Title : Sustainable extraction of benzaldehyde from apricot kernels with simultaneous cyanide gas treatment
Abstract:
Benzaldehyde is extensively used as an additive in the flavour and fragrance industry, because of its aromatic properties. It can be naturally derived from kernels of prunus family fruits, such as apricots. Benzaldehyde is produced in apricot kernels when amygdalin is hydrolyzed by the β-glucosidase enzyme, both of which are naturally found within the kernels. However, the generation of toxic cyanide gas (HCN) as a byproduct of this reaction limits the feasibility of applying this process on commercial scale. The main objective of this study was to develop a sustainable method for extracting benzaldehyde from apricot kernels, which are a waste byproduct of fruit processing industry in New Zealand. Ultrasound assisted hydrodistillation (UAHD) is used to extract benzaldehyde rich essential oil (EO) from apricot kernels, while treating HCN containing off gas simultaneously through catalytic oxidation in a bubble column reactor. Here, hydrogen peroxide (H₂O₂) and copper sulphate (CuSO₄) were used as the oxidant and the catalyst, respectively in the oxidation reaction. Taguchi design was used to optimize EO extraction by evaluating the effects of liquid-to-solid ratio, sonication time, ultrasound amplitude, and hydrodistillation (HD) time. The optimal conditions; liquid-to-solid ratio of 8.5:1, sonication time of 35 minutes, ultrasound amplitude of 55%, and HD time of 2.5 hours resulted in 2.07 times higher benzaldehyde yield, 49.3% lower energy consumption, and 49.1% reduced carbon footprint compared with conventional HD. These findings establish UAHD as a sustainable, efficient, and environmentally friendly method for extracting benzaldehyde rich EO from apricot kernels. The influence of gas flow rate, H₂O₂ concentration, and CuSO₄ dosage on HCN oxidation was experimentally evaluated to establish the reaction kinetics. The kinetic parameters were subsequently applied to optimize an integrated extraction–treatment process, achieving increased benzaldehyde yields during apricot kernel essential oil extraction while ensuring effective HCN abatement in the off-gas stream. Overall, the developed process enables the sustainable production of benzaldehyde-rich apricot kernel essential oil by eliminating HCN emissions and converting them into harmless end-products.
