A novel biomass derived activated carbon mediated AC@ZnO/NiO bifunctional nanocatalyst to produce high-quality biodiesel from dairy industry waste oil: CI engine performance and emission

In the current study, biomass-derived activated carbon (AC) with zinc oxide/nickel oxide (AC@ZnO/NiO) bifunctional nanocatalyst with enhanced surface area is utilized for the generation of biodiesel from dairy waste scum oil (DWSO). The synthesized AC and AC@ZnO/NiO catalysts are characterized through XRD, BET, CO2- TPD, NH3-TPD, FTIR, FESEM with EDX, and TEM. Besides, the response surface methodology (RSM) of computational modelling with the central composite design (CCD) algorithm is used to optimize the reaction conditions of ultrasonication-assisted biodiesel production. A maximum 97.81% yield of dairy waste scum oil methyl ester (DWSOME)/biodiesel was attained at optimum reaction parameters of a methanol to oil molar ratio of 11.24:1, an AC@ZnO/NiO loading of 2.41 wt%, an ultrasonic time of 36.62 min, and an ultrasonic power of 240.45 W. The AC@ZnO/NiO nanocatalyst demonstrated noble catalytic strength up to seven cycles with a minor decrement in biodiesel yield. The kinetic study for the conversion of DWSO to DWSOME fits well with a pseudo -first-order reaction. The activation energy (Ea) of 50.88 kJ/mol and frequency factor (A) of 33.1105 were found from a kinetic study. Moreover, the thermodynamic analysis shows that the enthalpy and entropy of the acti-vation process are found to be 48.14 kJ/mol and-0.129 kJ/mol.K, respectively. In addition, HNMR and FTIR analyses were conducted for DWSOME. The fuel properties of DWSOME were found in the range of ASTM 6751 standards. Furthermore, the influence of adding DWSOME to diesel at various engine loads on engine perfor-mance and emissions of a CI diesel engine indicated acceptable results of diesel engine performance. Finally, the economic feasibility study also conducted in the present study.