## 3 Photocatalytic Materials for Water Treatment
### Nanostructured Photocatalysts  
Nanoscale materials offer larger surface areas, shorter diffusion paths for charge carriers, and more active sites for reactions. Nanostructures such as nanoparticles, nanorods, nanotubes, and core-shell structures are engineered to optimize the photocatalytic behavior by increasing the surface area, shortening the diffusion paths for the charge carrier, and increasing the number of active sites [68; 104; 105]. Nanoparticles provide high surface-to-volume ratios. Nanorods and nanotubes improve directional charge transport. Core-shell structures enable precise control over interface properties and reactivity. Table 6 provides an overview of various nanostructured photocatalysts, emphasizing their nanostructures, enhancements, and specific applications in water treatment and environmental remediation. This categorization supports a clearer understanding of material development trends and provides a structured reference for researchers exploring the heterogeneous photocatalysis in water treatment. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Photocatalyst** & **Target Pollutant** & **Light Source** & **Irradiation Time** & **Method of Synthesis** & **Removal Efficiency, \%** & **Ref.** \\ \hline BiVO\({}_{4}\)-Bi\({}_{2}\)WO\({}_{6}\) & CIP & Visible light (150 W Xenon lamp) & 60 min & Organic additive-free, microwave-assisted method & 76.8 & [68] \\ \hline Bi\({}_{2}\)S\({}_{3}\)/BiOBr & CIP (10 mg/L) & Visible-light irradiation (\(\lambda>420\) nm) & 180 min & Anion exchange strategy & 42 of COD & [73] \\ \hline SmS\({}_{2}\)/BiMoO\({}_{6}\) & CIP (10 mg/L) & Visible light (5 W LED white lights) & 120 min & Hydrothermal & 90 & [96] \\ \hline CdS-TiO\({}_{2}\) & Hydrochloride (TCH), 50 mg/L & Visible light (500 W Lynp) & 8 h & – & 87.06 & [65] \\ \hline Type II AgI/CuBi\({}_{2}\)O\({}_{4}\) & Tetracycline (TC), 10 mg/L & Visible light (300 W Xenon lamp) & 60 min & Hydrothermal Impregnation-hydrothermal hydrothermal hydrothermal hydrothermal hydrothermal & 80 and 90 & [87; 90] \\ 3D CdIr\({}_{5}\)4/2D ZnO & TCH (10 mg/L) & Visible light (250 W Xenon lamp) & 40 min & & 94.04 & [87; 90] \\ \hline Z-scheme AgI/BiVO\({}_{4}\) & Tetracycline (TC), 20 mg/L & Visible light (300 W Xenon lamp) & 60 min & Deposition-precipitation precipitation & 94.91 & [97] \\ \hline TiO\({}_{2}\)/Fe\({}_{3}\)O\({}_{4}\) & Tetracycline (TC), 50 mg/L & 10 W UVC lamp & 60 min & \
\begin{tabular}{p{113.8 pt}} Wet chemical ion exchange \\ \end{tabular} & 98 & [97] \\ \hline In\({}_{2}\)S\({}_{5}\)/InVO\({}_{4}\) & Tetracycline (TC), 10 mg/L & Visible light (300 W Xenon lamp) & 60 min & Hydrothermal & 71.4 & [98] \\ \hline MnO\({}_{2}\)/CNK-OH-M & TOC in pharmaceutical wastewater & Visible light (300 W Xenon lamp) & 120 min &
\begin{tabular}{p{113.8 pt}} Calcination- impregnation \\ \end{tabular} & 74.9 & [103] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Photocatalytic degradation activity toward antibiotics and pharmaceutical pollutants (CIP, hydrochloride, tetracycline, and TOC in pharmaceutical wastewater) using different heterojunction photocatalysts (reused from [PERSON] et al., 2022 [102], under Elsevier License 6000951320125, 2 April 2025). Figure 7 illustrates the key types of nanostructured photocatalysts designed to enhance the photocatalytic performance for environmental applications. These include nanoparticles, nanorods nanotubes, and core-shell structures, each offering unique structural and functional advantages [42; 50; 104; 106]. Nanoparticles are depicted as small, spherical entities with high surface-to-volume ratios that provide abundant active sites for photocatalytic reactions. Nanorods are elongated structures that facilitate directional charge transport and improved light absorption due to their geometry.