259 results about "Ferric ion" patented technology

The invention relates to the technical field of water treatment agent preparation and environmental governance material processing, in particular to polymeric ferric sulfate and a preparation method thereof.The preparation method comprises the steps that steam condensation recycled water of a thermal power plant of an aluminum factory is mixed with ferrous sulfate and concentrated sulfuric acid to form a reaction solution, oxygen is introduced for an oxidative polymerization reaction, and a liquid intermediate is generated; gradient cooling is carried out on the liquid intermediate to control the molar ratio of ferric ions to hydroxyl, and a porous solid precursor is formed through concentration and closed aging; crushing the precursor, performing graded drying by adopting a rotary kiln and flash drying, and synchronously spraying a hydrophobic modifier to reduce the surface hydroxyl activity; the powdery product is secondarily dried in a nitrogen inert environment, and moisture absorption and agglomeration are inhibited. The invention solves the problems of mixed crystal forms, delayed release of effective components and secondary pollution in the traditional process. The obtained product is uniform in crystal form, concentrated in particle size distribution, remarkably improved in dissolution rate and storage stability, and suitable for black and odorous water body treatment and industrial sewage treatment.

The invention provides a leakage point pressure difference response high-strength blocking agent based on iron ion dynamic cross-linked latex and a preparation method thereof, and the raw materials comprise the following components in parts: 60-120 parts of latex, 60-120 parts of deionized water, 5-15 parts of an activator, 5-10 parts of a defoamer, 100 parts of a terminator, 100 parts of a stabilizer, 10 parts of a 20% ferric chloride solution, and the balance of water. Rubber particles are dynamically crosslinked through ferric ions, and the plugging strength is remarkably improved. Compared with a traditional differential pressure plugging agent, the plugging strength for small holes with the diameter of 0.5 mm reaches 35.67 MPa and is improved by about 238%, and the plugging strength for large holes with the diameter of 1 mm reaches 9.68 MPa and is improved by about 428%. And the plugging device is suitable for plugging conditions with higher leakage point pressure difference. In addition, the plugging agent can realize rapid and high-strength plugging of an underground pipe column, and provides a more efficient and more reliable solution for well site construction.

The invention discloses a production method of ferrous dihydrogen phosphate, which comprises the following steps of: changing an iron source of iron-process iron phosphate from traditional iron blocks or iron powder into oxide scale, compounding phosphoric acid and sulfuric acid into mixed acid, and controlling the granularity of the oxide scale and the components and acidity of the mixed acid to solve the problems of dissolution and passivation of the oxide scale. According to the method, iron oxide scale can be better dissolved, the residual problem of ferric ions is solved by reducing excessive iron blocks or iron powder, undissolved impurities such as carbon, silicon and iron are removed by filtering, and finally, the stability problem of a reaction system is solved by adjusting the pH value of the system through industrial phosphoric acid and pure water, so that a ferrous dihydrogen phosphate solution required for producing iron phosphate is obtained. The production cost of an iron source required by iron phosphate is greatly reduced, other impurities are not contained, and mixed acid-containing filtrate and washing water generated in the production process can be recycled through an evaporation device.

The invention relates to multi-dynamic-bond synergistic self-repairing polyurethane and a preparation method thereof, and belongs to the technical field of polyurethane. The polyurethane is prepared from the following raw materials: poly (dihydric alcohol), diisocyanate, a pyridine chain extender, catechol and ferric ion salt. A main chain of polyurethane is formed by chain extension of polydihydric alcohol and diisocyanate through a pyridine chain extender, an end group is a catechol group exposed after end sealing of a catechol substance, on one hand, ferric ions and the catechol group form a metal coordination bond, and on the other hand, ferric ions and nitrogen atoms on pyridine form a coordination bond; the polyurethane contains multiple dynamic bonds, including coordination bonds of pyridine and iron ions, coordination bonds of catechol and iron ions, and hydrogen bonds between macromolecular chains. When the material is subjected to external pressure, the material has relatively good damping capacity due to internal friction force in a molecular chain; meanwhile, the polyurethane has good self-repairing capability at room temperature.

