A new organophosphorus insecticides removal process using fly ash

Fly ash and soil mixtures with a range of fly ash content from 1 to 100% we re used to study adsorption and desorption of four organophosphorus insecti cides, ethyl parathion, methyl parathion, fenitrothion and fenthion, in bat ch experiments. The object of the study was to develop a treatment process using fly ash as sorbent material to isolate/immobilize organic contaminant s from aqueous solutions. The adsorption isotherms fit the Freundlich equat ion x/m=KdC1/n. The K-d values increase with the increase of the fly ash co ntent. The isotherms seem to fit the S type, in mixtures of soil with a fly ash content from 0 to 10%, which implies that adsorption becomes easier as the concentration in the liquid phase increases. In mixtures of soil with a fly ash content from 25 to 50% the isotherms become L type and correspond to a decrease of site availability as the solution concentration increases . Finally in mixtures of soil with a fly ash content over 50%, C type adsor ption was observed which correspond to a constant partition of the insectic ides between the bulk solution and the adsorbent. Mass balance estimations show that the mean percent amounts of insecticides for a range of concentra tion 0.5-15 mg/l, removed by adsorption in the soil sample are 81.56% for e thyl parathion, 48.97% for methyl parathion, 67.06% for fenitrothion and 86 .65% for fenthion. The adsorption increases as the fly ash content increase d and reach the 100% in the "pure" fly ash. The adsorbed amounts of insecti cides in mixtures of soils with >50% fly ash content, are up to 99%. In con trast, the amounts of desorption in water decrease as the fly ash content i ncrease. The results of this research demonstrate that the fly ash shows a significa nt capacity for adsorption of organophosphorus compounds from aqueous solut ion and can be used for pesticide removal process.