Although some formulations (out of 28) presented very slow decomposition rate of
methyl orange, others were rapid, but they left behind porous TiO2 skeleton that are suitable for long-term and high-speed photocatalytic applications.
It is clearly concluded that the obtained ZnO nanocatalysts represent an excellent candidate with the commercial ZnO catalyst with high catalytic activity in the degradation of the
methyl orange dye (MO) as well as paraquat herbicide.
It is evident that
methyl orange is better adsorbed than Eriochrome Black T.
0.5 g CA0, CA1, CA2, CA3, CA4, CA5, CE (CA4 without amino protection), and activated carbon powder (ACP) were put into 50 mL 37.57 mg/L
methyl orange solution, respectively.
As to
methyl orange degradation, the photocatalytic activity of immobilized PU/Ti[O.sub.2] was showed as follows (Figure 9).
Aliquots (3 mL) of each flask were withdrawn at different time intervals (1, 2, 3 and 4 days) and the optical density was measured at 618 nm for malachite green, 462 nm for
methyl orange and 485 nm for Congo red.
0.5 g of the catalyst was weighed and added into the hydrogenation flask containing a solution of 150 mL
methyl orange (0.0199 mM).
The highest photodegradation of
methyl orange under visible light was achieved by C-doped Ti[O.sub.2] (0.0% Ag) photocatalyst probably due to the high surface area for adsorption of the contaminant and also enhanced visible light absorption.
The mechanism on photodecolorization of azo dyes with methyl red and
methyl orange as a model of compound is illustrated in Figures 6 and 7, respectively.
The following chemicals were of analytical reagent grade and used without further purification: ferric nitrate (Sigma Aldrich Reagent Co., Ltd.), calcium hypochlorite (Shun Chemical Reagent Co., Ltd.), potassium hydroxide (Chongqing Chuandong Reagent Co., Ltd.), and
methyl orange (ChengDu Kelong Chemical Co., Ltd.).
ZnONPs were one pot fabricated by direct precipitation; their photocatalytic activity for environmental application was carefully investigated by using decoloring
methyl orange (MeOr) under sunlight.