Abstract In this work, highly efficient photocatalytic degradation of bentazone herbicide was demonstrated using Schiff-base derived chitosan (ChdSb)/copper oxide (CuO) nanoparticles (NPs). For the formation of ChdSb/CuO NPs, chitosan's derivatization with 1-hydroxy-2-acetonaphthone was initiated first, followed by the impregnation of CuO NPs. The formed composite was thoroughly characterized by making use of many different techniques for the surface morphology, conjugation/coating, optical properties, crystal nature, and its size, etc. Following the physical characterization, the photocatalytic performance of ChdSb/CuO NPs tested in the presence of sterilized buffers of 4, 7, and 9 and direct sunlight in the winter season indicated for improved catalytic activity. The observation of such photocatalytic activity can be due to the shift in bandgap energy from 2.12 to 2.45 eV which caused the trapping of OH radicals by the holes in the valence band to further produce a powerful oxidizing agent. Also, with the help of various other substrates like benzoic acid, azide ion, acrylamide, rose bengal, and triphenylphosphine, we confirmed for the involvement of OH radicals in the photocatalytic activity. Besides, the p-nitroacetophenone-pyridine (PNAP/PYR) used as an actinometer helped to determine the quantum yield of bentazone hydrolysis. The observed half-life and rate constant of bentazone photocatalytic degradation in buffer solutions at different pHs of 4, 7, and 9 were found to be (1.31 & 0.53), (0.88 & 0.79), and (0.89 & 0.79), respectively. Similarly, the quantum yields for the bentazone photocatalytic degradation in the mentioned buffers were found to be 2.72 × 10-7, 3.31 × 10-7, and 4.14 × 10-7 M respectively. From the comparison of results, the degradation rate of bentazone in these buffers was found to be increasing in the order of pH 9 = pH 7 > pH 4. On testing of the reproducibility, we found that the prepared nanocomposite can be utilized for at least six times without any loss to its photocatalytic activity and thereby confirming for the potential role in sustainable degradation of herbicides and other industrial dyes.

中文翻译：

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席夫碱衍生的壳聚糖浸渍氧化铜纳米粒子：一种有效的阳光直射光催化剂

摘要 在这项工作中，使用席夫碱衍生的壳聚糖 (ChdSb)/氧化铜 (CuO) 纳米粒子 (NPs) 证明了高效光催化降解灭草松除草剂。为了形成 ChdSb/CuO NPs，首先用 1-羟基-2-乙酰萘衍生壳聚糖，然后浸渍 CuO NPs。通过对表面形态、共轭/涂层、光学性质、晶体性质及其尺寸等多种不同技术，对形成的复合材料进行彻底表征。 根据物理表征，ChdSb/CuO NPs 的光催化性能在4、7 和 9 的无菌缓冲液的存在以及冬季的阳光直射表明催化活性得到改善。观察到这种光催化活性可能是由于带隙能量从 2.12 eV 转移到 2.45 eV，这导致价带中的空穴捕获 OH 自由基以进一步产生强氧化剂。此外，在苯甲酸、叠氮离子、丙烯酰胺、玫瑰红和三苯基膦等各种其他底物的帮助下，我们证实了 OH 自由基参与光催化活性。此外，用作光度计的对硝基苯乙酮-吡啶 (PNAP/PYR) 有助于确定苯达松水解的量子产率。在不同 pH 值 4、7 和 9 的缓冲溶液中观察到的苯达松光催化降解的半衰期和速率常数分别为 (1.31 & 0.53)、(0.88 & 0.79) 和 (0.89 & 0.79)。相似地，发现在上述缓冲液中灭草松光催化降解的量子产率分别为 2.72 × 10-7、3.31 × 10-7 和 4.14 × 10-7 M。从结果的比较中发现，苯达松在这些缓冲液中的降解速率以 pH 9 = pH 7 > pH 4 的顺序增加。 在测试重现性时，我们发现制备的纳米复合材料至少可以使用六次，而其光催化活性没有任何损失，从而证实了除草剂和其他工业染料可持续降解的潜在作用。