The effects of ion identity and ionic strength on the dissolution rate of a gibbsitic bauxite

Mogollón, J.L.; Pérez-Diaz, Alberto; Mónaco, Salvador Lo

doi:10.1016/s0016-7037(99)00351-8

Cited by 26 publications

(22 citation statements)

References 32 publications

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“…The previous study had measured the average residence time at each flow rate in the flow through packed bed reactor after having put mineral particles in the vessel (Zhang et al 1992). This kind of experimental system has been used to perform kinetic experiments previously, or it is called column experiment (Cama et al 1999;Hellmann 1995;Hellmann et al 1989;Mogollon et al 1996Mogollon et al , 2000Weissbart and Rimstidt 2000;Zhang and Hu 1996;Zhang et al 1990aZhang et al , b, 2000Zhang et al , 2002.…”

Section: Apparatusmentioning

confidence: 99%

Dissolution Kinetics of Dolomite in Water at Elevated Temperatures

Zhang

et al. 2007

Aquat Geochem

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Kinetic experiments of dolomite dissolution in water over a temperature range from 25 to 250°C were performed using a flow through packed bed reactor. Authors chose three different size fractions of dolomite samples: 18-35 mesh, 35-60 mesh, and 60-80 mesh. The dissolution rates of the three particle size samples of dolomite were measured. The dissolution rate values are changed with the variation of grain size of the sample. For the sample through 20-40 mesh, both the release rate of Ca and the release rate of Mg increase with increasing temperature until 200°C, then decrease with continued increasing temperature. Its maximum dissolution rate occurs at 200°C. The maximum dissolution rates for the sample through 40-60 mesh and 60-80 mesh happen at 100°C. Experimental results indicate that the dissolution of dolomite is incongruent in most cases. Dissolution of fresh dolomite was non-stoichiometric, the Ca/Mg ratio released to solution was greater than in the bulk solid, and the ratio increases with rising temperatures from 25 to 250°C. Observations on dolomite dissolution in water are presented as three parallel reactions, and each reaction occurs in consecutive steps aswhere the second part is a slow reaction, and also the reaction could occur as follows:The following rate equation was used to describe dolomite dissolution kineticswhere Rr ij refers to one of each reaction among the above reactions; k ij is the rate constant for ith species in the jth reaction, a i stands for activity of ith aqueous species, n is the stoichimetric coefficience of ith species in the jth reaction, and define n ¼ n ij .The experiments prove that dissolved Ca is a strong inhibitor for dolomite dissolution (release of Ca) in most cases. Dissolved Mg was found to be an inhibitor for dolomite dissolution at low temperatures. But dissolution rates of dolomite increase with increasing the concentration of dissolved Mg in the temperature range of 200-250°C for 20-40 mesh sample, and in the temperature range of 100-250°C for 40-80 mesh sample, whereas the Mg 2+ ion adsorption on dolomite surface becomes progressively the step controlling reaction. The following rate equation is suitable to dolomite dissolutions at high temperatures from 200 to 250°C.where Àr Ca 2þ refers to dissolution rate (release of Ca), m Ca 2þ and m Mg 2þ are molar concentrations of dissolved Ca and Mg, k ad stands for adsorption reaction rate constant, K Mg refers to adsorption equilibrium constant.At 200°C for 40-60 mesh sample, the release rate of Ca can be described as:Àrðmol m À2 s À1 Þ ¼ 0:55 Â 10 À4 ðm Ca Þ À0:36 þ 0:135 Â 10 À4 ðm Mg Þ=ð1 þ 0:14 m Mg Þ

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Section: Apparatusmentioning

confidence: 99%

Dissolution Kinetics of Dolomite in Water at Elevated Temperatures

Zhang

et al. 2007

Aquat Geochem

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“…Thus effects on dissolution rate may be related to both the pH and the identity of the anions present. Mogollon et al (2000) found a catalytic effect of SO 4 2Ϫ on the dissolution rate of natural gibbsite, whereas Ganor et al (1999) and Mogollon et al (2000) reported an inhibitory effect of chloride, nitrate, and perchlorate on gibbsite dissolution rates. In the presence of PO 4 3Ϫ , dissolution rates are almost independent of pH (Bloom and Erich, 1987).…”

Section: Introductionmentioning

confidence: 99%

The dissolution rates of gibbsite in the presence of chloride, nitrate, silica, sulfate, and citrate in open and closed systems at 20°C

Dietzel

Böhme

2005

Geochimica et Cosmochimica Acta

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“…There are also reports on an increased rate of surface protonation and hence an enhanced dissolution rate with increasing ionic strength of the solution. The surface charge of the oxides and hydroxides has been reported to increase with increase in ionic strength (Mogollon et al, 2000). Consequently, the results from this study indicate that the ionic strength effects on dissolution rate of clay (R Al ) are obvious only at pH 4 probably due to the effect of I on DG r and not due to the primary kinetic effect.…”

Section: Effect Of Ph and Ionic Strength On Clay Dissolution Ratementioning

confidence: 53%

“…It is also important to mention here that the effect of experimental parameters such as ionic strength becomes visible when the dissolution occurs in close to equilibrium conditions e.g. experiments at pH 4 in this study (Mogollon et al, 2000). The Fe/Si ratios were slightly higher than the original clay in the pH range 1-3, and generally lower than the original clay for the experiments at pH 4.…”

Section: Stoichiometry Of Clay Dissolution At Steady Statementioning

confidence: 60%