Determination method for free sulfuric acid in arsenic-containing and zinc-containing acidic leachate

Abstract

The invention discloses a method for determining free sulfuric acid in arsenic-containing and zinc-containing acidic leachate. Comprising the following steps: 1) sampling VS1 mL of the arsenic-containing and zinc-containing acidic leachate, transferring into a 100 mL volumetric flask, adding a saturated potassium ferrocyanide solution of which the volume is two times of that of the transferred sample, fixing the volume to 100 mL by using deionized water, uniformly mixing, filtering, and taking VS2 mL of filtrate as a to-be-detected sample by using a transfer pipette; 2) adding two drops of a methyl orange aqueous solution into a conical flask containing a sample to be detected, titrating with a sodium hydroxide standard solution until red becomes yellow, and recording the volume V1 mL of the consumed sodium hydroxide standard solution; adding 4 drops of phenolphthalein alcohol solution, continuously titrating with the sodium hydroxide standard solution until stable pink appears, and recording the volume V2 mL of the consumed sodium hydroxide standard solution; and 3) calculating to obtain the sulfuric acid concentration in the arsenic-containing and zinc-containing acidic lixivium. The method can accurately measure the content of free sulfuric acid in the arsenic-containing acidic zinc sulfate solution.

Description

Technical Field

[0001] The invention relates to a method for determining sulfuric acid, in particular to a method for determining free sulfuric acid in an acidic leaching solution containing arsenic and zinc. Background Art

[0002] The iron alum slag and high acid leaching slag produced by hydrometallurgy are hazardous solid wastes and must be treated harmlessly according to environmental protection requirements. When smelting-reduction fuming treatment is adopted, the valuable components zinc, lead, indium and impurity component arsenic in the slag enter the zinc oxide fume together.

[0003] For the complex zinc oxide dust, a multi-stage leaching method of sulfuric acid system is often used to comprehensively recover the valuable components of zinc, lead and indium. From the perspective of process development and production management, the sulfuric acid concentration in the leachate during the leaching process needs to be monitored and regulated. Therefore, the analysis method of the sulfuric acid concentration of the leachate during the production process is indispensable.

[0004] In the prior art, neutralization titration is usually used to analyze the acidity of zinc-containing solutions in wet zinc smelting. For example, the sulfuric acid content of acidic leaching solutions and spent electrolytes is determined by neutralization titration using methyl orange as an indicator and sodium hydroxide standard solution to obtain the sulfuric acid content.

[0005] However, for complex zinc oxide dust with high arsenic content, acid leaching will inevitably produce arsenic-containing leachate. When the leachate is subjected to neutralization titration, a large amount of zinc has already formed zinc arsenate precipitation at a pH value of 3.1-3.4, which seriously affects the neutralization titration process, and the existing acidity analysis method cannot be used here. Therefore, a method for determining free sulfuric acid in an acidic leachate containing arsenic and zinc is urgently needed in the prior art. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for determining free sulfuric acid in an acidic leaching solution containing arsenic and zinc.

[0007] The object of the present invention is achieved through the following technical scheme: A method for determining free sulfuric acid in an acidic leaching solution containing arsenic and zinc, comprising the following steps: 1) Use a pipette to sample the acidic leaching solution containing arsenic and zinc. S1 mL, transfer to a 100 mL volumetric flask, add twice the volume of the sample, saturated potassium ferrocyanide solution, and then dilute to 100 mL with deionized water, mix well and filter, and use a pipette to take the filtrate V S2 mL was placed in a conical flask as the sample to be tested; 2) Add 2 drops of 0.1% mass concentration methyl orange aqueous solution to the conical flask containing the sample to be tested, and titrate with sodium hydroxide standard solution until the red color changes to yellow. Record the volume of sodium hydroxide standard solution consumed as V. 1mL; add 4 drops of 0.1% mass concentration phenolphthalein alcohol solution, continue titrating with sodium hydroxide standard solution until a stable pink color appears, and record the volume of sodium hydroxide standard solution consumed as V 2 mL; 3) The concentration of sulfuric acid in the arsenic-containing and zinc-containing acidic leaching solution is: C H2SO4 = 100C NaOH (2V 1 –V 2 ) / (2V S1 ·V S2 ) (Formula 1) In formula 1, C H2SO4 is the sulfuric acid concentration, mol / L; C NaOH is the concentration of sodium hydroxide standard solution, mol / L.

