Natural Monocrystalline Pyrite as Sensor for Potentiometric Redox Titrations. Part I. Titrations with Permanganate

Abstract

and As(III) with standard potassium permanganate solution, are presented. The titration end point (TEP) was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III) were carried out in HCl (1.2 M) and H 2 SO 4 solutions (0.1-4.5 M), whereas oxalate was determined in H 2 SO 4 (0.1-4.5 M). Iron(II) and hexacyanoferrate(II) were titrated in H 2 SO 4 and also in H 3 PO 4 solutions (0.1-4.5 M). The titrations of Mn(II) were performed in H 2 P 2 O 7 2-media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP) are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II) in H 3 PO 4 (240-330 mV/0.1 mL). Reversed titrations were also performed and accurate and reproducible results were obtained.

An electrochemical sensing approach for scouting microbial chemolithotrophic metabolisms

“…For 0.5K medium, this displacement is higher, due to a higher concentration of the oxidizing agent (the ferrous iron solubilized from the mineral plus the ferrous iron present on the medium). Previous studies have characterized these phenomena and they have linearized the response of E corr as function of the concentration of oxidizing agent [45].…”

Full-pattern analysis of time-of-flight neutron transmission of mosaic crystals

“…The diverse electric and magnetic properties and their interplay in pyrite type compounds have attracted much interest. In particular, the structural, optical, electronic and other properties of natural iron pyrite have been investigated by solidstate physicists and chemists for many years (Sato, 1985;Birkholz, 1992;Antonijevic et al, 2002). More recently, owing to their excellent light absorbing and electronic properties, the pyrite compounds have attracted an enormous amount of research attention in the field of photovoltaic materials (Schlegel & Wachter, 1976;Schieck et al, 1990), and the possible relation of the physical properties to chemical composition has been investigated by several authors (Ferrer & Sá nchez, 1992;Echarri & Sá nchez, 1974).…”

Natural mineral pyrite and analytical application thereof in precipitation titrations in non-aqueous solvents

“…17,18 Accordingly, it can be expected that pyrite behaves as an electrochemical sensor. Pyrite was used as an indicator electrode for acid-base titrations in non-aqueous media, 19 for precipitation titration in aqueous media, 20 and for redox titrations in nonaqueous solvents. 21 There are no literature data about its use in precipitation titrations in non-aqueous media.…”

“…If a sufficiently impenetrable layer of elemental sulfur was formed at the mineral surface, it would be suggested that this sulfur layer may passivate the surface to further oxidation by preventing the passage of oxidants to reach the surface. Antonijevic ´et al 20 performed potentiometric precipitation titration in aqueous media and they noticed that the pyrite electrode exhibited a smaller sensitivity than expected as a consequence of the formation of elemental sulfur on the mineral surface. McGuire et al 33 used perchloroethylene, methanol and hexane for the extraction of elemental sulfur from the sulfide mineral surface, due to its solubility in these solvents.…”