28 results about "Magnesium bicarbonate" patented technology

The invention discloses a method for mechanically activating and intensifying decomposition of mineral type rare earth ore and smelting separation, which comprises the following steps of: S1, adding the mineral type rare earth ore serving as a raw material into ore grinding equipment, and mechanically activating under the action of microwaves; s2, mixing the mechanically activated mineral type rare earth ore obtained in the step S1 with concentrated sulfuric acid, performing sulfating roasting decomposition to obtain sulfating roasted ore, and treating tail gas generated by roasting; and S3, the sulfated roasted ore obtained in the step S2 is leached through a magnesium bicarbonate solution, neutralization and impurity removal are conducted, and after solid-liquid separation is conducted, a sulfuric acid rare earth solution and leaching residues are obtained. The mineral type rare earth ore is subjected to mechanical and microwave activation treatment, so that the granularity of mineral particles is reduced, generation of a new reaction surface is promoted, a mineral crystal structure is deformed, a rare earth phase is subjected to favorable change, wrapped rare earth mineral components are fully exposed and are fully contacted and reacted with acid, and the activation performance of the rare earth ore is improved; and a higher rare earth yield is obtained.

This invention discloses a method for co-filling coal-fired power plant solid waste, comprising the following steps: uniformly mixing solid waste generated from thermal power plants with sodium aluminate and magnesium bicarbonate to obtain a cementitious material; uniformly mixing solid waste generated from coal mines with the cementitious material, water, and a polymer solution to obtain a filling slurry; and transporting the filling slurry to the target goaf for filling, followed by curing under natural conditions. This invention achieves for the first time the integrated and comprehensive utilization of low-value coal-fired power plant solid waste such as fly ash, desulfurization gypsum, slag, and coal gangue generated by thermal power plants and coal mines. It can effectively and safely fill goaf areas such as mine pits and shafts formed by mining, and effectively solve the problem of sustainable and comprehensive disposal of the aforementioned coal-fired power plant solid waste.

The application provides a porous spherical high-activity magnesium oxide and a preparation method thereof; the preparation method of the porous spherical high-activity magnesium oxide comprises the following steps: S1, obtaining a magnesium bicarbonate solution; S2, performing spray drying on the magnesium bicarbonate solution to obtain light magnesium carbonate solid powder, wherein the light magnesium carbonate solid powder has a hollow spherical structure; and S3, performing calcination on the light magnesium carbonate solid powder to obtain the porous spherical high-activity magnesium oxide. The high-activity magnesium oxide with a porous hollow spherical structure can be obtained, and the prepared magnesium oxide reaches the product standard of activity-180 in the standard HG / T 3928-2012 Industrial Active Light Magnesium.

The application relates to the technical field of water quality monitoring, analysis and treatment, and discloses a rare earth mother liquor efficient recovery method and system based on surrounding water quality monitoring. The method comprises the following steps: performing component analysis on the rare earth mother liquor, and establishing a surrounding water quality monitoring network; based on the components and water quality data, the mother liquor is divided into three types A, B and C; type A is subjected to magnesium bicarbonate precipitation, type B is mixed with filtrate and subjected to gradient extraction through a DOAM-PPA extractant, and type C is separated through ion exchange resin, and finally, high-purity rare earth products are prepared through pH grading elution crystallization. The application solves the problems of low resource utilization efficiency caused by the lack of differentiated processing in the traditional technology and the technical problem that the existing process and environmental monitoring lack a linkage mechanism and cannot realize dynamic optimization of process parameters.

The invention belongs to the technical field of industrial sludge treatment, and particularly relates to a method for removing magnesium ions in alkaline sludge. The method for removing the magnesium ions in the alkaline sludge comprises the following steps: (1) dehydrating the alkaline sludge, and mixing the dehydrated alkaline sludge with water to obtain a mixture; (2) carrying out carbonization treatment on the mixture obtained in the step (1) to convert Mg (OH) 2 in the alkaline sludge into Mg (HCO3) 2; (3) carrying out solid-liquid separation on the mixture obtained in the step (2) to obtain primary magnesium-removed sludge and a magnesium-containing carbonized solution; and leaching the primary magnesium-removed sludge to obtain the magnesium-removed sludge. According to the method for removing the magnesium ions in the alkaline sludge, Mg (OH) 2 is selectively converted into soluble magnesium bicarbonate by utilizing low-concentration carbon dioxide, and generated CaCO3 is basically insoluble, so that efficient separation of magnesium and calcium in the sludge is realized; the high-quality sludge product is obtained, and high-purity Mg (OH) 2 can be recycled from the desorption liquid to serve as a flame retardant or a chemical raw material, so that the magnesium resource is recycled.