[0008] Aiming at the problem that the acidic leachate containing arsenic and zinc cannot be directly subjected to neutralization titration analysis, the present invention adopts a method of removing zinc by potassium ferrocyanide precipitation to remove zinc in the solution, and the sample to be tested obtained after precipitation and filtration separation is a mixed solution of sulfuric acid and arsenic acid, and a sodium hydroxide standard solution is used as a titrant, and methyl orange and phenolphthalein are respectively used as indicators to judge two pH step points in the titration process, so as to calculate the content of sulfuric acid in the mixed solution according to Formula 1.

[0009] The beneficial effects of the present invention are as follows: the present invention can quickly determine the content of free sulfuric acid in an acidic leaching solution containing arsenic and zinc, and the determination process is easy to operate. DETAILED DESCRIPTION

[0010] The present invention is described in detail below. Example 1

[0011] 1) For the acidic solution containing arsenic and zinc with a zinc content of 128.5 g / L and an arsenic content of 11.35 g / L, use a pipette to take a sample V S1 Transfer 20 mL of the sample into a 100 mL volumetric flask, add 40 mL of saturated potassium ferrocyanide solution, twice the volume of the sample, and then dilute to 100 mL with deionized water. Mix well and filter. Use a pipette to take the filtrate V S2 10 mL of the sample to be tested was placed in a conical flask; 2) Add 2 drops of 0.1% mass concentration methyl orange aqueous solution to the conical flask containing the sample to be tested, and titrate with 0.0983 mol / L sodium hydroxide standard solution until the red color changes to yellow. Record the volume of sodium hydroxide standard solution consumed as V. 1 mL is equal to 11.20 mL; add 4 drops of 0.1% mass concentration phenolphthalein alcohol solution, continue titrating with sodium hydroxide standard solution until a stable pink color appears, and record the volume of sodium hydroxide standard solution consumed as V2 Equal to 14.45 mL; 3) The concentration of sulfuric acid in the arsenic-containing and zinc-containing acidic leaching solution is: C H2SO4 = 100C NaOH (2V 1 –V 2 ) / (2V S1 ·V S2 ) = 0.1954 mol / L. Example 2

[0012] 1) For the acidic solution containing arsenic and zinc and containing 128.5 g / L zinc and 11.35 g / L arsenic described in Example 1, a pipette was used to sample V S1 20 mL, transfer to a 100 mL volumetric flask, then use a pipette to add 20 mL of 0.1 mol / L standard sulfuric acid solution to the 100 mL volumetric flask, add 40 mL of saturated potassium ferrocyanide solution, and then dilute to 100 mL with deionized water, mix well and filter, and use a pipette to take the filtrate V S2 10 mL of the sample to be tested was placed in a conical flask; 2) Add 2 drops of 0.1% mass concentration methyl orange aqueous solution to the conical flask containing the sample to be tested, and titrate with 0.0983 mol / L sodium hydroxide standard solution until the red color changes to yellow. Record the volume of sodium hydroxide standard solution consumed as V. 1 mL is equal to 15.30 mL; add 4 drops of 0.1% mass concentration phenolphthalein alcohol solution, continue titrating with sodium hydroxide standard solution until a stable pink color appears, and record the volume of sodium hydroxide standard solution consumed as V 2 Equal to 18.40 mL; 3) The concentration of sulfuric acid in the arsenic-containing and zinc-containing acidic leaching solution is: C H2SO4 = 100C NaOH (2V 1 –V 2 ) / (2V S1 ·V S2 ) = 0.2998 mol / L.

[0013] The recovery rate of the added standard sulfuric acid solution was 104.4%.

[0014] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for determining free sulfuric acid in an acidic leaching solution containing arsenic and zinc, characterized in that The steps include: 1) Use a pipette to sample the acidic leaching solution containing arsenic and zinc. S1 mL, transfer to a 100 mL volumetric flask, add twice the volume of the sample, saturated potassium ferrocyanide solution, and then dilute to 100 mL with deionized water, mix well and filter, and use a pipette to take the filtrate V S2 mL was placed in a conical flask as the sample to be tested; 2) Add 2 drops of 0.1% mass concentration methyl orange aqueous solution to the conical flask containing the sample to be tested, and titrate with sodium hydroxide standard solution until the red color changes to yellow, and record the volume of sodium hydroxide standard solution consumed as V1 mL; add 4 drops of 0.1% mass concentration phenolphthalein alcohol solution, and continue to titrate with sodium hydroxide standard solution until a stable pink color appears, and record the volume of sodium hydroxide standard solution consumed as V2 mL; 3) The concentration of sulfuric acid in the arsenic-containing and zinc-containing acidic leaching solution is: C H2SO4 = 100C NaOH (2V1–V2) / (2V S1 ·V S2 ) (Formula 1) In formula 1, C H2SO4 is the sulfuric acid concentration, mol / L; C NaOH is the concentration of sodium hydroxide standard solution, mol / L.