26 results about "Sodium dithionite" patented technology

The invention discloses a high-yield method for reducing dinitro and retaining sensitive protecting groups, which comprises the following steps: adding water, sodium dithionite and sodium carbonate into a container, stirring and clarifying, and dropwise adding a mixed solution containing raw materials; after the reaction is finished, extracting, separating liquid, concentrating, and purifying by silica gel column chromatography to obtain a product and a byproduct; the raw material is a compound containing a carbon-carbon double bond, a p-methoxybenzyl protecting group, a t-butyloxycarboryl protecting group and dinitro. Adding a byproduct into a phosphoric acid mixed solution for reaction; and after the reaction is finished, adding dichloromethane and water, dropwise adding triethylamine to adjust the pH value, extracting, separating liquid, drying, concentrating, and purifying by silica gel column chromatography to obtain the product. According to the method, a sodium hydrosulfite / sodium carbonate system and phosphoric acid step-by-step treatment strategy is adopted, reduction of dinitro is achieved under mild conditions, meanwhile, PMB protecting groups, Boc protecting groups and C-C double bonds are reserved, and the problem that stability and high yield of the protecting groups cannot be considered at the same time in an existing method is solved.

This invention belongs to the field of epoxy resin synthesis technology, specifically relating to epoxy resin and an anhydrous epoxy resin synthesis process. The anhydrous epoxy resin synthesis process of this invention includes the following steps: dissolving bisphenol A in an organic solvent, adding sodium dithionite and mixing thoroughly, then adding solid sodium hydroxide, reacting under negative pressure and heating conditions, filtering after the reaction, adding the sodium bisphenol A solution to epichlorohydrin containing solid sodium hydroxide, and heating to carry out the resin synthesis reaction; after the reaction, performing solid-liquid separation, collecting the liquid phase and performing vacuum distillation to remove the solvent and unreacted epichlorohydrin, obtaining the epoxy resin. The anhydrous epoxy resin synthesis process provided by this invention avoids epichlorohydrin hydrolysis and is a novel epoxy resin synthesis process that is low-cost, highly efficient, and ensures excellent product color. The epoxy resin prepared by this invention guarantees product quality, with low color and low epoxy equivalent.

This invention belongs to the field of soil manganese extraction technology, and discloses a stepwise extraction method and application for manganese species in soil. First, exchangeable manganese is extracted using magnesium chloride; then, manganese carbonate and sulfides are extracted using hydrochloric acid; next, active Mn(III) bound to organic matter is extracted using pyrophosphate solution under alkaline pH; then, manganese oxides are dissolved using hydroxylamine hydrochloride; and finally, manganese bound to crystalline iron and manganese oxides is extracted using sodium dithionite solution. This stepwise extraction scheme accurately quantifies the concentration of active Mn(III) species bound to organic matter in the soil. Experimental results show that the extraction method of this invention can effectively separate different forms of manganese in soil. In particular, PP extraction successfully distinguishes Mn(III) bound to organic matter without introducing interfering substances such as iron minerals that may interfere with dissolution.

The invention discloses a hexavalent chromium polluted underground water green remediation system and application. The hexavalent chromium polluted underground water green remediation system comprises a remediation well body and a non-contact sustainable electron injection system arranged in the remediation well body. The repair well main body comprises a shaft and a through hole formed in the wall of the shaft; the non-contact sustainable electron injection system comprises a medicament chamber and a graphite cathode plate; the medicament chamber is a closed space enclosed by a proton exchange membrane and a sealing plug, and a graphite anode plate and a sodium dithionite solution are accommodated in the medicament chamber; the graphite cathode plate is electrically connected with the graphite anode plate; according to the non-contact sustainable electron injection hexavalent chromium polluted underground water green remediation method, a reducing agent does not need to be added into a water-containing layer, the secondary pollution risk caused by the reducing agent and a product thereof is avoided, and green and efficient hexavalent chromium underground water remediation is achieved.