This invention discloses a method for the comprehensive utilization of calcium and magnesium solution and CO2, comprising the following steps: S11: using high-salt calcium and magnesium wastewater and CO2 tail gas as raw materials, the high-salt calcium and magnesium wastewater contains CaCl2 and MgCl2, water-soluble amine is added to the high-salt calcium and magnesium wastewater and mixed, and CO2 tail gas is introduced to carry out a mineralization reaction, generating calcium carbonate precipitate, water-soluble amine hydrochloride and magnesium bicarbonate; S12: solid phase calcium carbonate is obtained by solid-liquid separation, oil-soluble amine is added to the separated liquid phase, HCl in the water-soluble amine hydrochloride is extracted, the water-soluble amine is regenerated, and oil-soluble amine hydrochloride and magnesium carbonate trihydrate precipitate are generated; S13: after phase separation, the aqueous phase is separated by solid-liquid separation to obtain liquid phase water-soluble amine and solid phase magnesium carbonate trihydrate, and the oil-soluble amine hydrochloride in the oil phase is pyrolyzed to obtain regenerated oil-soluble amine and HCl gas. This invention utilizes a water / oil dual-phase amine-enhanced calcium-magnesium solution mineralization CO2 and an extraction-pyrolysis synergistic regeneration cycle process to achieve harmless treatment and resource utilization of both calcium-magnesium-containing high-salt wastewater and CO2 tail gas.

This invention discloses a method for recycling magnesium salts in the nickel-cobalt industry, relating to the treatment of wastewater containing metal ions. The method involves reacting magnesium sulfate wastewater generated after multiple extractions with medium and strong alkalis, adding trace amounts of surface treatment agents, and generating a mixed precipitate of magnesium hydroxide and sulfate. Part of the aqueous phase is filtered out using a filter press and returned to the raw material slurry. The remaining mixed slurry is pumped into a high-pressure reactor, and carbon dioxide is introduced into the reactor while maintaining a certain pressure. Simultaneously, a composite nanocatalyst, La-doped Fe3O4@SiO2, is introduced to prepare a mixed slurry of soluble magnesium bicarbonate and insoluble sulfate. After rapid filtration, the synthesized magnesium bicarbonate filtrate is used to replace the liquid alkali and saponify the blank organic phase. The carbon dioxide generated during the saponification reaction is recycled. The saponified organic phase is then sent to different extraction production lines for purification and separation of the multi-metal mixed liquid, achieving a virtuous cycle in the production system.

The disclosure relates to a process for producing magnesium hydrogen carbonate and / or calcium hydrogen carbonate. An anion exchanger loaded with bicarbonate ions is provided, and a solution containing magnesium salt and / or calcium salt is then passed through the anion exchanger.

The present application relates to the technical field of chemical production, and particularly relates to a magnesium oxide preparation method, comprising the following steps: step S1: carbonizing dolomite lime milk to obtain a carbonized solution, wherein the carbonized solution comprises magnesium bicarbonate; step S2: mixing magnesium hydroxide with the carbonized solution to carry out magnesium precipitation to obtain a magnesium carbonate precipitate; and step S3: calcining at least part of the magnesium carbonate precipitate to obtain a magnesium oxide product. Compared with the prior art, the present application uses magnesium hydroxide to carry out magnesium precipitation, thereby avoiding the step of high-temperature pyrolysis of the carbonized solution in the prior art, and reducing energy consumption and production cost.

This invention belongs to the field of water treatment and provides a zero-discharge hardness removal process using aluminum-based adsorbents. The process involves uniformly mixing sodium and aluminum salts in a solution to obtain a mixed solution; performing ion exchange with a cation exchange resin using this mixed solution to obtain an aluminum-based adsorbent; treating water with this aluminum-based adsorbent to adsorb calcium or magnesium ions, forming nano-sized aluminum hydroxide precipitates that adhere to the aluminum-based adsorbent framework, and collecting the effluent; regenerating the aluminum-based adsorbent with carbon dioxide gas to displace calcium or magnesium bicarbonate, collecting the effluent, and allowing it to settle to form calcium carbonate or magnesium carbonate precipitates, thus obtaining the final product. This hardness removal process does not use any chemical agents, only carbon dioxide gas as a regenerator. The regeneration process produces no waste liquid and simultaneously achieves carbon dioxide fixation and hardness ion removal, meeting the requirement of zero discharge.

