ADSORPTION AND DESORPTION OF MALEIC HYDRAZIDE AS A FUNCTION OF SOIL PROPERTIES

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Abstract
The relationships between maleic hydrazide (MH) adsorption and selected properties for 22 soils were studied by determining adsorption isotherms in aqueous media and calculating simple correlation coefficients among Kf values, from Freundlich equation isotherms, and the soil properties. The results of these correlations showed that MH adsorption by soils was essentially dependent upon specific surface area, clay content, and pH, but not organic matter content. When the soils were grouped according to their mineralogical components, MH adsorption-soil property relationships were shown to be dependent upon the soil clay mineralogy. For one group of soils with phyllosilicates as essential clay mineral components and free iron content (Fet) below 5%, MH adsorption was directly related to clay content and surface area, and the free iron oxides content (Fef) was inversely related to MH adsorption capacity. For a second group of soils with iron oxides and oxyhydroxides as essential clay mineral components and Fef > 5%, soil pH was the only variable related to MH adsorption. Desorption of MH from soils showed a hysteresis effect that was attributed partially to MH precipitation, or biodegradation, or both. © Williams & Wilkins 1987. All Rights Reserved.