The present invention relates to the technical field of test and detection, and particularly to an on-line measurement method and device for total iron in power station water vapor. A catalytic reagent is added to the water sample to be measured and acts through an ultraviolet light oxidizer, so as to completely convert the colloidal iron in the water sample into ferric ions. The dissolution and conversion of the colloidal iron are completed without adding acid throughout the process. Since no acid is added during the process of converting the whole colloidal iron into dissolved iron, only a chromogenic reagent needs to be added to accurately measure the total iron content in the water sample, and it is also easier to realize the on-line measurement of total iron in the water sample. When the total iron content in the water sample is less than 10 μg / L, the water sample enters the concentration system for concentration and then optical measurement, so that the low-concentration total iron in the water sample can also be accurately measured. This measurement method can automatically measure the total content in the water sample on-line, avoid manual sampling and detection, can monitor the total iron in the water sample in real time, and has a lower detection limit and more accurate detection results, which is beneficial to the adjustment of the water condition during the start-up and shutdown stages of the power station.

The invention belongs to the technical field of ferrophosphorus recovery, and provides a method for removing fluorine from a ferrophosphorus acid solution in a lithium iron phosphate battery recovery process. The method comprises the following steps: introducing a ferrophosphorus acid solution into a device, then introducing air, nitrogen, argon, helium and other gases which do not react with sulfuric acid, phosphoric acid, ferric ions and water, enabling water to enter a gas phase from the solution through gas-liquid contact with the ferrophosphorus acid solution, and enabling HF to enter the gas phase along with the water through hydrogen-bond interaction force between the HF and water molecules. According to the method, the total amount of fluorine in the ferrophosphorus solution is reduced, the concentration is not changed, no impurity component is introduced, and the obtained acid-containing tail gas can be recycled and enriched to obtain an HF aqueous solution or a fluoride salt aqueous solution.

A raw material solution containing trivalent iron ions, or trivalent iron ions and ions of a metal element that partially substitutes Fe sites, and an alkaline aqueous solution for neutralizing the raw material solution are added to a reaction system to adjust the pH of the reaction system from 1.0 to 3.0 or lower. Hydroxycarboxylic acid is added to the obtained reaction solution and the pH of the reaction system is then neutralized from 7.0 to 10.0 or lower. The obtained precipitate of a substituent metal element-containing iron oxyhydroxide is coated with silicon oxide, followed by heating so as to form particles of ε-iron oxide in which Fe sites are partially substituted by other metal elements, and then, a slurry containing the particles is classified. The iron-based oxide magnetic powder has a particle shape close to a perfect sphere and is suitable for use in a magnetic recording medium.

The invention discloses a preparation method of polydihydroxyindole and application of the polydihydroxyindole in hair dyeing, and belongs to the field of functional materials and the field of daily cosmetics. The polydihydroxyindole is obtained in the mode that Boc-true melanin is formed after true melanin is protected through phenolic hydroxyl groups, the Boc-true melanin is subjected to oxidative degradation, separation and purification and then deprotection, the true melanin is naturally extracted melanin or chemically synthesized melanin or melanin synthesized through a microbiological method, and the oxidative degradation method is an enzymatic oxidative degradation method. The obtained polydihydroxyindole is moderate in molecular weight and has excellent permeability on hair, a strong alkaline condition is not needed in the oligomer dyeing process, and hair quality damage can be reduced; the polydihydroxyindole is oxidized again in the hair dyeing process to generate melanin, and under the condition that the pH is 5-7, and in the presence of ferric ions, the polydihydroxyindole can be more tightly combined with keratin on the hair to coat the outer layer of the hair, so that the hair color is deepened, and the effects of dyeing and protecting the hair are achieved.

