Removal of organophosphorus insecticides from aqueous solution by adsorption on microporous pillared clays and mesoporous alumina aluminum phosphates

Al-pillared montmorillonite (ecaza), Fe-Al-pillared montmorillonite (ecfaza ) and mesoporous alumina aluminum phosphates (AAPs) were contacted with aqu eous solutions of organophosphorus insecticides, ethyl parathion, methyl pa rathion, fenitrothion and fenthion, at a concentration ranging between 1 an d 10 mg l(-1), in batch equilibrium experiments, in order to determine thei r adsorption properties. The removal of organophosphorus compounds by the a dsorbents increased in the following order: methyl parathion<fenitrothion<f enthion<ethyl parathion. In the case of ethyl parathion, the more lipophili c insecticide, the increased affinity allowed adsorption to occur much more efficiently than in the case of other compounds. At equilibrium ecaza mont morillonite adsorbed 96.4% of ethyl parathion, 92.3% of fenthion, 92.3% of fenitrothion and 87.6% of methyl parathion. The adsorption of selected orga nophosphorus insecticides on mesoporous AAPs was much less pronounced compa red to the two clays but increased with the ratio of P/A1, as the surface a cidity of those solids also increased. The AAP mixture with a ratio P/Al=0. 6 adsorbed 81% of ethyl parathion, 83.1% of fenthion, 39.8% of fenitrothion and 61.4% of methyl parathion. The amounts of insecticides decomposed duri ng the treatment increased in AAPs after 24 hours and especially in those w ith a higher P/Al ratio (=0.6) and reach 70.5% for ethyl parathion, 59.2% f or fenthion, 32.5% for fenitrothion and 54.8% for methyl parathion.