Phosphate Mineral Dissolution Using Condensed Phosphoric Acid
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Solution Overview
Problem
Existing methods for recovering metals from phosphate minerals like monazite and xenotime, such as rare earth elements, thorium, and uranium, require fine grinding and harsh conditions, posing safety hazards and increasing costs due to extended residence times and inefficient dissolution processes.
Innovation Solution
A process involving the use of condensed phosphoric acid at temperatures between 215° C. and 300° C. for metal-bearing materials, followed by leaching with ion exchange resins and precipitation techniques to dissolve metals efficiently, reducing the need for fine grinding and minimizing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fine grinding of monazite is performed to maximize surface area, then dissolution efficiency is improved, but safety hazards increase due to alpha radiation from inhaled or ingested dust particles
Solution Approach 1:
The patent changes the chemical parameter by using phosphoric acid instead of conventional reagents, which enables effective dissolution without requiring fine grinding. This parameter change resolves the contradiction by maintaining high dissolution efficiency while eliminating the need to create hazardous fine dust particles
Solution Approach 2:
The patent replaces the mechanical grinding system with a chemical dissolution system. Instead of mechanically reducing particle size to increase surface area, the process uses phosphoric acid to chemically dissolve the metal-bearing material, thereby achieving high dissolution efficiency without generating hazardous dust
2Productivity
If fine grinding of monazite is performed to maximize surface area, then dissolution efficiency is improved, but operating costs and capital costs increase due to larger plant size requirements
Solution Approach 1:
The patent changes the chemical parameter by using phosphoric acid, which enables effective dissolution at coarser particle sizes. This reduces the need for extensive grinding infrastructure and smaller plant size, thereby lowering both capital costs and operating costs while maintaining high dissolution efficiency
3Productivity
If conventional methods using 70% sodium hydroxide at higher than 140° C. are used, then metal hydroxides are produced, but the process cannot effectively break down xenotime which is often a key component of ores rich in monazite
Solution Approach 1:
The patent applies phosphoric acid as a universal reagent that can effectively process both monazite and xenotime, unlike conventional methods that are specialized for only one mineral type. This multi-functional approach resolves the contradiction by maintaining high metal recovery rates while expanding the process's ability to handle diverse phosphate minerals
Solution Approach 2:
The patent changes the chemical parameter by using phosphoric acid instead of sodium hydroxide, which fundamentally alters the dissolution mechanism to be effective against both monazite and xenotime structures, thereby improving both recovery rate and mineral versatility
4Productivity
If sulphuric acid at a purity of 93% is used at between 200° C. and 400° C. to produce metal sulphates, then xenotime can be broken down, but the process does not directly dissolve the metals into solution, requiring extended residence times
Solution Approach 1:
The patent changes the chemical parameter by using phosphoric acid instead of sulphuric acid, which enables direct dissolution of metals into solution rather than merely converting to sulphates. This parameter change resolves the contradiction by achieving high dissolution rates while significantly reducing the required residence time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves high metal recovery rates, up to 99% dissolution of metals, with safer and more economical operations by avoiding fine grinding and significantly reducing residence times.
Implementation Method 1
contacting the metal-bearing material with condensed phosphoric acid at a temperature of greater than 215° C. and less than 300° C. for a period of time sufficient to at least partially dissolve the metal-bearing material; to provide a leaching solution containing metal ions
Implementation Method 2
followed by leaching with ion exchange resins
Data Source
AI summary
The present invention relates to a process for recovering metals from metal-bearing material, said process comprising the step of contacting the metal-bearing material with condensed phosphoric acid at a temperature of greater than 215° C. and less than 300° C. for a period of time sufficient to at least partially dissolve the metal-bearing material; to provide a leaching solution containing metal ions. The invention is applicable to a range of metals including the rare earth elements, as well as thorium and uranium. The invention is applicable to a range of metal-bearing materials, particularly phosphate minerals such as monazite and xenotime.