1,721,045 research outputs found
Chitosan-based adsorbents for antibiotic removal with insights from batch and dynamic studies: A review
No full textRemoving antibiotics from water systems is an urgent concern for modern society due to their toxicity and potential long-term ecological consequences. Among many treatment methods, adsorption by chitosan composites has proven to be one of the most promising approaches due to their biodegradability, abundant functional groups (amino and hydroxyl), and ease of modification. This review offers a detailed and up-to-date overview of the applications of chitosan-based composites for antibiotic removal, focusing on their effectiveness in both batch and dynamic (fixed-bed column) operations. It highlights that tetracycline is the most studied contaminant, and magnetic chitosan materials are the predominant adsorbents used. Chitosan-metal-organic frameworks composites exhibit some of the highest reported adsorption capacities. Adsorption is influenced by factors such as pH, initial concentration, and adsorbent dosage, with electrostatic attraction, hydrogen bonding, and π-π interactions identified as the main mechanisms. Kinetic analyses show that the pseudo-second-order model best describes adsorption rates, while the Langmuir isotherm often fits equilibrium data well. Both batch and dynamic (fixed-bed) studies demonstrate substantial removal efficiencies, although dynamic systems better simulate real wastewater treatment conditions and offer improved adsorbent utilization. This review emphasizes the possibility of using chitosan adsorbents in removing antibiotics and calls for further dynamic studies to validate their application in wastewater treatment
From laboratory- to industrial-scale plants: Future of anaerobic digestion of olive mill solid wastes
No full text: In this review, the main properties of olive mill solid waste, the primary by-product of olive oil production, and its feasibility as a feedstock for anaerobic digesters operating at laboratory-, pilot- and industrial-scales are discussed in detail. Nutrient addition and thermal pretreatments were found to have the potential to address the challenges arising from the high carbon-to-nitrogen ratio, the low pH, and the high concentration of phenolic compounds. Furthermore, anaerobic co-digestion with different organic feedstocks has been identified as one of the most promising options to solve the aforementioned problems and the seasonality nature of olive waste, while improving the efficiency of anaerobic treatment plants that operate throughout the whole year. The insights generated from this study show co-digestion with wastes from animal farming to be the most environmentally and economically sustainable method for improving anaerobic digestion processes with olive mill solid waste
Removal of tetracycline and crystal violet from aqueous solutions by magnetic chitosan-lipid free Chlorella vulgaris biocomposite
No full textThe overuse and improper disposal of organic dyes and antibiotics, such as Crystal Violet (CV) and Tetracycline (TC), endanger aquatic ecosystems and water quality. In this work, a novel magnetic biocomposite was prepared by incorporating magnetite, chitosan, and residual biomass of Chlorella vulgaris after lipid extraction and applied for the adsorptive removal of TC and CV from water-based solutions. The highest removal of TC and CV occurred at pH 8, with the adsorption efficiency being influenced by the biocomposite dosage, the starting level of pollutants, and the time allowed for interaction. The adsorption behavior of TC aligned well with the Langmuir and Temkin adsorption isotherms, while the Langmuir model best described the CV one, indicating that this process follows monolayer-type adsorption, with the highest adsorption capacities of 864.382 mg/g for TC and 305.097 mg/g for CV. Kinetic studies showed that a pseudo-second-order model described the adsorption process, suggesting chemisorption as the primary mechanism. The thermodynamic evaluation indicated that the process was spontaneous and endothermic. This study highlights the effectiveness of the proposed biocomposite in removing antibiotics and dyes from water as an operative and sustainable adsorbent
Effect of encapsulating agent on physical-chemical characteristics of olive pomace polyphenols-rich extracts
