Method of preparing ammonium dimolybdate from a molybdenum-containing solution

Abstract

The invention belongs to the technical field of chemical separation and particularly relates to a method of preparing ammonium dimolybdate from a molybdenum-containing solution. The method includes the steps of: (1) stirring the molybdenum-containing solution and adding ammonium sulfide to regulate the color of the solution from blue into colorless status, and allowing the solution to stand, feeding a supernatant through a paperboard filter to obtain a filtrate, which serves as a raw material for the next acid precipitation step; (2) stirring the filtrate by means of anchor-type blades, addingindustrial concentrated sulfuric acid, regulating pH value to 2.5-2.8, stirring the mixture for 30 min and performing ion exchange column adsorption to prepare crude ammonium tetramolybdate; (3) heating pure water to boiling, adding the crude ammonium tetramolybdate, regulating the pH value to 6.5-7.0, filtering the liquid while hot, feeding a filtrate into a crystallization kettle, performing vacuum evaporation concentration, and filtering the liquid when 55% of water is evaporated, feeding a mother liquid to the step (2) for acid precipitation again, and drying crystals to prepare ammoniumdimolybdate. The method is short in process and low in cost, is high in recovery rate, is free of environmental pollution, and is far better than other preparation processes of ammonium dimolybdate.

Description

technical field [0001] The invention belongs to the technical field of separation chemistry, and in particular relates to a method for preparing ammonium dimolybdate from a molybdenum-containing solution. Background technique [0002] Ammonium dimolybdate, also known as ammonium dimolybdate, is a white powder, usually used to prepare catalysts, metal molybdenum, pigments; or used as metal surface treatment, slow release agent or trace element fertilizer, etc. [0003] The raw material of traditional ammonium molybdate production is Pyrite, and the production process is Pyrite-roasting-industrial molybdenum oxide-pickling-ammonia leaching-crude ammonium molybdate solution-magnesium chloride impurity removal (high temperature impurity removal, generally at a temperature of Above 90°C) - ammonia sulfide removal - fine ammonium molybdate solution - nitric acid precipitation - ammonium tetramolybdate - ammonia solution - evaporation crystallization - ammonium dimolybdate. The pr...

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Problems solved by technology

The production of ammonium molybdate by the above-mentioned method is the method widely used in China at present, and is characterized in that the equipment is simple, the investment is small, and the processing capacity is small, but the method has the following disadvantages: (1) the industrial molybdenum oxide leaching rate is not high during ammonia leaching, and the slag Medium molybdenum is not easy to recycle, resulting in low recovery rate and high cost; (2) The impurity removal effect is poor, and the chemical properties of the product are difficult to meet the national standard requirements; (3) The raw material adaptability is poor, and only high-quality molybdenum concentrate can be used as raw material products (4) The working environment is poor and the equipment is easy to corrode; (5) It is not easy to implement automatic control; (6) Environmental protection emissions (such as waste water, waste gas and waste residue, etc.) are difficult to meet the national requirements. Ammonia consumption, acid precipitation A large amount of nitric acid is consumed, a large amount of high-concentration ammonia-nitrogen compounds are produced, and the discharge of ammonia-nitrogen seriously exceeds the standard. It is necessary to spend a lot of money to solve the treatment of ammonia-nitrogen waste. This is the biggest disadvantage brought by the traditional process.