Alteration of compacted bentonite by diffusion of highly alkaline solutions

Fernández, Raúl; Mäder, Urs; Rodríguez, Manuel Pozo; Villa, Raquel Vigil de la; Cuevas, Jaime

doi:10.1127/0935-1221/2009/0021-1947

Cited by 67 publications

(25 citation statements)

References 36 publications

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“…Therefore, red mud addition to soils produces an unintended alkaline extraction liberating organic matter to solution. Along with clay mineral dissolution (Fernandez et al 2009;Deng et al 2006) and sorption reactions (Konan et al 2012), the reaction of alkalinity with natural organic matter will therefore be one of the main short term mechanisms for pH buffering in red mud / soil mixtures. Also, at higher red mud loadings, where alkalinity may be present in excess, the supply of extractable organic matter may limit DOC concentrations.…”

Section: Resultsmentioning

confidence: 99%

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

Lehoux

Lockwood

Mayes

et al. 2013

Environ Geochem Health

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Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e. proportional to red mud addition, of up to 4 pH units (e.g. pH 7  11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon (DOC) and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33% w/w); experiments using this soil also had much lower aqueous Al, As, and V concentrations. Gypsum addition to soil / red mud mixtures, even at relatively low concentrations (1% w/w) was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca 2+ supplied by the gypsum with OH -and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for treatment of red mud affected soils. The observed inhibition of trace metal release within red mud affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long term increases in soil salinity.g

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Section: Resultsmentioning

confidence: 99%

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

Lehoux

Lockwood

Mayes

et al. 2013

Environ Geochem Health

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“…The objective was to detect any uptake of K + / Na + and Ca 2+ during the experiments against a background of Mg 2+ in the exchange and to facilitate the formation of reaction by-products due to the rapid precipitation of Mg phases under alkaline conditions. The detailed procedure is reported in Fernández et al (2009).…”

Section: Mg-homoionisation Of Febex Bentonitementioning

confidence: 99%

Geochemical constraints on the stability of zeolites and C–S–H in the high pH reaction of bentonite

Fernández

Rodríguez

Villa

et al. 2010

Geochimica et Cosmochimica Acta

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“…Clay host rock formations are favoured in the design of the geological disposal facility, which act to limit the ingress of groundwater and reduce the mobility of radionuclides. However, in the pore solution of Portland cements (PC), pH values of 13.5 or even higher are often encountered [1,2], which can lead to a local degradation of the clay-based barriers [3,4]. Cements with lower pH values help to improve the compatibility with the clay barrier and prevent the formation of an extended alkaline plume [5].…”

Section: Introductionmentioning

confidence: 98%