Regeneration and circulation method of ferric trichloride etching solution
Technical Field
The invention relates to a method for regenerating and recycling a recyclable ferric trichloride etching solution, which is particularly suitable for regenerating and recycling etching waste liquid such as iron, steel, copper and the like.
Background
The metal etching such as steel and iron is widely applied in various fields of national life, and FeCl is adopted3The etching liquid is used in etching various kinds of steel, iron, copper, etc. and may be used in making metal word board, pattern roller, etc. for printing, etching sheet parts with difficult machining, such as metal screen, small hole, grating, etc. and in carving metal surface of board, instrument, etc. FeCl in etching process3Fe in etching solution3+Gradually changed into Fe2+The etching capability is lost, the total iron content is increased, the yield of the ferric trichloride etching waste liquid is high, heavy metals such as Cr, Ni, Cu, Mo, Mn, Zn, Al and the like carried in metal materials enter the waste liquid besides a large amount of Fe, the discharge does not reach the standard, and a large amount of iron and the like are used as wastes to cause waste of resources. At present, the domestic aims at FeCl3The regeneration and recycling methods of the etching waste liquid are many, and can be classified into a precipitation method, a chemical oxidation regeneration method, an extraction method, an electrolysis method and the like. The precipitation method regeneration (patent CN1540036 and patent CN1566401) mainly uses concentrated or roasted waste liquid to obtain FeCl3The recovery of ferric trichloride is realized by crystallization recovery and redissolution, the energy consumption in the process of concentration or roasting is high, and the recovery rate is limited. The chemical oxidation regeneration method (Chinese patent applications CN1309194, CN107162276A, CN101462803, CN106348509A and CN206872949U and the like) mainly adopts chlorine gas and H2O2、NaClO3The ferric trichloride is regenerated by auxiliary reagents such as an oxidant, HCl and the like, and the toxic and oxidizing effects of the oxidant existThe method has the problems of limited effect or extra impurity ions added in the oxidant, etc., the increment of waste liquid in the regeneration process, the regeneration cycle times are limited, the discharge amount of the waste liquid is increased, and the practical production application is limited. The extraction method (patent CN1470674 and patent CN101497484) mainly uses organic solvent extraction to obtain separation of iron, nickel and the like, and then obtains FeCl through back extraction3The recycling has the problems of complex process, high cost, further treatment of the extractant and the like, and is not suitable for large-scale industrial application. In recent years, electrochemical methods (patents CN106958021A, CN107059011A, CN206872948U, CN206033893U, CN104131285A, CN104451688A and CN103710706A) are frequently applied to the regeneration technology of ferric trichloride waste liquid, and currently, diaphragms are often used to separate the cathode and the anode of an electrolytic cell, and during electrolysis, Fe in the waste liquid in the anode region is separated2+Oxidation to Fe3+Realizes the regeneration and recycling of part of the waste liquid, and the waste liquid in the cathode area is generated due to Fe3+Reduction to Fe2+In the oxidation reverse process, the waste liquid in the cathode chamber can be recycled only through anode secondary oxidation treatment, or is discarded after subsequent treatment (such as replacement or extraction of precipitated iron powder), so that the regeneration cost and the discharge of solid waste are increased, the total recycling rate of the waste liquid is low, and the production and application requirements are difficult to meet.
Disclosure of Invention
The invention mainly aims at the problems in the current electrolytic method and provides a 'diaphragm-one-time pass process' technology. The diaphragm of the electrolytic cell is divided into a cathode chamber and an anode chamber, and Fe is contained in the anode chamber by all the waste liquid2+Is oxidized into Fe3+And the waste liquid is completely regenerated and recycled. The cathode chamber solution adopts conductive electrolyte, and utilizes a diaphragm, anions in the electrolyte can exchange with the anode solution to achieve charge balance and material balance, and Fe does not occur3+Reduction to Fe2+The reverse oxidation process of the method has the advantages that secondary electrolysis and subsequent treatment are not needed for the catholyte, the method is clean and low in consumption, the regeneration efficiency is greatly improved, meanwhile, the production cost is further reduced by combining a chemical impurity removal method, online or offline regeneration can be carried out, the process flow adopts automatic control, and the practical application requirement of recycling the ferric trichloride etching waste liquid is met.
