Removal of Toxic Metal Ions in Water by Photocatalytic Method

Abstract

Aims: To study the photocatalytic method for decreasing the concentration of Cu(II),  Cd(II), Cr(VI), and Pb(II) in the solutions. Study Design: The photocatalytical process was proceeded for single solutions containing respective Cu(II), Cd(II), Cr(VI), and Pb(II) ions. Reaction time, photocatalyst dose, and solution pH were optimized. The influence of Cr(VI), Cd(II) and Pb(II) ions on the Cu(II) removal was also evaluated. Place and Duration of Study: Laboratory of Analytical Chemistry, Chemistry Department, Gadjah Mada University, Indonesia. June 2013 – January 2014. Methodology: Photocatalytic process was carried out by  irradiating  100 ml of  4 single solutions containing 10 mg/L of Cu(II),  Cd(II), Cr(VI) and Pb(II) added with TiO2 with UV lamp having 290-390 nm of the wavelength, for certain time. The same procedure was also taken place with variation of  photocatalyst dose (10, 25, 50, 75, and 100 mg for 100 ml solution), irradiation time (1, 3, 5, 10, 25, 50, and 75 h), and solution pH (1, 3, 5, 7, 9, and 13), and for 3 solutions containing Cu(II), that was added  with Cd(II), Cr(VI), and Pb(II) respectively.  The concentrations of Cu(II),  Cd(II) and Pb(II) ions in the solutions were measured by AA Spectrophotometer  and by spectrophotometer UV-Visible for Cr(VI) ion. Results: The maximum effectiveness of the photocatalytic  process can be obtained by using 50 mg of TiO2, in 24 h and at pH 5, that can take  Cu(II), Cr(VI), Cd(II) and Pb(II) out from the solutions as high as 45.56%, 77.72%, 15.23%, and 40.32%, by photocatalytic reduction, adsorption on TiO2 and photocatalytic oxidation, respectively. The presence of Cr(VI) and Cd(II) can decrease Cu(II) photo reduction from  45.36% into 15.24% and into 40.53%, meanwhile Pb(II)  improves the photo reduction from 45.56 into 58.76% for low Pb(II) concentration. Conclusion: The concentration of the toxic Cu(II) and Cr(VI), Cd(II), and Pb(II) ions can be successfully decreased by photocatalytic process through different mechanisms. The removal of the metal ions was controlled by photocatalyst dose, irradiation time, and solution pH. The presence of Cr(VI) and Cd(II) can inhibit Cu(II) photoreduction due to the competition,  meanwhile  Pb(II) with low concentration promotes Cu(II) photoreduction by synergic effect.