The current work aimed to optimize the photocatalysis of Basic Red (BR51) in hair dye greywater (HDG) using zinc oxide nanoparticles (ZnO NPs) by response surface methodology (RSM). The independent factors included ZnO NPs dose (10–200 mg), pH (3–9) and BR51 (1–10 ppm). The photocatalysis efficiency of the ZnO NPs was determined based on the decolorization of BR51 and chemical oxygen demand (COD) reduction. The photocatalysis mechanism was investigated based on the ZnO NPs analyses by field emission scanning electron microscopy/energy dispersive X-ray analysis (FESEM/EDX), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis and differential scanning calorimetry (TGA/DSC), atomic force microscope (AFM), and Raman spectroscopy. The optimal operating factors for the photocatalysis of BR51 were recorded at 131.56 mg of ZnO NPs, pH 3, and 7.47 ppm of BR51, where 72.18 vs. 70.93% of BR51 removal and 82.71 vs. 83.56% of COD removal were the observed and predicted results recorded with an R² coefficient of 0.92. The independent variables exhibited a significant (p < 0.05) interaction with 95% of confidence level. FESEM and AFM analysis showed that the grain sizes of ZnO NPs were uniform before photodegradation but aggregated afterwards. FTIR analysis revealed the main functional groups of ZnO NPs that contributed to the removal process were –C–O, =C–H, C=C, –C–O–C, and OH. TGA revealed a mass loss and exothermic reaction due to desorption of the chemisorbed water. Raman spectroscopy indicated the crystal structure of ZnO for ZnO NPs (before) and the decrease in the crystalline quality for ZnO NPs (after). These findings indicated that ZnO NPs have a high potential for the photocatalysis of BR51 in HDG.

当前的工作旨在通过响应表面方法（RSM）使用氧化锌纳米颗粒（ZnO NPs）优化染发灰水（HDG）中碱性红（BR51）的光催化。独立因素包括ZnO NPs剂量（10–200 mg），pH（3–9）和BR51（1–10 ppm）。ZnO NPs的光催化效率基于BR51的脱色和化学需氧量（COD）的降低来确定。基于ZnO NPs的场发射扫描电子显微镜/能量色散X射线分析（FESEM / EDX），傅里叶变换红外（FTIR）光谱，热重分析和差示扫描量热法（TGA / DSC）对光催化机理进行了研究，原子力显微镜（AFM）和拉曼光谱。在131.56 mg ZnO NPs上记录了BR51光催化的最佳操作因子，。观察到的和预测的结果记录的COD去除率为83.56％，R ²系数为0.92。自变量表现出显着的（p <0.05）与95％的置信水平互动。FESEM和AFM分析表明，ZnO NPs的晶粒尺寸在光降解前是均匀的，但随后会聚集。FTIR分析显示，导致去除过程的ZnO NP的主要官能团为–C–O，= C–H，C = C，–C–OC–C和OH。TGA显示由于化学吸附的水的解吸导致质量损失和放热反应。拉曼光谱表明，ZnO NPs的ZnO晶体结构（前）和ZnO NPs的晶体质量下降（后）。这些发现表明，ZnO NPs对HDG中的BR51具有光催化作用。