290 results about "Divalent metal" patented technology

The invention provides a purification technology for regenerated DMT in a chemical recovery process of waste polyester, which comprises the following steps: S1) mixing divalent metal salt, trivalent metal salt, an alkaline reagent and water, and carrying out vacuum drying on the reaction product to obtain a layered double-metal hydroxide precursor; s2) mixing the precursor with a solution containing functional anions, and carrying out vacuum drying on a product obtained after intercalation modification to obtain functional anion modified layered double hydroxide; s3) carrying out electrostatic self-assembly on the hydroxylated hexagonal boron nitride and the layered double-metal hydroxide, carrying out suction filtration on the obtained mixed solution on a carrier, and drying to obtain an adsorption film; s4, the waste polyester alcoholysis solution is adsorbed through the adsorption film.According to the pretreatment technology for purification of the waste polyester alcoholysis solution, the purified alcoholysis solution has higher purity, and meanwhile the difficulty of follow-up reduced pressure distillation purification of regenerated DMT is effectively reduced.

The invention discloses three-dimensional reticular porous MOFs / MXene cellulose composite aerogel as well as a preparation method and application thereof, and belongs to the technical field of aerogel. The preparation method comprises the following steps: adding divalent metal salt into an MXene aqueous dispersion to obtain a mixed dispersion I; sequentially adding the mixed dispersion liquid I and a borax aqueous solution into the mixed dispersion liquid of cellulose nanofibers and polyvinyl alcohol under a heating condition, stirring and dispersing, cooling, and freeze-drying to obtain double-crosslinked network aerogel; the preparation method comprises the following steps: preparing a bi-crosslinked network aerogel, immersing the bi-crosslinked network aerogel into a solution containing imidazole ligands for an in-situ reaction, and then washing and drying to obtain the three-dimensional network porous MOFs / MXene cellulose composite aerogel which has high MOFs loading capacity and excellent stability, can realize efficient adsorption of antibiotics, and is simple in preparation method and suitable for large-scale production.

The invention relates to the technical field of biological tissue adhesives, in particular to a biological tissue adhesive composition. The biological tissue adhesive composition comprises a powder A, a powder B and a powder C, wherein the powder A is obtained by curing calcium silicate and acidic calcium phosphate in a curing liquid, curing, drying and crushing; powder B: bivalent metal salt; powder C: phosphorylated amino acid; and an aqueous solvent; the biological tissue adhesive is used for bone adhesion and bone repair. According to the biological tissue adhesive composition provided by the invention, a silicate / hydroxyapatite composite material with a bone induction function is synthesized through optimized bone cement reaction, a curing liquid is added to react with phosphorylated amino acid, and a bone adhesive material is obtained through organic and inorganic material coordination reaction; the bone repairing and regenerating capability and the bone bonding capability are good.

The present invention provides a silica / hydrotalcite composite slow-release fertilizer and a preparation method thereof, comprising the following steps: uniformly mixing amorphous silica, a divalent metal salt, a trivalent metal salt, and water to obtain a mixed solution; subjecting the mixed solution to a hydrothermal reaction, followed by filtering, washing, and drying to obtain a silica / hydrotalcite nanocomposite material; calcining the silica / hydrotalcite nanocomposite material to obtain a silica / metal oxide nanocomposite material; and loading inorganic and organic fertilizers onto the silica / metal oxide nanocomposite material to obtain a silica / hydrotalcite composite slow-release fertilizer. This preparation method is simple, highly feasible, low-cost, and easily scalable for industrial production. The layered and pore-channel structure of the silica / hydrotalcite nanocomposite material effectively provides ample space for the loading of nutrients, thereby improving the slow-release efficiency of nutrients in the fertilizer, increasing nutrient utilization efficiency, reducing fertilization frequency, and minimizing potential environmental impacts.

The invention discloses a gamma-polyglutamic acid and hydrophilic polysiloxane composite material and application thereof, and belongs to the technical field of medical antibacterial coating materials. The gamma-polyglutamic acid and hydrophilic polysiloxane composite material is prepared from a hydrophilic polysiloxane aqueous solution and a gamma-polyglutamic acid aqueous solution through an ionic cross-linking reaction, the hydrophilic polysiloxane is prepared by sequentially carrying out click chemical reaction and ionization modification on polysiloxane with a side chain containing vinyl and a sulfydryl-containing compound; the sulfydryl-containing compound also contains a carboxylic acid group or an amino-terminated group; when the sulfydryl-containing compound further contains carboxylic acid groups, the raw materials of the ionic cross-linking reaction further comprise an aqueous solution containing divalent metal cations. The composite material has low swelling rate and good antibacterial performance, and can be used for long-acting stable antibacterial. As an antibacterial coating, the composite material is suitable for the surfaces of medical apparatuses and instruments made of different materials, and has a wide application prospect.

