Aqueous Leaching Research Articles

Aqueous oxidation of coal-associated pyrite and standard pyrite mineral towards understanding the depyritization kinetics and acid formations

In coal mining areas, the ambient atmospheric and aqueous oxidation of pyrite minerals (FeS2) associated with coal as well as the other accompanying strata is significant in understanding the extent of acid mine drainage (AMD), the cause of severe environmental pollution. Therefore, in this paper, the oxidation kinetics of the coal-associated pyrite (CAPy) present in a coal sample (TpHM1) has been studied via aqueous leaching depyritization experiments at variety of temperatures and time intervals without the incorporation of any oxidizer. The outcomes obtained are juxtaposed with the standard pyrite mineral (SPM) oxidation at the same experimental conditions. Also, the coal and SPM slurry residues and filtrates obtained after aqueous leaching at 25 °C and 90 °C for 0 h and 24 h, respectively, were extensively analyzed through high-resolution transmission electron microscopy (HR-TEM), Powder X-ray diffraction (P-XRD), and X-ray-photoelectron spectroscopy (XPS) for evaluation of the mineralogical composition and proportions of iron and sulfur components during progression of the oxidation reaction. Both the reactions obey pseudo first-order kinetics during pyrite (FeS2) oxidation but a significant difference in the experimentally found activation energies (Ea) and rate constants (k) values of oxidation kinetics of both CAPy and SPM may be attributed to the varied geochemical compositions of the coal associated pyrite (CAPy). The rate constant for CAPy is much greater than that of SPM implying a higher Ea around 10.838 kJ/mol for SPM as compared to 1.941 kJ/mol for CAPy. The CAPy in coal (TpHM1) is more susceptible to atmospheric oxidation than that of SPM, leading to the formation of acid mine drainage with lower pH. In this paper, the pH values on the basis of stoichiometric pyrite oxidation reaction were calculated and compared with the pH values obtained after aqueous leaching of CAPy to interpret the extent of acid formation and pyrite dissolution. Hence, with the assistance of the current study, further studies on the effects of mineral impurities, whereabouts of pyrite minerals in coal seams, the significance of compositional differences in the CAPy, the effect of metal oxides, and the role of alkalinity producing neutralizing agents of coal in the oxidative dissolution process of pyrite can be investigated.

An Unprecedented Tridentate-Bridging Coordination Mode of Permanganate Ions: The Synthesis of an Anionic Coordination Polymer-[CoIII(NH3)6]n[(K(κ1-Cl)2(μ2,2',2″-(κ3-O,O',O″-MnO4)2)n∞]-Containing Potassium Central Ion and Chlorido and Permanganato Ligands.

A unique compound (compound 1) with structural features including an unprecedented tridentate-bridging coordination mode of permanganate ions and an eight-coordinated (rhombohedral) κ1-chlorido and tridentate permanganato ligand in a potassium complex containing coordination polymer (CoIII(NH3)6]n[(K(κ1-Cl)2(μ2,2',2″-(κ3-O,O',O″-MnO4)2)n∞) with isolated regular octahedral hexamminecobalt(III) cation was synthesized with a yield of >90%. The structure was found to be stabilized by mono and bifurcated N-H∙∙∙Cl and N-H∙∙∙O (bridging and non-bridging) hydrogen bonds. Detailed spectroscopic (IR, far-IR, and Raman) studies and correlation analysis were performed to assign all vibrational modes. The existence of a resonance Raman effect of compound 1 was also observed. The thermal decomposition products at 500 °C were found to be tetragonal nano-CoMn2O4 spinel with 19-25 nm crystallite size and KCl. The decomposition intermediates formed in toluene at 110 °C showed the presence of a potassium- and chloride-containing intermediates combined into KCl during aqueous leaching, together with the formation of cobalt(II) nitrate hexahydrate. This means that the CoIII-CoII redox reaction and the complete decomposition of the permanganate ions occurred in the first decomposition step, with a partial oxidation of ammonia into nitrate ions.

