Mixed Rare Earth Concentrate Leaching via Plasma Surface Modification
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Solution Overview
Problem
Current industrial processes for smelting mixed rare earth concentrates face challenges such as resource waste, radioactive contamination, and inadaptability to large-scale production due to issues like sulfur-containing and fluorine-containing tail gases, ammonia-nitrogen wastewater, and high requirements for pre-impurity removal, limiting the green and sustainable development of the rare earth industry.
Innovation Solution
A method involving surface modification of mixed rare earth concentrates using a plasma gas flow, followed by mineral phase transformation to cerium oxyfluoride, acid leaching, and alkaline leaching to separate rare earth, phosphorus, and fluorine elements, reducing oxidation and enhancing leaching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If concentrated sulfuric acid roasting is used, then production cost is reduced and process continuity is improved, but sulfur-containing and fluorine-containing tail gas is produced causing environmental pollution
Solution Approach 1:
The patent changes the chemical parameters of the roasting process by using concentrated nitric acid instead of concentrated sulfuric acid, and controlling the roasting temperature range (80-120℃) to prevent decomposition. This parameter change eliminates sulfur-containing and fluorine-containing tail gas while maintaining process continuity and productivity.
Solution Approach 2:
The patent creates an inert roasting environment by using concentrated nitric acid which forms a protective oxidation atmosphere, preventing the decomposition of rare earth minerals and avoiding the formation of harmful sulfur-containing and fluorine-containing gases that would otherwise be produced in conventional sulfuric acid roasting.
2Ease of manufacture
If concentrated sulfuric acid roasting is used, then production cost is reduced, but resource waste and radioactive contamination occur
Solution Approach 1:
The patent implements comprehensive resource recovery by separating and recovering phosphorus from the leaching solution, and by ensuring complete dissolution of rare earth minerals. The process recovers valuable elements (rare earths, phosphorus, fluorine) from what would otherwise be waste residues, eliminating resource waste while maintaining cost-effectiveness.
Solution Approach 2:
The patent converts the previously harmful residues containing phosphorus and thorium into valuable resources. By using concentrated nitric acid roasting followed by selective leaching, the process transforms the insoluble salt residues into soluble forms that can be recovered, turning environmental liabilities into economic benefits.
3Object-affected harmful factors
If caustic soda decomposition is used, then environmental pollution is reduced, but pre-impurity removal is required reducing process adaptability
Solution Approach 1:
The patent performs preliminary oxidation action by using concentrated nitric acid roasting before leaching. This preliminary treatment converts all rare earth minerals into oxide forms and removes organic matter, eliminating the need for pre-impurity removal steps while maintaining environmental friendliness. The roasting process prepares the material in advance for efficient leaching.
Solution Approach 2:
The concentrated nitric acid roasting process serves multiple functions simultaneously: it oxidizes rare earth minerals to soluble forms, removes organic impurities, eliminates sulfur-containing and fluorine-containing emissions, and prepares the material for selective leaching. This multi-functionality provides both environmental benefits and process adaptability without requiring separate pre-treatment steps.
4Device complexity
If conventional leaching methods are used, then simple separation is achieved, but leaching efficiency is low due to oxidation issues
Solution Approach 1:
The patent changes the chemical parameters by using concentrated nitric acid instead of conventional leaching agents, and by controlling the roasting temperature (80-120℃) and acid concentration. These parameter changes enable complete dissolution of rare earth minerals while preventing oxidation of Cerium(III) to Cerium(IV), thereby improving leaching efficiency without increasing process complexity.
Solution Approach 2:
The patent uses concentrated nitric acid as an intermediary substance that facilitates the transformation of rare earth minerals into soluble oxide forms during roasting. This intermediary treatment enables subsequent efficient leaching by creating a chemical state that is highly reactive and soluble, thereby improving leaching efficiency while maintaining process simplicity.
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 method effectively separates and recovers rare earth, phosphorus, and fluorine elements, increasing the comprehensive resource utilization rate of mixed rare earth concentrates while minimizing environmental impact and improving process adaptability to large-scale production.
Implementation Method 1
performing a surface modification on the mixed rare earth concentrate under the action of a plasma gas flow
Implementation Method 2
performing a mineral phase transformation on the surface-modified mixed rare earth concentrate to transform a bastnaesite phase in the mixed rare earth concentrate into a cerium oxyfluoride
Implementation Method 3
acid leaching the mineral phase transformation product to obtain an acid leachate and an acid leaching residue, where the acid leachate comprises a rare earth ion and a fluoride ion
Implementation Method 4
alkaline leaching the surface-modified acid leaching residue to obtain an alkaline leachate and an alkaline leaching residue, where the alkaline leachate comprises a phosphorus element
Data Source
AI summary
A method for leaching separation of a mixed rare earth concentrate includes: completing surface modification on the mixed rare earth concentrate under the action of a plasma gas flow, and obtaining a surface-modified mixed rare earth concentrate; performing mineral phase transformation on the surface-modified mixed rare earth concentrate, transforming a bastnaesite phase in the mixed rare earth concentrate into a cerium oxyfluoride, and obtaining a mineral phase transformation product containing the cerium oxyfluoride; performing acid leaching on the mineral phase transformation product, and obtaining an acid leachate and an acid leaching residue; completing surface modification on the acid leaching residue under the action of a plasma gas flow, and obtaining a surface-modified acid leaching residue; and performing alkaline leaching on the surface-modified acid leaching residue, and obtaining an alkaline leachate and an alkaline leaching residue.