Iron Phosphate Recovery From Slag With Multi-Stage Impurity Removal
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Solution Overview
Problem
Existing methods for recycling iron phosphorus slag from lithium iron phosphate batteries are inefficient in removing metal impurities like aluminum, titanium, and copper, resulting in iron phosphate products with high impurity content.
Innovation Solution
A method involving the use of an alkaline solution to separate aluminum and iron, followed by acid treatments to remove carbon, titanium, and copper impurities, ultimately producing anhydrous iron phosphate with low impurity content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional physical methods are used to recycle lithium iron phosphate batteries, then lithium element extraction is achieved, but iron phosphorus slag with high metal impurity content is produced as waste
Solution Approach 1:
The recycling process is divided into multiple sequential purification stages: (1) magnetic separation to remove ferrous metals, (2) acid leaching to dissolve iron phosphate, (3) selective precipitation to remove aluminum and calcium impurities, and (4) filtration to obtain high-purity iron phosphate powder. This multi-stage segmentation approach effectively separates lithium recovery from impurity removal, achieving both high lithium extraction efficiency and high iron phosphate purity.
Solution Approach 2:
The invention extracts and removes specific impurity elements (aluminum, calcium, magnesium) from the iron phosphorus slag through selective chemical reactions. Aluminum is removed by adjusting pH to precipitate aluminum hydroxide, calcium is removed by adding carbonate to precipitate calcium carbonate, and magnesium is removed by adding hydroxide to precipitate magnesium hydroxide. This targeted extraction of impurities enables production of high-purity iron phosphate while recovering lithium in earlier process stages.
2Ease of manufacture
If iron phosphorus slag is treated as low-value industrial waste or cement filler, then disposal is simple, but iron and phosphorus elements are underutilized and wasted
Solution Approach 1:
The invention reverses the conventional disposal approach by recovering valuable iron and phosphorus resources from iron phosphorus slag. Through acid leaching, iron phosphate is dissolved and then precipitated as high-purity product. The process achieves resource recovery while simplifying waste treatment, transforming low-value slag into high-value iron phosphate material that can be used in lithium iron phosphate battery production.
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 removes aluminum, carbon, titanium, and copper impurities, resulting in high-quality iron phosphate with low impurity content, suitable for use as a precursor in lithium iron phosphate batteries, while also being environmentally friendly and cost-effective.
Implementation Method 1
aluminum hydroxide and metallic aluminum in the iron phosphorus slag to react with the alkaline solution so as to be dissolved, and to allow iron in the iron phosphorus slag to react with the hydroxide ion in the alkaline solution to produce an iron hydroxide precipitate
Implementation Method 2
followed by acid treatments to remove carbon, titanium, and copper impurities
Implementation Method 3
ultimately producing anhydrous iron phosphate with low impurity content
Data Source
AI summary
A method for preparing iron phosphate from an iron phosphorus slag includes: adding the iron phosphorus slag into an alkaline solution to carry out a reaction followed by a solid-liquid separation to obtain a residue and a first filtrate containing meta-aluminate ion and phosphate ion; adding an acid solution into the first filtrate to carry out an aluminum-removing reaction followed by a solid-liquid separation to obtain a second filtrate containing phosphate ion; mixing the residue with an acid solution to carry out a carbon-removing reaction followed by a solid-liquid separation to obtain a carbon residue and a third filtrate containing iron ion, titanium ion, and copper ion; adding metallic iron into the third filtrate to carry out a titanium and copper-removing reaction followed by a solid-liquid separation to obtain a fourth filtrate containing ferrous ion; mixing an oxidant, the second filtrate, and the fourth filtrate to carry out a reaction followed by a solid-liquid separation and a sintering process in sequence to obtain the iron phosphate.