Iron Bicarbonate Research Articles

Atomic-Scale Studies of Fe3 O4 (001) and TiO2 (110) Surfaces Following Immersion in CO2 -Acidified Water.

Difficulties associated with the integration of liquids into a UHV environment make surface‐science style studies of mineral dissolution particularly challenging. Recently, we developed a novel experimental setup for the UHV‐compatible dosing of ultrapure liquid water and studied its interaction with TiO2 and Fe3O4 surfaces. Herein, we describe a simple approach to vary the pH through the partial pressure of CO2 (pCO2 ) in the surrounding vacuum chamber and use this to study how these surfaces react to an acidic solution. The TiO2(110) surface is unaffected by the acidic solution, except for a small amount of carbonaceous contamination. The Fe3O4(001)‐(2 ×2 )R45° surface begins to dissolve at a pH 4.0–3.9 (pCO2 =0.8–1 bar) and, although it is significantly roughened, the atomic‐scale structure of the Fe3O4(001) surface layer remains visible in scanning tunneling microscopy (STM) images. X‐ray photoelectron spectroscopy (XPS) reveals that the surface is chemically reduced and contains a significant accumulation of bicarbonate (HCO3 −) species. These observations are consistent with Fe(II) being extracted by bicarbonate ions, leading to dissolved iron bicarbonate complexes (Fe(HCO3)2), which precipitate onto the surface when the water evaporates.

STUDY OF CORROSION RESISTANCE OF SURFACE STRUCTURES FORMING ON LOW-ALLOYED STEEL SURFACE IN THE PRESENCE OF CATHOLYTE

The presence in the process fluid of oil fields of numerous corrosive agents, such as salt ions, dissolved gases, solids and microorganisms, provokes the destruction of oil and gas equipment. The greatest danger is acidic gases - carbon dioxide and hydrogen sulfide. Their simultaneous presence is especially dangerous. They are catalysts for the cathodic reaction of hydrogen depolarization of low alloy steel. In the presence of carbon dioxide and hydrogen sulfide, the formation of soluble corrosion products - iron bicarbonate - takes place. Therefore, one of the ways to prevent the development of electrochemical corrosion is the neutralization of acidic components of the process fluid. The main neutralizer in this case is a sodium hydroxide solution. However, the presence of sodium salts in oil can provoke a violation of the technological process of its further processing due to contamination of the resulting oil products and catalysts. In this regard, the development of a method for the non-reagent neutralization of acidic components of the technological environment of oil fields is an urgent task. The use of catholyte, a solution saturated with hydroxide ions, is proposed as a neutralizer of acidic components of the technological environment of oil fields. The research paper examined the principles of the formation of surface structures in the presence of catholyte. A comparative assessment of the corrosion resistance of iron hydroxide films in a reservoir water model obtained on low-alloy steel 09G2S in solutions of sodium hydroxide and catholyte is shown. The study made it possible to establish the effect of catholyte on the kinetics of corrosion, and also revealed the dependence of the corrosion rate of steel on the concentration of alkali and catholyte reagent at various pH values. Microscopic studies have shown that in the presence of catholyte a thinner (plastic) film is formed with high corrosion resistance and protective effect.

The resonance Raman spectrum of the metalloprotein ovotransferrin.

Using ovotransferrin it is shown that amino-acid side chains forming the metal binding site in coloured metalloproteins can be identified and monitored by resonance Raman spectroscopy. All major features above 800 cm−1 in the resonance Raman spectrum of iron–bicarbonate ovotransferrin could be assigned to histidine or tyrosine vibrational modes, by comparison with Raman and infrared data for these amino acids and related compounds. Comparison of the features due to ring modes of imidazole ligated to Fe3+ in ovotransferrin with those of aqueous histidine at pH 8.0 suggests that rearrangement of the ring π electrons takes place upon ligation. Although iron–bicarbonate and iron–oxalate ovotransferrin have similar visible absorption spectra, differences in their resonance Raman spectra are clearly distinguishable, but no evidence was found for the direct binding of bicarbonate or oxalate to the iron. Differences between the geometries of the two sites at which iron is bound in iron–bicarbonate ovotransferrin appeared to be small compared with the perturbation caused to these sites by replacing bicarbonate with oxalate.