The invention provides coal gangue-based artificial soil as well as a preparation method and application thereof. The preparation method of the coal gangue-based artificial soil comprises the following steps: S1, modifying coal gangue by adopting a solution containing citric acid and ethylenediamine tetraacetic acid to obtain modified coal gangue; s2, preparing the modified coal gangue into artificial soil. According to the invention, the citric acid can dissolve carbonate in the coal gangue, the released carbonate can be combined with heavy metals, and citrate ions and ferric ions can form a complex to destroy the outer layer of ferric oxide of the heavy metals; ethylenediamine tetraacetic acid can permeate into mineral lattices of the coal gangue, lattice bound state heavy metal is released through octahedral Al-O bond breakage, the ethylenediamine tetraacetic acid can capture heavy metal combined with citric acid, a more stable heavy metal complex is formed, the heavy metal complex carries strong negative charges, and the heavy metal complex can be separated from the coal gangue. And electrostatic repulsion can be generated on the surface of the coal gangue with negative electricity, so that the heavy metal removal effect is improved.

The invention belongs to the technical field of biological pharmacy, and particularly relates to a preparation method and application of a nano-drug carrier. The invention provides a preparation process based on a pre-polymerization-coordination-shaping sequence, which comprises the following steps: firstly, slightly combining chitosan and polyphenol under a near-neutral condition to form small particles with uniform size and good dispersity, so that adhesion among the particles is effectively reduced; then ferric ions are slowly introduced under the regulation and control of a weak chelating agent, so that the ferric ions are uniformly coordinated on the surfaces of the particles, and an inner layer which is compact in structure and has responsiveness to an acid environment or a competitive ligand is constructed; and finally, sodium alginate is introduced, crosslinking is performed through slow-release calcium ions, a flexible outer layer is formed, and the layer and the inner layer have a synergistic effect, so that the dilution resistance and the protein adsorption resistance of the carrier are remarkably enhanced.

The invention relates to the technical field of soil heavy metal pollution remediation, and discloses biochar loaded nano-iron as well as a preparation method and application thereof. The invention relates to a preparation method of biochar-loaded nano-iron, which comprises the following steps: by taking biomass as a raw material, modifying, carbonizing and activating to obtain modified biochar, then putting the modified biochar into a solution containing ferric ions to load iron ions to obtain biochar loaded with the iron ions, and drying the biochar loaded with the iron ions to obtain the biochar loaded with the nano-iron. And finally, reducing the iron ions in the biochar loaded with the iron ions by using a plant water extract to obtain the biochar loaded nano-iron. The biochar-loaded nano-iron provided by the invention is not easy to agglomerate, good in stability and high in heavy metal removal rate, the heavy metal removal rate can reach 73.1% within 15 days, and the biochar-loaded nano-iron can be widely applied to remediation of heavy metal pollution of soil.

A method of recovering active materials from a rechargeable battery comprises placing an active material of a rechargeable battery in a cathode chamber comprising a cathode of an electrochemical cell comprising the cathode chamber, an anode chamber comprising an anode, and a membrane separating the cathode chamber from the anode chamber, contacting the active material in the cathode chamber with an electrolyte comprising an acid, ferric ions, and ferrous ions, and dissolving at least one of lithium and cobalt from the active material into the electrolyte. Related apparatuses for recovering metals from active materials of rechargeable batteries are also disclosed.

The invention belongs to the technical field of iron ion detection, and particularly relates to a rapid detection method for ferric ions in water, which comprises the following steps: a fluorescent probe preparation step: taking trihydrate of copper nitrate and tryptamine, adding into a centrifuge tube in sequence, adding ultrapure water, performing ultrasonic dissolution, transferring into a high-pressure reaction kettle, and performing hydrothermal reaction to obtain a fluorescent probe; cooling to room temperature, centrifuging the obtained yellow green solution in a centrifugal machine, and filtering the supernate through a microfiltration membrane to obtain a copper-doped carbon quantum dot CuCDs stock solution, namely the fluorescent probe; analyzing and determining Fe < 3 + >: taking the diluent of the prepared CuCDs solution, adding the diluent into a centrifugal tube containing a Fe < 3 + > standard solution, uniformly mixing, carrying out fluorescent quantitative analysis and detection, and exploring the change rule of the fluorescence intensity ratio of CuCDs; according to the rapid detection method for Fe < 3 + > provided by the invention, the synthesized CuCDs have high sensitivity, can realize on-site rapid detection of Fe < 3 + > in a water medium, and shows a wide application prospect in the field of environmental monitoring.

