RU2033480C1 - Method of nickel extraction from spent concentrated solutions of electroless and electric nickel plating - Google Patents

Abstract

FIELD: recovery and utilization of spent solutions of electroless and electric nickel plating. SUBSTANCE: concentrated spent solutions are reduced to nickel hydroxide with the use of alkali subsequent electroextraction of nickel at current density D_c=2-6 A/dm², D_A=3-9 A/dm², temperature of 20 to 60 C, pH = 4-5 in cathode sections, pH = 1-2 in anode section, pH = 8-9 in middle sections with hydroxide in an installation with titanium cathodes and lead anode. The installation is divided into five sections by means of canvas or chlorine diaphragms, two extreme sections are filled with a solution of nickel sulfate at a concentration of 250 g/l, boric acid - 25 g/l, sodium sulfate - 150 g/l, two-sections - with a solution of nickel sulfate - 250 g/l, boric acid - 25 g/l, sodiumsulfate - 150 g/l with excess nickel hydroxide sediment on the section bottom, central section - with a solution of nickel sulfate at a concentration of 250 f/l, boric acid - 25 g/l, sodium sulfate - 150 g/l, sulfuric acid. EFFECT: facilitated procedure. 1 tbl, 1 dwg

Description

 The invention relates to the regeneration and disposal of spent solutions of chemical and electrochemical nickel plating.

 The problem of nickel regeneration from these solutions in the form of a commodity metal has not yet been completely solved; therefore, these solutions are usually subjected to reagent treatment in order to neutralize them and precipitate nickel in the form of various compounds.

 Currently, the greatest use has been made of the method of neutralizing nickel-containing solutions by precipitation of nickel from them in the form of hydroxide (US patent N 4789484, CL 02 F 1/72, published. 06.12.88).

 The disadvantages of the method are the need for the disposal of hydroxide, the inability to reuse nickel.

The closest in technical essence to the invention is a method for the extraction of nickel from sulfuric acid solutions with a concentration of 0.001-1.0 g / l of nickel in electrolysis with a cation exchange membrane when the initial solution is circulated through the cathode chamber at a speed of 1-20 m ³ / h, with an anode chamber filled with a solution of sulfuric acid and sulfate salt of an alkali metal in a molar ratio (1.5-6.0): 1 at a current density of 500-2500 A / m ² [1]
When using this method, only weakly concentrated effluents are subjected to cleaning; before cleaning the concentrated effluents, dosing devices or averagers are required to dilute the electrolytes to a concentration of 0.001-1.0 g / l. During electrolysis, the above method uses scarce materials: MK-40 cation exchange membrane, platinum titanium for the anode, mtilon (carbon-graphite fibrous material) for the cathode.

 The purpose of the invention is the extraction of Nickel from concentrated solutions in the form of a commodity metal.

 This is achieved by first converting nickel to hydroxide using an alkali of NaOH or KOH, followed by electroextraction using titanium cathodes and lead anodes during electrolysis, with tarpaulin or chlorine being used as diaphragms. The process of nickel deposition occurs when the lead anode is stable and the nickel concentration and acidity of the solution are constant.

 The drawing shows the installation with which the method of extraction of Nickel from spent solutions.

The installation is a rectangular bath with an acid-resistant lining, which is divided by diaphragms 1 into section 2, filled with a solution of nickel sulfate NiSO ₄ , boric acid H ₃ BO ₃ , sodium sulfate Na ₂ SO ₄ ; section 3, filled with a solution similar to section 2, and loaded with a precipitate of Nickel hydroxide Ni (OH) ₂ 4 at the bottom of the section; section 5, filled with a solution similar to section 2, and sulfuric acid H ₂ SO ₄ . Lead anodes 6 and titanium cathodes 7 are loaded into the installation.

 The method of extraction of Nickel from spent concentrated solutions of chemical and electrochemical nickel plating is as follows.

All sections per 1/3 of the volume are poured with a solution containing, g / l: NiSO ₄ 250, H ₃ CO ₃ 25, Na ₂ SO ₄ 150. In section 3, precipitate Ni (OH) ₂ and deionized water are added, the pH in the section should be 8-9. In section 2 add the above solution, consisting of Nickel sulfate, boric acid, sodium sulfate, the pH in the section should be 4-5. Sulfuric acid is added to section 5, the pH in the section should be 1-2.

 The level of solutions in the sections should be ≈ 2/3 of the volume.

 On the cathode and anode rods, respectively, titanium cathodes 7 and a lead anode 6 are strengthened.

 In section 3, periodically, as it dissolves, a precipitate of nickel hydroxide is loaded, the excess of which must constantly be at the bottom.

