Effects of the density of carboxyl groups in organic compounds on the photocatalytic reduction of Cr(VI) in a TiO2 suspension.
Photocatalytic reduction (PCR) of Cr(VI) in a TiO2 suspension was studied at pH 4 in the presence of organic compounds containing different numbers of carboxyl groups. The compounds studied were glycine (Gly), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA). In all the cases, near complete Cr(VI) removal was observed after 60 minutes. During PCR process, the aqueous Cr(VI) concentration measured with both Ion Chromatography and Atomic Absorption Spectrophotometery was different in the presence of IDA and EDTA as reaction proceeded while little difference was observed in a control test. This result suggests that a greater portion of reduced Cr(III) species was possibly dissolved through complex formation with IDA (Cr(III)-IDA) and EDTA (Cr(III)-EDTA) or with reaction intermediates (Cr(III)-organic complexes) during PCR compared to the control test. As the number of carboxyl group increased Cr(VI) reduction increased and showed a good linear relationship between initial rates of Cr(VI) reduction and adsorption density of carboxyl group of the surface of TiO2. The initial rate of Cr(VI) reduction in the presence of EDTA was 5 times greater than that in control. When the PCR process was applied in the treatment of real wastewater, an effective Cr(VI) reduction was observed with addition of EDTA.
Lee
Seung-Mok
SM
Department of Environmental Engineering, Kwandong University, Yangyang, Korea.
Cho
Il-Hyoung
IH
Chang
Yoon-Young
YY
Yang
Jae-Kyu
JK
D002384:Catalysis; D002857:Chromium / Q000737:chemistry* / Q000528:radiation effects*; D004492:Edetic Acid / Q000737:chemistry; D004595:Electroplating; D005998:Glycine / Q000737:chemistry; D006812:Humic Substances; D007098:Imino Acids / Q000737:chemistry; D007220:Industrial Waste; D009571:Nitrilotriacetic Acid / Q000737:chemistry; D010084:Oxidation-Reduction; D010777:Photochemistry; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods
D006812:Humic Substances; D007098:Imino Acids; D007220:Industrial Waste; D002857:Chromium; C009495:titanium dioxide; C074702:chromium hexavalent ion; D004492:Edetic Acid; D014025:Titanium; D009571:Nitrilotriacetic Acid; D005998:Glycine; C008109:iminodiacetic acid