To achieve the above object, the present invention adopts the following techniquesThe technical scheme is as follows: the ferric trichloride etching solution is suitable for etching various grades of stainless steel, copper materials, aluminum materials and the like, is particularly suitable for steel materials, and the obtained etching waste solution contains a certain amount of Fe3+、Fe2 +Allowing Ni to be contained2+、Cr3+、Cu2+、Mn2+、Zn2+、Al3+Plasma, and trace impurities of various forms such as C, Si, Mo, S, P, etc.;
the electrolytic tank for regenerating ferric trichloride adopts a diaphragm or an ion exchange membrane to be divided into a cathode chamber and an anode chamber, the iron trichloride waste liquid is added into the anode chamber, and Fe in the iron trichloride waste liquid in the anode chamber during electrolysis2+Is oxidized into Fe3+,Fe2+The conversion rate reaches more than 95 percent, the etching capability is completely recovered, and proper dilution and acidity adjustment are carried out by combining a chemical impurity removal technology to meet the production requirements of an etching line and the etching production requirements and are recycled; h in the cathode compartment+Is reduced to H2And gas is emptied according to the national emission requirements of combustible gas.
The method uses an electrolytic cell which is divided into a cathode chamber and an anode chamber by adopting a diaphragm or an ion exchange membrane, wherein the diaphragm or the ion exchange membrane only allows anion OH-、CO3 2-、SO4 2-、Cl-Etc. by the cation Fe3+、Fe2+、Na+、K+、H+And the like and gas cannot pass through; the electrode material is inert electrodes such as titanium, graphite or lead; the electrolyte added into the cathode chamber is Na+、K+、H+、OH-、CO3 2-、SO4 2-、Cl-、PO4 3-Dilute solution of any combination of various metal cations and anions with electrode inertia is added into the anode chamber, and ferric trichloride etching waste liquid to be recovered is added into the anode chamber;
the process flow of the regeneration and circulation method of the ferric trichloride etching solution is as follows in sequence: the etching machine, the reaction tank, the sedimentation tank, the electrolytic tank and the regulating tank are communicated with the liquid supplementing tank;
the regeneration and circulation method specifically comprises the following steps: FeCl flowing out of etching machine3The circulating liquid enters a reaction tank, a conventional chemical precipitator is added into the reaction tank, and the pH is adjusted to ensure that Ni in the waste liquid2+、Cr3+、Cu2+、Mn2+、Zn2+、Al3+Carrying out precipitation reaction on the plasma and a precipitator, then guiding the plasma into a sedimentation tank, standing and settling for 48 hours, and filtering the sediment regularly to obtain Fe-rich material3+、Fe2+The supernatant of (A) is introduced into the anode chamber, Fe in the waste liquid2+Oxidation to Fe3+The etching capability is recovered; the obtained regenerated liquid firstly enters an adjusting tank and then enters an etching machine to complete one-time cyclic utilization; electrolyte prepared in advance is added into the cathode chamber, and the electrolyte consumed in the electrolysis process is timely replenished.
In the regeneration and circulation process, automatic control is adopted, and the system mainly comprises a power supply voltage and current control system, a cathode chamber electrolyte concentration control and liquid level control system and H2A concentration monitoring system, an anode chamber oxidation-reduction detection system and a regenerated liquid acidity and density monitoring system.
The precipitant is one or more of sulfide, carbonate and phosphate.
The specific operation method for adding the conventional chemical precipitator into the reaction tank and adjusting the pH comprises the following steps: measuring the content of total metal elements in the ferric trichloride etching waste liquid to be regenerated by using an inductively coupled plasma mass spectrometer, determining the type and the adding amount of a precipitator in a reaction tank according to the content, simultaneously adjusting the pH value of the solution to be 2-3, and removing most heavy metal ions except Fe ions by precipitation and filtration.
The steel will be rich in Fe3+、Fe2+Before the supernatant is led into the anode chamber, the filtrate needs to be taken to measure the oxidation-reduction potential value, so as to obtain Fe in the waste liquid3+、Fe2+The waste liquid enters the anode chamber of the electrolytic cell, and the interface reaction of the inert anode electrode is as follows:
Fe2+-e→Fe3+
Fe2+ions are gradually oxidized to Fe3+Etching ofRecovering the liquid;
the inert cathode electrode interface reaction is as follows:
2H++2e→H2↑
h generated as described above2Directly introducing into an air outlet for emptying, monitoring the concentration of the electrolyte in the cathode chamber through a concentration detector, and replenishing in time.
The regenerated anode liquid enters an adjusting tank, the pH value of the anode liquid is readjusted to 1-2 and the specific gravity is 1.3-1.5 according to the measuring results of density and acidity monitors arranged in the tank body, and the regenerated anode liquid enters an etching machine after being qualified.
