Eco-Friendly Facile Conversion of Waste Eggshells into CaO Nanoparticles for Environmental Applications

Amongst the many types of food waste, eggshells contain various minerals and bioactive materials, and they can become hazardous if not properly disposed of. However, they can be made useful for the environment and people by being converted to environmentally friendly catalytic materials or environmental purification agents. Simple calcination can enhance their properties and thereby render them suitable for catalytic and environmental applications. This work aimed to prepare CaO from waste eggshells and examine its effectiveness in photocatalytic pollution remediation, electrocatalytic activity, optical sensing, and antibacterial activities. As opposed to other techniques, this calcination process does not require any chemical reagents due to the high purity of CaCO3 in eggshells. Calcium oxide nanoparticles were prepared by subjecting waste eggshells (ES) to high-temperature calcination, and the synthesized CaO nanoparticles were characterized for their structural, morphological, chemical, optical, and other properties. Furthermore, their photocatalytic degradation of methylene blue dye and antibacterial efficiency against Escherichia coli and Staphylococcus aureus were investigated. It was found that the green-converted CaO can be efficiently used in environmental applications, showing good catalytic properties.

Synthesis of beta-tricalcium phosphate catalyst from Herring fishbone for the transesterification of parsley seed oil

The transesterification of parsley seed oil using a heterogeneous catalyst prepared from Herring fishbone (HFB) was investigated in this study. The fishbone was calcined at 900^oC for 4 h to convert the calcium phosphate in the bone to beta-tricalcium phosphate. The prepared catalyst was then characterized by employing scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis to determine its morphology and elemental composition. The results obtained revealed beta-tricalcium phosphate (β-TCP) as the major constituent of the calcined HFB and also showed the presence of an insignificant portion of hydroxyapatite and calcium oxide. The synthesized heterogeneous catalyst showed good catalytic activity up to five times on reuse. The biodiesel yield of 93% was obtained using 3 wt% of catalyst amount, 65 ^oC temperature of the reaction, 1.5 h time, and 9:1 alcohol-to-oil ratio. Gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectrometry (FTIR) were utilized to characterize the produced biodiesel. Also, their fuel properties were within the American Society for Testing and Materials set limits.

Widely used catalysts in biodiesel production: a review

An ever-increasing energy demand and environmental problems associated with exhaustible fossil fuels have led to the search for an alternative renewable source of energy. In this context, biodiesel has attracted attention worldwide as an eco-friendly alternative to fossil fuel for being renewable, non-toxic, biodegradable, and carbon-neutral. Although the homogeneous catalyst has its own merits, much attention is currently paid toward the chemical synthesis of heterogeneous catalysts for biodiesel production as it can be tuned as per specific requirement and easily recovered, thus enhancing reusability. Recently, biomass-derived heterogeneous catalysts have risen to the forefront of biodiesel productions because of their sustainable, economical and eco-friendly nature. Furthermore, nano and bifunctional catalysts have emerged as a powerful catalyst largely due to their high surface area, and potential to convert free fatty acids and triglycerides to biodiesel, respectively. This review highlights the latest synthesis routes of various types of catalysts (including acidic, basic, bifunctional and nanocatalysts) derived from different chemicals, as well as biomass. In addition, the impacts of different methods of preparation of catalysts on the yield of biodiesel are also discussed in details.