The invention discloses application of colla corii asini bone-strengthening oral liquid to prevention and / or treatment of anemia, and belongs to the technical field of medicines, and the anemia comprises iron-deficiency anemia, renal anemia and myelosuppression anemia. The colla corii asini bone strengthening oral liquid can increase erythrocyte count, hemoglobin concentration, hematocrit, erythrocyte average hemoglobin amount, erythrocyte average hemoglobin concentration and / or erythrocyte average volume; the serum iron content is increased; a transporter divalent metal transporter and a membrane iron transporter are increased; the intestinal iron absorption is promoted. The composition specifically comprises urea nitrogen and creatinine; related indexes of renal anemia are improved; the immune index of renal anemia can be improved. The percentage of leukocytes and lymphocytes of anemia caused by myelosuppression can be recovered; the hemoglobin content is increased; the number of macrophage colony stimulating factors and / or bone marrow cells in serum is increased; the immunocompetence is improved; the proliferation of lymphoid B cells and macrophages is promoted.

The present invention relates to electrolyte repair and discloses a method for repairing an unbalanced battery electrolyte. The method comprises: mixing the anolyte and catholyte of an unbalanced battery to obtain a mixed electrolyte I; preparing a pentavalent ion electrolyte of metal cations in the mixed electrolyte I; mixing the pentavalent ion electrolyte with the mixed electrolyte I to obtain electrolyte II; obtaining RGB information of electrolyte II, wherein the amount of pentavalent ion electrolyte is such that the blue channel value in the RGB information of electrolyte II is maximized, to obtain electrolyte III; dividing electrolyte III into two portions, with one portion serving as the catholyte and an acid solution serving as the anolyte, and performing constant current electrolysis to obtain electrolyte IV; introducing an oxidizing gas into electrolyte III to oxidize the divalent metal cations to trivalent cations to obtain electrolyte V; and mixing the other portion with electrolyte V in equal volumes. This repair method has excellent repair effects and can improve the utilization efficiency of the unbalanced battery electrolyte.

The invention belongs to the field of resin preparation, and particularly relates to organic silicon modified phenolic resin as well as a preparation method and application thereof. The preparation method of the organic silicon modified phenolic resin comprises the following preparation steps: mixing a phenolic compound and an aldehyde compound, adding divalent metal salt into the mixture, uniformly stirring and mixing, adjusting the pH value of a reaction system, adding an organic silicon modifier, uniformly mixing, heating to react, adjusting the pH value of the system, washing and drying a product, thereby obtaining the organic silicon modified phenolic resin. The organic silicon modified phenolic resin is obtained. The prepared organic silicon modified phenolic resin is moderate in molecular weight, molecular weight distribution and specific viscosity and very good in spinnability; the fiber is prepared into a melt-blown non-woven material, and the melt-blown non-woven material is ultra-small in fiber diameter, high in porosity and small in pore diameter; and the melt-blown non-woven material also has the advantages of low thermal shrinkage rate, high residual carbon rate, excellent flame retardant property, thermal insulation property, good thermal protection property and long service life.

The invention discloses a method for preparing a denitrification composite carbon source by using kitchen waste, and relates to the technical field of kitchen waste resourceful treatment, and the method comprises the following specific steps: pretreatment, oil removal, hydrolytic acidification, solid-liquid separation, biochar preparation and carbon source compounding. Wherein the yield of volatile fatty acid (VFAs) can be remarkably improved by performing damp-heat pretreatment on fermentation, the biochar provides an adsorption carrier and a microorganism attachment site for the VFAs, the release period of a carbon source is prolonged, and a carbon source-carrier-catalyst ternary system is formed by the biochar, the VFAs and divalent metal cations, so that the denitrification rate is improved. The cost of the denitrification composite carbon source is obviously lower than that of a traditional commercial carbon source, and deep resource utilization of the kitchen waste is achieved.