A regeneration and circulation method of ferric trichloride etching solution can realize on-line or off-line intermittent operation.
The invention has the beneficial effects that: because the cathode chamber replaces the etching waste liquid with the inert conductive medium, the cathode chamber is not contacted with Fe in the etching waste liquid any more3+Avoid Fe3+Reduction to Fe2+The oxidation reverse process of the method is adopted, so that the catholyte does not need anode secondary electrolysis and subsequent treatment, and the ion selective permeation effect of the diaphragm is added, so that the ferric trichloride etching waste liquid entering the anode chamber is completely regenerated, the regeneration efficiency can reach more than 95 percent (the theoretical value is 100 percent), the operation process is simplified, the method is clean and low in consumption, and the method is suitable for online and offline production.
Drawings
In order to facilitate understanding for those skilled in the art, the present invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic flow chart of a method for regenerating and recycling an etching solution of ferric trichloride.
Detailed Description
Example 1
Batch operation: a certain volume of ferric trichloride etching waste liquid is taken, and ICP-MS is used for detecting that the waste liquid contains 205g/L total iron, 104mg/L Cr, 1069mg/L Mn and 741mg/L Cu. Adjusting pH of the waste liquid to 2-3, adding chemical precipitant into the waste liquid, filtering with a sedimentation tank, collecting supernatant, introducing into an anode chamber, respectively using titanium plate as cathode and anode, and having current density of 18A/dm2(ii) a The cathode chamber is added with electrolyte prepared in advance according to the concentrationThe detector monitors the concentration of electrolyte in the cathode chamber, supplements the electrolyte consumed in the electrolytic process in time and keeps the temperature between 50 ℃ and 60 ℃; fe in anode chamber waste liquid2+Oxidation to Fe3+Gradually recovering the etching capability, regenerating the etching waste liquid, Fe2+The concentration is 0.3g/L, and the conversion rate reaches 97 percent. The regenerated anode liquid enters an adjusting tank, and the pH value is 1.7 and the specific gravity is 1.41 after adjustment according to the measuring results of the density and acidity monitors arranged in the tank body, so that the anode liquid returns to the etching machine again.
Example 2
And (3) online operation: monitoring ferric trichloride etching waste liquid randomly, and detecting that the waste liquid contains 178g/L total iron, 243mg/L Cr, 1927mg/L Mn and 5964mg/L Ni by using ICP-MS; carrying out precipitation and impurity removal treatment regularly, adjusting the pH value to 2-3 during treatment, adding a chemical precipitator into a reaction tank, filtering the mixture by a precipitation tank for later use, and avoiding precipitation treatment during online operation; the etching waste liquid is directly and continuously led into the inlet at the lower end of the anode chamber and flows out of the anode chamber from the outlet at the upper end. Respectively using titanium plate as cathode and anode, and current density is 16A/dm2. Adding prepared electrolyte into the cathode chamber, timely replenishing electrolyte consumed in the electrolysis process, and keeping the temperature between 50 and 60 ℃. Fe in anode chamber waste liquid2+Oxidation to Fe3+Gradually recovering the etching capability, regenerating the etching waste liquid, Fe2+The concentration is maintained to be lower than 12g/L, and the cumulative conversion rate reaches more than 95 percent; the regenerated liquid returns to the etching machine again.
Example 3
A certain volume of ferric trichloride etching waste liquid is taken, and ICP-MS is used for detecting that the waste liquid contains 193g/L of total iron, 89mg/L of Cr, 44mg/L of Ni, 1033mg/L of Mn and 569mg/L of Cu. Regulating the pH value of the waste liquid to 2-3, adding chemical precipitant into the waste liquid, filtering in a sedimentation tank, and introducing the supernatant into an anode chamber by using a graphite plate as a cathode and an anode respectively. Current density 20A/dm2. Adding prepared electrolyte into the cathode chamber, timely replenishing electrolyte consumed in the electrolysis process, and keeping the temperature between 50 and 60 ℃. Fe in anode chamber waste liquid2+Oxidation to Fe3+Gradually recovering the etching capability, regenerating the etching waste liquid, Fe2+The concentration is 0.5g/L, and the conversion rate reaches 95 percent. The regenerated anode liquid enters an adjusting tank, and the pH value is 1.3 and the specific gravity is 1.38 after adjustment according to the measuring results of the density and acidity monitors arranged in the tank body, so that the anode liquid returns to the etching machine again.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.