High-purity separation method of iron ions from an aqueous solution containing heavy metal ions

Abstract

The present invention discloses a high-purity separation method of iron ions from an aqueous solution containing heavy metal ions, wherein after pretreatment of an aqueous solution containing heavy metal ions, sedimentation containing iron ions are collected, nitric acid or sulfuric acid is added for dissolution, and then a reducing agent is added to the dissolved solution; and after heating and sealing reaction, red sedimentation is generated at the bottom, The sedimentation has a high purity, and the residual amount of iron in the solution is less than 0.4 mg/L. In the method, iron ions in the solution can be converted to hematite crystals at a high purity, and the solution has an excellent retention rate of heavy metal ions, the reaction time is short, the separation efficiency is high, the operation is simple, and the cost is low.

Claims

1. High-purity separation method of iron ions from an aqueous solution containing heavy metal ions, comprising the following steps: selecting an aqueous solution containing heavy metal ions, including the heavy metal in the aqueous solution refers to a metal with a density of greater than 4.5 g/cm.sup.3 and a concentration of greater than 0.02 mg/L; pretreating an aqueous solution containing heavy metal ions by adding ferric salt to the aqueous solution; adjusting the pH value of the aqueous solution to 8-11; and collecting sedimentation at the bottom; dissolving sedimentation to obtain a dissolved solution by using a nitric acid solution or a sulfuric acid solution, until crystals are generated at the bottom or the pH value of the aqueous solution is −0.5-1.9; treating the dissolved solution with a reducing agent to obtain a treated aqueous solution; conducting hydrothermal reaction by transferring the treated aqueous solution into a reactor, with a degree of filling of the reactor being 30%-80%, heating the reactor in an airtight manner to 120-500° C., keeping the temperature for 0.1-48 h, and naturally cooling it to room temperature; and judging a reaction endpoint by opening the reactor, and red sedimentation is generated at the bottom, wherein the sedimentation is mainly Fe.sub.2O.sub.3 with a purity of greater than 98.5%, an amount of residual iron in the supernatant is less than 0.4 mg/L, and a retention rate of heavy-metal ions is greater than 95%, wherein if the amount of residual iron in the supernatant is more than 0.4 mg/L, repeat conducting the hydrothermal reaction.

2. The method of claim 1, wherein in the step of adding ferric salt to the aqueous solution, the ferric salt comprise polymerization ferric chloride, polymeric ferric sulfate or polymerized ferric nitrate and the added dosage are separately 0.1-1 g/L.

3. The method of claim 1, wherein the concentration of nitric acid or sulfuric acid in the step of dissolving sedimentation is 35%-65%; and the solution treated with nitric acid or sulfuric acid, the concentration of iron ions is higher than 100 mg/L, and the concentration of heavy metal ions is higher than 40 mg/L.

4. The method of claim 1, wherein after the sedimentation is dissolved with nitric acid solution, the reducing agent is added directly into the solution obtained by dissolving.

5. The method of claim 1, wherein the dissolving sedimentation is performed by using the sulfuric acid solution, and after the sedimentation is dissolved, sodium nitrate or sodium nitrite is added into the solution obtained by dissolving, and then the reducing agent is added.

6. The method of claim 5, wherein an added dosage of sodium nitrate or sodium nitrite is calculated according to a molar ratio of sodium nitrate or sodium nitrite to iron ions in the solution to be greater than 0.5.

