Affiliations: Department of Chemistry, Winston-Salem State
University, 601 S. Martin Luther King, Jr., Drive, Winston-Salem, North
Carolina 27110, USA | Department of Chemistry, North Carolina Agricultural
and Technical State University, 1601 E. Market Street,Greensboro, North
Carolina 27411, USA
Abstract: Aqueous solutions of azo dyes undergo degradation to form harmless
intermediates and colorless products following irradiation by visible light in
the presence of titanium dioxide thin films. The dyes that were studied in this
work are: Chicago Sky Blue 6B and Benzopurpurin 4B. Results obtained indicated
that complete mineralization of the dyes took place under the experimental
conditions. There was an increase in conductivity after the complete
mineralization experiments possibly indicating the formation of ions such as
NO_3^- and SO^{2-}_4. Chemical oxygen
demand (COD) measurements show a decrease in organic matter for both dyes
following complete degradation. The effect of how changing experimental
conditions such as pH, temperature and starting concentrations of dyes affected
the rate of dye degradation was measured. There was an increase in the rate of
disappearance of the dye color at lower pH. High concentrations of dye
solutions required long degradation time.