Monazite Slag Recovery via Low-Acid Leaching and Closed-Loop Extraction
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Solution Overview
Problem
Current methods for processing monazite slag result in the accumulation of radioactive waste, hindering environmental management and rare earth plant operations, as they fail to effectively recover valuable elements like uranium, thorium, and rare earths, leading to environmental harm and economic obstacles.
Innovation Solution
A method involving acid leaching, pressure filtration, and water washing of monazite slag, followed by secondary acid leaching and extraction using specific agents like di(2-ethylhexyl)phosphoric acid and primary amine, to separate and recover uranium, thorium, and rare earths, with a closed-loop circulation process that eliminates radioactive waste discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional processing methods are used on monazite slag, then the processing operation can be performed, but radioactive waste accumulates and environmental harm occurs
Solution Approach 1:
The patent applies discarding and recovering by separating valuable elements (uranium, thorium, rare earths) from monazite slag through acid leaching and extraction processes. The valuable elements are recovered into solution phases while the depleted slag is discarded as non-radioactive or low-radioactivity waste, thus eliminating the accumulation of radioactive waste while maintaining processing productivity.
Solution Approach 2:
The patent converts the harmful radioactive waste problem into a beneficial resource recovery opportunity. By treating monazite slag with acid solutions and applying extraction agents, the process transforms what was previously waste material into valuable uranium, thorium, and rare earth products, while the remaining slag loses its radioactivity hazard.
2Quantity of substance
If acid leaching and extraction processes are applied to recover valuable elements, then recovery rate increases, but process complexity and acid consumption increase
Solution Approach 1:
The patent applies segmentation by dividing the recovery process into distinct sequential stages: acid leaching to dissolve valuable elements, pressure filtration to separate solids from liquids, and multiple extraction steps using different agents (di(2-ethylhexyl)phosphoric acid for thorium, primary amine for rare earths). This segmented approach enables high recovery rates while making the complex process manageable and systematic.
Solution Approach 2:
The patent applies parameter changes by systematically varying acid concentrations (0.25-0.5 mol/L), temperatures (40-100°C), and extraction agent types to optimize the recovery of different valuable elements. These parameter adjustments enable selective extraction and high recovery rates while controlling process complexity through defined operating conditions.
3Quantity of substance
If multiple extraction agents and steps are used to achieve high recovery rates, then valuable elements are recovered, but water and acid consumption increase
Solution Approach 1:
The patent applies discarding and recovering to water and acid resources by implementing a closed-loop system where process waters and acid solutions are recycled and reused. The pressure filtration and water washing steps generate liquid phases that are treated and reused in subsequent leaching operations, significantly reducing fresh water and acid consumption while maintaining high valuable element recovery rates.
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
This method achieves high recovery rates of uranium, thorium, and rare earths, reduces waste water and acid consumption, and simplifies the process flow, enabling economic and environmentally friendly recovery of valuable elements while preventing radioactive waste discharge.
Implementation Method 1
adding monazite slag into a 0.25 mol/L-0.5 mol/L inorganic strong acid solution according to a monazite slag/acid ratio of 1 kg:(1-15) L, heating to 40° C.-100° C., stirring for 5 h-8 h
Implementation Method 2
filtering the slurry to obtain filtration slag and filtrate
Implementation Method 3
adding water into the filtration slag in the step (2) to wash, stopping washing when the pH value of a water washing solution is 2-3
Data Source
AI summary
The invention relates to a separation and recovery method for radioactive waste slag and specifically relates to a separation and recovery method for monazite slag. The separation and recovery method comprises the following steps: acid leaching, pressure filtration, water washing, extraction of valuable components and treatment of filtration slag. The separation and recovery method provided by the invention performs low-acid and low-temperature leaching on monazite slag, so that a liquid phase and a solid phase are easy to separate; after an ore dressing process is adopted for performing ore dressing and alkali decomposition on secondary slag, closed-loop circulation and recovery of uranium, thorium and rare earth is realized; and simultaneously, extraction raffinate waste acid is recycled, so that the emission of waste water is reduced, the consumption of sulfuric acid and fresh water and the treatment cost of the waste water are reduced, the production cost is reduced, the recovery rate of the valuable elements, namely the uranium, the thorium and the rare earth is more than 97%, and the whole process has no emission of the radioactive waste water and waste slag.