Impact of Organic Acid Addition on the Formation of Precipitated Iron Compounds

Abstract

In this work, acetic and citric acids were used along with ammonium chloride in the removal of iron from reduced Hatinh ilmenite. Iron removal was carried out at 70ºC, 4 liter/min of air flow rate, 7/1 of liquid/solid ratio and 0.5% NH<sub>4</sub>Cl as catalyst. After 9 hours, metallic iron was decreased from 30.3% in reduced ilmenite to 0.5% in synthetic rutile. The addition of 0.4% acetic acid into NH<sub>4</sub>Cl solution reduces removal time to 5 hours, residual metallic iron (RMI) was also 0.5%. The addition of 0.4% citric acid also reduces removal time to 5 hours, RMI was reduced to 0.33%. The rusting rate of metallic iron increased when acid concentration increased from 0.1 to 1%. The results indicated that acetic and citric acids could be used as additional catalysts along with NH<sub>4</sub>Cl in the removal of metallic iron in reduced ilmenite. The acid have the capability to form complexes with iron and also showed impact on the formation of precipitated iron compounds.

Acetic Acid and Sodium Acetate Mixture as an Aeration Catalyst in the Removal of Metallic Iron in Reduced Ilmenite

“…On the other hand, after 6 h of leaching at 50ºC, residual metallic iron was still above 5.0 %. A similar spread in results across the temperature ranges was found for aerations based on ammonium chloride [10] Reaction rates appear to be the only major difference between the 2 catalysts, the AASAM slurry required only 6.0 h of aeration to reach the same stage of completion as ammonium chloride in 9.0 h…”

“…Reduced ilmenite was prepared following the experimental procedure described in previous work [10,15], the compositions were given in Table 1. In a typical aeration experiment, 40g of reduced ilmenite were added to 280 ml of the reaction solution.…”

“…At L/S ratio equal to 7, most of metallic iron (98%) has been successfully rusted. Generally, low L/S ratio is used in industrial aeration for saving ammonium chloride and also reduced equipment capacity [10]. In that case, aeration time was extended to ensure the removal of metallic iron.…”

“…The possibility of combining acetic acid and sodium acetate as a catalyst also investigated. The choices of acetic acid were based on its potential to assists iron rusting [10]. Meanwhile, sodium acetates provides addition acetate ion to the aeration solution.…”

Soluble Catalysts for the Oxygen Reduction Reaction, and Their Application to Becher Aeration

“…In the scientific literature, a few compounds that form coordination complexes with iron have been tested to see if they can accelerate Becher aeration or influence the phase composition of the iron­(II,III) oxide hydroxides formed. These test compounds include organic acids such as acetic, tartaric, and citric acids; − multidendate ligands such as ethylenediammonium dichloride; various phenolic and aldehydic compounds such as pyrogallol, saccharin, starch, and formaldehyde; and sugars such as glucose and sucrose . One group has even suggested the addition of ferrous chloride .…”