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硝酸盐污染是一种普遍存在于自然界的现象[1]. 据报道,我国多地的地下水[2]、饮用水[3]等水体中硝酸盐含量超标,可能导致铁血红蛋白症、消化系统疾病等危害公众健康[1, 4]. 目前常用的去除方法包括反渗透、离子交换、吸附法、化学还原[5]、电还原[6]和生物法[7],但这些方法存在着能耗高、去除效率低和氮气转化率低等问题. 高级还原技术(ARPs,advanced reduction processes)是一种新型的处理方法,利用激发生成活性自由基(CO2·−和ecb−),高效高选择性地去除水体中的硝酸盐[8]. 然而,同相技术需要投加大量甲酸、乙酸等小分子有机酸和重金属离子[9 − 11],影响水体pH(酸性条件),因金属超标和副产物生成,增加二次污染风险,在实际中应用存在困难. 相比较,紫外光催化结合异相技术具有药剂投量低、易循环使用等优点,因此成为当前的研究热点.
目前,钛基材料作为常见的催化剂,存在还原效率和氮气转化率低等问题. 在紫外/乙醇体系中,钛基材料将硝酸盐还原为NH4+[12],在可见光下氮气转化率仅为32%[13]. 为提高硝酸盐去除率和氮气转化率,通常采用负载贵金属(如Pd[12]、Pt[14]、Au和Ag[15])或耦合半导体材料(如H3PW12O40/TiO2[16]、g-C3N4/TiO2[17]、Ti3C2/TiO2[18])等方法. 然而,这些方法存在成本高、循环性差等问题. 因此,仍需合适的钛基催化剂改性方法,以提高硝酸盐还原效能.
研究表明,钙钛矿、尖晶石等多金属氧化物具有窄带隙且合适的EVBM,具有较高的硝酸盐还原效能,如LiNbO3(二次谐波效应)[19]、Pd/GdCrO3[20]和天然钛铁矿[21]的氮气转化率超90%,但普遍存在材料的回收性能差问题. 其中,铁基材料具有易循环回用的铁磁性,且载流迁移率高和带隙能低[22]. 铜铁复合材料中Cu(Ⅲ)/Cu(Ⅱ)和Fe(Ⅲ)/Fe(Ⅱ)的内置电场促进硝酸盐降解,如AgBr(Ag)/MIL-101(Cr)/CuFe2O4[23]. 而铜铁改性的钛基材料可提高催化性能[24],如Ag/CuFe2O4/TiO2[25],及Cu/Fe/TiO2还原硝酸盐效能提升4.7倍(但氮气转化率低)[24],受到研究者关注. 综上铜铁钛催化剂具有高效去除硝酸盐潜能,但在光催化还原硝酸盐为氮气的领域缺乏相应研究. 因此,开发更为高效、高氮气转化率、易回收且循环性能好的催化材料,将有重要现实意义.
本研究采用改性的溶剂热法和化学沉淀法成功制备了AgCl(Ag)/CuFexTix+1Oy光催化材料. 通过调控不同AgCl(Ag)掺杂量和铜铁钛配比,制备了一系列复合材料,并利用SEM、XRD、XPS和UV-vis等方法进行表征,以获得更高硝酸盐去除率和氮气转换率的催化材料,并探究了复合材料在实际水处理中光催化还原硝酸盐的效能.
氯化银(银)-铜铁钛氧化物光催化材料制备及还原硝酸盐性能
AgCl(Ag)/CuFexTix+1Oy for photocatalytic reduction of nitrate
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摘要: 本研究采用改性的溶剂热法和化学沉淀法制备氯化银(银)-铜铁钛氧化物(AgCl(Ag)/CuFexTix+1Oy)复合光催化材料,用于去除水中的硝酸盐. 分析表明,AgCl(Ag)促进CuFexTix+1Oy产生光生电子,并促进光生电子-空穴对的分离,从而提高复合材料光催化还原硝酸盐性能. 研究重点探究了复合材料在紫外/甲酸体系中的光还原性能,并将其应用于实际水处理中. 实验结果表明:当AgCl掺杂量为40%(按质量算),且铜铁钛的配比为1:2:3时,光催化还原硝酸盐的效果最佳. 在150 min时,硝酸盐去除率达94.6%,去除速率为(0.0188 ± 0.0017) min−1,氮气转化率达99.0%. 在实际水处理中,该体系对自来水和模拟地下水的硝酸盐去除率分别为87.4%和80.9%,氮气转化率均大于70%,显示出良好的应用潜力.
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关键词:
- 氯化银(银)-铜铁钛氧化物 /
- 高级还原 /
- 硝酸盐 /
- 氮气转化率
Abstract: A photocatalyst AgCl(Ag)/CuFexTix+1Oy were prepared by synthetic methods including solvothermal and chemical precipitation methods. The analysis revealed that the presence of AgCl(Ag) facilitated the generation of photogenerated electrons in CuFexTix+1Oy, while inhibiting the recombination of electrons and holes, consequently enhancing photocatalytic efficiency. This article took nitrate as the removal object and investigated the photoreduction capabilities of the composite materials in the UV/formic acid system as well as their potential application in realistic water. The experimental results indicated that the optimal outcome was achieved when the AgCl doping concentration was 40% by massand the ratio of copper, iron, and titanium was 1:2:3. After150 minutes of reaction, the nitrate removal rate was 94.6%, the degradation rate reached (0.0188 ± 0.0017) min−1, and the nitrogen conversion rate reached 99.0%. Additionally, in implementation in realistic water treatments, the system exhibited nitrate removal rates of 87.4% for tap water and 80.9% for simulated groundwater, with a nitrogen conversion rate exceeding 70%. These results suggesting a promising potential for application.-
Key words:
- AgCl(Ag)/CuFexTix+1Oy /
- APRs /
- nitrate /
- nitrogen conversion rate
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表 1 水质指标
Table 1. Water quality indicators
指标
Indicators自来水
Tap water模拟地下水
Simulated groundwaterpH 7.1 7.3 TOC/(mg·L−1) 1.92 3.00 DO/(mg·L−1) 8.21 8.50 硫酸盐/(mg·L−1) 55.2 384.0 氯化物/(mg·L−1) 21.1 142.0 碳酸氢盐/(mg·L−1) 41.0 122.0 硝酸盐/(mg ·L−1 N) 5.5 27.1 -
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