Nickel recovery operating modes:
The current density D _to = 2-6 A / DM ² ; D _A = 3-9 A / dm ² ; T = 20-60 ^{° C,} pH (section 3) = 8-9 pH (section 2) = 5.4, the pH (section 5) = 1.2.

 High temperature is maintained due to Joule heat and is regulated by the interelectrode distance.

__→ Ni
2H⁺+2

__→ H₂
Свинцовый анод 6, находясь в кислой среде, работает стабильно. За счет анодного процесса (2H₂O-4

__→ O₂+4H⁺ образуются ионы водорода, которые за счет электрического поля мигрируют через диафрагмы 1 в секцию 3 и взаимодействуют с находящейся здесь гидроокисью никеля 4.Ni(OH)₂+2H⁺__→ Ni⁺²+H₂O. Образующиеся ионы никеля мигрируют через диафрагму 1 в секцию 2, поддерживая там постоянную концентрацию никеля. Для поддержания гидроокиси никеля во взвешенном состоянии в секции 3 проводят перемешивание (барботаж сжатым воздухом).When electrodes are connected to a direct current source, two processes occur on titanium cathodes:
Ni ⁺² +2

__ → Ni
2H ⁺ +2

__ → H ₂
Lead anode 6, being in an acidic environment, works stably. Due to the anode process (2H ₂ O-4

__ → O ₂ + 4H ⁺ hydrogen ions are formed which migrate through the diaphragm 1 to section 3 due to the electric field and interact with the nickel hydroxide 4.Ni (OH) ₂ + 2H ⁺ __ → Ni ⁺² + H ₂ O located here. The resulting nickel ions migrate through the diaphragm 1 to section 2, maintaining a constant concentration of nickel there. To maintain the nickel hydroxide in suspension, section 3 is mixed (sparging with compressed air).

 So, in the proposed method, obstacles to the practical implementation of the electroextraction of nickel from concentrated solutions are easily and simply eliminated.

 Indeed, the concentration of nickel ions remains constant in the cathode zone, since the discharge of nickel ions at the cathode is compensated by their delivery from section 3. At the same time, constant acidity (pH) is maintained here, since the acid formed on the anode 6 is consumed to dissolve nickel hydroxide 4 and therefore gets into the cathode zone. And finally, the lead anode 6, being in an acidic environment, is reliably passivated and stably works.

 The test results are shown in the table.

It can be seen from the above data that during a long electrolysis, nickel is released with a high current efficiency. The acidity of the electrolyte decreases with time, due to the alkalization of catholyte due to the release of hydrogen at the cathode. Therefore, after 30-40 hours of electrolysis, the electrolyte is adjusted for pH by the addition of H ₂ SO ₄ (in our case, the pH was adjusted after 40 hours of bath operation). As can be seen from the table, the mass of the lead anode 6 throughout the whole process remains unchanged, which indicates the stability of the anode process.

 Technical appraisal and economic advantages of the proposed method consist in exceptional simplicity and accessibility for use in any enterprise having nickel-containing solutions. There is a continuous process of producing compact, nickel-free impurities suitable for reuse, for example, as soluble anodes in a nickel bath. Reagents are used in small quantities only for the preparation of anolyte, catholyte. In addition, this method eliminates damage to the environment.

Claims (1)

METHOD FOR REMOVING NICKEL FROM WASTE CONCENTRATED SOLUTIONS OF CHEMICAL AND GALVANIC NICKELING, including electrochemical deposition of nickel in an electrolyzer divided by diaphragms on the cathode and anode spaces, characterized in that, in order to ensure the extraction of nickel from the nickel solution from concentrated solutions, nickel is converted into nickel metal solutions in hydroxide, and electrodeposition is carried out at a current density of D _to 2 ^o C 6 A / dm ² , D _a 3 ^o C 9 A / dm ² , a temperature of 20 60 ^o C at a constant end nickel nitration and acidity of the solution in an electrolyzer with titanium cathodes and a lead anode, divided by tarpaulin or chlorine diaphragms into five sections, while the two extreme sections are filled with a solution of nickel sulfate with a concentration of 250 g / l, boric acid 25 g / l, sodium sulfate 150 g / l, while maintaining the pH of the solution in these sections 4-5, two sections with a solution of nickel sulfate with a concentration of 250 g / l, boric acid 25 g / l, sodium sulfate 150 g / l, with an excess of nickel hydroxide precipitate at the bottom of the section, pH of the sections 8 9, and the central race thief nickel sulfate at a concentration of 250 g / l, boric acid 25g / l, sodium sulfate 150 g / l of sulfuric acid while maintaining the pH of the solution in this section February 1.

Images