The invention discloses a bio-based degradable plastic preparation method, which comprises: adding polylactic acid into dichloromethane, stirring until the system is in a transparent state, dropwise adding into an activated cellulose dispersion liquid, stirring, adding graphene oxide and a glyoxal solution, continuously stirring, adjusting the system to be acidic, stirring in an ice-water bath, heating to 100-110 DEG C, vigorously stirring, and cooling to the room temperature, thereby obtaining the bio-based degradable plastic. Performing vacuum freeze drying and crushing to obtain activated polylactic acid; the preparation method comprises the following steps: adding montmorillonite into hydrochloric acid, adding sodium dithionite, stirring, filtering, washing, adding butyl titanate, carrying out ball milling, adding water, continuously grinding, dehydrating, drying, cooling and crushing to obtain activated montmorillonite; polystyrene, polyamide, a compatilizer, an antioxidant and activated polylactic acid are stirred, activated montmorillonite is added, stirring is performed, and a premix is obtained; and carrying out extrusion granulation on the premix, carrying out hot pressing and deflation on granules, and then maintaining the pressure at 5-10MPa for 1-5 minutes to obtain the bio-based degradable plastic.

This invention relates to the field of filtration and dust removal technology, specifically disclosing a high-efficiency dust removal device and method for a sealed silo. The device includes a dust collection box fixedly installed on the outside of the top of the silo body. An air inlet pipe communicating with the silo body is fixedly installed on the lower side of the dust collection box, and a first pump body is installed outside the air inlet pipe. A horizontally arranged mounting plate is fixedly installed in the middle of the silo body, and a filter cylinder for filtering large particles is installed below it. A filter plate for filtering small particles is installed on the inner side of the middle position of the mounting plate. This high-efficiency dust removal device and method for a sealed silo employs a novel structural design. The air filtered by the filter plate enters the interior of a limiting cover. Sodium dithionite particles inside the limiting cover react with oxygen in the air (a strong reducing agent that reacts rapidly with oxygen), achieving the purpose of removing oxygen and reducing the possibility of subsequent dust explosions.

The invention discloses an ammonia leaching process of copper oxide ore, which comprises the following steps: crushing and grinding the copper oxide ore, adding an activating agent into the obtained ore pulp for activating treatment, sequentially adding ammonia liquor and sulfide for leaching treatment and precipitation reaction, and filtering, and copper sulfide concentrate and filtrate are obtained. Compared with a conventional ammonia leaching process, the ammonia leaching process of the copper oxide ore has the advantages that the copper oxide ore is sequentially subjected to crushing, ore grinding, activating treatment, leaching treatment and precipitation reaction, the copper leaching rate of the copper oxide ore can be remarkably increased, meanwhile, agent consumption and environmental pollution are reduced, and the ammonia leaching process is suitable for efficient recovery of complex and difficult-to-treat copper oxide ore; the method has the advantages of simplicity in operation, low cost, high leaching efficiency, good leaching effect, environmental friendliness and the like, and is high in use value and good in application prospect.

The invention discloses a synthesis method of 3-hydroxyazetidine hydrochloride, and belongs to the technical field of organic synthesis. According to the method, tert-butylamine and epichlorohydrin are used as starting raw materials, and a target product is prepared through three-step reaction of cyclization, acetylation and deacetylation in sequence. The method is characterized in that in the acetylation reaction step, a step-by-step strategy that hydroxyl is subjected to monoacetylation at low temperature, and then tert-butyl acetylation is carried out by heating under the conditions that Lewis acid is used for catalysis and sodium hydrosulfite is used as a binding agent is adopted; the binding agent can effectively capture fallen tert-butyl, and side reaction between the fallen tert-butyl and the intermediate is avoided. By optimizing the synthesis route and the purification process, the problems of high raw material cost, high hydrogenation deprotection safety risk, more side reactions, difficulty in intermediate purification, poor product crystallization effect and the like in the prior art are solved. The obtained product is high in purity (greater than or equal to 98%) and good in crystal form, and the whole process is good in safety, simple and convenient to operate and more suitable for industrial production.

The invention provides a preparation method of spiro-structure sulfonium salt, which comprises the following steps: S1, carrying out nucleophilic substitution and oxidation reaction on (1R, 3S, 4S)-5-(2-bromo-1, 1, 2, 2-tetrafluoroethyl) bicyclo [2.2. 1] heptane-2, 3-diol and sodium hydrosulfite to obtain 2-(5, 6-dihydroxy bicyclo [2.2. 1] heptane-2-yl)-1, 1, 2, 2-tetrafluoroethane-1-sodium sulfonate, and carrying out a reaction on (1R, 3S, 4S)-5-(2-bromo-1, 1, 2, 2-tetrafluoroethyl) bicyclo [2.2. 1] heptane-2, 3-diol and sodium hydrosulfite to obtain (1R, 3S, 4S)-5-(2-bromo-1, 1, 2, 2- S2, carrying out ion exchange reaction on the 2-(5, 6-dihydroxy bicyclo [2.2. 1] heptane-2-yl)-1, 1, 2, 2-tetrafluoroethane-1-sodium sulfonate and triphenylsulfonium chloride salt to obtain triphenylsulfonium: 2-(5, 6-dihydroxy bicyclo [2.2. 1] heptane-2-yl)-1, 1, 2, 2-tetrafluoroethane-1-sulfonate; S3, carrying out ion exchange reaction on the triphenylsulfonium: 2-(5, 6-dihydroxy bicyclo [2.2. 1] heptane-2-yl)-1, 1, 2, 2-tetrafluoroethane-1-sulfonate and the triphenylsulfonium: 2-(5, 6-dihydroxy bicyclo [2.2. 1] heptane-2-yl)-1, 1, 2, 2-tetrafluoroethane-1-sulfonate to obtain 2, 2, 2-tetrafluoroethane-1-sulfonate and adamantanone formic acid are subjected to a ketal reaction under the acidic condition, and the spiro-structure sulfonium salt is obtained.

