzle further. This method is the same as the ettringite compound salt precipitation method. It has the advantages of using less reagents, not adding any harmful elements to the system, and simple operation. At the same time, this method has better treatment effect, less reagent consumption, and economical raw materials. Easy to obtain, less sedimentation, good settling performance, less water loss, and lower cost for the same treatment effect, which is half of the ettringite composite salt precipitation method. This method can not only treat sulfate-containing rare earth mining wastewater, but also reach the "Discharge Standards for Water Pollutants in Ionic Rare Earth Mine Mining" (DB36 1016-2018) The first-level standard value is less than 800 mg/L discharge requirements, and as long as the dosage of chemicals is adjusted, it can be treated to meet the national "Sewage Comprehensive Discharge Standard" GB8978-1996 一The grade standard is less than 250 mg/L, which meets the wastewater reuse requirements of some enterprises. The invention is an environment-friendly treatment method, which can be widely used in the treatment of wastewater containing sulfate radicals discharged in the fields of ore dressing, metallurgy and the like.

Detailed ways

In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the technical solutions in the specific embodiments of the present invention are clearly and completely described below to further illustrate the present invention. Obviously, the described specific implementation The form is only a part of embodiment of this invention, and it is not all form.

Example 1

Measure 1 L of aqueous solution containing sulfate ions with a concentration of 1000 mg/L, add 1.5 g of calcium dihydrogen phosphate, and then add 5 drops of thymolphthalein 90% ethanol solution indicator with a mass concentration of 1‰, stirring at a speed of 300 r/min , react for 3 minutes, then stir and adjust the speed at 150 r/min to add calcium oxide, the amount added is enough to make the solution change from colorless to blue, so that the pH value of the solution is ≥ 9.4, react for 60 minutes, slow speed 40 r/ Stir for 10 min, then stand still for 20 min, carry out solid-liquid separation, send the solid to dry treatment, add flocculant polyferric chloride to the liquid and stir at a speed of 150 r/min at the same time, add the amount so that the solution turns from blue to Colorless, that is, pH<9.4, add 3 drops of phenolphthalein 90% ethanol solution indicator with a mass concentration of 5‰ in the solution, and add flocculant polymerized ferric chloride while continuing to stir, so that the solution changes from bright red to light red, That is, control the pH ≥ 8, stir at a medium speed of 100 r/min for 4.5 minutes, stir at a slow speed of 20 r/min for 5 minutes, let it stand for 20 minutes, settle and centrifuge to remove the flocculated precipitate; in the solution after the flocculated precipitate is separated Add acid to turn the solution from light red to colorless, i.e. pH<8.0 can be discharged, and the effluent sulfate radical is 655mg/L, reaching the first-level standard value of Jiangxi Province's "Discharge Standards for Water Pollutants in Ionic Rare Earth Mine Mining" (DB36/1016-2018) emission requirements.

Example 2

Measure 1 L of aqueous solution containing sulfate ions with a concentration of 1000 mg/L, add 3 g of calcium dihydrogen phosphate, and then add 5 drops of thymolphthalein 90% ethanol solution indicator with a mass concentration of 1‰, stirring at a speed of 300 r/min , react for 6 min, then stir and adjust the speed at 200 r/min to add calcium oxide, the amount added is enough to make the solution change from colorless to blue, so that the pH value of the solution is ≥ 9.4, react for 90 min, slow speed 60 r/ Stir for 20 min, then stand still for 30 min, carry out solid-liquid separation, send the solid to dry treatment, add flocculant polyferric chloride into the liquid and stir at a speed of 200 r/min at the same time, add the amount so that the solution turns from blue to Colorless, that is, pH<9.4, add 3 drops of phenolphthalein 90% ethanol solution indicator with a mass concentration of 5‰ in the solution, and add the coagulant ferric chloride while continuing to stir, so that the solution changes from bright red to light red, That is, control the pH ≥ 8, stir at a medium speed of 120 r/min for 6 minutes, stir at a speed of 30 r/min for 10 minutes, let stand for 30 minutes, settle and centrifuge to remove the flocculated precipitate; add acid to the solution after the flocculated precipitate is separated Turn the solution from light red to colorless, i.e. pH < 8.0, it can be discharged, and the sulfate radical in the effluent is 386 mg/L, which reaches the first-level standard value of Jiangxi Province's "Discharge Standards for Water Pollutants in Mining Ionic Rare Earth Mine" (DB36/1016-2018) emissions requirements.