The invention discloses a core-shell nano-enzyme composite spray gel dressing and a preparation method and application thereof.The dressing comprises a component A prepared from sodium alginate, N-isopropylacrylamide PNIPAM, core-shell nano-enzyme and curcumin and a component B of a divalent metal salt solution, and the component A and the component B are sprayed at the same time to form the core-shell nano-enzyme composite spray gel dressing. The preparation method of the core-shell nano enzyme comprises the following steps: mixing potassium ferrocyanide, ferric trichloride and polyvinylpyrrolidone to obtain a Prussian blue nano particle precursor solution; carrying out ultrasonic emulsification treatment and replacement on the curcumin core solution and the Prussian blue nanoparticle precursor solution; and freeze-drying to obtain the core-shell nano-enzyme. Through rapid ionic crosslinking of sodium alginate and divalent metal ions and the temperature-sensitive phase change characteristic of the temperature-sensitive polymer poly (N-isopropylacrylamide), the gel dressing is rapidly formed, the damaged skin is effectively covered and protected, the excellent antioxidant, anti-inflammatory and antibacterial capabilities are achieved, and the healing cycle of the radiodermatitis wound can be remarkably shortened.

The invention provides a Bi-doped SnO catalyst and a preparation method and application thereof, a gas diffusion electrode and a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The preparation method comprises the following steps: mixing divalent metal tin salt, a regulator and bismuth salt in water to obtain a mixed solution; and mixing the mixed solution with a sodium hydroxide solution, and reacting to obtain the Bi-doped SnO catalyst. The preparation method is simple, rapid, low in cost, green and free of organic solvent or high-temperature treatment, and the prepared catalyst is stable in structure and lasting in performance. The Faraday efficiency of a gas diffusion electrode prepared by adopting the Bi-doped SnO catalyst for synthesizing formic acid through electrocatalytic reduction of CO2 at-850 mA / cm < 2 > is as high as 98%, the gas diffusion electrode can stably run for more than 140 h under N2 purging in a solid electrolytic tank, and the concentration of formic acid continuously produced exceeds 5 mol / L.

A method for capturing carbon dioxide, by: (i) contacting carbon dioxide gas with an aqueous solution containing: (a) an aqueous solvent, (b) an amine-containing sorbent of the formula H2N—(CR2)n—NH2, wherein n is an integer of 3-12 and R is independently selected from H, CH3, CH2CH3, (CH2)mOH, and (CH2)pNH2 for each instance of R, wherein m and p are independently selected from 0-3; and (c) a monovalent or divalent metal salt of the formula MacXbd where M is a monovalent or divalent metal, X is an anion other than carbonate or bicarbonate, a is +1 or +2, b is −1 or −2, and a·c=b·d; wherein the contacting step results in precipitation of a complex carbamate salt of the formula H2N—(CR2)n—NHC(O)O−Ma and / or a complex dicarbamate salt of the formula Ma-O(O)CHN—(CR2)n—NHC(O)O−Ma; and (ii) separating the precipitated solid from the aqueous solvent, optionally followed by thermal regeneration of the amine-containing sorbent.

The invention discloses an inhibitor for relieving cement false setting as well as a preparation method and application thereof. The inhibitor comprises the following components in parts by weight: 5-10 parts of a retarding component, 0.5-3 parts of a surface active component and 87-94 parts of a metal impurity component, the retarding component is selected from one or more of sodium tripolyphosphate, sodium hexametaphosphate, hydroxyethylidene diphosphonic acid, amino trimethyl phosphonic acid, ethylenediamine tetra (methylene phosphonic acid), pentasodium diethylene triamine penta (methylene phosphonic acid) and 2-phosphonobutane-1, 2, 4-tricarboxylic acid; the metal impurity component is monovalent or divalent metal sulfate. The inhibitor can effectively relieve / solve the problems that the flowing property of fresh concrete becomes poor and the viscosity is sharply increased due to cement false setting, the working performance of the concrete is kept stable, and it is guaranteed that the concrete is easy to construct.

The present invention provides a grease composition and an axle bearing in which the grease composition is sealed.SOLUTION: The grease composition of the present invention contains a base oil, a thickener, and an additive, the additive contains an organic metal salt of a divalent metal and an inorganic metal salt of a divalent metal, the total mass of the metal content of the organic metal salt and the metal content of the inorganic metal salt is 1.00% by mass or more based on the grease composition, and the metal content of the organic metal salt with respect to the total mass of the metal content of the organic metal salt and the metal content of the inorganic metal salt is 0.20 or more on a mass basis.SELECTED DRAWING: None

