Ag/TiO2光催化还原硝酸氮

利用化学还原法制备不同Ag掺杂量TiO₂纳米催化剂，采用TEM、XRD、XRF和UV-Vis对催化剂进行表征。考察了催化剂在紫外光(254 nm)和可见光照射下还原初始浓度100 mgN·L^-1水相硝酸氮的活性和效果。重点考察了紫外光照射下Ag掺杂量、不同空穴捕获剂(甲酸、甲醇、乙酸、乙醇、草酸、草酸钠等)及甲酸浓度对硝酸氮还原的影响；对硝酸氮转化率和总氮去除率、形成亚硝酸氮、氨氮浓度及氮气选择性的影响。甲酸浓度为0.030 mol·L^-1、Ag掺杂量为1.0wt%时催化剂效果最佳。此时，硝酸氮、总氮的转化率分别为98.43%、78.13%；亚硝酸氮浓度为零，转化的硝酸氮中只有20.76%转化为氨氮，氮气选择性为79.24%。可见光下进行光催化还原反应时，硝酸氮转化率仅37.98%，但氮气的选择性较高。

Photocatalytic Reduction of Nitrate by Ag/TiO2 Catalyst

Ag/TiO₂ catalysts were prepared by a simple chemical reduction method and characterized by TEM, XRD, XRF and UV-Vis and further tested for photo-catalytic nitrate reduction under germicidal UV (254 nm) and visible light irradiation. The effects of Ag content, hole scavengers (such as formic acid, acetic acid, ethanol and oxalic acid, sodium oxalate), concentration of formic acid on N removal were investigated. Best catalytic activity for photocatalytic reduction of nitrate (100 mgN·L^-1) with the presence of formic acid was obtained when the content of Ag was 1.0wt%, the concentration of formic acid was 0.030 mol·L^-1. Best nitrate conversion after 2 h UV irradiation, reached 98.43% and N₂-N selectivity was 79.24%, no nitrite was detected, and 20.76% converted nitrate existed in NH₄-N form. A higher selectivity for N₂ (92%) was obtained by using visible light illumination (300 W), although the nitrate conversion was only 37.9%.