Phenol Recovery Research Articles

Olive Mill Wastewater Polyphenol-Enriched Fractions by Integrated Membrane Process: A Promising Source of Antioxidant, Hypolipidemic and Hypoglycaemic Compounds

The valorisation of food wastes is a challenging opportunity for the green, sustainable, and competitive development of industry. The recovery of phenols contributes to the sustainability of olive waste sector, reducing its environmental impact and promoting the development of innovative formulations of interest for pharmaceutical, nutraceutical, and cosmeceutical applications. In this work, olive mill wastewater was treated through a combination of microfiltration (MF), nanofiltration (NF), and reverse osmosis (RO) in a sequential design to produce polyphenol-enriched fractions that have been investigated for their chemical profile using ultra-high-performance liquid chromatography (UHPLC), and their potential antioxidant, hypolipidemic, and hypoglycaemic activities. RO retentate exhibited the highest content of hydroxytyrosol, tyrosol, oleuropein, verbascoside, vanillic acid, and luteolin. In particular, a content of hydroxytyrosol of 1522.2 mg/L, about five times higher than the MF feed, was found. RO retentate was the most active extract in all in vitro tests. Interestingly, this fraction showed a 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS) radicals scavenging activity with an IC50 value of 6.9 μg/mL and a potential inhibition of lipid peroxidation evaluated by the β-carotene bleaching test with IC50 values of 25.1 μg/mL after 30 min of incubation. Moreover, RO retentate inhibited α-amylase and α-glucosidase with IC50 values of 65.3 and 66.2 μg/mL, respectively.

Selective Phenol Recovery by Catalytic Cracking of Thermal Decomposition Gas from Epoxy-Based Carbon-Fiber-Reinforced Plastic

In order to promote the recycling of carbon fiber reinforced plastic (CFRP), catalytic cracking of hazardous gases generated by thermal decomposition from epoxy-based CFRP composites was performed....

Aqueous two-phase extraction of phenolic compounds from Sedum dendroideum with antioxidant activity and anti-proliferative properties against breast cancer cells

Sedum dendroideum, a traditional medicinal plant, has a wide variety of pharmacological activities, attributed to phenolic compounds. Despite that there are several methods available for the extraction of phenolic compounds, their use has several disadvantages, evidencing the need for the development of alternative methods. In this study, ethanol-salt aqueous two-phase systems (ATPS) were employed for the extraction of phenolic compounds from S. dendroideum. The effect of different system parameters on the partition of phenolic compounds were studied, including the volume ratio (VR), tie-line length (TLL), sample loading, and sodium chloride addition. Also, thermodynamics of partition process was addressed. Furthermore, systems top phase antioxidant activity and anti-proliferative properties against MCF-7 breast cancer cells were evaluated. A system with VR 3, TLL 40% w/w, 5 mg of crude extract/g of ATPS, and 3% w/w NaCl, showed the highest phenolic compounds recovery in the top phase (17.98%). Thermodynamic studies indicated that polarity governs the partition of phenolic compounds. The system with a VR 3, TLL 40% w/w, 5 mg of crude extract/g of ATPS, and without NaCl exhibited the highest antioxidant activity. HPLC analysis revealed no alteration on phenolic compounds profile after ATPS extraction. Whereas, the top phase of a system with VR 3, TLL 40% w/w, 5 mg of crude extract/g of ATPS, and 5% w/w of NaCl showed maximum inhibition of cell proliferation at 168 h (89.66%). The potential application of S. dendroideum as an anticancer agent is reported for the first time. ATPS could be used as an alternative extraction technique for further evaluation of phytochemical composition and pharmacological activities of phenolic compounds from S. dendroideum.

