An-Najah Staff

Purification of agricultural soil from toxic organic contaminants using solar-driven photodegradation was studied in the present research. This type of degradation was based on the availability of sunlight as a major source of power, low cost catalyst, mild reaction conditions needed and possible photochemical degradation process. The aim of this work is to find an effective and a low cost processes to mineralize chlorinated hydrocarbons contaminating agricultural soils. The model contaminant studied here was 3- chlorophenol as a hazardous compound that may result from factories and house-hold dumped detergents.

The present study involved two scales: The laboratory scale for photodegradation of the contaminant and the pilot-plant scale. The optimum conditions for the photodegradation that resulted in the laboratory scale have been extended to pilot-plant scale. The effect of several factors, such as, concentration of the contaminant, irradiation time, concentration of the catalyst, pH value and the particle size of catalyst had been studied in the laboratory scale. The pilot-plant scale study for the photodegradation of contaminant at larger scale.

Two forms of the catalystswere used: the commercial zinc oxide (ZnO) and the nanoparticle sized ZnO which was prepared in the laboratory. UV-visible spectra, Photoluminescence spectra, XRD and SEM imaging wereall usedcharacterize both systems. Degradation percentage, turnover number, turnover frequency and quantum yield were calculated to assessthecatalyst efficiencies. The results of the laboratory scale assays showed an increase of the percentage of photodegradation with increasing the concentration of catalyst and irradiation time until certain limit. A decrease in the percentage of photodegradation with increasing the concentration of contaminant was observed. Acidic medium wasfound to be more suitable for the degradationthan basic medium. There was no significant difference betweenthepowder or spray forms ofthe catalyst. The results of the pilot- plant assay sat a certain concentration of the catalyst and the contaminant and the pH showed an increase in percentage of degradation with increasing time. These results have confirmed the laboratory results. GC- Mass Spectrophotometer was used to show the degradation products.