Oxidative degradation of hydrocortisone in presence of attapulgite

Role of Ferric Iron in the Oxidation of Hydrocortisone by Sepiolite and Palygorskite

“…The hydrocortisone-clay interactions were carried out in an aqueous medium as described earlier (Cornejo et al, 1980;Hermosin et al, 1981). The quantity of hydrocortisone adsorbed by the clays was measured by the decrease in the intensity of the UV absorbance of the supernatant liquid at 254 nm after centrifuging to separate the clay.…”

“…The quantity of hydrocortisone adsorbed by the clays was measured by the decrease in the intensity of the UV absorbance of the supernatant liquid at 254 nm after centrifuging to separate the clay. High-pressure liquid chromatography (HPLC) was also used to measure the amount of hydrocortisone degraded by the clays (Cornejo et al, 1980;Hermosin et al, 1981).…”

“…Palygorskite has been shown to cause oxidation of hydrocortisone, and structural Fe z+ and surface-ad- sorbed free iron oxides have been suggested as possible sources of its reactivity (Cornejo et al, 1980). The ESR spectra in Figure 1 show that both of these components are present in palygorskite.…”

“…Both signals are weaker in sepiolite than in palygorskite and depend on the amount of total iron in the clays. These values for sepiolite and palygorskite are 3.2 mg/g and 26.6 rag/g, respectively (Cornejo et al, 1980;Hermosin et al, 1981). The low iron content of sepiolite minimizes the possiblity of electron-electron interactions arising from neighboring paramagnetic ions in the structure.…”

“…It has been shown that Fe z+ is the principal source of oxidizing action of the surface of palygorskite (Miller et al, 1964). This fact has been checked in a study of the oxidation of hydrocortisone in the presence of that clay (Cornejo et al, 1980). As sepiolite generally contains less iron than palygorskite, its effect on the oxidative degradation of hydrocortisone is much smaller than that of palygor-4 Present address: Centro de Edafologia y Biologia Aplicada del Cuarto, C.S.I.C., Apartado 1052, Sevilla, Spain.…”