38results about How to "Reduce the content of hexavalent chromium" patented technology

The invention provides an alkali-acid double-cycle process for treating brown iron type nickel laterite ore. In the process, a brown iron type depleted nickel laterite ore is used as a raw material and undergoes roasting reaction with alkali such as sodium hydroxide, potassium hydroxide and the like or carbonate thereof at high temperature, and then the roasted materials are subjected to waster washing and liquid-solid separation to form alkali filter liquor rich in valent metal salts such as water-soluble chromate, aluminate and the like and insoluble filter cakes, wherein the filter liquor can be fully utilized to prepare chromium salt and aluminum salt and the recycle of alkali media is realized; and the filter cakes can be used for extracting nickel and cobalt through a subsequent pressurized and acid leaching process, the acid leaching dregs are high-grade fine iron powder, and acid media in the acid leaching liquor can be recycled.

The invention relates to the field of a chemical industry and particularly relates to a method for preparing anhydrous sodium sulfate from chromium-containing mirabilite as a by-product in the production process of sodium dichromate. The method comprises dissolving a certain concentration of chrome-containing mirabilite in chromium-containing waste water, adding quantitative sodium thiosulfate into the waste water to promote reduction of hexavalent chromium into trivalent chromium under 0.1-1 Mpa at 80-190 DEG C, wherein the trivalent chromium in a form of chromium trioxide hydrate is precipitated, adding a small amount of sulfuric acid to neutralize, filtering to acquire the chromium trioxide hydrate, removing impurities, carrying out decoloration, evaporating to precipitate anhydrous sodium sulfate crystals, and carrying out continuous centrifugal separation and drying. The method is simple and easy, utilizes cheap raw materials, has low energy consumption and a high automation degree and is suitable for large-scale production. The quality of the industrial anhydrous sodium sulfate product obtained by the method meets the requirements of class I products in the GB / T 6009-2014 industrial anhydrous sodium sulfate standard.

The invention relates to a two-stage deep wet detoxification method for industrial chromium slag, and belongs to the field of treatment of industrial chromium slag. The grinding fineness of chromium slag ore is -0.074 mm%: 90; first stage water leaching solid-to-liquid ratio is 6: 1, constant-temperature water bath is carried out at 75-85 DEG C, and stirring is carried out for 1-2 hours at the speed of 90-110r / min; solid-liquid separation is carried out to obtain an orange red hexavalent chromium liquid; an obtained solid is subjected to second stage acid leaching, and sodium metabisulfite isadded into an obtained liquid until the liquid becomes dark green; calcium oxide is added into the dark green trivalent chromium liquid to form grey green chromium hydroxide precipitate, and a clearliquid obtained through filtering is recycled as return water; wherein the second stage acid leaching solid-to-liquid ratio is 3: 1, and constant-temperature water bath is carried out at 80-90 DEG C;concentrated sulfuric acid is added, the dosage of the concentrated sulfuric acid is 700-740 kg / t, and soaking is conducted for 4-6 h; excessive ferrous sulfate is added for treating for 4-6 hours; calcium oxide is added to adjust the pH value of an obtained slag slurry to be greater than 6; ore washing is conducted, washing water is recycled as return water, and waste residues are filtered and discharged. According to the two-stage deep wet detoxification method, the indexes after treatment are far lower than those in the national chromium slag landfill standards, the standard of first-time treatment landfill is achieved, the rebound risk is avoided, and the harm of chromium slag discharge treatment landfill to the environment is fundamentally avoided.

The invention relates to the field of a chemical industry and particularly relates to a method for preparing anhydrous sodium sulfate from chromium-containing mirabilite as a by-product in the production process of sodium dichromate. The method comprises dissolving a certain concentration of chrome-containing mirabilite in chromium-containing waste water, adding quantitative sodium thiosulfate into the waste water to promote reduction of hexavalent chromium into trivalent chromium under 0.1-1 Mpa at 80-190 DEG C, wherein the trivalent chromium in a form of chromium trioxide hydrate is precipitated, adding a small amount of sulfuric acid to neutralize, filtering to acquire the chromium trioxide hydrate, removing impurities, carrying out decoloration, evaporating to precipitate anhydrous sodium sulfate crystals, and carrying out continuous centrifugal separation and drying. The method is simple and easy, utilizes cheap raw materials, has low energy consumption and a high automation degree and is suitable for large-scale production. The quality of the industrial anhydrous sodium sulfate product obtained by the method meets the requirements of class I products in the GB / T 6009-2014 industrial anhydrous sodium sulfate standard.