The effect of entropy on the structure and aqueous leaching resistance of nano monazite-type phosphates

Monazite, with its unique chemical composition and stable crystal structure, shows significant potential for immobilizing high-level radioactive waste. In this study, a series of monazite ceramics were synthesized to study the effect of entropy change on their structure and aqueous durability. The synthesized ceramics exhibit a monoclinic structure (P21/n), with an average grain size below 80 nm. MCC-1 leaching tests reveal that the normalized leaching rate decreases over time but increases with higher entropy. The five-element high-entropy ceramics have an average leaching rate of 4.2 × 10⁻³ g·m⁻2 d⁻1. Notably, the higher leaching rate in high-entropy nanocrystalline monazites is likely attributed to the reduced grain size. The presence of numerous grain boundaries tends to mitigate the precipitation inhibition effect typically associated with high-entropy ceramics. These findings offer insights into the role of entropy and grain size in ceramic materials for radioactive waste immobilization.

The complex effect of dissolved organic carbon on desorption of per- and poly-fluoroalkyl substances from soil under alkaline conditions

Per- and poly-fluoroalkyl substances (PFASs) are contaminants of emerging concern, yet the understanding of factors that control their leaching and release from contaminated soils remains limited. This study aimed to investigate the impact of dissolved organic carbon (DOC) on the release of PFASs—specifically, perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA)from soils contaminated by aqueous film forming foam (AFFF). Batch aqueous leaching experiments were conducted on AFFF-contaminated soils under alkaline solution conditions (pH 9.5, 10.5, and 12) as it enhances leaching of both PFAS and DOC. Leaching of PFOS was significantly increased under alkaline conditions. Although the leaching of PFAS generally increased with pH, PFOS appeared to be more retained under the very alkaline pH conditions used in this study. At the same solution pH, leaching of PFOS and DOC was less in Ca(OH)2 than in NaOH. The retention of PFOS under these conditions may be attributable to the shielding of the negative charge of the soil components and colloids (e.g., DOC and clay minerals) in the leachates and/or the screening of negative charges on head groups of PFOS due to the high concentration of divalent cations. Solution chemistry affected desorption of PFOS more than PFHxS and PFOA. The study highlights that the influence of DOC on PFAS leaching and transport can be very complex, and depends on leachate chemistry (e.g., pH and cation type), PFAS chemistry, the magnitude of PFAS contamination and factors that influence the solid:liquid partitioning of organic carbon in soil.

Thermogravimetry as a research tool for the development of an ammonium sulphate roasting process for selective metal extraction from minerals

AbstractThe ammonium sulphate roasting process involves reacting mineral-bearing materials with ammonium sulphate via a solid–solid roasting process and subjecting the resulting roast residue to aqueous leaching. This process enables the simultaneous, non-selective co-extraction of strategic metals from the starting materials. However, effective separation of the extracted metals is often mandatory to produce quality products of high purity. In this study, the combined application of thermogravimetric analysis, X-ray powder diffraction and inductively coupled plasma optical emission spectrometry confirmed the non-selectivity of the process when applied to a South African diamond mine residue residue roasted with ammonium sulphate in a 1:2 mass ratio (m/m) at 450 °C for 2 h, with magnesium, iron and aluminium being co-extracted into water-soluble metal sulphates. Thermogravimetry was then applied to develop a multi-step, multi-temperature selective roasting process using mixtures of pure commercial metal sulphate salts. The first step of the modified process successfully separated iron and aluminium sulphates from magnesium-sulphates in the roast residues by thermally decomposing soluble iron and aluminium sulphates into insoluble oxides via calcination at 750 °C for 2 h. This temperature was lower than the one at which magnesium sulphates convert into magnesium oxide. In the second and final step, iron and aluminium were recovered from the oxide minerals via solid–solid re-roasting with ammonium sulphate at 450 °C for 1 h, causing the oxides to revert back to their water-soluble sulphate forms. The effectiveness of the modified process was subsequently verified using a diamond mine residue, showing that the soluble iron and aluminium contents in the magnesium-bearing leachate could be reduced by over 90%.