Box-Behnken experimental design for a green extraction method of phenolic compounds from olive leaves

Olive leaves are important olive by-products due to their high content of phenolic compounds and elenolic acids, which possess antioxidant, antimicrobial, anti‐atherogenic and anti‐inflammatory properties, among others. Thus, pressurized liquid extraction was used to obtain a high recovery of these compounds from olive leaves. A Box-Behnken design was performed to optimize the PLE conditions of temperature (50−200 °C), % ethanol-water (0–100 %) and extraction time (5−20 min) in order to obtain the highest content of simple phenols, secoiridois, flavonoids, elenolic acids, total compounds and extraction yield from olive leaves. Olive leaf extracts were analyzed by high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). The highest content of total compounds was 158.7 ± 0.4 mg g-1 d.w obtained at 105 °C, 100 % ethanol and 5 min, whereas the highest extraction yield was 43 ± 3% obtained at 198 °C, 100 % ethanol and 5 min. Therefore, multi-response analysis was carried out using desirability function to optimize the PLE conditions for both total compounds and yield. These optimal conditions were 138 °C, 100 % EtOH and 5 min obtaining 144 mg g-1 d.w. of total compounds and 42.2 % of yield. The optimal temperature of 138 °C has shown a great phenolic recovery and 100 % ethanol has been shown to be a safe solvent to use in the food industry. In addition, short extraction times (5 min) mean lower energy consumption and lower costs. Therefore, these PLE optimum conditions could be implemented on an industrial scale.

Resource recovery from industrial wastewaters by hydrophobic membrane contactors: A review

Abstract Hydrophobic membrane contactors (HMCs) are emerging as a promising alternative to conventional mass transfer and adsorption technologies for various wastewater treatment applications. The key advantages of this technology include large mass transfer area-to-volume ratios, no phase dispersion, ease of operation, and low energy consumption. More importantly, removed species have the potential to be concentrated in the stripping phase, allowing for recovery and recycled use. In this review, major applications of HMCs for resource recoveries from industrial wastewaters are summarized. We first start with the discussion on recoveries of ammonia nitrogen, dissolved methane, and cyanide from wastewaters via gas transfer HMCs. Next, we highlight the use of HMCs as a tool for liquid-liquid extraction for the recovery of phenol and heavy metal ions. The different process principles, mass transfer phenomena, and challenges facing each application are outlined and examined. We then focus in detail the Achilles heels of HMCs, namely membrane wetting and fouling, discussing their impacts on membrane and process performances, as well as the current mitigation methods. Last but not least, we share our insights and present the outlook for the HMCs, addressing critical gaps and recommendations for future research in areas such as fouling and wetting, long-term and scaled-up operations, economic feasibility as well as other ideas to reduce mass transfer resistance.

Enzyme pretreatment improves the recovery of bioactive phytochemicals from sweet basil (Ocimum basilicum L.) leaves and their hydrodistilled residue by-products, and potentiates their biological activities

In the present study, the effect of enzyme pretreatment on essential oil recoveries from sweet basil (Ocimum basilicum L.) leaves was evaluated. Moreover, the consideration on the use of hydrodistilled residue by-products as a source of bioactive phytochemicals with antioxidant, antimicrobial, and repellent effects against the stored-grain pest Tribolium castaneum was examined. Results showed that the enzymatic pretreatment increased the extraction yield of essential oil by 400, 417, and 478% in hemicellulase-, cellulase-, and viscozyme-treated samples, respectively. Phenylpropanoids including methyl cinnamate, methyl eugenol, eugenol and estragol were found as the main components, and were particularly abundant in cellulase-treated samples. From the hydrodistilled residue of enzyme-treated samples, better recoveries of total phenols (TPC) (258.3–470.9 mg GAE/g extract) and flavonoids (TFC) (59.4–94.3 mg QE/g extract) were observed. Using the DPPH, ABTS, and FRAP assays, a strong antioxidant activity of the rosmarinic-rich extract was observed. Such an activity which was mediated through electron transfer mechanism was highly correlated with the TPC, TFC and rosmarinic acid content. The in vitro bioassay showed that methanol extract (6.29 and 12.58 µL/cm2) had repellent activity against the stored-grain pest Tribolium castaneum. These results suggest the potential of enzyme pretreatment to promote the use of hydrodistilled residue by-products as a valuable source of natural antioxidants and repellents ingredients.