The invention provides a method for biological detoxification of chromium slag and preparation of a biological organic fertilizer. The method comprises the steps: mixing biological solid waste, the chromium slag and an organic conditioner, then carrying out aerobic composting, to obtain the biological organic fertilizer having the hexavalent chromium content reaching standards. The biological solid waste and the organic conditioner are adopted for composting to detoxify the chromium slag, the waste is used for treating the waste, and the method has the characteristics of low investment, low cost, diverse treatment ways, good detoxification effect and the like; and the biological organic fertilizer prepared after composting can realize resource utilization of the chromium slag directly.

The invention discloses a method for preparation of sodium chromate by low-nitrogen roasting of chromite and continuous leaching of clinker. The method includes the steps of: (1) selecting chromium ore powder, sodium carbonate and return slag; (2) mixing the selected raw materials uniformly, then feeding the mixture into a rotary furnace, carrying out oxygen-fuel combustion through a total oxygen-fuel system, and controlling the temperature of the materials at 850DEG C-1150DEG C; (3) directly and uniformly injecting pure oxygen gas into the raw material under a material bed in the rotary furnace, and carrying out pure oxygen roasting reaction on the raw material in the rotary furnace; and (4) injecting the roasted clinker into a wet vertical mill, adding a sodium chromate dilute solution or pure water through a metering pump, stirring the substances uniformly, conveying the mixture to a belt filter through a transfer trough, and conducting continuous leaching and filtering to obtain sodium chromate. The method has the characteristics of low energy consumption, high sodium chromate yield, low chromium ore consumption, and low content of nitrogen oxide generated in the flue gas, canachieve continuous production, improves the production efficiency, and can realize clean emission.

The invention provides a method for reducing the content of hexavalent chromium in chromium oxide green. The method includes the step: adding reducing agents into the chromium oxide green with the discharging temperature of 60-400 DEG C in a production process to obtain a chromium oxide green product. According to the method, the hexavalent chromium in the chromium oxide green can be reduced, thecontent of water soluble objects in the chromium oxide green product is reduced, the problem of yellowing of the product is solved, the recovery rate of chromium metal is increased, the method is simple to operate and less in reducing agent dosage, the reducing agents are added in the cooling process, an original process cannot be affected, and the reducing agents are volatilized and decomposed inthe reducing process, so that the purity of the chromium oxide green cannot be affected.

A stainless steel 347 metal core welding wire with low hexavalent chrome emission and a preparation method of the welding wire are suitable for the field of welding materials. The welding wire comprises the following components: 0.025-0.07wt.% of C, 45-60wt.% of Cr, 25-31wt.% of Ni, 4-7wt.% of Mn, 0.66-1.5wt.% of Si, 0.3-2wt.% of Ti, 0.3-2wt.% of Zn, 0.3-2wt.% of Zr, 0.25-1.2wt.% of Nb, and the balance of Fe and unavoidable impurities. The welding wire and the preparation method ensure that the mechanical property of welding wire deposited metal is matched with that of base metal, and a stainless steel belt is replaced with a carbon steel belt, so that the cost is lowered; 30-60% of the total amount of hexavalent chrome (Cr<+6>) in welding fume is reduced; a welding operation environment is improved; and in addition, the welding wire and the preparation method have the advantages that splattering is low, and the combination property of the formed deposited metal is excellent.

The invention discloses a low hexavalent chromium 316 austenitic stainless steel metal core welding wire and a preparation method of the low hexavalent chromium 316 austenitic stainless steel metal core welding wire, and belongs to the field of welding material. Steel bands for the welding wire are low carbon steel bands with the following chemical components: carbon (C): 0.025-0.078 wt. %; silicon (Si): 0.06 wt. %; manganese (Mn): 0.33 wt. %; sulfur (S): <= 0.025 wt. %; and phosphorus (P): <= 0.03 wt. %. The chemical composition mass fraction of the welding wire powder includes: C: 0.025-0.078 wt. %; chromium (Cr): 48-57 wt. %; nickel (Ni): 28-33 wt. %; Mn: 4-6 wt. %; molybdenum (Mo): 2.8-5 wt. %; Si: 0.63-1.5 wt. %; titanium (Ti): 0.5-1 wt. %; zinc (Zn): 0.5-1 wt. %; zirconium (Zr): 0.5-1 wt. %; and ferrum (Fe): allowance. Compared with the prior art, the adopted steel bands are the low carbon steel bands, cost is reduced, at the same time welding dust content amount corresponds to that of a solid core welding wire, emission load of harmful Cr (VI) can be reduced by 20%-28% compared with the solid core welding wire, and welding electric arc is stable, spatter is small, weld forming appearance is attractive, and deposited metal is excellent in comprehensive performance.

