Reducing Iron Oxide Content in Phosphoric Acid Using Polyacrylates and Phosphonic Acids
Gustavo Paiva Ribeiro1, Sandra Cristina Dantas2, Eloízio Júlio Ribeiro1
1Faculdade de Engenharia Química, Universidade Federal de Uberlândia, Avenida João Naves de Ávila 2121, Bloco 1 K, Campus Santa Mônica, Uberlândia, Minas Gerais CEP 38408-144, Brazil.
ACS Omega
|January 8, 2026
Summary
Iron oxides in phosphoric acid reduce fertilizer quality. A diethylenetriamine penta (phosphonic methylene) (DTPMP) solution effectively removed iron oxides, improving the P2O5/Fe2O3 ratio by 59%.
Area of Science:
- Chemical Engineering
- Agricultural Chemistry
- Inorganic Chemistry
Background:
- Phosphoric acid is crucial for phosphate fertilizers, but iron oxide contaminants decrease fertilizer quality and value.
- Brazilian phosphate rocks, often from igneous sources, contain high iron oxide levels, posing processing challenges.
- Complete iron oxide removal during industrial concentration is unfeasible due to phosphate loss.
Purpose of the Study:
- To evaluate two compounds for removing iron oxides from phosphoric acid.
- To improve the quality of phosphoric acid produced from high-contaminant phosphate ores.
- To enable the utilization of phosphate rock concentrates with elevated contaminant levels.
Main Methods:
- Tested a polyacrylate/phosphonic acid mixture and a 60% diethylenetriamine penta (phosphonic methylene) (DTPMP) solution.
- Assessed iron oxide removal efficiency and impact on the P2O5/Fe2O3 ratio.
- Determined optimal reaction conditions: 55°C, 14h precipitation time, 5.57% DTPMP (w/w).
Main Results:
- The polyacrylate mixture showed limited effectiveness in contaminant removal.
- The DTPMP solution acted as an effective iron chelating agent.
- Fe2O3 content was reduced by 40%, and the P2O5/Fe2O3 ratio increased by 59%.
Conclusions:
- Diethylenetriamine penta (phosphonic methylene) (DTPMP) is an effective chelating agent for removing iron oxides from phosphoric acid.
- Optimized DTPMP treatment significantly enhances phosphoric acid quality for fertilizer production.
- This method offers a viable solution for processing high-iron phosphate ores, improving economic feasibility.
Related Concept Videos
04:01Factors Affecting Solubility
36.6K
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
36.6K
03:38Polyprotic Acids
31.7K
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
31.7K
01:23Titration of Polyprotic Acids with a Strong Base
2.8K
Titration of a polyprotic acid, which contains multiple ionizable protons, involves distinct dissociation steps, each with its own dissociation constant (Ka). Each successive Ka is weaker than the previous one. In the titration of a polyprotic acid like sulfurous acid with a strong base such as sodium hydroxide, the base first neutralizes the initial ionizable proton, forming an intermediate species (e.g., hydrogen sulfite ions). This step's titration curve resembles that of a weak...
2.8K
02:08Titration of a Polyprotic Acid
102.9K
A polyprotic acid contains more than one ionizable hydrogen and undergoes a stepwise ionization process. If the acid dissociation constants of the ionizable protons differ sufficiently from each other, then the titration curve for such polyprotic acid generates a distinct equivalence point for each of its ionizable hydrogens. Therefore, titration of a diprotic acid results in the formation of two equivalence points, whereas the titration of a triprotic acid results in the formation of three...
102.9K
01:17Carboxylic Acids to Primary Alcohols: Hydride Reduction
4.7K
Carboxylic acids, upon reaction with strong reducing agents such as lithium aluminum hydride followed by hydrolysis, undergo reduction to form primary alcohols.
4.7K
01:19Acid Halides to Alcohols: LiAlH4 Reduction
3.8K
Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
3.8K