Unravelling protein corona formation on pristine and leached microplastics

Upon entering the environment, the surface properties of pristine plastics are rapidly altered due to interactions with exogenous biomolecules, contaminants, and even microbiota, which ultimately alter their ecological impacts. When present in biological fluids or high protein environments, micro(nano)plastics bind with proteins, which form a protein corona around the particle. Although a significant body of literature exists on protein corona formation on nanomaterials, less is known about how the physiochemical properties of microplastics may influence protein corona formation. This study utilises quantitative proteomics to quantify protein binding to pristine and leached microplastics. Pristine polyethylene (PE) beads (50 and 500 μm), polyamide (PA) fibres (100 μm), polyethylene terephthalate fibres (500 μm), and fragments (< 300 μm), as well as pristine and leached textile microfibres comprised of PET, recycled PET, PA or cotton were incubated for 24 h in bovine serum albumin solution (2 mg mL−1) to form a protein corona. Protein adsorption to microplastics was dependant on particle surface area to volume ratio but only when additives were absent. For environmentally relevant textile microfibres, cotton microfibres adsorbed significantly more protein than synthetic microfibres. Fourteen-day aqueous leaching increased the zeta potential of all microfibres. However, only PA fibres adsorbed significantly higher protein on the leached fibres compared to their pristine counterparts. Overall, the presence of chemical additives in microplastics strongly influenced protein corona formation, and this phenomenon should be incorporated into routine microplastic toxicity assessment.Graphical

Leaching of palladium from spent Pd/Al2O3 catalysts by coupled ultrasound-microwave technique

The recycling and reuse of spent Pd/Al2O3 catalysts have tremendous social, environmental, and economic benefits. Calcined-ClO2 and NH4Cl aqueous leaching method was investigated to recover Pd from spent Pd/Al2O3 catalysts, and ultrasound-microwave was introduced to intensify the leaching process, after which the surface morphology, valence, and content of major elements, and crystalline shape of carriers of the spent Pd/Al2O3 catalysts before and after the leaching were determined and analyzed. The results showed that ultrasonic-microwave-enhancement increased the leaching rate and shortened the leaching time of Pd in comparison with the conventional leaching experiments, and the leaching rate of Pd at 10 min of ultrasonic-microwave-enhanced leaching was 31.1 %, which was 13.6 % higher than that of the conventional conditions. The optimal process conditions: calcination temperature was 200 °C, calcination time was 90 min, the dosage of ClO2 was 15 % (V/Vall), the concentration of NH4Cl was 2 mol/L, the dosage of HCl (1 mol/L) was 15 % (V/Vall), the leaching power was 400 W, leaching temperature was 90 °C, leaching time was 60 min, and the liquid–solid ratio was 10:1. Eventually, the leaching rate of palladium was 80.6 %, and the average retention rate of carrier was about 94 %.

Aqueous Leaching of Ultrashort-Chain PFAS from (Fluoro)polymers: Targeted and Nontargeted Analysis

Aqueous Leaching of Ultrashort-Chain PFAS from (Fluoro)polymers: Targeted and Nontargeted Analysis

Advanced characterization of secondary phases formed during long-term aqueous leaching of spent nuclear fuel

Advanced characterization of secondary phases formed during long-term aqueous leaching of spent nuclear fuel

Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals, that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage (AMD) through oxidation pyrite minerals. The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India. In order to have a comprehensive overview of the AMD problem in Makum coalfield, the physico-chemical, geochemical, and petrological characteristics of the coal and overburden (OB) samples collected from the Makum coalfield (Northeast India) were thoroughly investigated. The maceral compositions reveal that coal features all three groups of macerals (liptinite, vitrinite, and inertinite), with a high concentration of liptinite indicating the coal of perhydrous, thereby rendering it more reactive. Pyrite (FeS2) oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and (OB) samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods, and to replicate the actual mine site leaching. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment. The Rare earth element (REE) enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB. These experiments reveal the change in conductivity, acid producing tendency, total dissolved solid(TDS), total Iron(Fe) and dissolved Sulfate(SO42−) ions on progress of the leaching experiments. Moreover, the discharge of FeS2 via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics. A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station. Apart from neutralisation of AMD water, this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

