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Photocatalytic reduction of chromium(VI) in aqueous solution using dye-sensitized nanoscale ZnO under visible light irradiation

机译:染料敏化纳米ZnO在可见光照射下光催化还原水溶液中的铬(VI)

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Photocatalytic removal of Cr6+ from aqueous solution using dye-sensitized nanoscale ZnO under visible light irradiation was studied in this work. First, nanoscale ZnO was prepared by the co-precipitation method. Then, sensitization of nanoscale ZnO by Alizarin Red S dye followed. Further, nanoscale ZnO and dye-sensitized nanoscale ZnO (designated nanoZnO and nanoZnO*, respectively) were both characterized by various photospectrometry methods, such as scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), EDS-mapping, transmission electron microscopy (TEM), and X-ray diffractometry (XRD). It was found that both types of prepared particles are spherical in shape with a size range of 20 to 50 nm. XRD patterns showed that both nanoZnO and nanoZnO* had the same crystalline structure of zincite. In the photocatalytic reduction aspect, effects of different light sources and dosage of nanoZnO* on Cr6+ reduction ([Cr6+]initial = 20 mg/L) were evaluated in this work. Treatment of chromium(VI)-bearing wastewater under the conditions of using 1.0 g/L of nanoZnO*, neutral pH, irradiation of household fluorescence lamps for 6 h and 17 h would yield Cr6+ removal efficiencies of about 68% and 90%, respectively. When the household fluorescence lamps were replaced by visible-light lamps of 400–500 nm in wavelength, the corresponding removal efficiencies dropped to about 50% and 75%, respectively. When nanoZnO* was irradiated by sunlight under almost the same experimental conditions, the Cr6+ reduction efficiency increased up to 90%. In summary, sensitizing nanoscale ZnO with Alizarin Red S dye for photocatalytic applications using visible light is feasible. The relevant reaction mechanism and pathways were also proposed in this work.
机译:本文研究了染料敏化的纳米ZnO在可见光照射下从水溶液中光催化去除Cr6 + 。首先,通过共沉淀法制备了纳米级的ZnO。然后,用茜素红S染料敏化纳米级ZnO。此外,纳米级ZnO和染料敏化纳米级ZnO(分别指定为nanoZnO和nanoZnO *)都通过各种分光光度法来表征,例如扫描电子显微镜(SEM),扫描电子显微镜-能量色散X射线光谱法(SEM-EDS) ),EDS映射,透射电子显微镜(TEM)和X射线衍射(XRD)。发现两种类型的制备的颗粒均为球形,尺寸范围为20至50nm。 XRD图谱表明,纳米ZnO和纳米ZnO *具有相同的锌酸盐晶体结构。在光催化还原方面,本工作评估了不同光源和纳米ZnO *用量对Cr6 + 还原([Cr6 + ]初始 = 20 mg / L)的影响。在使用1.0 g / L的纳米ZnO *,中性pH,家用荧光灯照射6小时和17小时的条件下处理含铬(VI)的废水,其去除Cr6 +的效率约为68%,并且分别为90%。当家用荧光灯替换为波长为400-500 nm的可见光灯时,相应的去除效率分别降至约50%和75%。在几乎相同的实验条件下,当日光照射纳米ZnO *时,Cr6 +的还原效率提高了90%。总而言之,用茜素红S染料敏化纳米级ZnO在可见光的光催化应用中是可行的。在这项工作中还提出了相关的反应机理和途径。

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