Example 3

Measure 1 L of aqueous solution containing sulfate ions with a concentration of 1000 mg/L, add 4 g of calcium dihydrogen phosphate, and then add 5 drops of thymolphthalein 90% ethanol solution indicator with a mass concentration of 1‰, stirring at a speed of 300 r/min , react for 10 min, then stir and adjust the speed at 300 r/min to add calcium oxide, the amount added is enough to make the solution change from colorless to blue, so that the pH value of the solution is ≥ 9.4, react for 100 min, slow speed 50 r/min Stir for 30 minutes, then stand still for 40 minutes, carry out solid-liquid separation, send the solid to dry treatment, add flocculant polyferric chloride into the liquid, and stir at a speed of 300 r/min at the same time, adding the amount so that the solution turns from blue to Colorless, that is, pH<9.4, add 3 drops of phenolphthalein 90% ethanol solution indicator with a mass concentration of 5‰ in the solution, continue to stir, and add flocculant ferric chloride at the same time to make the solution change from bright red to light red, that is, control pH ≥ 8, stirring at a medium speed of 120 r/min for 3 minutes, stirring at a low speed of 45 r/min for 15 minutes, standing still for 40 minutes, settling and centrifuging to remove the flocculated precipitate; add acid to the solution after the flocculated precipitate is separated The solution turns from light red to colorless, that is, it can be discharged when the pH is less than 8.0, and the sulfate radical in the effluent is 178 mg/L, which meets the requirements of the national "Integrated Wastewater Discharge Standard" GB8978-1996 first-level standard.

The main technical features, basic principles and related advantages of the present invention have been described above. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the concept or basic features of the present invention. In some cases, the present invention can be implemented in other specific forms. Therefore, no matter from any point of view, the above-mentioned specific embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, so it is intended that All changes within the meaning and range of equivalency of the claims are embraced in the present invention.

In addition, it should be understood that although this specification is described according to various implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should regard the specification as a In general, the technical solutions in the various embodiments can also be properly combined to form other embodiments that can be understood by those skilled in the art.

Claims (10)

1. a method for improving the calcium method to process the rare earth mining waste water containing sulfate radical, is characterized in that, comprises the following steps: A. Add calcium dihydrogen phosphate to rare earth wastewater containing sulfate, the dosage is 1-6:1 by mass ratio of calcium dihydrogen phosphate to sulfate, add indicator Ⅰ dropwise, stir at a speed of 300 r/min, and carry out within a preset time Reaction, stir and adjust the speed and add calcium oxide, the amount added is enough to make the solution change color and keep, so that the pH value of the solution is ≥ 9.4, slowly stir the reaction, stand still, carry out solid-liquid separation, send the solid to dry treatment, and send the liquid to Subsequent reaction processing; B. Add flocculant to the separation solution and stir at the same time. The amount added is such that the solution becomes colorless, that is, pH<9.4. Add indicator II dropwise. After the solution changes color, stir, and add flocculant to make the solution lighten, pH≥8. , stirring at a medium speed, stirring at a slow speed, standing still, settling, and centrifuging to remove the flocculation sediment; C. Add acid to the solution after separating the flocculation precipitate to make the solution colorless, pH<8.0, and it can be discharged. 2. a kind of improved calcium method according to claim 1 handles the method that contains sulfate radical rare earth exploitation waste water, it is characterized in that, in A step, indicator I is the Thymolphthalein 90% ethanol solution of mass concentration 1 ‰, The dosage is 3-10 drops. 3. A method for treating sulfate-containing rare earth mining wastewater by an improved calcium method according to claim 1, characterized in that, in step A, the preset reaction time is 1 to 10 min. 4. a kind of improved calcium method according to claim 1 handles the method for the mining waste water containing sulfate radical rare earth, it is characterized in that, in A step, stirring speed regulation 150～300 r/min adds calcium oxide, and add-on is with The solution turns from colorless to blue. 5. a kind of improved calcium method according to claim 1 handles the method for containing sulfate radical rare earth exploitation waste water, it is characterized in that, in A step, the slow stirring after adjusting pH is 20～60 r/min, and the reaction time 60-120 minutes, let stand for 20-60 minutes. 6. a kind of improved calcium method according to claim 1 handles the method that contains sulfate group rare earth exploitation waste water, it is characterized in that, in B step, flocculant is polyferric chloride, and consumption makes solution change from blue to no color. 7. A kind of improved calcium method according to claim 1 treats the method for sulfate-containing rare earth mining waste water, it is characterized in that, in B step, the stirring speed regulation of adding flocculant is 150～300 r/min. 8. a kind of improved calcium method according to claim 1 handles the method that contains sulfate radical rare earth exploitation waste water, it is characterized in that, in B step, indicator II is the Thymolphthalein 90% ethanol solution of mass concentration 5 ‰, The dosage is 3-10 drops, and the solution is bright red. 9. a kind of improved calcium method according to claim 1 handles the method for sulfate-containing rare earth mining waste water, it is characterized in that, in B step, when pH is adjusted for the second time, solution changes from bright red to light red. 10. a kind of improved calcium method according to claim 1 handles the method for sulfate-containing rare earth mining waste water, it is characterized in that, in B step, the time of medium-speed stirring is 1～10min, and rotating speed is 80～130 r/ min; the time for slow stirring is 5-20 min, the speed is 20-60 r/min; the standing time is 20-60 min.