Metal Doped TiO₂ And Photocatalytic Removal Of Nitrate From Water

The nano-TiO₂ has been the focus of photocatalyst studies because of its high activity,stability in acid or alkaline solution, low cost and other advantages. TiO₂ is often used as acatalyst for the organic pollution control as welll as the inorganic pollution control, whichstarted in recent years. The inorganic nitrogen in the water contains ammonium nitrogen,nitrite nitrogen and nitrate nitrogen. Ammonia, nitrite and nitrate in the water are the mainenvironmental pollutants from industrial, domestic and agricultural released Nitrogen to water,other sources of pollution come from landfilling leachates, aminal farms etc. In this paper,metal doped TiO₂ are prepared and characterized. Also investigated are their photocatalyticnitrate reduction activity and Nitrogen removal effect from water, main research contents andconclusions are as follows:(1) Ag／TiO₂ catalysts were prepared by a simple chemical reduction method,characterized by TEM, XRD, XRF and UV-VIS and further tested for photo-catalytic nitratereduction under germicidal UV (254nm) and visible light irradiation. The effects of Agcontent, hole scavengers (such as formic acid, acetic acid, ethanol and oxalic acid, sodiumoxalate) , concentration of formic acid on N removal were systematically investigated. Bestcatalytic activity for photocatalytic reduction of nitrate (100mgN／L) with presence ofintroduced CO₂ was obtained when the content of Ag was 1.0wtï¼…, the concentration offormic acid was 0.030mol／L. Best nitrate conversion after 2h UV irradiation, reached 98.43ï¼…and N₂-N selectivity was 79.24ï¼…, no nitrite was detected, and 20.76ï¼…converted nitrateexisted in NH₄⁺-N form. A higher selectivity for N₂ (92ï¼…) was obtained by using visible lightillumination (300W), although the nitrate conversion was only 37.9ï¼….(2) Fe⁰／TiO₂ catalysts were prepared by a simple chemical reduction method,characterized by TEM, XRD, XRF and UV-VIS and further tested for photo-catalytic nitratereduction under germicidal UV (254nm) irradiation. The effects of Fe⁰ content, holescavengers (such as formic acid, acetic acid, ethanol and oxalic acid, sodium oxalate) ,concentration of formic acid on N removal were systematically investigated. Best catalyticactivity for photocatalytic reduction of nitrate (100mgN／L) with presence of introduced CO₂was obtained when the content of Fe⁰ was 0.5wtï¼…, the concentration of formic acid was 0.050mol/L. Best nitrate conversion after 2h UV irradiation, reached 52.06% and N₂-Nselectivity was 72.04%, no nitrite was detected, and 27.96% converted nitrate existed inNH₄⁺-N form.