The invention provides a preparation method of a boron adsorbent based on layered dihydroxide. The preparation method comprises the following steps: firstly, preparing layered dihydroxide LDHs from divalent metal salt M < 2 + > and trivalent metal salt M < 3 + >; then dispersing LDHs in a solvent to obtain slurry, adding a polyhydroxy organic matter into the slurry, and drying to obtain polyhydroxy organic matter intercalated hydrotalcite; the polyhydroxy organic matter is selected from meglumine, sodium gluconate, citric acid and / or tartaric acid, and finally calcining and grinding to obtain the boron adsorbent. According to the preparation method disclosed by the invention, the polyhydroxy organic matter is inserted, so that the obtained product has double effects of intercalation and surface functionalization, and active sites of reaction are increased while the interlayer spacing is increased, so that the adsorption capacity is greatly improved, and the adsorption capacity of the obtained product is remarkably higher than that of other adsorbents based on layered dihydroxide.

The invention relates to a method for preparing phenol from benzene. According to the method, a bimetallic composite oxide is used as a catalyst, oxygen is used as an oxidant, acetonitrile is used as a solvent, ascorbic acid is used as a reducing agent, and benzene is converted into phenol. The preparation method of the bimetallic composite oxide catalyst comprises the following steps: mixing a trivalent metal M < 3 + >-containing salt, a divalent metal Z < 2 + >-containing salt, NaOH and Na2CO3 according to a certain ratio, fully and uniformly grinding, standing for crystallization, washing with deionized water to be neutral, drying and grinding, and roasting in air to obtain the final catalyst. The method provided by the invention has the advantages of high efficiency, simple catalyst preparation method, low cost and the like.

The present application provides an adhesive composition for a polarizing film, which contains a cationic trapping agent having a coordination site capable of coordinating a metal component with 2 or more teeth, and a reactive group. In particular, the present application provides a polarizing film having a polarizer, and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer, wherein the adhesive layer is a cured product layer of the adhesive composition for a polarizing film. It is preferable that the polarizer contains a metal component capable of becoming a divalent metal cation in water.

The invention discloses a bimetallic oxide supported catalyst as well as a preparation method and application thereof. The bimetallic oxide supported catalyst comprises a bimetallic oxide carrier and a metal active component supported on the surface of the bimetallic oxide carrier; the bimetallic oxide carrier contains a divalent metal element oxide and a trivalent metal element oxide; the divalent metal element oxide is selected from at least one of oxides of Mg, Ca, Sr, Zn and Mn; the trivalent metal element oxide is selected from at least one of oxides of Al, In, Fe, Cr and Ce; the metal active component is selected from at least one of Pd, Pt, Ru, Ni and Co; in the bimetallic oxide supported catalyst, the mass of the metal active component is 0.1-20 wt% of the mass of the metal oxide carrier.

The invention relates to an efficient synergistic treatment method for perfluorinated compounds and bisphenol compounds in water, which comprises the following steps: mixing aluminum salt and divalent metal salt according to a certain proportion, and heating and coprecipitating under an alkaline condition to obtain layered double hydroxides (LDH); adding the synthesized LDH into sewage containing a perfluorinated compound and a bisphenol compound in sequence, or directly adding the synthesized LDH into the sewage containing the perfluorinated compound and the bisphenol compound at the same time, and adjusting the sewage to be alkaline so as to complete adsorption of the perfluorinated compound and the bisphenol compound; the ultraviolet lamp is adopted to irradiate and adsorb LDH of two pollutants at the same time, so that the LDH is efficiently and synergistically degraded. According to the invention, perfluorinated compounds and bisphenol compounds in water can be rapidly removed, and in-situ or ex-situ synergistic degradation of the two pollutants can be realized under the condition that an oxidizing agent or a reducing agent is not additionally added.

The invention relates to a ZnAl-LDH-based material as well as a preparation method and application thereof in sludge treatment. The ZnAl-LDH-based material is prepared from a divalent metal salt solution and a trivalent metal salt solution through a coprecipitation method, divalent metal comprises Zn and Cu, and trivalent metal is Al; the molar weight ratio of the divalent metal to the trivalent metal is (1-3): 1, and the ratio of the molar weight of Cu to the total molar weight of the divalent metal is (0-0.5): 1. The ZnAl-LDH-based material is used for promoting the organic sulfide in the sludge to be converted into sulfoxide sulfur and sulfone sulfur. Compared with the prior art, a series of ZnAl-LDH-based materials with proper specific surface areas and pore volume structures are prepared, and low-valence organic sulfides in municipal sludge can be promoted to be directionally converted into sulfoxide sulfur and sulfone sulfur; the method has a wide application prospect in the field of improving the high-added-value utilization of organic sulfide-containing wastes such as municipal sludge.

