MARC全文
02h0025387 20110919105716.0 cr un||||||||| 110919s2002 xx ||||f|||d||||||||eng | AAI3038068 0493516824(ebk.) : CNY371.35 NGL NGL NGL a332 ; a875 Bostick, Benjamin Carlos. Characterization of ion sorption on metal sulfide minerals using macroscopic and spectroscopic approaches [electronic resource] / Benjamin Carlos Bostick. 2002. 234 p. : digital, PDF file. Source: Dissertation Abstracts International, Volume: 63-01, Section: B, page: 0155. ; Adviser: Scott Fendorf. Thesis (Ph.D.) -- Stanford University, 2002. Sulfide minerals commonly form in anoxic environments, often sorbing trace elements. The mechanism of such sorption is a critical factor in determining their transport and fate in the environment. Consequently, this research examines the sorption of three such elements, arsenic, molybdenum, and zinc on sulfide mineral suspensions and in soils subject to periodic reduction. Arsenite sorption to sphalerite (ZnS), galena (PbS), amorphous iron sulfide (FeS), and pyrite (FeS2) was investigated as a function of solution composition and using X-ray absorption spectroscopy (XAS). Sorption to each followed a Langmuir isotherm, and increased sharply above pH 5 to 6. Spectroscopic investigation revealed that a large change in arsenic coordination accompanied sorption on sulfide minerals. An As3S3(SH)3-type surface complex was formed on ZnS and PbS, while As(III) was reduced to As(-I) on FeS and FeS2 and a surface precipitate similar in structure to FeAsS was formed. This surface precipitate was also formed upon arsenite sorption to estuarine soils from Pescadero, California, although it was partially converted to orpiment over time. Importantly, arsenite was irreversibly retained on each of these sulfide minerals except PbS; thus, arsenic will likely be stable in sulfidic, anoxic environments. However, oxidation may release arsenic in these systems.;Other ions react in distinct manners. Molybdate and tetrathiomolybdate are most strongly retained to pyrite under acidic conditions. Molybdate formed a weak bidentate-mononuclear sorption complex on FeS2 that was reversibly adsorbed while tetrathiomolybdate adsorption was irreversible and it formed a Mo-Fe-S cubane on the FeS2 surface, in which the Mo is triply coordinated to surface-bound sulfur atoms. Zinc was often sequestered in a contaminated wetland as ZnS, ZnCO3, ZnO and Zn adsorbed on (hydr)oxides. Zinc speciation was dynamic, responding to changes in overlying water depth. The fractions of ZnS and ZnCO3 were highest under flooded conditions, while adsorbed Zn species occurred predominantly under oxic conditions (dry or shallow water depths). Therefore, the dynamic nature of sulfidic environments needs to be considered when determining trace element partitioning. Environmental geochemistry. ; Sulfide minerals Absorption and adsorption. Electronic books. aeBook. aCN bNGL http://proquest.calis.edu.cn/umi/detail_usmark.jsp?searchword=pub_number%3DAAI3038068&singlesearch=no&channelid=%CF%B8%C0%C0&record=1 NGL Bs919 rCNY371.35 ; h1 bs1107