An electrochromic material and a method for preparing the anodic electrochromic material thereof. The anodic electrochromic material used in the electrochromic material is bis(dimethyldihydrophenazinyl) ether. The steps are as follows: preparing a prepolymer solution; adding the cathodic electrochromic material; adding the anodic electrochromic material, and stirring until homogeneous. The method for preparing the anodic color-changing material involves preparing a moistened 2,2'-oxobis(5,10-dihydrophenazine) from 4,4'-oxobis(1,2-phenylenediamine) and catechol. The moistened 2,2'-oxobis(5,10-dihydrophenazine) is then added to acetonitrile, sodium dithionite, sodium carbonate, methyl iodide, and methyltributylammonium chloride to obtain a crude 2,2'-oxobis(5,10-dimethyl-5,10-dihydrophenazine). The crude 2,2'-oxobis(5,10-dimethyl-5,10-dihydrophenazine) is then added to toluene and ethanol to prepare a bis(dimethyldihydrophenazinyl) ether. The advantages of this invention are that it saves on the use of anodic electrochromic materials, reduces costs, and better meets color requirements.

A process for the preparation of a compound of formula (I) wherein R1 is selected from one or more of the following: alkyl, substituted alkyl, haloalkyl, cyanoalkyl, alkoxy, halogen, haloalkoxy, amino, aminoalkyl, alkylsulfonyl, arylsulfonyl, alkylsulfanyl and hydroxyl wherein n is selected from 1, 2 or 3, the process comprises reacting a compound of formula (II) with 2-haloheptafluoropropane in the presence of sodium dithionite (Na2S2O4) and an aqueous buffer, where the aqueous buffer comprises an acid and a base.

The application discloses a preparation method and application of LiFePO4 / C composite material, and the preparation method comprises the following steps: adding sodium hydrosulfite into a titanium white by-product ferrous sulfate heptahydrate aqueous solution for reduction, then adding citric acid for complexation, carrying out a hydrothermal reaction on the solution after the complexation to obtain a LiFePO4 precursor, and calcining the precursor to obtain the LiFePO4 / C composite material. Through multifunctional design of raw materials, the traditional multi-step process is integrated into a reduction-complexation-hydrothermal synthesis integrated process. The improvement not only shortens the process route, but also significantly reduces the use amount of auxiliary materials and energy, thereby greatly reducing the cost of preparing the high-performance LiFePO4 / C composite material by using the ferrous sulfate of the titanium white by-product, and realizing efficient utilization of materials and energy.

This application discloses an intramolecular hydrogen bond-enhanced anthraquinone derivative, its synthesis method, and its application, relating to the field of electrochemical energy storage. The acetic acid-modified anthraquinone RH-DA or AE-DA is 2,2'-(3-carboxyl-1,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2,7-diyl)diacetic acid and 2,2'-(1,8-dihydroxy-3-(hydroxymethyl)-9,10-dioxo-9,10-dihydroanthracene-2,7-diyl)diacetic acid. Rhein or aloe-emodin is dissolved in NaOH, glyoxylic acid solution and sodium dithionite are added, and after stirring, sodium dithionite is added again. After stirring and cooling to room temperature, hydrogen peroxide solution and HCl solution are added, causing precipitation. After washing with HCl, the precipitate is dried in a vacuum drying oven to obtain a black-green solid RH-DA or a yellow-green solid AE-DA. Its application in alkaline aqueous organic flow batteries is also disclosed.

