Optimization of Pulsed Electric Field as Standalone “Green” Extraction Procedure for the Recovery of High Value-Added Compounds from Fresh Olive Leaves

Olive leaves (OLL) are reported as a source of valuable antioxidants and as an agricultural by-product/waste. Thus, a twofold objective with multi-level cost and environmental benefits arises for a “green” standalone extraction technology. This study evaluates the OLL waste valorization through maximizing OLL extracts polyphenol concentration utilizing an emerging “green” non-thermal technology, Pulsed Electric Field (PEF). It also provides further insight into the PEF assistance span for static solid-liquid extraction of OLL by choosing and fine-tuning important PEF parameters such as the extraction chamber geometry, electric field strength, pulse duration, pulse period (and frequency), and extraction duration. The produced extracts were evaluated via comparison amongst them and against extracts obtained without the application of PEF. The Folin-Ciocalteu method, high-performance liquid chromatography, and differential scanning calorimetry were used to determine the extraction efficiency. The optimal PEF contribution on the total polyphenols extractability (38% increase with a 117% increase for specific metabolites) was presented for rectangular extraction chamber, 25% v/v ethanol:water solvent, pulse duration (tpulse) 2 μs, electric field strength (E) 0.85 kV cm−1, 100 μs period (Τ), and 15 min extraction duration (textraction), ascertaining a significant dependence of PEF assisting extraction performance to the parameters chosen.

KINETICS OF GRINDING OF VEGETABLE RAW MATERIALS DURING ELECTRIC DISCHARGE EXTRACTION

The influence of the degree of grinding of the particles of growing raw materials during electric discharge extraction on the quality of the obtained extracts was studied. Each discharge during electro-discharge extraction contributes to the grinding of a part of the raw material, which is confirmed by granulometric analysis. The particle size of the raw material should be controlled, since excessive grinding of the extracts results in cloudy, difficult to clarify and poorly filtered. The design of the extraction chamber is proposed, in which the grounded electrode is made in the form of a perforated plate, called a false bottom, with the optimal size of the holes and their density, which eliminates the over-grinding of the raw material particles, which leads to the production of turbid and difficult-to-filter extracts. Since the extraction of raw materials is carried out at a certain ratio of solid-liquid phases, the volume of the chamber from the sieve to the bottom does not significantly affect the kinetics of the extraction process itself, since it is intended for collecting the smallest particles of processed raw materials, the mass of which does not exceed 15-16% of the loaded mass of raw materials. The device of the extraction chamber, due to the high turbulence and intensive mixing of the suspension under the action of cavitation and shock waves initiated by the discharge in the liquid, allows you to remove small particles of raw materials less than 1 mm in size from the working area of the chamber. The results of the study show that the extraction of target components from various raw materials using a chamber with a false bottom can significantly reduce the content of the smallest particles of raw materials in the extract. It facilitates the filtration of the extract, reduces the filtration time, significantly reduces the likelihood of turbidity of the solution due to suspension, which improves the quality of the extract. Experimental studies of the developed electric discharge chamber with a false bottom, conducted with various types of plant raw materials, confirm the effectiveness of extraction in the chamber of the proposed design.

Performance comparison of microwave cavities used for extraction operations

In the agri-food industry world, billions of tons of waste are produced every year. This represents both a direct loss (due to the failure to exploit their potential value, and their nutritional and energy content) and indirect loss, due to their necessary treatment and/or disposal. Some substances contained in the wastes, of potential high value, can be recovered by means of extraction. Conventional extraction processes involve the use of solvents, which end up requiring an additional process of separation from the solute identified as the desired product. In recent years, extraction techniques have been proposed without the use of solvents. This work compares the performance of two microwave cavities used for extraction operations, both working at 2.45 GHz.A calorimetric analysis performed by following the heating rate and temperature evolution in rack of 25 beakers filled with 25 mL of water, coupled with the solution of the heat transfer balance in the system, allowed to build the spatial distribution of the electromagnetic power dissipated as heat in each of the beakers. Fluid-dynamics aspects related to the recovery of the vapour phase produced during the extraction were also analyzed, with particular emphasis on the mean residence time of the vapour fraction in the extraction chamber as a function of its configuration.

SUPERCRITICAL FLUID EXTRACTION OF MOLYBDENUM COMPLEXES AND ITS ISOTOPES WITH CARBON DIOXIDE

Separation of molybdenum complexes and its isotopes by supercritical fluid extraction (SFE) with carbon dioxide was experimentally investigated. The type of modifier, which provides increasing the efficiency of the metal and its isotopes separation, was determined. Extraction of molybdenum isotope complexes was carried out in the updated SFE-U unit at a constant value of the initial pressure P = 20 MPa and constant temperatures of the upper (T1 = 35 ⁰C) and bottom (T2 = 45 ⁰C) flanges of the extraction chamber. The exposure time of the extract and the level along the extraction chamber height, from which the eluent was sampled, were set in the experiments. It is shown, that at a certain sampling height and at certain exposure times, change in the natural content of Mo isotopes in the extracts takes place.

