High Purity Iron Oxide Preparation via Sequential Purification
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Solution Overview
Problem
Current methods for producing high-purity iron(III) oxide from hydrochloric acid solutions containing iron chloride result in impurities like NiO and alkali components, with challenges in achieving the desired purity levels and minimizing costs and equipment expenditure, particularly in industrial-scale processes.
Innovation Solution
A process involving the reduction of free acid concentration, electrolytic cementation of heavy metals, precipitation using flocculants and sulfur-containing compounds, and thermal decomposition to produce high-purity iron(III) oxide with minimal NiO and alkali content, utilizing existing systems and reducing waste, while maintaining low manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pyrohydrolysis methods are used to produce iron(III) oxide, then the production process is simple, but the purity of iron(III) oxide is insufficient with high NiO content
Solution Approach 1:
The purification process is divided into multiple sequential steps: step i) reduces free acid concentration, step ii) removes heavy metals by electrolytic cementation, step iii) precipitates heavy metal and Si components using flocculants, step iv) precipitates remaining Ni components using sulfur-containing compounds, and step vi) performs thermal decomposition. This segmentation allows each step to target specific impurities, achieving high purity (≥99.50% Fe2O3, NiO ≤0.013%) while managing process complexity through systematic organization.
Solution Approach 2:
The process selectively extracts and removes specific impurities from the hydrochloric acid solution containing iron chloride. Heavy metals are extracted via electrolytic cementation, Si components are extracted through flocculation precipitation, and Ni components are extracted using sulfur-containing compounds. This targeted extraction approach removes impurities without affecting the iron chloride, enabling high-purity iron(III) oxide production.
2Manufacturing precision
If multiple purification steps are added to increase purity, then impurity content decreases, but manufacturing costs increase
Solution Approach 1:
The process utilizes parameter changes to achieve purification at low cost. Step i) changes the concentration parameter by reducing free acid concentration. Steps iii) and iv) change the pH value parameter to control precipitation of different impurities. These parameter adjustments use inexpensive reagents and existing equipment, achieving high purity (≥99.50% Fe2O3) without significantly increasing manufacturing costs.
3Manufacturing precision
If conventional purification methods are used, then the process is simple, but alkali components contaminate the iron(III) oxide
Solution Approach 1:
The process converts the potentially harmful effect of pH adjustment into a beneficial purification mechanism. By carefully controlling pH value changes during precipitation steps, the process selectively precipitates impurities (heavy metals, Si components, Ni components) while keeping iron in solution. The pH adjustments are designed to precipitate contaminants without introducing alkali components into the final product, achieving high purity iron(III) oxide with Na2O <0.008% and K2O <0.001%.
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 iron(III) oxide with a purity of at least 99.50% Fe2O3 and a maximum NiO mass fraction of 0.013%, effectively minimizing impurities and maintaining the system configuration, with reduced costs and environmental impact.
Implementation Method 1
reducing the concentration of the free acid in the hydrochloric acid solution containing iron chloride by adding a metal and/or a metal alloy
Implementation Method 2
deposition of heavy metals by electrolytic cementation
Implementation Method 3
precipitation of heavy metal components and/or optionally Si components using at least one flocculant
Implementation Method 4
addition of organic and/or inorganic compounds which have functional groups containing sulfur and precipitation of Ni components
Implementation Method 5
thermal decomposition of the filtrate containing or consisting of an iron chloride solution to iron (III) oxide and hydrogen chloride
Data Source
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AI summary
The invention relates to a process for producing iron(III) oxide from a hydrochloric acid iron chloride-containing solution comprising or consisting of the steps: i) reducing the concentration of the free acid in the hydrochloric acid iron chloride-containing solution; ii) deposition of heavy metals by electrolytic cementation; iii) precipitation of heavy metal components and/or optionally Si components; iv) precipitation of remaining Ni components; v) filtration of the dispersion; vi) thermal decomposition of the filtrate to iron(III) oxide and hydrogen chloride.