Study of the leaching process for dust chamber sublimates followed by the extraction of niobium and zirconium into solution

The material composition of the sublimates from dust chambers in titanium chlorinators has been studied by chemical, X-ray and microprobe analysis methods. Studies of the phase composition of dust chamber sublimates have shown that the object consists of aqueous and anhydrous chloride phases to a greater extent. Two forms of niobium present, such as oxychloride and oxide niobium were found. The presence of zirconium in sublimates has a chloride and oxychloride nature. Experiments for the aqueous leaching of dust chamber sublimates were conducted to determine the optimal process conditions: S:L ratio = 1:8, leaching time = 1 hour, temperature = 25℃. Studies were conducted to choose an acidic reagent for cake leaching followed by the conversion of niobium and zirconium into a solution. A solution consisting of HF+H2SO4 was selected as an acidic reagent for cake leaching. Optimal conditions for the extraction of niobium and zirconium into solution were established, such as 25% [18M HF] +75% [7M H2SO4], S:L ratio = 1:3, temperature = 90 °C, duration of the leaching process = 120 minutes. Under these leaching conditions, the extraction of niobium, zirconium, and titanium into solution was 94.06%, 84.95% and 32.35%, respectively. The elemental and phase composition of the residue from acid leaching of cake were determined.

Green method for recovery of cannabinoids from Cannabis sativa flowers: pH-controlled aqueous leaching

Cannabis sativa is a remarkable plant containing a wide variety of valuable secondary metabolites, especially cannabinoids, which are valued for their clinical relevance. In this investigation, an efficient and environmentally friendly method to recover cannabinoids from cannabis plant tissues using organic solvent-free pH-controlled solution has been developed. The impact of leaching pH and solid/liquid ratios on the recovery of thirteen acidic and neutral cannabinoids from a wide range of cannabis plant tissues, which are either high tetrahydrocannabinol (THC) or high cannabidiol (CBD) cultivars in fresh, dried and decarboxylated forms, was investigated. The results revealed acidic cannabinoids, the predominant cannabinoids in fresh and cannabis dried at low temperature, were recovered efficiently at pH ≥ 12, demonstrating the potential of alkaline leaching to replace the conventional alcohol leaching widely utilized in the cannabis industry. Alkaline leaching also enables a highly efficient means of obtaining a cannabinoid concentrate directly from fresh material and avoids the long (4–6 d) and energy-intensive drying process. Alkaline leaching was also viable for neutral cannabinoid recovery from decarboxylated cannabis at low solid/liquid ratio. Finally, the stability of cannabinoids in leached solutions at room temperature and in the dark was tracked and analyzed for up to 15 d. These data offer the cannabis industry a range of options for cannabinoid storage and extraction during the enrichment processes.

Universal and efficient extraction of lithium for lithium-ion battery recycling using mechanochemistry

The increasing lithium-ion battery production calls for profitable and ecologically benign technologies for their recycling. Unfortunately, all used recycling technologies are always associated with large energy consumption and utilization of corrosive reagents, which creates a risk to the environment. Herein we report a highly efficient mechanochemically induced acid-free process for recycling Li from cathode materials of different chemistries such as LiCoO2, LiMn2O4, Li(CoNiMn)O2, and LiFePO4. The introduced technology uses Al as a reducing agent in the mechanochemical reaction. Two different processes have been developed to regenerate lithium and transform it into pure Li2CO3. The mechanisms of mechanochemical transformation, aqueous leaching, and lithium purification were investigated. The presented technology achieves a recovery rate for Li of up to 70% without applying any corrosive leachates or utilizing high temperatures. The key innovation is that the regeneration of lithium was successfully performed for all relevant cathode chemistries, including their mixture.

