Synthesis of oxygen-containing iron powders and water purification from iron ions by glow discharge of atmospheric pressure in contact with the solution

Abstract

The formation of precipitation under the action of a direct current atmospheric pressure discharge in air on an iron sulfate (II) solution, which was the cathode and anode, was studied. As turbidimetric kinetics measurements have shown, the process, which proceeds both in the cathode and in the anode, has two stages. At the first stage (slow), a colloidal solution is formed, which then (the second stage, faster) is destroyed with the formation of a flocculent precipitate. The characteristic process times for both stages were found depending on the discharge current, the increase of which led to an increase in the deposition rate. The deposition rate in the cell with a liquid cathode was higher than in the cell with a liquid anode. For this reason, the amount of precipitate formed in the cell with the liquid cathode was greater than in the cell with the liquid anode at the same treatment time. Particle sizes of colloidal solutions and sediments were determined by scanning electron microscopy and dynamic light scattering . The sizes of both colloidal particles and sediment particles for the liquid anode were significantly smaller than for the liquid cathode. X-ray diffraction analysis showed that the precipitations obtained are amorphous, and their calcination turns them into γ-Fe2O3. Based on the data of elemental analysis and others, the composition of micelles was proposed, which included Fe(OH)3, SO4–, and H2O. An analysis of the mechanisms of the processes showed that the most probable chain of transformations involves the oxidation of Fe2+ by HO2 and H2O2 molecules to Fe3+, which irreversibly reacts with OH– to form Fe(OH)3.

Plasma-solution synthesis of iron (III) oxide

“…From the expression SP = [Fe 3+ ]•[OH -]=3.8 •10 -38 it follows that at a concentration of [Fe 3+ ] = 5 mmol/l the pH of the solution will be 2.3. Also, according to the handbook [11], the beginning of the precipitation of iron(III) hydroxide corresponds to pH ~ 2.3, and the complete precipitation of the precipitate can be observed already at pH = 4.1. That is, in an acidic environment, iron(III) hydroxides and insoluble basic salts, especially iron III hydroxosulfates), should be formed.…”

“…The discharge current was varied from 30 to 70 mA. The setup scheme is described in more detail in [11].…”

Factors Governing the Formation of Oxygen-Containing Copper Powders in a Plasma-Solution System

“…We used aqueous solutions of copper (II) nitrate (analytical grade) with concentrations of 0.005 and 0.1 mol•L −1 . The experimental setup used in the study was described in detail elsewhere [14,15]. Briefly, the discharge cell was H-shaped, consisting of two identical parts, 100 ml in volume, connected through a cellophane membrane.…”

“…Thus, the treatment of solutions of metal salts (Cd 2+ , Zn 2+ , In 3+ ), whose cations are not strong reducing agents and do not have a variable valence, leads to the formation of the corresponding hydroxy compounds only in the liquid anode [15,24,25]. The treatment of salts of metals with variable valence (MnO 4− , Cr 2 O 7 2− , Fe 2+ ) results in their transformations both in the liquid cathode and in the anode [14,26,27]. Copper ions also have variable valence (Cu 2+ and Cu + ).…”

Increase of Productivity and Neutralization of Pathological Processes in Plants of Grain and Fruit Crops with the Help of Aqueous Solutions Activated by Plasma of High-Frequency Glow Discharge

“…An alternative approach is the activation of solutions using a high-frequency glow discharge in water vapor [ 15 , 16 , 17 ]. Glow discharge is a type of stationary self-sustaining electric discharge, which is formed at low pressure and low current.…”