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The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. [1]
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The δ 34 S value, recorded by sulfate in marine evaporites, can be used to chart the sulfur cycle throughout earth's history. [ 7 ] [ 4 ] The Great Oxygenation Event around 2,400 million years ago altered the sulfur cycle radically, as increased atmospheric oxygen permitted an increase in the mechanisms that could fractionate sulfur isotopes ...
[4] [5] [6] The CALPHAD approach is based on the fact that a phase diagram is a manifestation of the equilibrium thermodynamic properties of the system, which are the sum of the properties of the individual phases. [7] It is thus possible to calculate a phase diagram by first assessing the thermodynamic properties of all the phases in a system.
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Sulfur is present in the environment in solids, gases, and aqueous species. Sulfur-containing solids on Earth include the common minerals pyrite (FeS 2), galena (PbS), and gypsum (CaSO 4 •2H 2 O). Sulfur is also an important component of biological material, including in the essential amino acids cysteine and methionine, the B vitamins ...
Simplified diagram of the Hybrid sulfur cycle. The hybrid sulfur cycle (HyS) is a two-step water-splitting process intended to be used for hydrogen production.Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (instead of a thermochemical) reaction for one of the two steps.
During the reduction half-cycle of the stochiometric cycle, the metal oxide is reduced and forms a new metal oxide with different oxidation states (Fe 3 O 4 → 3FeO + 1/2 O 2); a non-stochiometric cycle's reduction of the metal oxide will produce vacancies, often oxygen vacancies, but the crystal structure remains stable and only a portion of ...