The invention discloses hot elution equipment and method applicable to ex-situ remediation of chromium-contaminated soil. The hot elution equipment comprises a heating pipe. A heater is mounted on theheating pipe; the heating pipe is connected with a hot elution pool; the heater is a circular ring consisting of a gas inlet pipe, a communicating pipe, a burner and a bracket; and a distance from the bracket to the circle center of the heater is equal to the outer diameter of the heating pipe. The chromium-contaminated soil is firstly dissociated by a crushing sieve and a drum mud machine. Afterbeing dissociated, the soil is immersed in the elution pool, and then immersed and eluted mud enters the hot elution pool after being heated; and the mud is subjected to leaching grading and solid-liquid separation after being subjected to hot elution remediation to obtain clean soil. The equipment disclosed by the invention is simple in structure, reasonable in design and high in operability. After the chromium-contaminated soil is treated by the hot elution equipment, the content of hexavalent chromium in the soil is substantially reduced, a field remediation goal is achieved, and secondarypollution of the hexavalent chromium to the surrounding environment is avoided; a foundation is laid for the ex-situ remediation and treatment of the soil in a chromium-contaminated site.

The invention provides a nickel passivation solution and a preparation method thereof. The nickel passivation solution contains the following components: 1-10g / L of chromic anhydride, 30-100g / L of phosphoric acid, 20-50g / L of dimethylformamide and 1-10g / L of methyl triethoxysilane. The invention also provides a method for passivating a nickel surface by adopting the nickel passivation solution. By adopting the nickel passivation solution provided by the invention, a stable and permanent passivation layer can be formed on the metallic nickel surface and the salt mist resistance time is greatly lengthened. Meanwhile, the nickel passivation solution provided by the invention has lower content of hexavalent chromium and is safe and environment-friendly.

The treatment method for reducing the content of hexavalent chromium in leather provided by the present invention is characterized in that the aqueous solution of reducing agent with a mass percentage concentration of 0.5-3.0% is sprayed on finished leather and semi-finished leather after wet operation, or the same concentration The aqueous solution of reducing agent is used to treat the semi-finished leather after wet operation in the drum. The reducing agent used is at least one of ferrous sulfate, ferrous chloride, ammonium ferrous sulfate, sodium sulfite, potassium sulfite and sodium thiosulfate. The invention can be used not only for the treatment of finished leather whose hexavalent chromium content exceeds the standard, but also for the treatment of semi-finished leather in the process of tanning, so as to prevent the generation of hexavalent chromium in the finished leather. The process and operation of the present invention are simple, the source of the reducing agent is abundant, the price is low, the treatment cost is low, the process after tanning and the quality of the leather are not affected, and the content of the treated leather or hexavalent chromium is below 3mg / kg, or the detection is not good. out.

The invention discloses a method for preparing sodium chromate by low-nitrogen roasting of chromite ore and continuous leaching of clinker, comprising the following steps: (1) selecting chromite ore powder, soda ash and returned slag; (2) mixing the selected raw materials After uniformity, it is sent to the rotary kiln, and the oxy-fuel system is used for oxy-fuel combustion, and the temperature of the material is controlled at 850°C-1150°C; (3) The pure oxygen gas is directly and evenly injected into the rotary kiln under the raw material bed , the raw material is roasted with pure oxygen in the rotary kiln; (4) The roasted clinker is poured into the wet vertical mill, and the sodium chromate light solution or pure water is added through the metering pump. After stirring evenly, it is passed through the transfer tank Sodium chromate is obtained after being sent to a belt filter for continuous leaching and filtering. The invention has low energy consumption, high output of sodium chromate, low consumption of chromium ore, low content of nitrogen oxides in flue gas, low consumption of chromium ore, low content of nitrogen oxides in flue gas, and can realize continuous production, improve Increased productivity and clean emissions.

The invention proposes a film-forming method for adjusting and controlling the performance of a trivalent chromium chemical conversion film on the surface of a hot-dip galvanized aluminum alloy coating, which belongs to the field of chemical conversion film-forming technology, and can solve the problems of hexavalent chromium and film-forming quality that are prone to occur in existing film-forming methods Inhomogeneity and technical problems such as high voltage, high current density, and low efficiency used in auxiliary film formation. The film forming method includes putting the hot-dip galvanized aluminum alloy coating into the trivalent chromium chemical conversion diluent, and after standing still for a while, applying a pulsed cathode square wave potential to it to chemically convert into a film at a certain temperature, wherein the heat The galvanized aluminum alloy coating is the cathode, and the counter electrode is the anode; after the above-mentioned product is cleaned and dried at normal temperature, a trivalent chromium chemical conversion film is obtained on the surface of the hot-dip galvanized aluminum alloy coating. The invention can be applied to the structure and performance control of the trivalent chromium chemical conversion film on the surface of the hot-dip galvanized aluminum alloy coating, so as to be applied to the temporary protection of the hot-dip galvanized aluminum alloy coating.