Phenol Recovery from Aromatic Solvents by Formation of Eutectic Liquids with Trialkyl-2,3-dihydroxypropylammonium Chloride Salts

Trialkyl-2,3-dihydroxypropylammonium chloride salts have been investigated as liquid eutectic-forming salts for the extraction of phenol from aromatic-rich model oil (toluene), demonstrating how the increased partitioning of phenol from oil-phases can be combined with reduced co-miscibility of the salt with aromatic hydrocarbons through the introduction of the dihydroxypropyl-function.

Effect of extraction variables on total phenol yield in some selected legumes indigenous to Nigeria

There are increasing research efforts on the possibilities of the utilization of natural sources of bioactive compounds for the dietary management of certain degenerative diseases due to their deleterious health effects associated with the the use of synthetic chemicals. Therefore, this study evaluated the yield of total phenol from bambaranut, cowpea, red bean and pigeon pea. A set of single factor experiments, namely solvent types (acetone, ethanol and methanol), solvent concentration (20 – 100 %, v/v), extraction time (30 – 50 min) and extraction temperature (40 – 60 °C), were evaluated for the optimization of total phenol recovery. The results show that extraction variables significantly (p < 0.05) affected the total phenol yield. Ethanol at 60% concentration (v/v) incubated at 50 °C for 40 min gave the highest total phenol (217.11 mg/100 g) yield in bambaranut. In cowpea, ethanol at 90% concentration (v/v) incubated at 50 °C for 50 min gave the highest total phenol (192.61 mg/100 g). Methanol at 100% concentration incubated at 50 °C for 40 min gave the highest total phenol (212.00 mg/100 g) in the red bean while methanol at 100 % concentration (v/v) incubated at 50 °C for 40 min gave the highest total phenol (196.33 mg/100 g) in pigeon pea.

Optimization and modeling of two-phase olive-oil washing wastewater integral treatment and phenolic compounds recovery by novel weak-base ion exchange resins

In light of the Circular Economy concept, recently emerged as a need for sustainable production, olive oil industry should be concerned to transform the whole process into environmentally friendly, which necessarily implies the treatment of the wastewater by-produced in olive mills. In this work, concentration and recovery of high-added value phenolic compounds from two-phase olive-oil washing wastewater (OOWW) and parallel effluent treatment by a ‘green process’ based on novel weak-base ion exchange (IE) resins was addressed. The key operating input factors of the resin process for the treatment and valorization of OOWW were studied, optimized and further modelled. A Box-Behnken design was implemented and the obtained data were analyzed by ANOVA and interpreted by RSM methodology. The process was ulteriorly modelled by a second-grade quadratic fitting equation comprising the significant operating variables. The optimization of the IE process performance (20.3 °C, pH0 6.7 and 114 g/L Mresin) ensured up to 92.5% recovery of total phenols concentration. Moreover, the purified stream presented good quality (56.6–83.7 mg L−1 total phenols), following standard recommendations by the FAO. The obtained information would be of key importance for the scale-up of the proposed IE operation. Both the treatment and revalorization of OOWW would help implement a definite sustainable production process of olive-oil.

Pulsed electric field (PEF) as pre-treatment to improve the phenolic compounds recovery from brewers' spent grains

Brewers' spent grain (BSG) is the most abundant by-product obtained from beer production. However, it contains some bioactive compounds such as phenolic compounds, therefore, the valorization of BSG is important to recovery these compounds and reused them as functional ingredients in food industry. Therefore, in this work, pulsed electric field (PEF) has been used as extraction pre-treatment. PEF parameters such as electric field strength E (0.5, 1.5, 2.5 kV/cm), frequency (50, 100, 150 Hz) and total time of treatment (5, 10, 15 s) were optimized in order to maximize the content of flavan-3-ols, flavonoids, phenolic acid derivates and total free phenolic compounds. Optimal conditions to the maximum value of total free phenolic compounds were the following: 2.5 kV/cm, 50 Hz and 14.5 s. Concentrations of total free and bound phenolic compounds from BSG under these PEF optimum conditions were 2.7 and 1.7 times, respectively, higher than in case of the extraction without PEF pre-treatment, indicating an improvement in the phenolic recovery with the use of PEF as a pre-treatment in brewers spent grain samples.