Chemical characteristics, leaching, and stability of the ubiquitous tire rubber-derived toxicant 6PPD-quinone.

We here report chemical characteristics relevant to the fate and transport of the recently discovered environmental toxicant 6PPD-quinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione or "6PPDQ"). 6PPDQ is a transformation product of the tire rubber antioxidant 6PPD that is ubiquitous in roadway environments, including atmospheric particulate matter, soils, runoff, and receiving waters, after dispersal from tire rubber use and wear on roadways. The aqueous solubility and octanol-water partitioning coefficient (i.e. log KOW) for 6PPDQ were measured to be 38 ± 10 μg L-1 and 4.30 ± 0.02, respectively. Within the context of analytical measurement and laboratory processing, sorption to various laboratory materials was evaluated, indicating that glass was largely inert but loss of 6PPDQ to other materials was common. Aqueous leaching simulations from tire tread wear particles (TWPs) indicated short term release of ∼5.2 μg 6PPDQ per gram TWP over 6 h under flow-through conditions. Aqueous stability tests observed a slight-to-moderate loss of 6PPDQ over 47 days (26 ± 3% loss) for pH 5, 7 and 9. These measured physicochemical properties suggest that 6PPDQ is generally poorly soluble but fairly stable over short time periods in simple aqueous systems. 6PPDQ can also leach readily from TWPs for subsequent environmental transport, posing high potential for adverse effects in local aquatic environments.

Hexaamminecobalt(III)] Dichloride Permanganate—Structural Features and Heat-Induced Transformations into (CoII,MnII)(CoIII,MnIII)2O4 Spinels

We synthesized and characterized (IR, Raman, UV, SXRD) hexaamminecobalt(III) dichloride permanganate, [Co(NH3)6]Cl2(MnO4) (compound 1) as the precursor of Co–Mn–spinel composites with atomic ratios of Co:Mn = 1:1 and 1:3. The 3D−hydrogen bond network includes N–HO–Mn and N–HCl interactions responsible for solid-phase redox reactions between the permanganate anions and ammonia ligands. The temperature-limited thermal decomposition of compound 1 under the temperature of boiling toluene (110 ∘C) resulted in the formation of (NH4)4Co2Mn6O12. which contains a todorokite-like manganese oxide network (MnII4MnIII2O1210−). The heat treatment products of compounds 1 and [Co(NH3)5Cl](MnO4)2 (2) synthesized previously at 500 ∘C were a cubic and a tetragonal spinel with Co1.5Mn1.5O4 and CoMn2O4 composition, respectively. The heating of the decomposition product of compounds 1 and 2 that formed under refluxing toluene (a mixture with an atomic ratio of Co:Mn = 1:1 and 1:2) and after aqueous leaching ((NH4)4Co2Mn6O12, 1:3 Co:Mn atomic ratio in both cases) at 500 ∘C resulted in tetragonal Co0.75Mn2.25O4 spinels. The Co1.5Mn1.5O4 prepared from compound 1 at 500 ∘C during the solid-phase decomposition catalyzes the degradation of Congo red with UV light. The decomposition rate of the dye was found to be nine times faster than in the presence of the tetragonal CoMn2O4 spinel prepared in the solid-phase decomposition of compound 2. The todorokite-like intermediate prepared from compound 1 under N2 at 115 ∘C resulted in a 54 times faster degradation of Congo red, which is a great deal faster than the same todorokite-like phase that formed from compound 2 under N2.

Study of Forms of Compounds of Vanadium and Other Elements in Samples of Pyrometallurgical Enrichment of Ash from Burning Oil Combustion at Thermal Power Plants.