The application discloses a method for preparing high-performance rare earth polishing powder from lanthanum cerium sulfate, and belongs to the technical field of rare earth polishing powder preparation. The method mainly comprises the following steps: precipitating lanthanum cerium sulfate solution and magnesium bicarbonate solution in a parallel flow feeding mode. The precipitated product is aged, washed, once separated from liquid, beaten, fluorinated, twice separated from liquid, dried at low temperature, calcined at high temperature, and broken and classified by air flow milling, so that a rare earth polishing powder product with good polishing and etching capacity is successfully prepared. The application selects lanthanum cerium sulfate as the original liquid, has a short separation process, low transformation cost, and is easy to popularize and promote in industrialization. The residual part of sulfate in the precipitated product can effectively adjust the hardness of the rare earth polishing powder particles and homogenize the morphology, so as to improve the cutting performance of the polishing powder. The magnesium salt wastewater and the fluorination wastewater generated in the application can be all reused to the production line for preparing the rare earth polishing powder, and zero wastewater discharge is realized in the whole process.

The application discloses a method for separating soluble rare earth complex in magnesium sulfate wastewater, and belongs to the technical field of rare earth hydrometallurgy wastewater treatment. The method comprises the following steps: taking the magnesium sulfate wastewater after transformation reaction of P507 and rare earth sulfate as raw materials, adjusting the pH value, filtering, stirring the filtrate by high shear emulsification, standing, filtering, and obtaining the magnesium sulfate wastewater without rare earth complex, so that the soluble rare earth complex in the magnesium sulfate wastewater is separated. The method can effectively utilize the magnesium resources, prevent equipment and pipeline from being scaled, improve the water solubility of the magnesium sulfate wastewater, improve the filtering performance of the magnesium sulfate wastewater, and is low in water treatment cost.

The present invention provides a high-dielectric-strength bast fiber insulation paper and a preparation method thereof. The invention comprises the following steps: cutting bast fibers into bast segments of a preset length and soaking the segments in water to obtain pretreated bast segments; adding alkali and anthraquinone to the pretreated bast segments for treatment and steaming to obtain steamed pulp; performing enzyme treatment on the steamed pulp with pectinase, and washing the pulp several times after the enzyme treatment to obtain pectin-degraded bast fiber pulp; performing cold alkali extraction treatment on the pectin-degraded bast fiber pulp, and washing the pulp several times after the cold alkali extraction treatment to obtain cold alkali-treated pulp; performing pressure-free delamination and pressure beating on the cold alkali-treated pulp to obtain pulped pulp; purifying the pulped pulp with hydrochloric acid to obtain acid-treated pulp; treating the acid-treated pulp with magnesium bicarbonate to obtain acid-acid-treated pulp; and making paper with the acid-acid-treated pulp to obtain high-dielectric-strength bast fiber insulation paper.

The application discloses an aerogel fire extinguishing agent and a preparation method thereof. The aerogel fire extinguishing agent is prepared from the following raw materials by simple mixing and hydrothermal reaction, and then the solid product after the hydrothermal reaction is subjected to CO2 supercritical drying: 10-30 parts of graphene aerogel powder, 1-5 parts of Mg(HCO3)2 powder, 0.1-0.5 parts of inorganic fiber, 0.01-0.1 parts of sodium dodecyl sulfonate and 50-100 parts of water. The inorganic fiber is combined with the layered porous graphene aerogel to form a stable product structure, the magnesium bicarbonate is effectively dispersed on the surface of the graphene and in the graphene aerogel, and the fire extinguishing substance is gradually released along with the progress of the fire extinguishing process, so that the rekindling is effectively prevented. The specific structure is constructed to synergistically combine the simple raw materials, so that the prepared fire extinguishing agent has the excellent characteristics of rapid cooling, non-rekindling, environmental friendliness, high-efficiency toxic gas adsorption and the like, the fire extinguishing efficiency is higher, the ignition prevention effect is better, the battery combustion fire can be effectively extinguished, and the application value is extremely high.