The invention belongs to the technical field of textile chemical industry, and particularly relates to a preparation and low-temperature bleaching method of primary-color alginate fibers, in particular to a low-temperature bleaching process. Aiming at the problems of non-uniform whiteness, large damage caused by traditional oxidation bleaching and the like of alginate fibers due to raw material difference, a reduction bleaching process is innovatively adopted, thiourea dioxide or sodium hydrosulfite is used as a bleaching agent, a mixed solution of sodium metasilicate and sodium hydroxide is used as an alkaline agent, and bleaching is performed under the conditions that the pH is 7-11 and the temperature is 40-80 DEG C. According to the method, through the synergistic effect of the alkaline agent and the bleaching agent and in combination with a calcium chloride protection mechanism, fiber damage is remarkably reduced, the whiteness is stably larger than or equal to 50, process wastewater pollution is low, and clean production is achieved. According to the invention, the technical bottleneck of alginate fiber bleaching is broken through, and the application range of alginate fiber in high-grade textiles is widened.

The invention discloses a sodium dithionite preparation process waste gas filtering treatment device, and relates to the technical field of waste gas filtering treatment, the sodium dithionite preparation process waste gas filtering treatment device comprises a tank body, a plurality of waste gas filtering layers are installed on the inner wall of the tank body, and a pressurization air entraining piece is arranged between every two adjacent waste gas filtering layers. According to the invention, through the arrangement of the pressurization air entraining piece, when the movable sleeve block moves upwards, waste gas between adjacent waste gas filtering layers can enter a space defined by an inner connection corrugated sleeve, an outer connection corrugated sleeve, a pressing ring and a positioning ring through a second one-way valve; when the movable sleeve block moves downwards, a pressing ring extrudes waste gas located between an external connection corrugated sleeve and an internal connection corrugated sleeve, and at the moment, the waste gas located between the external connection corrugated sleeve and the internal connection corrugated sleeve is exhausted through a first one-way valve and a first gas guide hose, so that the impact force of the waste gas flowing towards an upper waste gas filtering layer is increased; the waste gas is prevented from remaining between the adjacent waste gas filtering layers, and meanwhile, the waste gas filtering treatment efficiency of the equipment is also improved.

The embodiment of the application discloses a cellulose fiber and a dyeing method thereof. The method comprises the following steps: mixing strong alkali and sodium dithionite in concentrated ammonia water to obtain a reduction solution; adding vat dyes to the reduction solution, reducing for 10-60 minutes under the environment of 30-50 DEG C, and cooling to room temperature to obtain a vat dyeing solution; adding liquid ammonia to the vat dyeing solution to obtain a liquid ammonia vat dyeing solution; and immersing cellulose fiber into the liquid ammonia vat dyeing solution for dyeing, and then carrying out oxidation and soaping in air to obtain dyed cellulose fiber. The vat dyeing solution prepared by using concentrated ammonia water can be easily mixed with liquid ammonia in any proportion, and the liquid ammonia vat dyeing solution containing different water contents can be easily prepared. In addition, the presence of water in the liquid ammonia vat dyeing solution can maintain the reduction state of the vat dyes in the dyeing process, thereby avoiding the problem that the vat dyes are oxidized and the fiber is not dyed through.

The application relates to a phosphorus-free neutral rust remover and a preparation method, and relates to the technical field of rust removal.The phosphorus-free neutral rust remover comprises the following components in proportion by weight: 5-10 parts of sodium hydrosulfite, 5-10 parts of phosphorus-free washing agent, 0.5-2 parts of dispersant, 10-20 parts of phosphorus-free chelating agent and 67-84 parts of water; the phosphorus-free washing agent is obtained by compounding oxalacetic acid and polyether compounds.The specific phosphorus-free washing agent obtained by compounding oxalacetic acid and polyether compounds, the specific reducing agent of sodium hydrosulfite, the phosphorus-free chelating agent and the dispersant are compounded to prepare the phosphorus-free neutral rust remover.The phosphorus-free neutral rust remover can selectively and efficiently remove iron rust on the surface of stainless steel and will not damage the metal base, and the problems of low safety, poor rust removal effect and corrosion of the metal base of the existing rust remover are solved.

Wide heavy silk satin refining process, belong to silk bleaching technical field. 1) soaking, 2) pretreatment, 3) preliminary refining, 4) refining, 5) washing, 6) pickling, 7) washing, 8) pH value adjustment;Step 2) pretreatment, 3) preliminary refining and 4) refining respectively adopt the way of soaking silk fabric in aqueous solution for treatment;The aqueous solution is aqueous solution of soda ash 5.5-7g / L, aminotri (methylene) phosphonic acid 5-19g / L, sodium hydrosulfite 0.5-1g / L, dispersing agent 2-14g / L, adjust the pH value of aqueous solution to 11-11.5, temperature 91-98℃, according to silk fabric and aqueous solution bath ratio 1:35-38, soak for 50-60 minutes;The wide heavy silk satin refining process has good gloss, brightness and hand feeling, and the refining is uniform, and the first success rate is high.