The invention provides a regenerated resin preparation technology based on waste polyester alcoholysis byproducts, which comprises the following steps: S1) mixing a divalent metal salt, a trivalent metal salt and an alkaline reagent, carrying out hydrothermal reaction, and freeze-drying to obtain layered double hydroxides; s2) mixing porous boron nitride, layered double hydroxides, crown ether and water, performing freeze drying after deposition to obtain a self-assembled solid material, and performing ball milling to obtain a hybrid material; and S3) carrying out esterification reaction on the oligomer byproduct obtained by alcoholysis of the waste polyester, the carboxylic acid organic matter and the hybrid material, and then carrying out polymerization reaction to obtain the regenerated resin. The invention also provides a preparation method of the hybrid material. The invention provides a regenerated resin preparation technology, which effectively inhibits the degradation effect and the end-capping effect of potassium ions on molecular chain polycondensation reaction by introducing a hybrid material, shows excellent polymerization catalytic performance, and provides a new way for high-value utilization of waste polyester alcoholysis byproducts.

This invention provides a method for forming a perovskite material from multiple evaporation sources. [Solution] In the present invention, (i) a first evaporation source comprising a mixture of co-sublimable organic halides, and (ii) a second evaporation source comprising one or more metal halides having the following formula (I), wherein B(X y X' 1-y )2(i) a method is provided which comprises the steps of co-sublimating a second evaporation source, where B is a divalent metal cation, X and X' are different halides, 0 ≤ y < 1, and (iii) one or more different organic halides from one or more other evaporation sources, and / or (iv) one or more inorganic halides from one or more other evaporation sources, wherein the perovskite material comprises three or more different cations in addition to the B cation.

The invention discloses a method for adsorbing and separating high-purity gas, which belongs to the technical field of chemical separation and comprises the following steps of: separating and purifying mixed gas or isotope by using an adsorption separation medium; the adsorption separation medium is a microporous metal organic framework material which is thermally synthesized from divalent metal salt and a ligand 1, 5-dihydrobenzo [1, 2-d: 4, 5-d '] bis ([1, 2, 3] triazole) through a solvent. The microporous metal organic framework material has a uniformly distributed microporous structure, a high specific surface area and excellent thermal stability and chemical stability, and high-selectivity separation of rare gas xenon / krypton, methane / propane / ethane, propylene / ethylene, ethane / ethylene and xenon isotopes can be realized through pressure swing / temperature swing adsorption; the adsorbent has ultrahigh adsorption and storage capacity for xenon, propane, propylene and ethane, and high-purity (greater than or equal to 99.99%) xenon, krypton, methane, ethylene and ethane and high-purity isotopes of 129Xe and 131Xe can be obtained after separation.

This invention discloses a method and system for selective separation of monovalent and divalent ions in an alginate fiber coagulation bath based on electrodialysis, belonging to the field of fiber production and membrane separation technology. The method and system integrate a selective electrodialysis device into a traditional coagulation bath circulation system. Utilizing an ion exchange membrane with monovalent and divalent cation selectivity, sodium ions accumulated in the coagulation bath are selectively migrated and removed under the action of an electric field, while divalent metal ions are efficiently retained, thereby maintaining a stable molar ratio of divalent ions to sodium ions in the coagulation bath within the required process range. Compared to traditional methods, this invention eliminates the need for large-scale replenishment of divalent metal salts or full replacement solution, significantly reducing production costs and resource waste. It achieves online regeneration and continuous circulation of the coagulation bath, significantly improving production stability, fiber quality, and resource utilization efficiency, and is suitable for the green and efficient production of various alginate fibers.

The invention provides a ferromanganese oxide and a preparation method and application thereof, and belongs to the technical field of secondary batteries. The molecular formula of the ferromanganese oxide is MnxFeyAaBbO3, A is tetravalent metal, B is divalent metal, 0.19 < = x < = 1.8, 0.19 < = y < = 1.8, 0 < = a < = 0.1, 0 < = b < = 0.1, 1.9 < = x + y + 3 / 2a + 3b < = 2.1, and primary particles of the ferromanganese oxide are sheet-shaped. The ferromanganese oxide provided by the invention is of a sheet structure, and more active sites can be provided to support efficient electrochemical reaction, so that the electrochemical performance of the positive electrode material prepared by taking the ferromanganese oxide as the precursor is improved. According to the preparation method of the ferromanganese oxide, part of the ferrous hydroxide precipitate is dissolved under the overalkaline condition, so that the coprecipitation effect is achieved, and the use of a complexing agent is avoided.