The present invention provides a method for recovering lead from lead sulfate waste, comprising: (1) mixing the lead sulfate waste, magnesium salt and water to form a slurry, then adding the slurry to a closed reactor, introducing carbon dioxide gas, heating, stirring, and filtering after the reaction to obtain a magnesium sulfate filtrate and a lead carbonate residue; the magnesium salt is one or more of magnesium oxide, magnesium hydroxide, magnesium carbonate, basic magnesium carbonate, and magnesium bicarbonate solution; (2) adding a fluorosilicic acid solution to the lead carbonate residue to obtain a lead fluorosilicate solution, electrolyzing the lead fluorosilicate solution to obtain electrolytic lead and electrolytic waste liquid; (3) adding calcium hydroxide to the magnesium sulfate filtrate, heating, stirring, and filtering after the reaction, and performing beneficiation and classification of the mixed residue through a hydrocyclone to obtain a light material mainly composed of magnesium hydroxide and a heavy material mainly composed of calcium sulfate. Compared with the prior art, the present invention has low cost, no wastewater generation, and good environmental benefits.

The invention discloses a preparation method of low-sulfate rare earth carbonate, which comprises the following steps: carrying out continuous precipitation reaction on a rare earth sulfate solution and a magnesium bicarbonate solution, and controlling CO2 partial pressure and pH value in the continuous precipitation reaction process to obtain a precipitation product; and carrying out solid-liquid separation and washing treatment on the precipitation product to obtain rare earth carbonate with low sulfate radicals. A rare earth sulfate solution is used as a raw material solution, a magnesium bicarbonate solution is used as a precipitator, rare earth sulfate and the magnesium bicarbonate solution are subjected to a continuous precipitation reaction, CO2 partial pressure and pH value in the reaction process are controlled, a precipitation product is subjected to solid-liquid separation and washing, and rare earth carbonate with low sulfate radicals is obtained. The method has the advantages of no ammonia nitrogen pollution residue, cyclic utilization and zero emission of magnesium salt, cyclic utilization of CO2 gas, low sulfate radical impurity content of the rare earth carbonate product and the like.

The invention relates to the technical field of water quality monitoring analysis and treatment, and discloses a rare earth mother liquor efficient recovery method and system based on surrounding water quality monitoring. The method comprises the following steps: performing component analysis on the rare earth mother liquor, and establishing a peripheral water quality monitoring network; based on the component and water quality data, the mother liquor is divided into A, B and C classes; the class A is precipitated by magnesium bicarbonate, the class B is mixed with the filtrate and is subjected to gradient extraction by a DOAM-PPA extraction agent, the class C is separated by ion exchange resin, and finally, the high-purity rare earth product is prepared by pH graded elution and crystallization. According to the method and the device, the problem of low resource utilization efficiency caused by lack of differentiated processing in the traditional technology is solved, and the technical problems that the existing process and environment monitoring are lack of a linkage mechanism and process parameter dynamic optimization cannot be realized are solved.

In some embodiments, the present invention relates to a method of precipitating magnesium carbonate, the method comprising the step of contacting a reactive magnesium containing solid material with an aqueous solution comprising magnesium bicarbonate to thereby precipitate magnesium carbonate. The method may relate to a method of precipitating magnesium carbonate, the method comprising the steps of: (i) Contacting a first reactive magnesium containing solid material with carbon dioxide in an aqueous solution, to thereby provide an aqueous solution comprising magnesium bicarbonate; and (ii) Contacting the aqueous solution comprising magnesium bicarbonate with a second reactive magnesium containing solid material to thereby precipitate magnesium carbonate. In other embodiments, the present invention relates to a method of producing magnesium oxide, an apparatus for precipitating magnesium carbonate, and magnesium carbonate when produced by the above methods.

This invention relates to a method for preparing calcined mineral-bonded multi-scale steel fibers for UHPC (Ultra-High-Pressure Polymer) and its composition by weight percentage: 61.13%–68.32% long steel fibers, 15.29%–17.09% short steel fibers, 2.71%–8.95% magnesium bicarbonate, 0.63%–2.18% alumina, 1.11%–3.86% glass powder, 0.04%–0.13% boron oxide, 10% PVA solution, and 0.1% adhesive. This invention uses calcined minerals obtained through high-temperature sintering to bond short steel fibers to the surface of long steel fibers, improving the dispersion and synergistic effect of steel fibers in UHPC. The hard calcined mineral crystals roughen the smooth surface of the steel fibers, improving the physical bonding properties between the cement paste and the fibers, thereby enhancing the mechanical properties of UHPC.

