Biodiesel production through transesterification of waste Pistacia- Terebinthus Oil by pharmaceutical waste as a heterogeneous catalyst: A sustainable solution for reducing external costs

A catalyst from the pharmaceutical waste of calcium and magnesium tablets was synthesized for biodiesel production from waste Pistacia-Terebinthus (PT) oil with the aim of creating added value and presenting a new approach for the management of such wastes. For this purpose, magnesium and calcium tablet wastes with a mass ratio of 70:30 (wt%) were calcined. The catalyst was investigated by several methods, such as thermal gravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, and CHNS/O elemental analysis. The high specific surface area of the catalyst confirms that the utilized synthesis method resulted in the formation of a high number of active sites in its structure, which allows it to function as a suitable catalyst for this reaction. Furthermore, the impact of effective parameters on the treansestrification reaction was optimized and investigated by designing the experiments and applying the RSM method. The maximum mass yield of 96 % was obtained in optimal conditions (temperature of 70 °C, catalyst loading of 4.498 wt%, methanol:oil ratio of 1.968 (vol:vol), and reaction time of 120 min). The reusability of the catalyst was investigated in four successive cycles. The mass yield of the last test declined from 96 % to 71.4 %. Gas chromatography-mass spectrometry analysis of the produced biofuel revealed that it comprises 91.37 % methyl ester compounds (64.28 % 12-Octadecenoic Acid, Methyl Ester). To evaluate the external costs of biofuel (B100) and compare it with diesel, combustion simulation was done with Diesel-RK software, which showed that its external costs were 0.05388 (€/Lit fuel) less than those of diesel.