Reactions between boron and clays

Abstract

Sorption of boron by Kent sand kaolinite, WilIalooka illite, and Marchagee montmorillonite in 0.01M CaCl2 is consistent with a mechanism described by the Langmuir equation, except that deviations occur at solution concentrations greater than about 10 �g B/ml. The quantity of boron adsorbed increases markedly with pH, and is rapid, reversible, and unaffected by the concentration of calcium chloride present. Complete desorption of surface boron, without significant solution of lattice boron, is achieved with 0.01M mannitol solution. Comparing the three clays at pH 7.5 on a surface area basis, the illite is most reactive (1.18 �g B/m2), followed by the kaolinite (0.28 �g B/m2) and the montmorillonite (0.02 �g B/m2). For illite, which is the most reactive of the three minerals, the magnitude of the above values emphasizes the small proportion (less than 1.4%) of the total surface area occupied by boron. Consideration of the reaction between boron and clays suggests that either boric acid molecules or borate ions could be the adsorbed species. Increasing sorption with pH could be explained either by the increasing proportion of borate ions to boric acid with pH or by a greater number of sites on the clay surface at higher pH values.

Surface complexation model of boron adsorption by calcareous soils

“…Hingston (1964) found that the treatment of illite with CaCO 3 at the rate of 2 % resulted in decreasing B sorption capacity at pH 7.5 and 8.3; however, addition of CaCO 3 at pH 9.5 did not significantly influence B sorption when compared to untreated illite at pH 8.5. Ichikuni and Kikuchi (1972) suggested that B sorption on CaCO 3 can likely occur through precipitation of low-solubility calcium borate, B replacement with carbon in CaCO 3 , and adsorption of B on CaCO 3 surfaces.…”

Boron Deficiency in Soils and Crops: A Review

“…. In fact, kaolinite adsorbs B the least (Hingston, 1964;Fleet, 1965). Frederickson & Reynolds (1959) proposed that most of the B in the clay mineral fraction of sedimentary rocks is contained in the illite fraction.…”

Studies on the Adsorption of Boron on Humic Acids

“…In early studies by Olson humus, values that were much higher than and Berger (1946), destruction of soil organic reported for B retention by clay minerals and matter by oxidation led to significant release whole soils (Hingston 1964; of B in plant-available form, and caused a O'Connor 1982;Evans 1987 x,x*Significant at P : 0.05 and P = 0.01, r$pectively. (Hatcher et al .…”

“…Sposito (1984) has also emphasized the value of spectroscopic methods for examining adsorption mechanisms. NMR (Knoeck and Taylor 1969) and spectrophotometric (Wildes and Neales 1969) 7.5 and, for B concentrations from 0 to 0.7 mol m-3 (Hingston 1964 Evans (1987).…”