The results of the processing of ash from the combustion of fuel oil after roasting with the addition of Na2CO3 followed by aluminothermic melting are presented. As a result, metallic nickel and vanadium slag were obtained. Studies of slag, metal, and deposits on the electrode were carried out. The resulting metal contains about 90 wt% Ni. The main phases of scurf on the electrode are a solid solution based on periclase (Mg1-x-y-zNixFeyVzO), sodium-magnesium vanadate (NaMg4(VO4)3), and substituted forsterite (Mg2-x-yFexNiySiO4). The processing of ash made it possible to significantly increase the concentration of vanadium and convert it into more soluble compounds. Vanadium amount increased from 16.2 in ash to 41.4-48.1 V2O5 wt% in slag. The solubility of vanadium was studied during aqueous leaching and in solutions of H2SO4 and Na2CO3. The highest solubility of vanadium was seen in H2SO4 solutions. The degree of extraction of vanadium into the solution during sulfuric acid leaching of ash was 18.9%. In slag, this figure increased to 72.3-96.2%. In the ash sample, vanadium was found in the form of V5+, V4+ compounds, vanadium oxides VO2 (V4+), V2O5 (V5+), and V6O13, and nickel orthovanadate Ni3(VO4)2 (V5+) was found in it. In the slag sample, vanadium was in the form of compounds V5+, V4+, V3+, and V(0÷3)+; V5+ was presented in the form of compounds vanadate NaMg4(VO4)3, NaVO3, and CaxMgyNaz(VO4)6; V3+ was present in spinel (FeV2O4) and substituted karelianite (V2-x-y-zFexAlyCrzO3). In the obtained slag samples, soluble forms of vanadium are due to the presence of sodium metavanadate (NaVO3), a phase with the structure of granate CaxMgyNaz(VO4)6 and (possibly) substituted karelianite (V2-x-y-zFexAlyCrzO3). In addition, spinel phases of the MgAl2O4 type beta-alumina (NaAl11O17), nepheline (Na4-xKxAl4Si4O16), and lepidocrocite (FeOOH) were found in the slag samples.

Crystal Engineering in Antisolvent Crystallization of Rare Earth Elements (REEs)

Antisolvent crystallization is a separation technology that separates the solute from the solvent by the addition of another solvent, in which the solute is sparingly soluble. High yields are achieved by using higher antisolvent-to-aqueous ratios, but this generates higher supersaturation, which causes excessive nucleation. This results in the production of smaller particles, which are difficult to handle in downstream processes. In this work, the effect of varying the organic (antisolvent)-to-aqueous (O/A) ratio and seed loading on the yield, particle size distribution, and morphology of neodymium sulphate product, during its recovery from an aqueous leach solution using antisolvent crystallization, was investigated. A batch crystallizer was used for the experiments, while ethanol was used as an antisolvent. Neodymium sulphate octahydrate [Nd2(SO4)3.8H2O] seeds were used to investigate the effect of seed loading. It was found that particle sizes increased as the O/A ratio increased. This was attributed to the agglomeration of smaller particles that formed at high supersaturation. An O/A ratio of 1.4 resulted in higher yields and particles with a plate-like morphology. The increase in yield was attributed to the increased interaction of ethanol molecules with the solvent, which reduced the solubility of neodymium sulphate. Increasing the seed loading resulted in smaller particle sizes with narrow particle size distribution and improved filtration performance. This was attributed to the promotion of crystal growth and suppression of agglomeration in the presence of seeds.

Oxidative exfoliation of spent cathode carbon: A two-in-one strategy for its decontamination and high-valued application

Spent cathode carbon (SCC) from aluminum electrolysis is a potential graphite resource. However, full use of the SCC remains a challenge, since it contains many hazardous substances (e.g., fluoride salts, cyanides), encapsulated within the thick carbon layers and thus posing serious environmental concerns. This work presents a chemical oxidative exfoliation route to achieve the recycling of SCC and the decontaminated SCC with high-valued graphene oxide (GO)-like carbon structures (SCC-GO) is applied as an excellent adsorbent for organic pollutants. Specifically, after the oxidative exfoliation, the embedded hazardous constituents are fully exposed, facilitating their subsequent removal by aqueous leaching. Moreover, benefiting from the enhanced specific surface areas along with abundant O-containing functional groups, the as-produced SCC-GO, shows an adsorption capacity as high as 347 mg·g−1 when considering methylene blue as a pollutant model, which exceeds most of the recently reported carbon-based adsorbents. Our study provides a feasible solution for the efficient recycling of hazardous carbonaceous wastes.