7. A high-purity separation method of divalent iron ions from solids containing heavy metal ions, comprising the following steps: (1) dissolving solids or sedimentation containing heavy metals and iron into a sulfuric acid solution, until the pH value of the solution is −0.5-1.9; (2) transferring the solution obtained in step (1) into a first reactor, with a degree of filling being 30%-40%; (3) closing the reactor in an airtight manner, after the temperature rises to 120° C., adding sodium nitrite through a feeding pipe, wherein the added dosage is calculated according to the molar ratio of sodium nitrite to iron ions to be greater than 0.5; (4) transferring a treated aqueous solution obtained from the step (3) into a second reactor, with a degree of filling of the reactor being 30%-80%, followed by adding a reducing agent into the solution obtained from the step (3), heating the reactor in an airtight manner to 120-500° C., keeping the temperature for 0.1-48 h, and naturally cooling it to room temperature; and (5) opening the reactor, and red sedimentation is generated at the bottom, wherein the sedimentation is mainly Fe.sub.2O.sub.3 with a purity of greater than 98.5%, the amount of residual iron in a supernatant is less than 0.4 mg/L, and the retention rate of ions is greater than 95%, wherein if the amount of residual iron in the supernatant is more than 0.4 mg/L, repeat the step (4).

8. The method of claim 7, wherein the concentration of used sulfuric acid is 35%-65%, and the solution treated with sulfuric acid, the concentration of divalent iron ions is greater than 100 mg/L, and the concentration of heavy metal ions is greater than 40 mg/L.

9. The method of claim 1, wherein the reducing agent is levulinic acid, or a mixture containing levulinic acid, the mixture comprises pyruvic acid, lactic acid, lactose, galactose and levulinic acid, and a mixture ratio of the pyruvic acid, lactic acid, lactose, galactose and levulinic acid in the mixture is 1:1:5:1:100.

10. The method of claim 9, wherein a dosage of added reducing agent is calculated according to a molar ratio of a sum of total molar amounts of each component in the reducing agent to iron in the solution is 0.1-10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an XRD graph of sedimentation with hematite as its main component;

(2) FIG. 2 is a morphology structural diagram of sedimentation with hematite as its main component;

(3) FIG. 3 is a diagram showing retention rate of Pt, Mg, As, Hg, In, Pb and Te;

(4) FIG. 4 is an XRD graph of hematite with a high crystallinity

(5) FIG. 5 is a morphology structural diagram of hematite with a high crystallinity;

(6) FIG. 6 is an XRD graph of red sedimentation at the bottom;

(7) FIG. 7 is a morphology structural diagram of red sedimentation at the bottom;

(8) FIG. 8 is a diagram showing analyzed content of each component.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(9) Embodiment 1: Separation Method of Iron (with the Iron Being Ferric Ions) from an Aqueous Solution Containing Heavy Metal Ions

(10) I. A pickling solution from precious metal processing was selected, wherein the pH was 1.1, and the main components were as follows: 1.4 mg/L of Pt, 28.8 mg/L of Mg, 3.7 mg/L of As, 1.5 mg/L of Hg, 2.6 mg/L of In, 114 mg/L of Pb, and 11.3 mg/L of Te, and the major anion was SO.sub.4.sup.2−.

(11) II. A polyferric sulfate flocculating agent was added at a dosage of 0.3 g/L, NaOH was used to adjust the pH value of a pickling solution to 10.5 to generate sedimentation containing iron, and the sedimentation was collected, and dried at 105° C. for 5 h for standby use.

(12) III. Sedimentation was added to nitric acid to be dissolved, with the concentration of nitric acid being 35%, after the pH of the solution was 0.3, adding of sedimentation was stopped. Then the content of Fe.sup.3+ was detected to be 8449 mg/L, while Pt was 41.2 mg/l, Mg was 611 mg/L, As was 105 mg/L, Hg was 46.4 mg/L, In was 78.5 mg/L, Pb was 3305 mg/L, and Te was 298 mg/L.

(13) IV. Levulinic acid was added to the solution, the added dosage was calculated according to the formula that the molar ratio of levulinic acid to total iron was 0.85, and the adding way was dry powder dosing.

(14) V. The mixed solution obtained in step (IV) was constantly stirred for 10 min at a rotating speed of 150 rpm, and was then transferred to a reactor with a degree of filling being 65%, the temperature rose to 320° C. directly, and was kept for 0.5 h, and then the mixed solution was cooled to room temperature naturally.