A novel electrochemically switched ion exchange system for phenol recovery and regeneration of NaOH from sodium phenolate wastewater

An electrochemically switched ion exchange (ESIX) system was proposed as a novel electrochemical method for the treatment of high concentration phenolic sodium salty wastewater, in which a ferric ferricyanide (FeHCF) coated electrode with rigid open framework can control the insertion/extraction of sodium (Na+) ions by switching the redox state of FeHCF. It is found that this ESIX system can not only remove the phenol and desalinate the phenol-containing wastewater simultaneously, but also regenerate the FeHCF coated electrode and produce sodium hydroxide (NaOH). In the series operation, more than 79% of phenol could be removed with energy consumption of 9.677 × 10−3 kWh mol−1, and meanwhile NaOH solution with a pH of 12.84 was generated with energy consumption of 2.083 × 10−3 kWh mol−1 during the recovery process of Na+ ions. It is expected that such an ESIX system can be applied for the treatment of phenol-containing high salinity wastewater.

Combination of enzyme-assisted extraction and high hydrostatic pressure for phenolic compounds recovery from grape pomace

The aim of this study was to evaluate the effect of enzyme-assisted extraction (EAE) and high hydrostatic pressure (HHP) on the recovery of phenolic compounds from grape pomace (GP). For this, GP was subjected to four conditions: (E1) EAE without HHP, (E2) EAE with the enzyme previously submitted to HHP, (E3) EAE simultaneously with HHP, (H4) HHP (without adding enzymes) at different pressures (50, 100 and 200 MPa) and times (0–30 min). HHP increased by up to 16 times the activity of the enzymes used in the extraction. Treatments with HHP were more efficient than the enzyme-assisted extraction, and the treatments E3 and E1 showed high inhibitory α-amylase activity. Results suggest that the application of HHP can be efficient and economical in the phenolic compounds recovery from GP when compared to other more complex processes that require longer processing time, adding value to a low-value industrial waste.

PH-Controlled fermentation of strawberry waste as phenol solubilisation method

The present study aims to use pH as a control parameter for the accumulation of target compounds. Solubilisation of wasted strawberry through fermentation at different operational pH (pH 4, 7, and 9) was evaluated. Methane as a target compound was achieved at pH 7, reaching a value up to 353 ± 10 mL CH4/g VS (VS, volatile solids). Operation at pH 9 was hardly controlled due to the low pH of the substrate and the accumulation of VFA. pH 9 resulted in the highest accumulation of VFA, mainly acetic acid. The operation at pH 4 resulted in the inhibition of the biogas production, leading to the concentration of soluble phenols up to 3 times the initial concentration in the reactors. The concentrations of pelargonidin 3-glucoside and p-coumaric acid showed a significant increase at pH 4 (p = 0.157 and p = 0.058, respectively). Acidogenic fermentation could be a suitable method to solubilise bioactive compounds from wasted strawberries without the necessity of high-energy pre-treatments. The low energy demand, i.e. 19 equivalent kJ/g gallic acid, as well as the high phenol solubilisation capacity, indicates that the acidogenic fermentation at pH 4 it is a promising method for the recovery of phenols from wasted strawberry.

Kiwi fruit residues from industry processing: study for a maximum phenolic recovery yield.

A response surface methodology was used to study the conditions for a maximum recovery of phenolics from processing kiwi fruit residues. Ethanolic extracts were prepared with different conditions of pH (2, 5, 10), temperature (30, 50 and 70ºC) and time (10, 20, 30min). Total phenolics, total flavonoids content and antioxidant activities by 2,2-diphenyl-1-picrylhydrazyl scavenging capacity and ferric reducing antioxidant power were determined. Samples from optimal extraction condition were injected HPLC-DAD system to access the phenolic profile and content. The best extraction conditions were pH solvent of 2, 70ºC of temperature and 20min of extraction. Ten phenolics were identified: caffeic acid and its derivatives, chlorogenic acid and ferulic acid, (+)-catechin, (-)-epicatechin), rutin and quercitrin. These phenolics often reported as having important antioxidant, anti-inflammatory, antiaging and anticancer activities, turn this residues and excellent source of bioactive compounds to be used in agro-food, cosmetics or phytochemical industries.

