Method for leaching platinum metals from automobile tail gas spent catalyst by microwave heating and melting

Abstract

The invention provides a method for leaching platinum metals from an automobile tail gas spent catalyst by microwave heating and melting, comprising the steps of: crushing and finely grinding the automobile tail gas spent catalyst, uniformly mixing sodium bisulfate serving as a leaching agent with the automobile tail gas spent catalyst, and heating under microwave at the temperature of 300-700 DEG C for 30-150min to obtain sinter; and leaching under water dissolving and stirring at normal temperature for 10-60min, carrying out solid-liquid separation, washing filter residue three times, discarding the filter residue, collecting filtrate and cleaning solution to obtain the solution rich in platinum metals Pd and Rh. According to the method, microwave heating is adopted to simultaneously leach Pd and Rh, the leaching rate of platinum metal Pd reaches 99.97%, the leaching rate of platinum metal Rh reaches 98.91%, and both the leaching rates are improved as compared with that of single wet method or pyrogenic process leaching; and the leaching process is simple, the process flow is short, the reagent is single, the reagent consumption amount is low, the solution contains few impurity elements, the leaching rate is high, the leaching time is short and the energy consumption is low, so that the method has wide industrial application prospects.

Description

technical field [0001] The invention relates to microwave heating, melting and leaching of platinum group metals in waste catalysts of automobile exhaust, belonging to the technical field of metallurgy and chemical industry. Background technique [0002] Platinum group metals (PGM) such as Pt, Pd, Rh, etc. have very good high temperature resistance and good chemical corrosion resistance, and have unique chemical properties such as reduction catalysis. Now the world's annual output of platinum group metals is about 300 tons, 90% of which come from Russia and South Africa. The reserves and output of platinum group metals in my country are very small, less than 1% of the world's reserves and output. The recovery and utilization of platinum group metals in exhaust gas catalysts is particularly important for our country. [0003] At present, the main methods for recovering platinum group metals from waste catalysts of automobile exhaust gas are: wet leaching, fire method and comb...

AI Technical Summary

Problems solved by technology

Atmospheric pressure acid leaching and pressurized acid leaching are used in industry, but the wet leaching process is only effective for the platinum group metals Pt and Pd in ​​the waste catalyst of automobile exhaust, while the platinum group metal Rh and its oxides are very effective. It is difficult to enter the solution, and often requires secondary treatment of the leaching slag, and pressure acid leaching requires special leaching equipment, which increases the cost and the risk of the operation process, so the extraction of platinum group metal Rh by wet leaching has always been a difficult problem

[0004] Due to the problems of wet extraction, many precious metal recycling companies adopt the fire method to recover precious metals, but the foundation of the fire process is to enrich the platinum group metals in the waste catalyst of automobile exhaust, which uses lead, copper, iron, nickel, etc. to capture sulfides such as iron sulfide and nickel sulfide have a strong affinity for platinum group metals to enrich platinum group metals by making slag. Alloys or mattes, the final recovery of platinum group metals is achieved through wet treatment, and the melting temperature of pyrotechnics is generally high, which has special requirements for equipment, and the addition of collectors also means the introduction of impurity elements and Reagent Consumption

[0005] There are also researches on the combination of wet process and fire process, mainly to remove part of the carrier first to improve the efficiency of subsequent treatment. The fire-wet combination aims to solve the problems existing in the two and achieve complementary advantages, but there is a long process flow. , increased smelting costs and other issues

[0006] Pressurized alkali leaching pretreatment-pressurized cyanidation method to extract platinum group metals from automobile exhaust waste catalysts. Metal wrapping increases the subsequent cyanidation leaching efficiency, and then uses hydrocyanic acid to pressurize the platinum group metals in the waste catalyst of automobile exhaust. The leaching rate of platinum group metals is greatly improved compared with conventional wet leaching, but its use Hydrocyanic acid is used, which is potentially dangerous to the environment. The conditions of pressurized leaching also increase the requirements for equipment, and the follow-up process must destroy CN alone. - , which increases the cost to a certain extent

[0007] Due to the high temperature and long-term action of the automobile catalyst during use, it will cause the carrier metal to wrap the platinum group metal and pollute the surface organic matter, which will increase the difficulty of leaching and extraction. Although there are many reports on various methods, each method has its own advantages. Disadvantages, generally speaking, the method is novel, and the method with higher leaching rate has the disadvantages of longer process flow, high leaching cost, and special requirements for equipment

The method with a short process flow has the disadvantages of low leaching rate and large consumption of reagents

Considering the difficulties in the extraction of platinum group metals from automobile exhaust waste catalysts, on the one hand, the carrier metal wraps the particles of platinum group metals, making it difficult to interact with solvents; on the other hand, the chemical properties of the platinum group metal Rh itself are stable and cannot Reacts with most reagents, making it difficult to leach