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营养盐(氮、磷等)在自然水体中的增加,导致水体生态系统生产力的不断增强,由此引起藻类水华的频繁发生[1]。过量繁殖的藻类可破坏水体生态系统的平衡,降低水域生态景观功能,并对饮用水的供应造成严重威胁[2-3]。传统的藻类水华控制方法主要包括机械打捞、投加絮凝剂或除藻剂以及水生植物控藻等[4]。机械打捞和投加絮凝剂的方法虽然见效快,操作简单,但该方法投资大,打捞/絮凝沉降的藻类不易进行处置,易造成二次污染;除藻剂投加的方法作用时间有限,并可能对水体的生态系统带来不利影响;水生植物控藻的方法对生态系统的影响较小,但处理周期较长,对突发的藻类水华爆发作用有限。
光催化氧化技术作为一种极具潜力的环境净化技术,因其具有较高的氧化能力、环境友好性且成本较低等特点而备受关注[5]。光催化氧化过程中,半导体材料可被光激发产生具有强氧化能力的羟基自由基(·OH),该基团可降解水体中的有机污染物并灭活水中的微生物,因此,许多的研究者将该技术应用于藻类水华的控制[6-7]。PINHO等[8]采用自然光激发的光催化材料对蓝藻水华水体进行处理,研究表明,光催化剂表面产生的活性组分不仅可造成铜绿微囊藻细胞的裂解,还可对藻细胞破裂释放的微囊藻毒素进行降解。
光催化除藻技术相对于传统的除藻方法,具有能耗低、无二次污染等特点,但在实际应用中,目前研究较多的纳米TiO2光催化剂存在禁带较宽、光生电子和空穴易复合等不足。另外,粉体催化剂不易分离,容易流失。为提高光催化剂对可见光的响应,采用较多的方法是对纳米TiO2进行可见光改性;为增加光催化剂的回收性能,通常将催化剂固定到适当的载体上。有研究[9]表明,窄禁带宽度的Ag3PO4与TiO2形成的异质结有助于光生电子-空穴的分离,提高材料的可见光响应,而石墨相氮化碳(g-C3N4)与Ag3PO4复合可提高Ag3PO4的稳定性[10]。
本研究采用光催化剂Ag3PO4和g-C3N4对TiO2进行共修饰,并将催化剂固载到漂浮型载体膨胀珍珠岩上,所制得的漂浮型光催化剂用来对铜绿微囊藻进行灭活,以期获得高效、低耗的藻类水华控制方法。
漂浮型Ag3PO4-g-C3N4共修饰TiO2复合可见光催化材料的除藻性能
Photocatalytic inactivation of algae using floating Ag3PO4-g-C3N4 co-modified TiO2 visible-light-responsive photocatalyst
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摘要: 以铝盐改性的膨胀珍珠岩为漂浮载体,使用溶胶凝胶-浸渍沉积法制备漂浮型Ag3PO4、氮化碳(g-C3N4)共修饰TiO2的可见光催化材料对铜绿微囊藻进行灭活,以获得高效、低耗的藻类水华控制方法。采用X射线衍射仪(XRD)、氮气吸附比表面积及孔径孔容分析仪(BET)、傅里叶红外光谱仪(FT-IR)、X射线光电能谱仪(XPS)和紫外-可见漫反射光谱仪(UV-vis DRS)等分析方法进行了材料表征。结果表明:Ag3PO4/TiO2的摩尔比变化可对催化剂的晶型结构、比表面积和表面官能团产生影响;Ag3PO4与g-C3N4对TiO2的共修饰可提高光催化剂的可见光响应;当Ag3PO4/TiO2的理论摩尔比为0.2时,催化剂的光催化除藻效果最佳;在催化剂的投加量为2 g·L−1,藻细胞的初始浓度为2.7×106 cells·mL−1时,经8 h可见光催化后,吸附-光催化对藻细胞的去除率达到85.19%。光催化除藻过程中起主要作用的活性基团贡献率为h+ > ∙OH > ∙
${\rm{O}}_2^ - $ ,光催化剂在重复利用3次后,对藻细胞的去除率仍可达到74.41%。同时,考察了水中腐殖酸、叶绿素、硝酸盐和六价铬离子共存对该材料光催化去除铜绿微囊藻的影响。以上研究结果可为有害藻类污染水体修复技术选择提供参考。Abstract: In this study, aluminum salt-modified expanded perlite was taken as a floating carrier, a sol-gel-impregnated deposition method was used to prepare a visible photocatalyst of floating Ag3PO4 and carbon nitride (g-C3N4) co-modified TiO2 to inactivate Microcystis aeruginosa, expecting to obtain an efficient, low-consumption algae bloom control method. The synthesized photocatalysts were characterized using XRD, N2 adsorption/desorption, FT-IR spectra, XPS and UV-vis DRS. Results showed that the change of Ag3PO4/TiO2 molar ratio had influence on the crystal structure, specific surface area and surface functional groups of the photocatalysts. The co-modification of TiO2 with Ag3PO4 and g-C3N4 could enhance the visible light response of the photocatalysts. When the theoretical molar ratio of Ag3PO4/TiO2 was 0.2, as-prepared photocatalyst had the highest photocatalytic inactivation efficiency of algae. After 8 h visible light irradiation, 85.19% of algae with an initial concentration of 2.7×106 cells·mL−1 could be removed at the photocatalyst dosage of 2 g·L−1. In the photocatalytic process for algae inactivation, the contribution rate of active groups playing main role was h+ > ∙OH > ∙${\rm{O}}_2^ - $ , and the removal rate of algae could reach to 74.41% for the photocatalyst after three successive cycles. The effects of humic acid, chlorophyll, nitrate and hexavalent chromium on the removal of Microcystis aeruginosa were also investigated. The above research results can provide a reference for the selection of remediation technologies for harmful algae-contaminated water bodies.-
Key words:
- photocatalyst /
- Ag3PO4 /
- floating /
- algae bloom
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表 1 mEP及Ag3PO4-g-C3N4-TiO2/mEP系列材料的比表面积、平均孔径及总孔容
Table 1. Specific surface area, average pore diameter and total pore volume of mEP and Ag3PO4-g-C3N4-TiO2/mEP serial materials
样品 比表面积/
(m2·g−1)平均孔径/
mm总孔容/
(cm3·g−1)mEP 66.5 2.5 0.041 Ag3PO4-g-C3N4-TiO2/mEP-5% 44.2 3.5 0.039 Ag3PO4-g-C3N4-TiO2/mEP-10% 24.8 3.3 0.022 Ag3PO4-g-C3N4-TiO2/mEP-20% 19.8 4.1 0.019 Ag3PO4-g-C3N4-TiO2/mEP-30% 18.8 3.5 0.018 -
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