The present application relates to the technical field of chemical production, and particularly relates to a magnesium oxide preparation method, comprising the following steps: step S1: obtaining dolomite milk by calcining and digesting dolomite; step S2: obtaining carbonization liquid by carbonizing the dolomite milk, wherein the carbonization liquid comprises magnesium bicarbonate; step S3: adding alkali to the carbonization liquid to carry out magnesium precipitation reaction, and obtaining magnesium carbonate precipitate; the amount of the alkali in the reaction system of the magnesium precipitation reaction is 1-1.2 times of the theoretical amount; the theoretical amount of the alkali is the theoretical amount of the alkali participating in the magnesium precipitation reaction; and step S4: calcining the magnesium carbonate precipitate to generate magnesium oxide. Compared with the prior art, the present application realizes low-temperature magnesium precipitation. By adding alkali to realize magnesium precipitation, magnesium precipitation can be realized at low temperature, and high-temperature pyrolysis is not needed for magnesium carbonate precipitation, so that the production energy consumption is greatly reduced, and the production cost is reduced.

This invention discloses a method for synthesizing magnesium aluminum hydrotalcite, comprising the following steps: (1) mixing magnesium oxide, magnesium bicarbonate, aluminum hydroxide, and sodium hydroxide, then adding an ethanol aqueous solution for wetting and grinding; (2) gradually increasing the temperature while grinding, and then maintaining the temperature for reaction; (3) after the reaction is completed, restoring to room temperature, filtering, washing with water, and drying to obtain magnesium aluminum hydrotalcite. The magnesium aluminum hydrotalcite obtained by this invention has high crystallinity, small particle size and good particle size dispersion, high purity, no impurities, and high yield.

The invention relates to a device and a method for removing sulfate radicals in ion type rare earth ore magnesium salt enrichment, which are characterized in that water is added into the magnesium salt enrichment to prepare slurry, the slurry is refined under stirring to expose mixed magnesium oxide and floats upwards under the stirring action, CO2 gas is introduced at a certain rate to carbonize magnesium oxide into magnesium carbonate / magnesium bicarbonate, and the magnesium carbonate / magnesium bicarbonate is added into the slurry to prepare the sulfate radicals in the ion type rare earth ore magnesium salt enrichment. After the reaction is finished, discharging fine slurry through an overflow port, filtering to obtain filter residues and filtrate, detecting the content of sulfate radicals in the filter residues, and if the content of sulfate radicals in the filter residues is less than 1%, terminating the operation; if the sulfate radical content of the filter residues is larger than or equal to 1%, the filter residues are repeatedly operated until the sulfate radical content of the filter residues is smaller than 1%. According to the method, new carnallite is not introduced, the phenomenon that the purity of the enriched product is reduced by the carnallite is avoided, meanwhile, magnesium oxide in the existing magnesium salt enriched product is fully utilized, and the content of rare earth in the enriched product can be further increased while sulfate radicals in the enriched product are removed.

The invention relates to the technical field of active magnesium oxide preparation, in particular to ultra-high-activity magnesium oxide prepared from light-burned powder through carbon dioxide carbonization and a method thereof.The light-burned powder is used as a raw material, the light-burned powder is subjected to carbonization modification treatment through carbon dioxide to promote the light-burned powder to form a magnesium carbonate-magnesium bicarbonate hydrate solution, and after insoluble substances are filtered out, the ultra-high-activity magnesium oxide is prepared; according to the preparation method, the technological process steps are simple, the raw materials are easy to obtain, and the cost is low.

The invention provides a purification process and equipment for preparing active magnesium oxide from magnesite powder, belongs to the technical field of magnesium oxide preparation, and solves the technical problems that the existing purification process and equipment cannot deeply remove magnesite impurities and cannot prepare high-purity and high-activity magnesium oxide. The invention relates to a purification process for preparing active magnesium oxide from magnesite powder. The purification process comprises the following steps: S1, light burning activation; s2, digestion and purification; s3, carbonizing and activating; s4, deeply removing impurities; s5, performing pyrolysis; s6, washing and drying; and S7, performing low-temperature calcination. According to the method, most soluble impurities, especially calcium impurities, are effectively removed through'digestion-separation ', then through'carbonization-deep impurity removal', the characteristics of the magnesium bicarbonate solution are utilized, iron heavy metal impurities are selectively precipitated and removed, the purity of the final product magnesium oxide is greatly improved, and the purity of the magnesium oxide can reach 98% or above.

