Mehmet Emin Argun

Supercritical-CO2 extraction, Soxhlet extraction, and ultrasound-assisted extraction methods were conducted in this study to recover valuable components, specifically phenolic antioxidant compounds, from orange peels. Basic operating parameters such as temperature and pressure, which affect the extraction efficiency of phenolic substances in orange peel with supercritical-CO2, were designed using the central composite design methodology. In the Soxhlet and ultrasound-assisted extraction methods, 2-hour extraction processes were carried out using ethanol at different concentrations (50%, 80% and 100%) as a solvent. Yield comparison was made by performing total phenolic content, antioxidant activity and total flavonoid content analyses in the extracts. The total phenolic content (TPC) in the extracts was determined to be 5034 mg GAE/L for supercritical-CO2 extraction at 61.5°C and 20 MPa. In comparison, Soxhlet extraction yielded a TPC of 1728 mg GAE/L, while the ultrasound-assisted extraction method resulted in a TPC of 4056 mg GAE/L. It was determined that the optimum operating parameters of supercritical-CO2 extraction were 60°C and 26.4 MPa in case all the responses were maximized. The best phenolic recovery was obtained at 100% ethanol in Soxhlet extraction and 80% ethanol in ultrasound-assisted extraction. Although supercritical-CO2 extraction is an environmentally friendly application, the recovery rate of valuable components from raw materials is lower than in Soxhlet extraction and ultrasound-assisted extraction. However, since the volume of the extracts obtained from the supercritical-CO2 extraction is small, the ratio of phenolic compounds is higher.

The evaluation of wastes from edible oil production industry has increasing importance because of resources deficiency and growing population day by day. It was aimed to investigate the recovery potential of oil and valuable components from sunflower oil production wastes by using supercritical CO2 (SC- CO2) extraction as a green extraction method. In this context oil amounts, total phenolic content (TPC), total flavonoid content and antioxidant activities were analysed. The waste samples obtained from filtration processes of the oil which were composed of oily bentonite (OB) and waxy perlite (WP). Soxhlet extraction was also applied on the waste samples to calculate extraction efficiencies of the SC- CO2. It was observed that oil recovery efficiency of OB (27%, v/v) were more effective than WP (11%, v/v). However, the efficiency increased to 37% by mixing expanded perlite and OB sample to absorb moisture content of the waste and to increase the diffusion of carbon dioxide more easily. The statistical evaluation of the experiments was also conducted to determine the effect of independent variables on the recovery efficiencys. Pressure was detected more effective variables on the recovery values than temperature. The maximum recovery efficiencies of the oil and TPC were obtained at the 50 oC, 22.1 MPa and 60 oC, 20 MPa, respectively.

In this study, the fate of naphthalene was investigated with a supercritical water oxidation process (SCWO). Also, the effectiveness of different operating conditions including pressure, temperature, residence time and oxidant dose on the formation of by-products was determined. The experimental sets were determined by the experimental design program and the effect of the selected variables on the removal of the naphthalene was associated statistically. According to obtained results, naphthalene by SCWO process was mineralized up to 98.5%. Removal efficiencies in sub- and supercritical conditions were between 94 and 100%. Derivatives of aldehyde, propanoic acid, benzene acetic acid and benzofuran were detected as by-products at many experimental conditions and also, some intermediates with a molecular weight higher than naphthalene were determined.