(15) VI. Brick-red sedimentation was generated at the bottom of the reactor. An XRD graph was as shown in FIG. 1 which showed that the main component of the sedimentation was hematite. For its morphology, please refer to FIG. 2.

(16) VII. After the reaction, the concentration of Fe.sup.3+ in a supernatant was 0.18 mg/L, no Fe.sup.2+ was generated, and the retention rate of Pt, Mg, As, Hg, In, Pb and Te was separately higher than 98.87%, as shown in FIG. 3.

(17) Embodiment 2: Separation Method of Iron (with the Iron Being Divalent Iron Ions) from Solids Containing Heavy Metal Ions

(18) I. A metal block of copper and zinc contained an iron impurity of 1.4 wt. %.

(19) II. The metal blocks of copper and zinc were dissolved in sulfuric acid of 35%, and when the pH value was 0.3, adding of metal block of copper and zinc was stopped.

(20) III. The concentration of iron in a solution was detected to be 5.2 g/L, the concentration of Cu was 3.3 g/L, and the concentration of Zn was 0.9 g/L, wherein the iron was divalent iron.

(21) IV. The solution in step (III) was transferred into a reactor, with a degree of filling being 30%, after the temperature rose to 120° C., a sodium nitrite aqueous solution at a concentration of 2M was added, and the added dosage was calculated according to the formula that the molar ratio of sodium nitrite to iron was 1.5. The temperature was kept for 18 h, and then the solution was cooled to room temperature naturally.

(22) V. Red sedimentation was generated at the bottom of a reactor, the concentration of iron ions in the supernate was 0.36 mg/L, and the concentrations of Cu and Zn were respectively 3.28 g/L and 0.89 g/L. After red sedimentation was dried, the XRD graph was as shown in FIG. 4, showing that the sedimentation was a hematite with a high crystallinity, with its morphology being as shown in FIG. 5. After being treated by adopting the present method, Cu and Zn in heavy metal wastewater containing Cu and Zn were enriched at a high purity.

(23) Embodiment 3: Separation Method of Iron (with the Iron Being Ferric Ions) from Solids Containing Heavy Metal Ions

(24) I. A silver block with the content of iron to be 4.2 wt. % was taken to be dissolved in a nitric acid of 65% and diluted for 10 times to obtain a nitric acid aqueous solution containing silver and iron. At this time, the content of silver in the aqueous solution was 4.5 g/L, the content of iron was 198 mg/L, and the irons were all ferric ions.

(25) II. The pH of diluted solution was 0.5, the solution was then transferred to a reactor, and a mixture containing levulinic acid was added to the reactor. The molar ratio of the added amount of the mixture to the iron ions was 1, and the mixture contained pyruvic acid, lactic acid, lactose, galactose and levulinic acid, with a mixture ratio of 1:1:5:1:100.

(26) III. the reactor in which the degree of filling was 65% was closed in an airtight manner, the temperature rose to 250° C. and the temperature was kept for 1.2 h, after which red sedimentation was generated at the bottom with a strong magnetic response. After red sedimentation at the bottom were separated with a magnet, the content of iron ions in the supernate was 0.31 mg/L, and the retention rate of Ag was higher than 99%.

(27) IV. An XRD graph of red sedimentation at the bottom was as shown in FIG. 6, the morphology was as shown in FIG. 7, and the component analysis was as shown in FIG. 8, showing that the content of AgO in red sedimentation was less than 0.3 wt. %.

(28) Although preferred embodiments of the present application have been described, however, once knowing basic inventive concepts, those skilled in the art can make additional alterations and modifications to these embodiments. Therefore, the appended claims intend to encompass the preferred embodiments and all the alterations and modifications falling within the scope of the present application. Apparently, those skilled in the art can make various changes and variations to the present application without departing from the spirit and scope of the present application. In this way, if these modifications and variations of the present application fall within the scope of claims of the present application and equivalent technologies, then the present application also tends to encompass these changes and variations.