In this work, natural-dye-sensitized photocatalysts (NDSPs) of $$\hbox {TiO}_{{2}}$$ were prepared by a simple wetness impregnation method, in which natural pigments of chlorophyll and curcumin were initially extracted from fresh parsley leaves and long roots of dried turmeric, respectively. The as-prepared NDSPs were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and UV–vis diffuse reflectance (DRS) spectroscopy. XRD and SEM studies verified intact structural and morphological properties for NDSPs of $$\hbox {TiO}_{{2}}$$ compared to non-sensitized nanostructures, while FT-IR and DRS analyses confirmed the presence of dye pigments on the surface of $$\hbox {TiO}_{{2}}$$ photocatalysts after the photosensitization process. A red-shift towards longer wavelengths was observed in band-gap energies of dye-sensitized samples. These NDSPs indicated efficient photocatalytic performances towards decomposing phenol in visible light irradiation. Phenol degradation experiments are systematically conducted to optimize four key operating parameters, including irradiation time, initial pH of the reaction mixture, dye-sensitized $$\hbox {TiO}_{2}$$ dosage and initial phenol concentration. Dye-sensitization using chlorophyll pigments results in the highest phenol degradation rate (85%) compared with that of samples sensitized with curcumin pigments (75%), which is perfectly in agreement with the corresponding band-gap energies. Photodegradation processes were modelled by the Langmuir–Hinshelwood kinetics, while the adsorption equilibrium was investigated based on Langmuir and Freundlich isotherms. Lastly, possible mechanisms involved in the process of phenol photodecomposition were proposed.

中文翻译：

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叶绿素/姜黄素敏化$$\mathrm{TiO}_{2}$$TiO2纳米颗粒降解苯酚的光学和光催化性能对比分析

在这项工作中，通过简单的湿浸法制备了 $$\hbox {TiO}_{{2}}$$ 的天然染料敏化光催化剂（NDSP），其中叶绿素和姜黄素的天然色素最初是从分别是新鲜的欧芹叶和干姜黄的长根。通过 X 射线衍射 (XRD)、扫描电子显微镜 (SEM)、傅里叶变换红外 (FT-IR) 和紫外-可见漫反射 (DRS) 光谱研究制备的 NDSP。XRD 和 SEM 研究证实了 $$\hbox {TiO}_{{2}}$$ 的 NDSP 与非敏化纳米结构相比完整的结构和形态特性，而 FT-IR 和 DRS 分析证实了染料颜料的存在$$\hbox {TiO}_{{2}}$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$为光催化剂处理过程后的催化剂表面。在染料敏化样品的带隙能量中观察到向更长波长的红移。这些 NDSP 表明在可见光照射下对分解苯酚具有有效的光催化性能。系统地进行苯酚降解实验以优化四个关键操作参数，包括照射时间、反应混合物的初始 pH 值、染料敏化 $$\hbox {TiO}_{2}$$ 剂量和初始苯酚浓度。与用姜黄素颜料敏化的样品 (75%) 相比，使用叶绿素颜料的染料敏化导致最高的苯酚降解率 (85%)，这与相应的带隙能量完全一致。光降解过程由 Langmuir-Hinshelwood 动力学建模，而吸附平衡是基于 Langmuir 和 Freundlich 等温线研究的。最后，提出了苯酚光分解过程中可能涉及的机制。