An electrochromic composition and a method for preparing the anodic electrochromic material thereof. The anodic electrochromic material used in the electrochromic composition is bis(dimethyldihydrophenazinyl)amine. The steps are as follows: preparing a prepolymer solution; adding a cathodic electrochromic material; adding an anodic electrochromic material, and stirring until homogeneous. The method for preparing the anodic color-changing material involves generating a moistened bis(5,10-dihydrophenazin-2-yl)amine from N⁴-(3,4-diaminophenyl)-1,2,4-phenyltriamine and catechol. The moistened bis(5,10-dihydrophenazin-2-yl)amine is then added to acetonitrile, sodium dithionite, sodium carbonate, methyl iodide, and methyltributylammonium chloride to obtain crude N,N-bis(5,10-dimethyl-5,10-dihydrophenazin-2-yl)amine. The crude N,N-bis(5,10-dimethyl-5,10-dihydrophenazin-2-yl)amine is then added to toluene and ethanol to prepare bis(dimethyldihydrophenazinyl)amine. The advantages of this invention are: it saves on the use of anodic electrochromic materials, reduces costs, and better meets color requirements.

The invention relates to the technical field of preparation of organic compounds, in particular to a preparation method of 2-((adamantane-1-carbonyl) oxy)-3, 3, 3-trifluoropropane-1-sulfonate triphenyl sulfonium salt. The preparation method comprises the following steps: slowly dropwise adding trifluoroepoxypropane into hydrobromic acid at a low temperature, so as to prepare 3-bromo-trifluoro-2-propanol; the preparation method comprises the following steps: carrying out esterification reaction on 1-adamantanecarboxylic acid and 1-adamantanecarboxylic acid under the catalysis of DMAP (Dimethylamino Phosphate) and EDCIHCl (Ethylenedicarboxylicacid) to prepare 3-bromine-1, 1, 1-trifluoropropyl-2-adamantane-1-carboxylic ester; carrying out heating reaction on the ester under the action of sodium hydrosulfite and sodium bicarbonate, and sulfonating to obtain sulfinate; oxidizing the sulfinate with hydrogen peroxide to obtain sulfonate of an anion part; the preparation method comprises the following steps: stirring sulfonate and triphenyl sulfonium chloride salt in an organic solvent to obtain a catalytic reaction solution, and carrying out post-treatment on the catalytic reaction solution to obtain the 2-((adamantane-1-carbonyl) oxy)-3, 3, 3-trifluoropropane-1-sulfonate triphenyl sulfonium salt. The preparation method disclosed by the invention is relatively short in synthetic route, has the characteristics of low cost and high efficiency, and is favorable for realizing industrial synthesis.

The invention discloses a preparation method and application of a LiFePO4 / C composite material. The preparation method comprises the following steps: adding sodium hydrosulfite into a titanium dioxide by-product ferrous sulfate heptahydrate aqueous solution for reduction, adding citric acid for complexing, carrying out hydrothermal reaction on the complexed solution to obtain a LiFePO4 precursor, and calcining the precursor to obtain the LiFePO4 / C composite material. Through the multifunctional design of the raw materials, the traditional multi-step process is integrated into a'reduction-complexation-hydrothermal synthesis' integrated process, so that the process route is shortened, and the use amount of auxiliary materials and energy is remarkably reduced, thereby greatly reducing the cost of preparing the high-performance LiFePO4 / C composite material by using the titanium dioxide byproduct ferrous sulfate; and high-efficiency utilization of materials and energy is realized.

