عنوان مقاله [English]
Limited information is available about the influence of organic acids on dissolution of fibrous clay minerals especially in saline conditions. A laboratory experiment was set up with a completely randomized design and factorial arrangement in three replications to identify the influence of studied parameters on release of magnesium, silicon, and aluminum from sepiolite and palygorskite minerals. Treatments included two types of mineral (sepiolite and palygorskite), two organic acids (citric, oxalic) and a control, and four salinity levels (0, 6, 12 and 24 dS/m). The concentrations of released elements were measured by atomic absorption spectrometry. Results showed that the amount of released elements is highly affected by the type of organic acids, salinity, and type of mineral. Among the organic acids, the amount of Mg and Al released from sepiolite and palygorskite in citric acid treated samples were greater than those from oxalic acid samples. However, oxalic acid was found to be more effective for extraction of Si from the minerals. With increasing salinity, the release of all elements was increased, however; in presence of organic acids the amount of released elements was reduced comparing with non-saline conditions. Moreover, the results illustrated that the ratio of released Si/(Al+Mg) in sepiolite samples was higher than palygoقskite, suggesting that sepiolite is less stable than palygorskite and is much more weathered under the conditions studied.