Abstract
The photocatalysis process over N-doped TiO2 under visible light is examined for Pb(II) removal. The doping TiO2 with N element was conducted by simple hydrothermal technique and using urea as the N source. The doped photocatalysts were characterized by DRUVS, XRD, FTIR and SEM-EDX instruments. Photocatalysis of Pb(II) through a batch experiment was performed for evaluation of the doped TiO2 activity under visible light, with applying various fractions of N-doped, photocatalyst mass, irradiation time, and solution pH. The research results attributed that N doping has been successfully performed, which shifted TiO2 absorption into visible region, allowing it to be active under visible irradiation. The photocatalytic removal of Pb(II) proceeded through photo-oxidation to form PbO2. Doping N into TiO2 noticeably enhanced the photo-catalytic oxidation of Pb(II) under visible light irradiation. The highest photocatalytic oxidation of 15 mg/L Pb(II) in 25 mL of the solution could be reached by employing TiO2 doped with 10%w of N content 15 mg, 30 min of time and at pH 8. The doped-photocatalyst that was three times repeatedly used demonstrated significant activity. The most effective process of Pb(II) photo-oxidation under beneficial condition, producing less toxic and handleable PbO2 and good repeatable photocatalyst, suggest a feasible method for Pb(II) remediation on an industrial scale.
Highlights
Lead (Pb), along with Cd, Hg, Cr(VI) and As, is categorized as the most toxic heavy metal [1]
It can be seen in the figure that N-doped TiO2 posed higher activity in the Pb(II) photo-catalytic removal both under visible and UV lights compared to the undoped TiO2 activity
Figu(1r0e) 5a.ndTh(4e) eTfifOe2c–tiNve(n15e)s; suonfdetrhedaPrkb(cIoI)ndpihtioonto; -aonxdidUaVtioanndovviesrib(le1)liTghiOt i2r,ra(2d)iaTtioiOn 2(–pNho(to5-), (3) TiO (10)caantadlys(4t )wTeiiOgh2–=N15(m15g),; vuonludmere doaf rPkb(cIoI)nsdoiltuiotinon; a=nd25UmVL,anPbd(IvI)isciobnlecelnitgrhattioinrra=d1i5atmiogn/(Lp, hotocat reaction time = 30 min and solution pH = 7). It can be seen in the figure that N-doped TiO2 posed higher activity in the Pb(II) photocatalytic removal both under visible and UV lights compared to the undoped TiO2 activity
Summary
Lead (Pb), along with Cd, Hg, Cr(VI) and As, is categorized as the most toxic heavy metal [1]. Figu(1r0e) 5a.ndTh(4e) eTfifOe2c–tiNve(n15e)s; suonfdetrhedaPrkb(cIoI)ndpihtioonto; -aonxdidUaVtioanndovviesrib(le1)liTghiOt i2r,ra(2d)iaTtioiOn 2(–pNho(to5-), (3) TiO (10)caantadlys(4t )wTeiiOgh2–=N15(m15g),; vuonludmere doaf rPkb(cIoI)nsdoiltuiotinon; a=nd25UmVL,anPbd(IvI)isciobnlecelnitgrhattioinrra=d1i5atmiogn/(Lp, hotocat reaction time = 30 min and solution pH = 7) It can be seen in the figure that N-doped TiO2 posed higher activity in the Pb(II) photocatalytic removal both under visible and UV lights compared to the undoped TiO2 activity. It is possible that the residue of urea in TiO2–N (15) covered the active sites on the TiO2 surface, thereby inhibiting the OH radical formation These conditions explain the decrease in the photo-oxidation. Same finding was found by some studies [16,17,18,19,20] Based on their Eg values, 15% of N-doped photocatalysts posed lowest Eg, suggesting the highest visible light absorption, and this showed the highest photo-oxidation effectiveness. The N content exhibited higher role than the Eg value did
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