Low-Molecular-Weight Phenols Recovery by Eco-Friendly Extraction from Quercus Spp. Wastes: An Analytical and Biomass-Sustainability Evaluation

In this work, chemical–physical protocols aimed at the implementation of eco-friendly and biomass-sustainable recovery processes of useful compounds from forestry and/or wood industry wastes were evaluated. Four species of interest in industrial and environmental fields (Quercus cerris, Quercus ilex, and Robinia pseudoacacia from Central Italy, Quercus petraea from France) were submitted to neutral extraction and analyzed by gaschromatography, with mass spectrometry identification of low-molecular-weight phenols. Moreover, Quercus petraea heartwood samples were submitted to three extraction/hydrolysis protocols in an alkaline environment, and the byproducts from the lignin degradation were identified and evaluated. The recovery of bioactive phenols from forestry wastes by applying eco-friendly extractive protocols may reveal a precious strategy for rethinking the management of such wastes, in line with the fundamentals of “circular economy”.

Efficient recovery of phenol from coal tar processing wastewater with tributylphosphane/diethyl carbonate/cyclohexane: Extraction cycle and mechanism study

Sodium sulfate wastewater is a kind of coal tar processing effluent containing highly concentrated phenol. Owing to its high toxicity, phenol pose a serious threat to the natural environment and human health. In this paper, a novel ternary extractant, tributylphosphane (TBP)/diethyl carbonate (DEC)/cyclohexane, was utilized to extract phenol from the wastewater. The combination of 20% TBP, 20% DEC, and 60% cyclohexane yielded a high extraction efficiency of 99.79% under the suggested conditions (time of 6 min, organic–aqueous volume ratio of 1, pH of 5.05 and temperature of 298.15 K). Fourier-transform infrared spectroscopy analysis illustrates that the extraction of phenol was enabled by intermolecular hydrogen bonding with both TBP and DEC. The stripping of phenol from the phenol-loaded extractant was carried out using an alkali solution, realizing the recovery of phenol resource and the regeneration of extractant. The stripping efficiency reached 96.29% when using 1 mol/L NaOH solution under certain conditions (contact time of 4 min, aqueous–organic volume ratio of 1, and temperature of 313.15 K). Additionally, the pH response analysis shows that the stripping process could be divided into four stages and more than 8 min of contact time leaded to the hydrolysis of the DEC. The ultra-high phenol recovery, up to 99.78%, was achieved from the actual wastewater via a two-stage extraction and back-extraction.

Development of a green innovative semi-industrial scale pilot combined microwave heating and centrifugal force to extract essential oils and phenolic compounds from orange peels

A new process for extraction of essential oils from orange peels (Citrus sinensis L.) using microwave and centrifugal (MW/C) force was studied. MW/C is a combination of microwave heating to explode the internal cells of biological material, and centrifugation to intensify diffusion, collection and separation of compounds of interest. MW/C is performed at atmospheric pressure with an injection of water vapor. A detailed study concerning optimization of different operating parameters like microwave power density and centrifugation was performed. MW/C has been compared to the hydrodistillation method. In addition of essential oils collection, in the aqueous phase several phenolic compounds can be obtained and valorized. Influence of the two main parameters was discussed first on essential oils and, in second part, on phenolic compounds recovery. The new combined MW/C process provided reduction in the extraction time compared to hydrodistillation method, with an advantage to collect in a same experiment volatile and nonvolatile compounds with high quality. Industrial relevanceThis work was carried out thanks to the investment of IFTS France, an international technical center worldwide known in the field of solid-fluid separations. Considering the huge amount of plant extracts this new combined system using microwave and centrifugal (MW/C) force may be suitable for scaling up. The results of this investigation on pilot reactors pave the way for the design of an industrial device.

