Disequilibrium calorimetry for determination of ultrasonic power in sonochemistry

Effect of ultrasound on mass transfer during vacuum impregnation and selected quality parameters of products: A case study of carrots

Many unit operations in the food industry are diffusional driven. These processes are usually very slow and difficult to handle for specific groups of raw materials. Vacuum impregnation (VI) is one example. Impregnating low-porous or densely-structured materials is problematic and often requires low pressure, which can negatively affect product quality and be expensive in energy consumption. This research aimed to evaluate ultrasound (US) as a factor in intensifying mass transfer and enhancing its effectiveness in the VI process. Experiments on impregnation enhanced with ultrasound applied at different stages of the process were carried out. Carrot, a difficult-to-process raw material, was impregnated with ascorbic acid as a mass transfer marker. The process's effectiveness and selected quality parameters were then analyzed. Ultrasound was found to have a positive influence on mass transfer during VI. The effects of ultrasound enhancement were different for particular processes, and depended on the stage of the application and duration of US exposure. The greatest increase in the tissue's ascorbic acid content (60% compared to the non-ultrasound-assisted process) was observed when ultrasound was applied continuously throughout the process. Applying ultrasound only during the relaxation (at atmospheric pressure) or aeration periods resulted in a similar effect - c.a. 20% increase in the marker's content. The smallest increase (10%) was observed when ultrasound was applied only during the vacuum period. Applying US did not result in any unfavorable color change. In most cases, pH decreased, which is favorable for the semi-product's stability. The carotenoid and phenolic compounds' content did not decrease. The results unequivocally indicate that ultrasound has great potential for use as a mass transfer accelerator in the VI process for low porosity materials. The effectiveness of the US is influenced not only by pressure but also by exposure duration. The synergistic effect observed using ultrasound-enhanced impregnation throughout the process confirmed this hypothesis.

Aqueous Acetamiprid Degradation Using Combined Ultrasonication and Photocatalysis Under Visible Light

Acetamiprid (ACE), a neonicotinoid pesticide widely used in pest control, was found in high concentrations in soils, rivers, and lakes. In the present study, ACE degradation was investigated using visible light driven photocatalysis over nitrogen-graphene oxide (N-GO) and palladium-graphene oxide (Pd-GO)-doped ZnO photocatalysts combined with ultrasonication implemented either as a pretreatment (sonolysis) or operated simultaneously with photocatalysis (sonophocatalysis). The effectiveness of the two ACE degradation processes was determined separately. The sonolysis pretreatment allowed reaching almost 40% acetamiprid conversion within 30 min of reaction. Pursuing with the photodegradation reaction in the presence of N-GO-ZnO and Pd-GO-ZnO resulted in a maximum conversion of 98% of ACE within 5 h. As for the sonophotocatalysis process, the reaction time was shortened from 5 to 2 h with 100% acetamiprid conversion. In addition, the photocatalysts were shown to keep their activity even after 5 sonophotocatalytic cycles, thus proving their reusability.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11270-022-05867-4.

Assessment of ultrasound-assisted vacuum impregnation as a method for modifying cranberries' quality

Combined vacuum impregnation and ultrasound was proposed as an alternative method to improve the infusion of ascorbic acid in berry fruit. The effect of ultrasound application at different stages of impregnation - vacuum, relaxation, and both stages - on the qualitative characteristics of impregnated cranberries was investigated. The quality assessment was based on porosity, color, antioxidant capacity, anthocyanin, polyphenol and structure compound content. Ultrasound-assisted vacuum impregnation contributed to higher ascorbic acid content, smaller relative color difference, and greater antioxidant properties. It was found that the degree of impregnation varies considerably and depends on the stage of using ultrasound. Due to more favorable quality attributes, the conclusion was reached that ultrasound should be applied during the relaxation stage of vacuum impregnation.

Nanogenerator for determination of acoustic power in ultrasonic reactors

This paper presents the novel use of a sonochemical reaction product as a sensing material in self-powered ultrasonic reactor devices for determination of ultrasound parameters. A piezoelectric nanogenerator was fabricated via sonochemical synthesis of SbSeI nanowires compressed into a bulk sample. The prepared device was used to develop two fast and simple evaluation methods for acoustic power in liquid. A calibration procedure was carried out for both methods using a VCX-750 ultrasonic processor. The ultrasound acoustic power was varied within a 150 W to 750 W range and the corresponding nanogenerator electrical responses were measured. The voltage signals of the first method fit the best with theoretical dependence. The second technique was based on the application of the Fast Fourier Transform (FFT) to the measured electric output. The results of these two approaches were convergent. Acoustic power values of 255(8) W and 222(7) W were determined for the Sonic-6 reactor using theoretical dependence fitting to experimental data and FFT analysis, respectively. Developed sensing technology possesses great potential for sonochemistry applications.

A new reactor for process intensification involving the simultaneous application of adjustable ultrasound and microwave radiation

Ultrasound (US) and Microwaves (MW) are effective methods for processes intensification. Their combined use in the same reactor can lead to remarkable results. Recently there has been a resurgence of interest in this field for new synthetic applications using reactors based upon existing technologies. We describe here a new type of apparatus in which the thermal energy is continuously removed from the system making possible the use of high power and adjustable ultrasonic and microwave densities throughout the process. The installation consists of a glass reactor located in a monomode applicator which is immersed at the same time in an ultrasonic device which can be operated at different frequencies and powers. A liquid, transparent to microwaves, was used to couple ultrasonic energy to the reactor and to remove the heat generated. Comsol software was used to get information about the distribution of ultrasonic and microwave energy between the reactor liquid and the coupling fluid. The performance was assessed using the conversion of p-nitrophenol into 4-nitrocatechol as a chemical dosimeter and a transesterification.

Ultrasonic and Heat Treatment of Crude Oils

One of the methods of influence on rheological properties of heavy high-viscosity crude oils is ultrasonic treatment. Ultrasonic treatment allows reducing the viscosity of crude oil and, therefore, reducing the costs of its production and transportation. In this paper, the influence of ultrasonic treatment on the rheological characteristics of crude oil (sample No. 1 API = 29.1, sample No. 2 API = 15.9) was investigated. An experimental method was developed. Experimental studies were carried out using the Physica MCR 102 rheometer. The influence of the intensity and duration of ultrasonic treatment on the viscosity of the initial crude oils was studied for 24 h. In addition, the rheological characteristics of the treated oil were investigated after its natural cooling to 293 K. The results are compared with similar results for thermal heating.