Effect of microwave pretreatment on the extraction of antioxidant‐rich red color betacyanin, phenolic, and flavonoid from the crown of Cylindra‐type beetroot (Beta vulgaris L.)

AbstractIn the context of “waste valorization,” recovery of biomolecules from agri‐food wastes by the innovative extraction technique has come to the forefront. In this investigation, the effect of microwave pretreatment on aqueous extraction of betacyanin (BC), phenolic, flavonoid, and antioxidant from the crown part of Cylindra‐type beetroot (Beta vulgaris L.) has been studied. Two major operating parameters of leaching, such as temperature and extraction time have been varied, ranging from 30°C to 60°C and 20–60 min, respectively to optimize the extraction of mentioned biomolecules through the response surface methodology technique. Moreover, the extraction of mentioned biomolecules by leaching was increased by microwave pretreatment (at 800 W for 3 min). As an example: the microwave‐assisted aqueous leaching process provided BC color compound 17.12 ± 0.37 mg/g dry matter (DM), total phenolic compounds (TPC) 57.89 ± 1.14 mg gallic acid equivalent (GAE)/g DM, total flavonoids content (TFC) 10.37 ± 0.00 mg quercetin equivalent (QUE)/g DM and total antioxidant activity (AA) 56.13 ± 0.92 mg ascorbic acid equivalent (ASE)/g DM. Whereas, BC, TPC, TFC, and AA were 3.04 ± 0.07 mg/g DM, 2.81 ± 0.11 mg GAE/g DM, 2.43 ± 0.41 mg QUE/g DM, and 4.38 ± 0.18 mg ASE/g DM by aqueous leaching process without microwave pretreatment. Subsequently, the existence of two major different BC, such as betanin and iso‐betanin have been examined by high‐performance liquid chromatography‐diode array detector‐electrospray ionization‐quadrupole‐time‐of‐flight. In addition, changes in the morphology of the plant matrix were pointed out by field emission scanning electron microscope. Our investigation has proven the positive impacts of microwave pretreatment on the extraction of mentioned bioactive compounds by infusion and maceration processes as well.Practical ApplicationsThe application of innovative emerging technologies for the effective scavenging of bioactive compounds from agro‐industrial discharges has been focused on. Under the study range, microwave‐assisted leaching extraction was found to be the most efficient method as it exhibited the utmost amounts of betacyanin, phenolic, flavonoid, and antioxidants in microwave‐assisted maceration and infusion processes. This investigation encourages the short‐time microwave pretreatment before the performance of traditional solid–liquid extractions in order to improve the extraction efficacy of plant compounds.

Antioxidant activity and cytotoxicity of Vacciniun corymbosum L. cultivated in Tucumán, Argentina

Among berries, blueberries (Vaccinium corymbosum L.) are considered one of the main sources of phenolic compounds and are appreciated for their high antioxidant activity. Due to the apparent relationship between phytochemicals in plants to the prevention of chronic diseases, the study of the content and physiological activity of phenolic compounds and other bioactive metabolites present in blueberries is interesting. In this work, Tucuman blueberries of the O'Neal variety were used, out of which four different extracts were obtained. One of them was obtained by sequential leaching with hydroalcoholic mixtures from frozen fresh fruits (E1), a second extract from aqueous leaching (E2), and acetone as solvent (E3). Spectrophotometric techniques were performed to quantify Total Phenols, Total Flavonoids and Anthocyanins. The extracts presented a similar quantitative profile of phenolic compounds. The antioxidant activity of the extracts obtained was evaluated using two different techniques (ABTS•+ and DPPH•). The extracts showed a free radical inhibitory activity and a similar reducing power. Through the acute toxicity test (24h) of the organic and aqueous extracts from the blueberry on C. elegans, .it was possible to determine that the extracts under study do not show toxicity for further study.