REACTIONS BETWEEN FULVIC ACID AND Cu 2+-MONTMORILLONITE*

Abstract-Shaking of water-soluble fulvic acid with Cu~+-montmorillonite at pH 2.5 increased the interlamellar spacing from 10.0 to 15 ' 1 A. The spacings were measured at ~ 0 % relative humidity. The extent of interlayer adsorption decreased with increase in pH. Differential thermal analysis and thermogravimetric examinations showed that in addition to interlayer adsorption, fulvic acid was also retained on external clay surfaces. The FA was held so tightly by the Cu~+-clay that> 3/4 of the total amount adsorbed, including degradation products formed from it, resisted ecomposition even when heated to 1000 ~ I.R. spectra showed that fl-diketone groups in fulvic acid reacted with Cu z+ in or on the clay to form acetylacetonate-type ch lates. Indications were obtained that the mechanism postulated for the FA-Cu~+-clay interaction may also apply to reactions between FA and mont-morillonite saturated with other di- and trivalent metal ions. Reactions of FA in aqueous solutions with metal ions in the presence of clays differ from those in the absence of clay. Montmorillonite appears to affect he conformation f the fulvic acid polymer in a way that favours reactions between C=O groups and metal ions, a type of reaction that has so far not been observed inaqueous olutions in the absence of clay