Iron Extraction from Flotation Refuse via Magnetic Separation and Oxalic Leaching
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Solution Overview
Problem
Current methods for extracting iron from flotation processing refuse, particularly those with high iron content, face challenges such as dissolution of the silicate backbone, impurity contamination with colloidal silicon dioxide, and inefficient separation of iron oxalate phases, leading to low-purity products and additional processing steps.
Innovation Solution
A method involving preliminary wet magnetic separation to isolate the iron-containing phase, followed by treatment with an oxalic acid solution at elevated temperature, hydrogen peroxide addition to convert divalent to trivalent iron oxalate, and controlled pH precipitation to enhance purity, including steps for separation and transformation into high-purity iron oxides like hematite and ferrihydrite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If leaching with oxalic acid is implemented on high iron content materials, then iron extraction efficiency is improved, but the silicate backbone dissolves and colloidal silicon dioxide contaminates the product
Solution Approach 1:
The patent applies preliminary magnetic separation to isolate the iron-containing phase from the silicate matrix before leaching with oxalic acid. This preliminary action prevents the silicate backbone from dissolving during leaching, thereby avoiding colloidal silicon dioxide contamination while maintaining high iron extraction efficiency from the concentrated iron phase.
Solution Approach 2:
The patent segments the processing into distinct stages: first magnetic separation to concentrate the iron phase, then leaching of the separated iron-containing material. This segmentation allows selective treatment of the iron phase without affecting the silicate matrix, resolving the contradiction between extraction efficiency and product purity.
2Productivity
If chemical reduction of trivalent iron to divalent iron is implemented during leaching, then leaching effectiveness is increased, but calcium and magnesium oxalates co-precipitate and cannot be separated from iron phase
Solution Approach 1:
The patent changes the pH parameter during precipitation to selectively precipitate iron hydroxide while keeping calcium and magnesium in solution. By controlling pH in the range of 8-10, iron is precipitated as hydroxide while alkaline earth metals remain dissolved, enabling separation without co-precipitation of calcium and magnesium oxalates.
Solution Approach 2:
The patent uses pH control as an intermediary mechanism to achieve selective precipitation. By adjusting pH, the solubility products of different metal hydroxides are exploited to separate iron from calcium and magnesium, acting as a mediator that enables selective recovery without direct chemical reduction.
3Ease of operation
If mixed phases are formed during separation of precipitates from oxalate solution, then separation simplicity is improved, but additional reverse dissolution and secondary precipitation steps are required
Solution Approach 1:
The patent uses pH control to achieve selective precipitation of iron hydroxide from the oxalate solution. By adjusting pH to 8-10, iron is selectively precipitated while other metals remain in solution, avoiding mixed phase formation and eliminating the need for reverse dissolution and secondary precipitation steps.
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-purity iron compounds with at least 82% iron content, overcoming previous limitations by reducing silicon dioxide contamination and improving the efficiency of iron extraction and separation processes.
Implementation Method 1
treatment of the refuse with an aqueous solution of oxalic acid with subsequent magnetic separation whereupon the iron containing phase is separated from the silicate non-magnetic phase
Implementation Method 2
treatment of the refuse with an aqueous solution of oxalic acid whereupon the iron passes into a soluble form
Implementation Method 3
adding continuously a 3-5% hydrogen peroxide solution to convert the divalent iron oxalate into a trivalent iron oxalate
Implementation Method 4
the oxalate solution obtained after the separation of the solid silicate phase is directed to a precipitator wherein it is mixed with an alkali hydroxide solution
Implementation Method 5
thermal treatment till its transformation into iron oxide or hydrated hematite
Data Source
AI summary
The method comprises the following steps: (a) Preliminary wet magnetic separation to separate the iron containing phase from the silicate non-magnetic phase; (b) Mixing the iron containing phase with 5-10% of aqueous alkali hydroxide at 45-100°C for 1-3 hours and separation of the iron containing phase as a pulp; (c) Leaching by treatment of the iron containing pulp of step (b) with hot 12-15% aqueous oxalic acid at continuous stirring and heating to 95°C for 1-3 hours adding continuously 3-5% of hydrogen peroxide solution; (d) Mixing of the oxalate solution of step (c) with an aqueous alkali metal hydroxide at 20-25° and pH 7-12, allowing it to stay for 1-2 hours; (e) Mixing the filtrate of step (d) with an aqueous alkali hydroxide at pH at least 12 and heating to 55-60°C for 1 hour.