The invention relates to the technical field of wastewater treatment and resource recovery, and discloses an organophosphorus degradation and recovery system based on double-cathode electro-Fenton reaction, comprising: an electrolytic tank for accommodating organophosphorus wastewater to be treated; the anode is arranged in the electrolytic tank and is electrically connected with an anode of a power supply; the oxidizing agent generating cathode is arranged in the electrolytic tank and is used for generating hydrogen peroxide in situ under a power-on condition; the metal reduction cathode is arranged in the electrolytic tank and is used for adsorbing and reducing ferric ions; the metal source is composed of zero-valent iron or iron alloy, is not directly and electrically connected with the power source, and is arranged in an electric field acting area established by the anode and the at least one cathode. Through the design of inductive slow-release iron supply and double-cathode collaborative circulation, a series of problems of uncontrollable iron ion release, high iron sludge yield, low catalyst utilization efficiency, difficulty in resource recovery and the like in the traditional electro-Fenton technology are effectively solved.

The invention belongs to the technical field of electrode materials, and particularly discloses a self-supporting electrolyzed water catalytic electrode material, a preparation method and application thereof, the self-supporting electrolyzed water catalytic electrode material comprises a foamed nickel-molybdenum alloy as a substrate, and the surface of the foamed nickel-molybdenum alloy is covered with a two-dimensional layered nickel-iron metal hydroxide. The nickel-molybdenum alloy self-supporting nickel-iron double-metal hydroxide obtained by the technology is used as a bifunctional catalyst for hydrogen evolution and oxygen evolution reaction in a non-acidic medium. The foamed nickel-molybdenum alloy is used as a raw material of a current collector and a catalytic active site at the same time, a fresh crystal nucleus is formed on the surface of the foamed nickel-molybdenum alloy through one-step ferric ion etching, then the foamed nickel-molybdenum alloy is placed in air, and the catalytic activity of the nickel-molybdenum alloy is improved under the combined action of water and oxygen. The nickel element from the foamed nickel-molybdenum alloy and the adsorbed iron element spontaneously grow on the surface of the nickel-molybdenum alloy to form the layered double-metal hydroxide nanosheet.

The invention discloses a method for separating vanadium and iron in a high-iron-vanadium electrolyte. The method comprises the steps of pH regulation and control, iron removal, vanadium extraction and vanadium reverse extraction. In the step of iron removal, an iron ion targeted complexing agent and a solid phase adsorbent are added into the high-iron vanadium electrolyte with the pH adjusted, reaction is conducted for 10-15 min under stirring, then direct filtering is conducted, and low-iron vanadium electrolyte and a solid phase are obtained; in the vanadium extraction step, vanadium in the low-iron vanadium electrolyte is extracted by adopting a mixed solvent of pretreated P204, TBP and sulfonated kerosene, and a vanadium-containing organic solution is obtained; and the vanadium reverse extraction comprises the step of carrying out reverse extraction on the vanadium-containing organic solution through a sulfuric acid solution with the concentration of 2.0-5.0 mol / L to obtain a vanadium electrolyte. The method can be used for treating iron ions in all valence states, particularly ferric ions which are easier to extract than vanadium ions, qualified vanadium electrolyte with the iron ion concentration meeting the industrial standard can be directly obtained after reverse extraction, and a complexing agent and an adsorbent can be recycled.

The invention discloses a recycling method of NF3 residual electrolysis liquid, and relates to the technical field of residual electrolysis liquid recycling treatment. The method comprises the following steps: step 1, removing Fe ions in the electrolytic residual liquid: firstly, adding hydrogen peroxide or oxygen into the electrolytic residual liquid for reaction, oxidizing ferrous ions into ferric ions, then adding ammonia water and sodium hydroxide or ammonium bicarbonate and sodium hydroxide into the solution for reaction, precipitating ferric ions in the form of ferric hydroxide; 2, hydrofluoric acid is added into the electrolyte solution obtained after iron removal to adjust the pH of filtrate to 3-12, the filtrate enters an extraction system, the nickel element in ammonium hydrogen fluoride is extracted out, and ammonium hydrogen fluoride is purified; and step 3, the nickel element separated from the electrolyte enters a second section to be extracted and synthesized into a nickel sulfate product.