The invention relates to the technical field of magnesium-containing calcium carbonate purification, in particular to a method for purifying magnesium-containing calcium carbonate. The method comprises the following steps: preparing magnesium-containing calcium carbonate slurry; mixing a stabilizer with the magnesium-containing calcium carbonate slurry to obtain mixed slurry containing the stabilizer; carrying out bubble treatment on the raw material gas to obtain fine bubbles with a preset average size; the preset average size is less than or equal to 100 microns; carrying out carbonization reaction on the fine bubbles and the mixed slurry under the condition of a preset stirring rotating speed, so that magnesium and calcium in the mixed slurry respectively form magnesium bicarbonate and calcium carbonate, and obtaining a mixed suspension; and carrying out solid-liquid separation on the mixed suspension to obtain a calcium carbonate product and a magnesium-containing liquid phase. According to the method, through multiple mechanisms of physical shearing, chemical complexing and electrostatic adsorption, the content of similar isomorphic magnesium, magnesite and basic magnesium carbonate is remarkably reduced, and the grade of a calcium carbonate product is effectively improved to 98% or above.

The invention discloses a continuous preparation method of an acyl fluoride compound, according to the continuous preparation method, in the presence of a catalyst, perfluoroolefin with a general formula of R1R2C = CR3R4 and carbonyl fluoride are subjected to an addition reaction to prepare the acyl fluoride compound with a general formula of CFR3R4-CR1R2-COF, R1, R2, R3 and R4 are independently selected from CnF2n + 1, and n is 0-6; the catalyst is a non-loaded body porous catalyst and consists of bicarbonate and hydrofluoride, and the bicarbonate is selected from one or more of lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate and barium bicarbonate; the hydrogen fluoride salt is selected from one or more of lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride and barium fluoride; the mass percentage ratio of the bicarbonate to the hydrofluoride is (0-60%): (40-100%). The method is mild in continuous reaction condition, easy to operate, almost free of byproducts and suitable for continuous production.

The invention discloses a rapid detection method for total hardness of domestic drinking water. The method comprises the following steps: respectively and accurately measuring three 50mL water samples in a 150ml conical flask, marking as 1, 2 and 3, respectively and sequentially adding 1mL-2mL buffer solution and 5 drops of chrome black T indicator, immediately titrating by using a Na2EDTA standard solution until the color of the solution is changed into pure blue from amaranth and does not fade within half a minute, immediately stopping titration, recording the consumption volume of EDTA, if the water sample contains metal interference ions, additionally taking the water sample, and if the water sample contains metal interference ions, recording the consumption volume of the EDTA. 0.5 mL of hydroxylamine hydrochloride and sodium sulfide solution or 0.5 mL of potassium cyanide solution is added for parallel titration, when the content of bicarbonate of calcium and magnesium in a water sample is large, the water sample needs to be acidified in advance, carbon dioxide is removed through heating, suspended solids or colloidal organic matter contained in the water sample can affect observation of an end point, the water sample can be evaporated to dryness in advance and ashed at 550 DEG C, residues are dissolved with pure water, then titration is conducted, and the content of calcium and magnesium in the water sample is measured. Each water sample is subjected to parallel titration operation for five times, each group of numerical values is recorded, the average value of the numerical values is taken, the total hardness of the tap water to be measured is calculated, and the total hardness limit value is 450 mg / L, soft water is 0-150 mg / L, medium hard water is 151-300 mg / L, hard water is 301-450 mg / L, and hard water is above 450 mg / L. The method can be used for rapidly detecting the total hardness of the domestic drinking water.

The application discloses a method for resource utilization of high calcium-magnesium phosphorus tailings, which comprises the following steps: adding a leaching agent and water into the phosphorus tailings to obtain a calcium-magnesium leaching solution and high-quality phosphorus ore; adding a pH regulator and a surfactant into the calcium-magnesium leaching solution to obtain a calcium leaching solution and magnesium hydroxide slag containing impurities through reaction and filtration; adding an alkaline substance into the calcium leaching solution and introducing CO2 to prepare light calcium carbonate and a salt solution; preparing a magnesium bicarbonate solution by introducing CO2 into the magnesium hydroxide slag after slurry preparation; and finally obtaining light magnesium carbonate through pyrolysis, filtration, washing and drying. The method realizes efficient separation of calcium and magnesium in high calcium-magnesium solid waste, and high-purity light calcium carbonate, light magnesium carbonate and high-quality phosphorus ore are prepared. In addition, the method realizes cyclic utilization of CO2 generated in the process, thereby reducing the emission of greenhouse gases. The method realizes high-value utilization of the phosphorus tailings, and has high product purity and simple process.