Figueiredo, M. Ondina

Silva, Teresa

Repositório do LNEG

Geophysical Research AbstractsVol. 12, EGU2010-8973, 2010EGU General Assembly 2010© Author(s) 2010Secondary iron sulphates in AMD: a minerochemical analysis on jarositesupporting the valorization of its geoenvironmental contributionTeresa Silva and Maria-Ondina FigueiredoINETI/LNEG, Unity of Mineral Resources and Geophysics, Apartado 7586, 2721-866 Amadora, Portugal(teresa.pena@ineti.pt)Currently, iron sulphates formed in abandoned sulphide-ore mines have a very negative connotation within acidmine drainage (AMD) because in general these secondary hydroxilated and/or hydrated minerals concentratea large span of toxic elements. However, this apparently penalizing feature may occasionally turn out to be apositive contribution, once sequestering such elements under the form of stable minerals significantly reducestheir spread in soils and rivers, as occurs for jarosite in what concerns lead.The application of an exergetic analysis to resources consumption and sustainability assessment [1] provides ameans of evaluating the degradation of mineral resources on Earth and a life cycle assessment (LCA) recentlyperformed on some secondary iron sulphates has emphasized their exergetic contribution [2]. With the purpose offurther exploring this positive aspect, and focusing on jarosite, a synopsis is presented on the structural featuresand geochemical tendencies of secondary iron sulphates liable of being exploited to promote their possible role.Jarosites (s.l.) - with general formula AB3(OH)6(SO4)2, where A is mainly K+, Na+, plus minor Ag+, Tl+,NH4+, Pb2+, Bi3+, and B is essentially Fe3+ (jarosite s.s.) or Al3+ (alunite) - have a trigonal crystal structure[3] and display Kagomé-type layers of corner-sharing B octahedra, [Fe/AlO2(OH)4], that give rise to uniquemagnetic properties [4]; the large cation A stays in pseudo-icosahedral coordination by 6 O-atoms from [SO4]tetrahedra and 6 hydroxyls shared with A octahedra [5].A synopsis is presented on the crystal-chemistry and geochemical tendencies of jarosite and the geochemistryof sediments in the abandoned mine of S. Domingos (southern Portugal, Iberian Pyrite Belt of polymetallicsulphide ores), is briefly described to illustrate the positive environmental role of jarosite as energy-saver withinthe particularly aggressive environment of abandoned sulphide-ore mines.[1] B. de Meester et al. An improved calculation of the exergy of natural resources for exergetic life cycleassessment (ELCA). Environ. Sci. Technol. 40 (2006) 6844-6851.[2] M.O. Figueiredo, T.P. Silva & J. Mirão (2007) How does the uptake of lead along acid mine drainage processesaffect the chemical exergy of jarosite in Exergetic Life Cycle Assessment (ELCA)? IEEES-3, 3rd Internat. Energy,Exergy & Environment Symp. (2007), CD-ROM, 4 pp., Edt. A.F. Miguel et al. (ISBN 978-989-95091-1-5).[3] B. Hendricks. The crystal structure of alunite and jarosite. Amer. Inst. Min. Metallurg. Engr. Technical Publ.22 (1937) 773-784.[4] A.S. Wills et al. Magnetic properties of pure and diamagnetically doped jarosites: model kagomé antiferro-magnets with variable coverage of the magnetic lattice. Phys. Rev B 61 (2000) 6156-6169.[5] S. Menchetti & C. Sabelli. Crystal chemistry of alunite series: crystal structure refinement of alunite andsynthetic jarosite. Neues Jahrb. Miner. Monatsch. Heft 9 (1976) 406-417.

Secondary iron sulphates in AMD : a minerochemical analysis on jarosite supporting the valorization of its geoenvironmental contribution [Abstract]

http://repositorio.lneg.pt/bitstream/10400.9/1200/1/34305.pdf

Secondary iron sulphates in AMD : a minerochemical analysis on jarosite supporting the valorization of its geoenvironmental contribution [Abstract]

Abstract

Similar works

Full text

Available Versions

Repositório do LNEG