Electrochemical study of orpiment (As2S3) dissolution in a NaOH solution

Crocoite PbCrO4 and mimetite Pb5(AsO4)3Cl: rare minerals in highly degraded mediaeval murals in Northern Bohemia

“…In alkaline conditions, the orpiment becomes less stable and tends to dissolve to thioarsenites (AsS 3 ) 3À and arsenites (AsO 3 ) 3À . [42] To oxidize trivalent arsenic and form thioarsenates (AsS 4 ) 3À and arsenates (AsO 4 ) 3À , the action of atmospheric oxygen is necessary.…”

A spectrophotometric study of the formation and deprotonation of thioarsenite species in aqueous solution at 22°C

“…Numerous other measurements of orpiment solubility have been reported (e.g. Lengke and Tempel, 2002;Floroiu et al, 2004;Darban et al, 2011) but these studies were not intended to provide detailed insight into the stoichiometry and stability of thioarsenite species.…”

Pretreatment of a refractory arsenopyritic gold ore using hydroxyl ion

“…The NaOHpretreated arsenopyrite shows a significant increase in reactivity. Because the arsenopyrite oxidation process is associated with realgar (As 2 S 2 ) and orpiment (As 2 S 3 ) (Lin and Zheng, 1996;Lázaro et al, 1997), the increased reactivity observed can possibly be associated with the formation of an arsenic ionic species during the oxidative process of As 2 S 3 (Darban et al, 2011).…”

“…It is important to note that the arsenic extraction decreases more dramatically than gold recovery. Darban et al (2011) reported that in the dissolution of orpiment, hydroxyl ions can be adsorbed onto the As surface sites and weaken the bond between the sulfur and arsenic with the possible generation of new chemical species. With the formation of arsenic oxyanions in the alkaline solution due to hydrolysis of arsenic, the species produced (ionic in nature) are released into the solution and are stabilized by dipole-charge interactions with the aqueous phase media.…”