| dc.description.abstract | Azo dyes represented by azo chromophores (-N=N-) are the largest class of dyes used in many industries especially textile industries. Other chemicals that mutagenic or toxic to the environment and human life will present in the water bodies if the wastewater effluent from
industries was released without treating them properly. There are many conventional treatment
methods in order to remove azo dyes in wastewater, for example adsorption, membrane
filtration, aerobic or anaerobic process and others. However, these conventional treatment
methods required high cost and generated other pollutants which difficult to be destroyed. In
order to minimize the cost for wastewater treatment but effective in removal of azo dye, solar
photocatalytic had been discovered by previous researchers. Therefore, the main purpose of
this research was to evaluate the mineralization of various azo dyes by solar photocatalytic
process. The main photocatalyst and azo dye used in this study was zinc oxide (ZnO) and New
Coccine (NC), respectively. In the first section, the study was to compare the solar
photocatalytic between decolorization of Orange G and New Coccine. The comparison
between the azo dyes was determined through several operating parameters such as with and
without solar light irradiation, initial dye concentration, catalyst dosage, pH and with and
without aeration. The results showed that concentration NC decreased rapidly in each
parameter and almost achieved 100 % removal efficiency compared to OG. The second
section in this study was to evaluate the effect of molecular structure of five azo dyes (Acid
Orange 7, Orange G, New Coccine, Reactive Black 5, Reactive Green 19) in photocatalytic
mineralization under solar light irradiation. Among these azo dyes, Reactive Green 19 showed
great performance in photocatalytic process and achieved 100 % of removal efficiency under
solar light irradiation. Moreover, this study also focused on the effectiveness of other
photocatalysts (CuO, Fe2O3, TiO2) on the degradation of dye and showed that photocatalyst
with higher band gap (ZnO) rapidly decolorized and mineralized the azo dye. The surface area
and patterns of all photocatalysts were also examined. The reduction in dye concentration was
determined by UV-Vis spectrophotometer. The mineralization of dye was examined by ion
chromatography (IC) and chemical oxygen demand (COD) measurement. The final
concentration of New Coccine achieved 100 % removal after 5 h irradiation time. Among all
the photocatalysts, ZnO showed highest removal which suggesting that it absorbs large
fraction of the solar spectrum and absorption of more light quanta. Batik wastewater also
showed great color removal within 10 h sampling and its COD concentration decreased from
1332 mg/L to 286 mg/L after 12 h irradiated time. Both of azo dyes and photocatalysts
followed pseudo-first-order rate constant and well fitted the Langmuir-Hinshelwood kinetic
model. In conclusion, either synthetic dye or real textile wastewater, both of them can be
degraded and mineralized by photocatalyst with presence of solar light. | en_US |