The present application discloses a sludge treatment slow-release material and a treatment method, and belongs to the technical field of sludge treatment. A water-soluble coating material forms a slow-release film on the surface of an iron-carbon micro-electrolysis filler, and the slow-release film slowly dissolves in the sludge to slowly release the iron-carbon micro-electrolysis filler. The iron-carbon micro-electrolysis filler undergoes a galvanic cell reaction in the sludge, and the generated divalent iron ions can catalytically activate persulfate to produce persulfate radicals and trivalent iron ions. The persulfate radicals can oxidize nitrogen-containing organic matter, and the trivalent iron ions react with phosphates to generate iron phosphate precipitates; the dissolved water-soluble coating material complexes with heavy metals, thereby achieving the purpose of removing nitrogen-containing organic matter, phosphorus-containing organic matter and heavy metals in the sludge. The slow-release material can slowly release the iron-carbon micro-electrolysis filler, thereby continuously producing stable divalent iron ions, prolonging the active time of persulfate, and then prolonging the treatment time of the slow-release material on the sludge, achieving the purpose of long-term repair.

The invention belongs to the technical field of microsphere preparation, and particularly relates to a magnetic microsphere and a preparation method thereof. Through cooperation of the cross-linking agent and the monomer, the polystyrene microsphere with good swelling and shrinking performance is provided; in the swelling process, introduced divalent and trivalent iron ions can be coordinated with carboxyl groups of the microspheres and are uniformly dispersed in the microsphere structure; then, by adjusting the pH value, the iron ions react to generate ferroferric oxide distributed in the microspheres and on the surfaces of the microspheres, and in the shrinkage process of the microspheres, the density of aromatic rings is reduced by the ferroferric oxide based on space occupation of the ferroferric oxide, so that background fluorescence is reduced, and the signal-to-noise ratio and sensitivity of fluorescence detection are improved. In addition, ferroferric oxide has an optical shielding effect and can be mutually matched with a coating layer arranged outside the microsphere, so that the fluorescence intensity of the polystyrene material magnetic microsphere is jointly reduced.

The present application provides a low-impurity high-specific-surface-area iron phosphate and its preparation method and application, which belongs to the field of lithium battery materials. The preparation method of the low-impurity high-specific-surface-area iron phosphate provided by the present application includes: providing a ferrous salt solution and a mixed solution containing an oxidant and a phosphorus source; mixing the ferrous salt solution with the mixed solution, and performing a precipitation reaction to obtain a reaction slurry; introducing an oxidizing gas into the reaction slurry, and then heating and aging to obtain a hydrated iron phosphate slurry; after solid-liquid separation, washing, drying and sintering of the hydrated iron phosphate slurry, a low-impurity high-specific-surface-area iron phosphate is obtained. In the above process of iron phosphate crystal transformation, under the oxidation action of the oxidizing gas, a trace amount of trivalent iron ions is always present in the system to inhibit the formation of other impurity phosphate precipitations, and at the same time, through the pore-forming action of the oxidizing gas, the microscopic morphology of the prepared iron phosphate is a porous structure, thereby preparing a low-impurity high-specific-surface-area iron phosphate.

The invention belongs to the technical field of chemical mechanical polishing, and relates to an alkaline gallium nitride polishing solution based on Fenton reaction and a preparation method thereof. The alkaline gallium nitride polishing solution provided by the invention comprises hydrogen peroxide, a silicon dioxide grinding material, sodium bicarbonate, ferric salt, a dispersing agent, a stabilizing agent, a complexing agent and deionized water. The application range of the Fenton reaction can be widened to alkaline conditions by catalyzing hydrogen peroxide through the iron-based ion complex, conversion of ferric ions to ferrous ions can be promoted by using the stabilizer, the catalytic action of the ferrous ions is enhanced, and the effective duration of the polishing solution is prolonged. The polishing solution provided by the invention is environment-friendly, does not corrode processing equipment, is low in cost and stable in property, does not need additional auxiliary equipment, is more convenient to operate, and can be stably stored for a long time.

