الفهرس 
Chapter One: IntroductionOnly 14 pages are availabe for public view
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Abstract
Its known that in acidic solutions the surfaces of photocatalysts are
positively charged this means that it cannot provide hydroxyl group
which are needed for hydroxyl radical formation. and the surface of
photocatalysis become negatively charged in alkaline solutions.
Predicting that degradation efficiency on the surface of alkaline
solution increased as this higher pH value can provide higher
concentration of hydroxyl ions to react with the holes to form hydroxyl
radicals in this work the effect of pH on methylene blue degradation
was studied by varying the pH from 2 to 12. Figure 3.30 showed that
at high pH12 degradation efficiency decreased to 85% and in acidic
medium degradation efficiency also decreased to 61% as in acidic
medium There was an increase in H+ concentration , adsorption of
cationic dyes will be low due to repulsive forces causing the reduction
of degradation efficiency (138,139) on the other hand in alkaline
medium the degradation of dyes is inhibited as the hydroxyl ions
compete with dyes molecules in adsorption on the surface of
photocatalysts[144] It was observed that the removal of dye by 1%
Cu2+/CdS was maximum at pH 6.5 to 7.5.