Abstract

The development of nontoxic bio-waste based catalyst for efficient recycling of textile dye wastewater to potable water is paramount to support a sustainable environment. This research work investigated a crystallographic evolution of CaO from the chicken eggshell wastes via a simple calcination process for the photocatalytic degradation of the methylene blue dye. The physicochemical properties of the activated CaO catalyst were studied using characterization techniques such as X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and scanning electron microscope (SEM). The crystallite size was estimated as ∼55 nm for the prepared CaO. The sharp bands at 358 cm⁻¹ and the broad band at 675 cm⁻¹ in the Raman spectroscopic analysis have revealed a function attributed to the Ca–O bonds. The energy band gap of prepared CaO was calculated by the Tauc equation using the UV-visible reflectance spectrum. The estimated energy band gap has a maximum value of 5.54 eV. However, a lower bandgap 2.27 eV was also estimated. SEM micrograph revealed the multi-arm/angular and rod-shaped microstructure with a width of 1–2 µm of the arm. The ring-shaped appearance encouraged the porous behavior of the prepared CaO. The photocatalytic activity of the prepared CaO was performed for the degradation of the methylene blue dye in distilled water under natural sunlight in the ambient environment. The maximum photocatalytic degradation efficiency was observed as ∼ 98% in 180 min. The research work incites the possible realistic application of bio-waste based inexpensive photocatalysts for textile/industrial wastewater remediation.

摘要

开发无毒生物废料基催化剂以将纺织品染料废水有效地循环利用到饮用水中，对于支持可持续环境至关重要。这项研究工作通过简单的煅烧工艺对亚甲蓝染料的光催化降解，研究了鸡卵壳废物中CaO的晶体学演变。使用X射线衍射（XRD），拉曼光谱，傅立叶变换红外（FTIR）光谱，紫外可见（UV-Vis）光谱和扫描电子显微镜（ SEM）。对于制备的CaO，微晶尺寸估计为〜55nm。358 cm ^-1处的锐带和675 cm处的宽带^-1拉曼光谱分析中的结果揭示了归因于Ca-O键的功能。通过Tauc方程使用UV-可见反射光谱计算制备的CaO的能带隙。估计的能带隙的最大值为5.54 eV。但是，也估计了较低的带隙2.27 eV。SEM显微照片显示了多臂/角和杆状的微结构，臂的宽度为1-2 µm。环形外观促进了所制备的CaO的多孔性能。所制备的CaO的光催化活性是在周围环境中在自然阳光下在蒸馏水中降解亚甲基蓝染料时进行的。在180分钟内观察到最大的光催化降解效率为〜98％。