Abstract：
Anthropogenic activities have been one of the crucial driving factors for water pollution globally, thereby warranting a sustainable strategy for its redressal. In this study, we have developed a hydrogel-biochar nanocomposite for catalytic reduction of water pollutants. To begin with, green synthesis of nickel oxide nanoparticles (NiO NPs) was accomplished from waste kinnow peel extract via the environmentally benign microwave method. The formation of NiO NPs was affirmed from different analytical techniques namely ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive spectroscopy (EDS). The FESEM images revealed spherical nature of NiO NPs. The average particle size was found to be 15.61 nm from XRD data. A novel hydrogel-biochar nanocomposite comprising the green NiO NPs, sunflower meal biochar and chitosan was prepared (Cs-biochar@ NiO) and explored as a nanocatalyst towards catalytic reduction of pollutants such as 4-nitrophenol, potassium hexacyanoferrate (III) and organic dyes methyl orange (MO), Congo red (CR), methylene blue (MB) in the presence of a reducing agent, i.e. NaBH4. Under optimized conditions, the reduction reactions were completed by 120 s and 60 s for 4-NP and potassium hexacyanoferrate (III) respectively and the rate constants were estimated to be 0.044 s-1 and 0.110 s-1. The rate of reduction was found to be faster for the dyes and the respective rate constants were 0.213 s-1 for MO, 0.213 s-1 for CR and 0.135 s-1 for MB. The assessment of the nanocatalyst in the reduction of binary dye systems depicted its selectivity towards the anionic dyes CR and MO. The nanocatalyst displayed effective reduction of dyes in real-water samples collected from different sources. Taken altogether, this study validates the design of sustainable hydrogel-biochar nanocatalyst for the efficient reduction of hazardous anthropogenic water pollutants.
摘要：
人为活动一直是全球水污染的关键驱动因素之一，因此，有必要采取可持续的战略来补救。在这项研究中,我们开发了一种水凝胶-生物炭纳米复合材料，用于催化还原水污染物。首先,通过环境友好的微波方法，从废金牛皮提取物中实现了氧化镍纳米颗粒（NiONPs）的绿色合成。NiONP的形成是从不同的分析技术，即紫外-可见（UV-Vis），傅里叶变换红外(FTIR),X射线衍射(XRD)场发射扫描电子显微镜（FESEM）和能量色散光谱（EDS）。FESEM图像揭示了NiONP的球形性质。从XRD数据发现平均粒度为15.61nm。一种包含绿色NiONP的新型水凝胶-生物炭纳米复合材料，制备了葵花粉生物炭和壳聚糖（Cs-biochar@NiO），并探索了作为催化还原4-硝基苯酚等污染物的纳米催化剂，六氰合铁酸钾（III）和有机染料甲基橙（MO），刚果红(CR),亚甲基蓝（MB）在还原剂的存在下，即NaBH4。在优化条件下，4-NP和六氰合铁酸钾（III）的还原反应分别在120s和60s内完成，速率常数估计为0.044s-1和0.110s-1。发现染料的还原速率更快，MO的相应速率常数为0.213s-1，CR为0.213s-1，MB为0.135s-1。对二元染料体系还原中纳米催化剂的评估描绘了其对阴离子染料CR和MO的选择性。纳米催化剂显示出有效减少从不同来源收集的真实水样品中的染料。总之，这项研究验证了可持续水凝胶-生物炭纳米催化剂的设计，以有效减少有害的人为水污染物。
