The Release of Aluminum from Aluminosilicate Minerals. II. Acid-Base Potentiometric Titrations

Cabrera, Francisco

doi:10.1346/ccmn.1979.0270206

Cited by 8 publications

(1 citation statement)

References 20 publications

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“…As aluminium oxides have PZNC similar to iron oxides, surface coatings of hydroxy-aluminium polymers on the permanently charged IL present in mixtures B and C would explain this behaviour. Van Raij & Peech (1 972), Laverdiere & Weaver (1 977) and Cabrera & Talibudeen (1978, 1979 also suggested the existence of strongly held aluminium blocking exchange sites on clay mineral surfaces.…”

Section: Results a N D Discussionmentioning

confidence: 99%

Charge properties of mixtures of minerals with variable and constant surface charge

Madrid

Díaz

Cabrera

1984

Journal of Soil Science

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Surface charge of mixtures of lepidocrocite and illite determined by adsorption of potential-determining and electrolyte ions is studied as a function of pH and NaCl concentration. Deviations between results obtained by both methods were a function of the illite content of the mixtures, and can be mainly attributed to coatings of hydroxyaluminium complexes on the constant charge surfaces of the clay mineral, which can react with H + ions or release exchange sites by precipitation of well-formed hydroxides. These coatings of aluminium complexes can cause H + consumptions similar to those due to lepidocrocite.Some ideas are put forward for modelling charge properties of mixed systems.

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Section: Results a N D Discussionmentioning

confidence: 99%

Charge properties of mixtures of minerals with variable and constant surface charge

Madrid

Díaz

Cabrera

1984

Journal of Soil Science

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Acid‐ and base titration behaviour of finnish mineral soils

Hartikainen¹

1986

J Plant Nutrition & Soil

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The acid‐ and base‐buffering properties of 84 non‐calcareous surface soil samples were studied by batch titration with HCI or KOH at a constant ionic strength of I = 0.1. The soil samples were classified according to their pH of zero point of titration (ZPT). Differential buffer values, dB(H) or dB(OH) (H+ or OH− as meq kg−1 needed to reduce or increase the soil pH sequentially by 0.5 units, respectively), were introduced to describe the course of titration curve and the intensity of buffer action. In all soils, the first acid‐buffer value, dB(H)0→0.5, varied from 8 to 78 meq kg−1 and the second one, dB(H)0.5→1, from 10 to 138 meq kg−1. The corresponding base‐buffer values, dB(OH)0→0.5 and dB(OH)0.5→1, ranged from 10 to 48 and from 14 to 44 meq kg−1, respectively. The most acid soils were most strongly buffered against acid, and the soils with the highest initial pH against base. The results reveal the acid‐buffering by exchange reactions to be very important. In the soils with ZPT≦5.4, the first acid‐buffer value was dependent on the content of organic matter and oxalate‐soluble Al, whereas in the more acid soils the role of clay became significant. Thus, it was concluded that at higher pHs the foremost inactivation of H+ is attributable to soil components of pH‐dependent charges, and the significance of constituents of permanent charges to increase with proceeding acidification. In strongly acid soils (ZPT≦4.8) the very effective buffering seemed to be primarily due to the dissolution of Al‐hydroxides and, thus, to exert detrimental effects on the edaphic environment. The general rank of soil factors explaining the variation in the base‐buffer values was in accord with the neutralization sequence, i.e. the strongest acid in the soil being neutralized first. In the strongly acid soils (ZPT≦4.8) the base‐buffer values seemed to depend on the clay as well as KCl‐ and NH4OAc‐extractable Al, whereas in the soils with higher initial pH mostly on organic C.

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