The invention discloses a method for separating and recycling silver and mercury in mercury removal residues, and belongs to the field of metal refining. The method comprises the following steps: performing size mixing on mercury-containing gold ore leaching pregnant solution xanthate process mercury removal residues, and performing stirring reaction under the conditions that the pH value is 12-13.5, the cyanide ion concentration is 3-10% and the reaction temperature is 30-50 DEG C; and after the reaction is finished, filtering the slurry to obtain mercury xanthate filter residues and silver-containing filtrate. And returning the silver-containing filtrate to the mercury-containing gold ore of the production system, removing mercury, performing zinc powder replacement treatment on the pregnant solution, and recovering silver metal. The method comprises the following steps: adding excessive concentrated nitric acid into xanthate mercury filter residues for oxidation treatment, adding ascorbic acid to eliminate the oxidability of the residual concentrated nitric acid after stirring reaction is completed, then adding water for dilution, adjusting the pH value to 8-10, then adding sodium hydrosulfite, and reducing mercury to obtain mercury metal. The method solves the problem of hazardous waste treatment of mercury-containing gold ore leaching pregnant solution xanthate-process mercury removal slag, and realizes separation and recovery of silver and mercury metals.

The present application belongs to the technical field of pesticide preparation, and particularly relates to a nematocidal granule containing 5-hydroxymethyl furfural and a preparation method thereof. The granule contains, by mass percentage, 1-20% of 5-hydroxymethyl furfural, 0.5-10% of a stabilizer, 0-10% of a binder I, 0-10% of a binder II, 0-4% of a lubricant, and the balance of a carrier; the stabilizer is one or more of sodium hydrosulfite, sodium metabisulfite, ascorbic acid, 2,6-di-tert-butyl-p-cresol, and acetylcholine. The pesticide granule prepared by the present application has good stability, is not prone to degradation of effective drug components, has good flowability, and has good mixing uniformity with soil, and has a positive significance for agricultural modernization.

The present application relates to the field of electrocatalysis, and provides a cobalt-based catalyst for electrocatalytic two-electron oxygen reduction and a preparation method thereof. Cobalt chloride hexahydrate, sodium dithionite and sodium citrate are used as reaction raw materials to synthesize Co@PBA precursor by a coprecipitation method; after washing and drying, the Co@PBA precursor is subjected to high-temperature calcination and then acid washing to obtain a cobalt-doped PBA derivative catalyst Co@PBA-750. The Co@PBA-750 precursor is synthesized by the coprecipitation method, and the cobalt-doped PBA derivative catalyst is prepared by high-temperature calcination and acid washing, which utilizes the unique metal-organic framework characteristics of PBA to in-situ convert into a nitrogen-doped carbon composite material with uniformly dispersed cobalt species during pyrolysis; the coprecipitation method with slow drop is used, and sodium citrate is used as a complexing agent and a morphology stabilizer to effectively control the nucleation and growth rate of the precursor and inhibit particle agglomeration, so that the Co@PBA-750 nanospheres with uniform size and good dispersion are synthesized.

This invention discloses a method and system for recovering large-area silver sintered layers based on low-temperature quenching and hydrometallurgical processes, belonging to the field of power semiconductor material recycling technology. The method includes: firstly, subjecting a bonded substrate assembly with a silver sintered layer to liquid nitrogen cryogenic quenching, followed by rapid transfer to a high-temperature heating platform. Utilizing intense thermal shock stress and thermal mismatch effects, the bonding interface between the silver layer and the substrate is weakened and destroyed, achieving low-damage mechanical peeling of the silver sintered layer. Next, the copper substrate and DBC board with the silver sintered layer are placed in an alkaline sodium thiosulfate solution, and under heating, oxygen introduction, and stirring conditions, oxidative complexation dissolution is performed to form a stable silver complex solution. Subsequently, sodium dithionite is added to the solution for selective chemical reduction to obtain high-purity silver powder. This method achieves efficient and high-purity recovery of the silver sintered layer, possessing advantages such as high recovery rate, controllable cost, and green process, and is particularly suitable for large-area silver sintered layer recovery.

The application discloses a preparation method of 4,5-dibromo-3-chlorothiophene-2-carboxylic acid. The preparation method comprises the following steps: dissolving compound I in an organic solvent I, then adding sodium hyposulfite and a bromination reagent in sequence, and performing a reaction under temperature rising to obtain a 4,5-dibromo-3-chlorothiophene-2-carboxylic acid crude product solution; pouring into ice water, adding an organic solvent II for extraction, washing and separating an organic phase, drying the obtained organic phase, filtering, concentrating, adding an organic solvent III for beating, filtering, and drying to obtain 4,5-dibromo-3-chlorothiophene-2-carboxylic acid. The application realizes the preparation of 4,5-dibromo-3-chlorothiophene-2-carboxylic acid in one step by adopting sodium hyposulfite to participate in the bromination reaction, the reagent used in the preparation is cheap and easy to obtain, the production cost of the target compound is reduced, the reaction time is shortened, the reaction yield is improved, and reliable reference is provided for the bromination of similar compounds.