Modelling hydraulic mixture movement along the extraction chamber bottom in case of hydraulic washout of the tuff-stone

This paper presents the research results of the pulp movement process along the extraction chamber bottom to the suction pipe of the pulp lifting device in case of downhole hydraulic mining the volcanic tuff-stone. The washout process and hydraulically operated transportation of the tuff-stone hydraulic mixture, when forming the extraction chamber, have been studied under various conditions and methods of exposure. As a result, the dominant parameters have been determined influencing the hydrodynamic washout technology as well as tuff-stone hydraulic mixture lifting to the alluviation map. The dependences have been substantiated of the washout process performance and transportation capacity of the hydraulic mixture flow on the determined parameters. To calculate the process of pulp flow-over along the extraction chamber bottom to the intaking hydraulic elevator headwall, the systems of equations have been determined based on the modelling the movement of tuff-stone hydraulic mixture along the extraction chamber bottom during hydraulic washout. The dependences of the contact strength of the tuff-stone samples mined by downhole method on the time spent in water are presented, resulting in determination of the tuff-stone weakening coefficient and the degree of its saturation with water.

Development and Performance Evaluation of a Manually-Operated Multipurpose Fruit Juice Extractor

A simply and manually-operated multipurpose fruit juice extractor was designed, constructed and its performance was evaluated in terms of juice yield, extraction efficiency, juice content, extraction loss and extraction capacity. The machine has two major parts which are: the extraction chamber and the structural frame. The extraction chamber is made of stainless steel and consists of a turning handle (f24.5 x 400mm), screw rod (f32 x 620 mm), compression plate (f100 mm), perforated inner cylinder (f115 x 180 mm), non-perforated outer cylinder (f120 x 180 mm) and discharge pipe. The structural frame (350 mm x 415 mm x 60 mm) is made of mild steel of U-channel section. The machine basically works on the principle of transmission of compressive force to rupture the juice cells of the fruit for the liberation of juice. Sweet orange, watermelon, red apple, green apple, pineapple, lime, lemon and grape were used for the performance evaluation process. Results obtained showed that pineapple had the highest values of juice yield (68.74%),juice content (66.40%), extraction capacity (92.85 g/min) and extraction efficiency (82.99%) while sweet orange and lime had the lowest extraction loss and extraction capacity of 1.67% and 29.81 (g/min) respectively.

Ανάπτυξη αυτόματων μικρο-τεχνικών προκατεργασίας δείγματος για τον προσδιορισμό μολύβδου και υδραργύρου με συνδυασμένες αναλυτικές τεχνικές

Με βάση τα πειραματικά δεδομένα της Διδακτορικής διατριβής προκύπτουν τα παρακάτω:1) Στην πρώτη πειραματική εργασία αναπτύχθηκε μια απλή και γρήγορη μέθοδος για την προσυγκέντρωση και τον προσδιορισμό μετάλλων με τη μικροτεχνική DLLME, σε συνδυασμό με την τεχνική FAAS. Στη μελέτη αυτή χρησιμοποιήθηκε, για πρώτη φορά, ως διαλύτης εκχύλισης, οργανικός διαλύτης ελαφρύτερος του νερού, όπως η DIBK, διευρύνοντας έτσι το σύνολο των διαθέσιμων αποτελεσματικών διαλυτών. Μελετήθηκε και σχεδιάστηκε ένα πρωτότυπο σύστημα προώθησης υγρών, το οποίο επιτρέπει την εν σειρά προώθηση μικρο-ποσοτήτων, διαλυτών ελαφρύτερων του νερού στη FAAS. 2) Στην δεύτερη πειραματική εργασία προτείνεται μια νέα αυτόματη μέθοδος μικροεκχύλισης υγρού -υγρού, το οποίο βασίζεται στην πλατφόρμα «σταγόνα σε έμβολο», χρησιμοποιώντας μια διάταξη SIA-LAV για τον προσδιορισμό μετάλλων σε συνδυασμό με την τεχνική FAAS. Για το σκοπό αυτό, κατασκευάστηκε και βελτιστοποιήθηκε ένας θάλαμος μικροεκχύλισης ροής, ο οποίος προσαρμόστηκε σε μία θύρα της βαλβίδας πολλαπλής επιλογής του συστήματος SIA. 3) Στην τρίτη πειραματική εργασία προτείνεται ένα νέο και ευέλικτο αυτόματο σύστημα εκχύλισης υγρού-υγρού, το οποίο βασίζεται στην εκχύλιση με αντιρροή σε συνδυασμό με την τεχνική FAAS για την προσυγκέντρωση και τον προσδιορισμό τοξικών μετάλλων. Η εκχύλιση βασίζεται στην αντίθετη ροή της υδατικής και της οργανικής φάσης, η οποία πραγματοποιείται σε ένα νέο ειδικά κατασκευασμένο θάλαμος μικροεκχύλισης (Extraction Chamber, EC) αντιρροής. Ο προτεινόμενος αυτός θάλαμος είναι κατάλληλος για χρήση οργανικών διαλυτών είτε ελαφρύτερων είτε βαρύτερων του νερού. 4) Στην τελευταία πειραματική μελέτη αναπτύχθηκε για πρώτη φορά ένα πρωτότυπο, πλήρως αυτοματοποιημένο σύστημα HS-SDME, το οποίο βασίζεται στην πλατφόρμα LIS για τον προσδιορισμό ανόργανου υδραργύρου, μέσω της επιτόπου παραγωγής ψυχρού ατμού υδραργύρου σε συνδυασμό με την τεχνική ETAAS. Στο προτεινόμενο σύστημα πραγματοποιείται ανάμιξη του δείγματος και του αναγωγικού αντιδραστηρίου εντός της σύριγγας, με αποτέλεσμα την απελευθέρωση των πτητικών ατμών υδραργύρο. Στο προτεινόμενο σύστημα, εφαρμόστηκαν για πρώτη φορά συνθήκες ελαττωμένης πίεσης σε LIS σύστημα για την αποτελεσματικότερη απελευθέρωση των ατμών του υδραργύρου.