Photocatalytical removal of lead ions from aqueous solution with immobilized tio2 powder on carbon based plastic plate in the presence of calcium oxalate and thiolactic acid

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Date
2006
Authors
Retnasamy, Vijenthi
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Abstract
Immobilized calcium oxalate followed by immobilized TiO2 on a carbon based PET (Polyethylene Terephthalate, PET) plastic plate was fabricated via electrophoretic deposition method. Photocatalytic removal rate of lead ions from aqueous solution was studied using this fabricated plate in the absence and presence of thiolactic acid (TLA). With the weight ratio fixed at 1 : 1 (Caox : TiO2), 100 mg/l of lead could be reduced to more than 98% within 75 minutes of illumination. Results also showed that the rates of the photocatalytic reduction of lead increased with pH. This effect was due to both reduction process and hydroxide precipitation. The removal rate of lead also reduced exponentially with the increasing concentration of lead. Other metal ions namely nickel, zinc, copper and argentums were able to be removed by this system in the following order; Ag+>Pb2+>Cu2+>Ni2+>Zn2+. The interference of these cations was also studied. Studies revealed the fact that the presence of cations (Ag+, Cu2+, Ni2+, Zn2+, Cd2+ and Hg2+) in the presence of Pb, does affect Pb’s photocatalytical removal rate. The presence of these cations affected the rate of a Pb’s removal in the following order; Zn2+ > Cu2+ > Cd2+ > Hg2+ > Ni2+ > Ag+. Electronegativity and reduction potential were found to be the possible root causes which contribute indirectly to Pb’s affected photocatalytical removal rate. Addition of 93 mg/l of TLA (0.1M) was found to be the optimum dosage of TLA. pH, value seemed not to affect the removal rate of lead’s in the presence of TLA. It was found to be slightly effective in acid medium. It was also observed, that in the presence of TLA the amount of Ca2+ released into the sample solution were 23 % more than the situation where TLA was not used. Studies suggested that the decrease of pH during the first 15 minutes of illumination may be due to the formation of carbonic acid and the formation of CaCO3 after the period of 15 minutes may have caused the pH of the sample to increase during illumination process. Characterization results suggested that the surface area of an illuminated plate, contain lead deposits on it as the analysis of the area and spot showed the presence of lead. Whereas, on the surface of another illuminated plate where TLA was used in the system during the illumination, the presence of sulfur and lead indicates the possible presence of PbS.
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Master
Keywords
Chemical science , Lead ions , Thiolactic acid , Calcium oxalate
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