The invention discloses a method for measuring the content of ferric ions in an iron-chromium flow battery electrolyte, which comprises the following steps: before the content of the ferric ions is measured, pretreating the electrolyte to be measured to remove the influence of Cr ions and other impurity ions in the electrolyte on an experimental result, and then titrating with a sodium thiosulfate standard solution; the method has the advantages that the method is suitable for directly measuring the content of the ferric ions under the coexistence condition of a large amount of ferrous ions, the problems that in the prior art, when a large amount of ferrous ions and a trace amount of ferric ions coexist, the error is large, and the accuracy is low are solved, and a technical guarantee is provided for capacity recovery and efficiency improvement of the electrolyte of the flow battery.

The invention relates to a water-containing alkaline composition for surface pretreatment of a metal coiled material and application of the water-containing alkaline composition. The invention provides a water-containing alkaline composition for surface pretreatment of a metal coiled material, the water-containing alkaline composition comprises 80-400ppm of ferric ions, the free alkalinity of the water-containing alkaline composition is not lower than 20 (10mL) points, and the sum of the concentrations of elements of cobalt, nickel, chromium and phosphorus in the water-containing alkaline composition does not exceed 30ppm. The water-containing alkaline composition is low in raw material cost, more environmentally friendly, wide in base material application range and high in metal coiled material surface pretreatment efficiency, a compact and uniform oxidation film can be obtained within very short treatment time, and preparation of the pre-coated metal coiled material with better paint binding force and corrosion resistance is facilitated.

The invention relates to the field of preparation of micro-emulsions, in particular to a polysaccharide-protein composite stable high-bioavailability ferrous micro-emulsion as well as a preparation method and application thereof. The preparation method of the polysaccharide-protein composite stable high-bioavailability ferrous microemulsion comprises the following steps: adding mineral substances into water, mixing, and carrying out first stirring treatment to obtain a core material solution; adding starch sodium octenylsuccinate, whey protein isolate and polysaccharides into water, mixing, and sequentially carrying out heating treatment and second stirring treatment to obtain a wall material solution; mixing the core material solution, the wall material solution and an emulsifier, and sequentially carrying out third stirring treatment and homogeneous emulsification treatment to obtain an emulsion; and carrying out spray drying treatment on the emulsion to obtain the product. The polysaccharide-protein compounded stable high-bioavailability ferrous microemulsion has excellent embedding rate and storage stability, can effectively protect ferrous ions and reduce the generation of ferric ions, and is beneficial to improving the bioavailability of ferrous iron.

The invention discloses a method for reducing the content of iron in rare earth chloride, which comprises the following steps: step 1, adding alkali slurry into heavy sand slurry containing ferrous ions to adjust the pH value to 1-2, then adding an oxidizing agent, and reacting for 2-3 hours at the temperature of 30-45 DEG C to oxidize the ferrous ions into ferric ions to obtain first rare earth slurry, the concentration of ferrous ions is 0.1-0.2 g / L; 2, the pH value of the first rare earth slurry is adjusted to 3.8-4.2, a reaction is conducted for 1.5-2.5 h at the temperature of 62-68 DEG C, so that ferric ions form precipitates, and second rare earth slurry is obtained; 3, carrying out solid-liquid separation on the second rare earth slurry to obtain an optimal solution filtrate and a filter cake; and step 4, performing removal, solid-liquid separation, evaporation and concentration on the optimal solution filtrate to obtain a rare earth chloride product with the iron content lower than 0.05%. The invention aims to introduce hydrogen peroxide in the thorium neutralization and deposition stage to reduce the accumulation of iron impurities in the circulation process.

The invention discloses a boiler make-up water treatment system and method, and belongs to the technical field of water treatment systems. Comprising the following steps: S1, pre-oxidation treatment; s2, flocculent precipitation; s3, primary filtering; s4, preparing biological activated carbon; s5, performing secondary filtration; s6, carrying out desalting treatment; and S7, TOC analysis. Through synergistic catalytic oxidation of ferrate and ozone, organic matters in a water source are degraded, and the biodegradability is further improved. Meanwhile, the final product ferric ions of the ferrate serve as a coagulant and are matched with an organic-inorganic composite flocculant to perform coagulation treatment on the pre-oxidized effluent, and under the action of pre-oxidation, the effect of coagulating and clarifying the effluent is improved, and meanwhile, the removal efficiency of micromolecule TOC is improved by strengthening the coagulation process. And carrying out deep adsorption and biodegradation on pre-oxidized effluent organic matters through biological activated carbon. TOC analysis is carried out on the effluent of the desalination unit, and when the TOC exceeds a threshold value, the ultraviolet advanced oxidation treatment unit is automatically started to carry out post-oxidation treatment on the effluent of the desalination unit, so that the TOC reaches the effluent index.