The invention discloses a method for testing the content of trivalent metal elements in a metal oxide, and belongs to the technical field of chemical analysis. The method comprises the following steps: firstly, reducing trivalent metal elements in a sample into divalent metal elements by using a reducing agent ammonium ferrous sulfate in a strong acid environment, wherein unreacted ammonium ferrous sulfate remains in a system; then, potassium permanganate is adopted for titration of unreacted ammonium ferrous sulfate, the end point is based on the fact that the solution becomes light pink and keeps color fastness for 15 seconds, and meanwhile a blank solution is set to eliminate system background interference; by comparing the difference between the blank titration volume and the sample titration volume and combining the titration concentration and the sample mass, the content of the trivalent metal elements in the sample can be accurately calculated. The method has the advantages of simplicity and convenience in operation, strong anti-interference capability, high detection precision and wide application range, is suitable for various metal oxide material systems, and is particularly suitable for quality control and performance analysis of new energy materials and catalysts.

The invention provides a positive electrode active material and a preparation method and application thereof, and belongs to the field of batteries. The positive electrode active material provided by the invention comprises layered double hydroxides, and the chemical formula of the layered double hydroxides is [M < 12 + x > M < 23 + y > M < 34 + z > (OH) 2 (x + y + z)] (A < n->) (y + 2z) / n.mH2O, m < 12 + > is a divalent metal cation, M < 23 + > is a trivalent metal cation, and M < 34 + > is a tetravalent metal cation; x is 1-4, y is 0-4, z is 0-4, and (y + z) is 1-4; m = 1-2, and n = 1-3; the interlayer spacing of the layered double hydroxide is equal to that of the positive electrode active material, the material structure stability in the oxidation-reduction reaction process can be maintained, the proper interlayer spacing is beneficial to reversible storage migration and intercalation / deintercalation of carbonate ions, and the electrochemical oxidation-reduction reaction and directional storage and conversion of charges are achieved.

The invention discloses a light-induced self-cleaning high-flux high-adhesion oil-water separation membrane and a preparation method thereof, the method comprises the following steps: S1, preparing a metal-polyphenol porous coordination polymer suspension, and drying to obtain a metal-polyphenol porous coordination polymer solid; s2, divalent metal nitrate polyhydrate, trivalent metal nitrate polyhydrate and PCP are mixed in water, alkali liquor is dropwise added to adjust the pH to be neutral, LDHs grow on the surface of a PCP solid in situ, and LDHs-PCP is obtained; s3, performing plasma treatment on the substrate filter membrane; and S4, dispersing LDHs-PCP in water, and carrying out suction filtration on the dispersion liquid onto the plasma modified substrate filter membrane to obtain the light-induced self-cleaning high-flux high-adhesion oil-water separation membrane. The oil-water separation membrane disclosed by the invention has high flux, super-hydrophilicity and underwater super-oleophobicity; the oil-water separator has high mechanical strength and illumination self-cleaning capability, and can stably operate for a long time in a high-strength oil-water separation process.

The present invention concerns a method for isolating DNA molecules having a size above a certain cut-off value from a DNA-containing sample. The method comprises a) contacting the sample with an aqueous composition comprising beads with a negatively charged surface, a molecular crowding agent, a dissolved salt comprising at least one divalent metal cation, and optionally a buffer for a time sufficient to bind DNA to the surface of the beads; b) separating the beads with bound DNA from the remaining composition; c) optionally washing the beads; and d) optionally eluting the bound DNA from the beads; wherein the ratio of the concentration of salt to the concentration of beads in the aqueous composition in step a) is at a value where an increase in the ratio leads to an increase in said cut-off value.

This invention belongs to the field of hydrogel materials and relates to a method for preparing a hydrogel, comprising the following steps: dissolving bisphosphonic acid-modified pectin in water or an aqueous solution, adding a divalent metal cation solution to mix and obtain a precursor solution, adding a gelling solution to initiate cross-linking and form a hydrogel, wherein the gelling solution is a solution containing monovalent metal ions with a pH of 7-9. The hydrogel has broad application prospects in the field of ready-to-use reagents. Adding the precursor solution to a cell culture device and lyophilizing it can be used to prepare ready-to-use reagent kits. Dropping a cell suspension into the ready-to-use hydrogel reagent kit and adding cell culture medium yields a hydrogel encapsulated with cells for three-dimensional culture.