Reactivity of Clay Minerals With Acids and Alkalies

Abstract

Abstract--One-g samples of a montmorillonite, a metabentonite, an illite, two kaolinites, and three halloysites were treated with 50 ml of hydrochloric acid (6-45 N, 1 : 1), acetic acid (4.5 N, 1 : 3), sodium hydroxide (2.8N), sodium chloride solution (pH 6.10; Na = 35%0; C1 = 21.5% 0), and natural sea water (pH 7.85; Na = 35.5%o; CI = 21.5%o) for a 10-day period in stoppered plastic vials. The supernatant solutions were removed from the clay minerals and analyzed for SiO2, A1203, CaO, MgO, Na~20, and K20. All the solutions removed some SiO2, A1~O3, and Fe203 from the samples, but the quantities were small. Sodium hydroxide attacked the kaolin group minerals more strongly than it did montmorillonite, metabentonite, or illite. Halloysite was more strongly attacked by hydrochloric acid than was any of the other experimental minerals. Hydrochloric acid removed iron oxide coatings from soil clay minerals, but acetic acid did not remove them completely. The samples most strongly attacked by HCI and NaOH were examined by X-ray diffraction. Acid treatment did not destroy the structure of the clays, but the halloysite structure was partially destroyed. Sodium hydroxide attacked the halloysite structure, as shown by chemical analysis and X-ray diffraction. These experiments show that treatment in dilute acids has no harmful effect in the preparation of clays for X-ray diffraction. Acetic acid is preferred to hydrochloric acid for this purpose. Hydrochloric acid cleans clay minerals by removing free iron oxide from the surface; acetic acid is less effective.

Integrated investigations on the adsorption mechanisms of fulvic and humic acids on three clay minerals

“…The homoionic clay minerals were freeze-dried and kept in a desiccator for later use. Homoionic Fe 3+ -vermiculite was prepared by sequential washing of the original vermiculite with 1 mol/L FeCl 3 [17], and partially de-iron-vermiculite was prepared by washing of the original vermiculite with 2 mol/L HCl to remove iron oxide from the vermiculite surface [18]. Then the excess FeCl 3 and HCl were removed in the same way as described above.…”

“…Then the excess FeCl 3 and HCl were removed in the same way as described above. The researches have shown that these treatments only slightly affect the crystal structures of clay minerals [17,18].…”

Paleoenvironmental controls on mineral assemblages in a shelf sequence: Te Kuiti Group, South Auckland, New Zealand

“…The nature of mineral components was recorded during petrographic examination of over 1000 thin sections of Te Kuiti Group rocks (Nelson 1973). Insoluble residues were prepared by digestion of samples in 4M acetic acid, known not to alter clay minerals (Ray et al 1957: Carroll & Starkey 1971. Heavy minerals were concentrated from the very fine and fine insoluble sand fractions by sedimentation through tetrabromoethane (sp.…”

X Ray and Inductively Coupled Plasma Atomic Emission Spectroscopy Analysis of Cristallographic Structure And Composition of Pavement Based Clay Materials

“…It was found [4] that waste wood incorporating in clay make it highly acidic, according. Dorothy Carroll et al [14] have shown that the acid attach has an influence in clay structure. The lattice constant expansion must be interpreted in acid reaction.…”