Analysis of polyphenols in apple pomace: A comparative study of different extraction and hydrolysis procedures

Apple pomace is a potential source of bioactive polyphenols. The objective of this study was to compare different methods for extraction of phenolic compounds. The content of free polyphenolic compounds in aqueous-methanol extracts was 5.56 mg gallic acid equivalents (GAE)/g dry weight (DW) pomace, with the major free phenolic compounds identified as chlorogenic acid, quercetin-3-O-galactoside, quercetin-3-O-rhamnoside, and phloridzin. Different order of sequential base and acid hydrolysis of the residue and then extraction by diethyl ether/ethyl acetate yielded 6.82–8.12 mg GAE/g DW of bound polyphenols. The major phenolics in the residue, after aqueous-methanol was subjected to base hydrolysis, were phloridzin, 4-hydroxybenzoic acid, and quercetin-3-O-galactoside, and subsequent acid hydrolysis further released significant amounts of 4-hydroxybenzoic acid and isoferulic acid. Extraction of the residue remaining after aqueous-methanol extraction subjected to acid hydrolysis released mainly 4-hydroxybenzoic acid, protocatechuic acid and isoferulic acid, and subsequent base hydrolysis further released significant amounts of protocatechuic acid, catechin and 4-hydroxybenzoic acid. Extracts obtained after direct acid or base hydrolysis yielded 5.55 mg GAE/g DW and 10.62 mg GAE/g DW, respectively. The absolute amounts of the individual phenolic compounds were different in different fractions after either direct base or acid hydrolysis. Regardless of the hydrolysis procedures, the extractions with higher phenolics contents showed the stronger antioxidant activities, as measured by oxygen radical absorbance capacity (ORAC). This work shows that extraction and hydrolysis procedure have substantial effects on the recovery of phenolics from apple pomace.

Bio-Functional and Structural Properties of Pasta Enriched with a Debranning Fraction from Purple Wheat.

A colored and fiber-rich fraction from the debranning of purple wheat was incorporated at 25% into semolina- and flour-based pasta produced on a pilot-plant scale, with the aim of increasing anthocyanin and total phenolic content with respect to pasta obtained from whole pigmented grains. The debranning fraction impaired the formation of disulfide-stabilized protein networks in semolina-based systems. Recovery of phenolics was impaired by the pasta making process, and cooking decreased the phenolic content in both enriched samples. Cooking-related losses in anthocyanins and total phenolics were similar, but anthocyanins in the cooked semolina-based pasta were around 20% of what was expected from the formulation. HPLC (High Performance Liquid Chromatography) profiling of phenolics was carried out on extracts from either type of enriched pasta both before and after cooking and indicate possible preferential retention of specific compounds in each type of enriched pasta. Extracts from cooked samples of either enriched pasta were tested as inhibitors of enzymes involved in glucose metabolism and uptake, as well as for their capacity of suppressing the response to inflammatory stimuli. Results of both biological tests indicate that the phenolics in extracts from both cooked pasta samples had inhibitory capacities higher than extracts of the original debranning fraction at identical concentrations of total bioactives.

Synthesis of humic-like acid from biomass pretreatment liquor: Quantitative appraisal of electron transferring capacity and metal-binding potential

The treatment of alkaline pretreatment liquor is critical for the clean production of biomass refinery industry. There is a compelling need to develop a simple technology for reuse of organic matter in the pretreatment liquor to achieve a more value-added product with high application potential in agriculture and benefit environmental sustainability. The objective of this study is to examine a strategy for synthesizing humic-like acid under H₂O₂ oxidation by using biomass pretreatment liquor as a precursor and evaluate their electron transferring capacity and metal-binding potential. The results show that 8% H₂O₂, a temperature of 40 °C, and a reaction time of 2 h yielded humic-like acid up to 2.9 g L−1. Meanwhile, the recovery of total phenols, total sugars, proteins, and amino acids in the pretreatment liquor was 82.8, 56.2, 78.1, and 64.2%, respectively. Compared to the commercial humic acid, humic-like acid has a more uniform particle size and higher C (22.5%), N (2.3%), O (33.8%), K (4.5%), and P (11.2%) contents. The hydroxyl and carboxyl group contents were 3.3 and 2.0 times higher in humic-like acid than that in humic acid, respectively. Moreover, humic-like acid has more electron transferring capacity as well as metal-binding potential than commercial humic acid, suggesting the great application potential for remediation of heavy metal polluted soils. The reported strategy of synthesizing humic-like acid from pretreatment liquor in this study would promote the process of cleaner production of biorefinery industry as well as circular economy in agriculture.