The invention discloses a fluorescent probe for targeting mitochondrial ferric ions as well as preparation and application of the fluorescent probe. The fluorescent probe is prepared by reacting cucurbit [7] uril with (E)-4-(4-(dimethylamino) styryl)-1-(3-(triphenylphosphonium) propyl) pyridine-1-onium bromide according to a molar ratio of 1: 1. The fluorescent probe can be used for detecting Fe < 3 + > ions, and has the characteristics of simple preparation method, convenience in operation, high sensitivity, high selectivity, low cost and rapidness in detection.

The invention discloses a method for testing the concentration of ferric ions in a citric acid cleaning solution, when the cleaning solution is combined with a color developing agent, namely a potassium thiocyanate solution, the cleaning solution is acidized in advance, firstly, citric acid is easy to form a stable complex with Fe < 3 + > at a relatively high pH value to hinder a subsequent color developing reaction and titration, and the concentration of ferric ions in the citric acid cleaning solution is not influenced; the protonated citric acid is subjected to pre-acidification treatment, so that the complexing ability of the protonated citric acid is destroyed, free Fe < 3 + > is released, hydrolysis of Fe < 3 + > is inhibited, and Fe < 3 + > is ensured to participate in subsequent reaction in an ionic state; besides, the acid environment can reduce the oxidation rate of Fe < 2 + >, avoid the introduction of additional errors due to the fact that Fe < 2 + > is oxidized into Fe < 3 + >, and improve the accuracy of a Fe < 3 + > concentration test result, so that the citric acid complexing effect is eliminated through the pre-acidification treatment, meanwhile, the oxidation interference of Fe < 2 + > is inhibited, and the detection precision is improved.

The invention provides a preparation method of a catalyst for an electrode. The preparation method comprises the following steps: S1, mixing raw materials including fluoride, ferric ion salt and a buffer solution to obtain an acidic corrosive liquid; s2, the nickel-based alloy base material is sequentially subjected to cleaning and first drying, and the treated nickel-based alloy base material is obtained; s3, the treated nickel-based alloy base material is subjected to corrosion treatment with an acidic corrosion solution and then subjected to ultrasonic treatment, separation and secondary drying in sequence, a catalyst for the electrode is obtained, and the catalyst for the electrode comprises a NiFe powder catalyst and a NiFe self-supporting catalyst; wherein the pH value of the buffer solution is 6-8. According to the preparation method disclosed by the invention, the NiFe powder catalyst and the NiFe self-supporting catalyst are simultaneously prepared in one step, so that the utilization rate of precursor salt is improved, and the cost is remarkably saved.

The invention provides a directional recovery method of pickling wastewater. According to the treatment method disclosed by the invention, a decomplexing agent is used for promoting a complex of fluorine, iron, chromium and nickel to be dissociated into free fluorine, then nanofiltration is adopted for realizing separation of the free fluorine, the iron, the chromium and the nickel, and a fluorine removal agent is added into the separated fluorine-rich solution for realizing fluorine recovery, so that the problem that the complex fluorine is difficult to recover is solved; meanwhile, according to the treatment method, a reducing agent is added into a separated solution rich in iron, chromium and nickel to promote ferric ions to be reduced into ferrous ions, then ion exchange resin is used for preferentially adsorbing chromium and nickel, the ion exchange resin containing chromium and nickel is subjected to desorption treatment, and then graded recovery of chromium and nickel is achieved through gradient pH regulation and control. And finally, pH regulation and control are carried out on the effluent obtained after ion exchange resin adsorption, iron recovery can be achieved, and therefore the problem that separation is difficult due to the fact that the pH of iron and chromium precipitates is close is solved.