No full textDuring the last years, olive industry wastes are considered as a potential source of extracts with antioxidant properties rich in polyphenols. The recovery of these added-value compounds can be interesting both for their beneficial properties and from an environmental point of view and several studies have been performed for the optimization and characterization of the phenolic compounds present in olive pomace liquid extracts. However, dried forms of natural extracts are associated with several advantages over liquid forms, such as limited storage costs, higher concentration and stability of target compounds. Spray drying is one of the most common techniques for the transformation of a liquid extract, or food formulation, into dried powder, due to low operative costs respect to other methods, and high flexibility, related to the large number of operative parameters that can be optimized, such as coating agent type and concentration, inlet temperature, feed flow and aspiration rate. In this study, an ethanolic extract rich in phenolic compounds from olive pomace (Taggiasca cultivar) was obtained by high pressure and temperature extraction and spray dried with different ratios of gum Arabic and maltodextrin as coating agents (0:100, 20:80, 40:60, 60:40, 80:20 and 100:0 % w/w). The total amount of coating agent was maintained constant and equal to 10 % w/v (100 g/L). Inlet temperature, feed flow and aspiration rate were 160 °C, 5 mL/min and 30 m3/h, respectively. For all products, moisture content, water solubility index, total polyphenol content, antiradical power and microencapsulation yield were determined. The results of this study show that the coating agent and process conditions led to the production of microencapsulated powders with improved water dissolution rate and a minimal loss in phenolics during the drying phase. The obtained microparticles, due to their high content in bioactive compounds and ease of handling, can have potential industrial applications as functional components for foods or nutraceuticals purposes
Chlorella vulgaris growth on digested urban sludge
No full textThe aim of this research was to investigate the effect of the addition of digested urban sludge on the growth medium of the microalga Chlorella vulgaris. The anaerobic digestion of biomass feedstock and/or the biodegradable fraction of wastes is widely recognized as a mature and cost-effective process for producing biogas, which is a valuable renewable primary-energy source. Anaerobically digested residues are effluents still rich in inorganic nutrients, with high chemical oxygen demand, which contribute to the eutrophication phenomenon. It is therefore necessary to further treat the effluent. Microalgae could potentially offer many advantages being able to use the organic carbon (heterotrophic growth) as well as inorganic nutrients such as nitrogen and phosphorus from the wastewater for their growth without an aerobic environment. In this study, an anaerobic digester (2.5 L), placed in a thermostatted water bath under mesophilic conditions (38 ± 1 °C) and pH 7.2–7.4, was employed. The mixed sludge (1.25 L) was daily fed with 30 mL of urbane sludge. Under pseudo-steady state conditions, the composition of biogas was nearly constant, and methane and carbon dioxide percentages ranged between 70.5–76.0 % and 13.2–19.5 %, respectively. The digested sludge was removed daily and centrifuged. The liquid phase was added in different percentages (100, 66 and 33 %) into the C. vulgaris medium to perform batch cultivations. The microalga concentration at the end of the experiments reached 2.72, 2.34 and 1.22 g/L when 66, 33 and 100 % of digested sludge liquid phase were used, respectively. These preliminary results suggest that combining microalgae production with municipal wastewater treatment could be made in an environmentally effective as well as economically viable way in a not distant future
subproductos de la uva: Extraccio ́n de compuestos polifenó licos usando co2 supercri{dotless} ́tico y disolventes orgá nicos líquidos - una investigación preliminar | [Grape by-products: Extraction of polyphenolic compounds using supercritical co2 and liquid organic solvent - a preliminary investigation]
No full textCultivation of Chlorella vulgaris in tubular photobioreactors: A lipid source for biodiesel production
No full textChlorella vulgaris was cultivated in two different 2.0 L-helicoidal and horizontal photobioreactors at 5 klux using the bicarbonate contained in the medium and ambient air as the main CO2 sources. The influence of bicarbonate concentration on biomass growth as well as lipid content and profile was first investigated in shake flasks, where the stationary phase was achieved in about one half the time required by the control. The best NaHCO3 concentration (0.2 g L-1) was then used in both photobioreactors. While the fed-batch run performed in the helicoidal photobioreactor provided the best result in terms of biomass productivity, which was (84.8 mg L-1 d-1) about 2.5-fold that of the batch run, the horizontal configuration ensured the highest lipid productivity (10.3 mg L-1 d-1) because of a higher lipid content of biomass (22.8 %). These preliminary results suggest that the photobioreactor configuration is a key factor either for the growth or the composition of this microalga. The lipid quality of C. vulgaris biomass grown in both photobioreactors is expected to meet the standards for biodiesel, especially in the case of the helicoidal configuration, provided that further efforts will be made to optimize the conditions for its production as a biodiesel source
High-pressure and high-temperature extraction of phenolic compounds from grape skins
No full textThis study focused on the use of a non-conventional extraction technology by employing high-pressure hightemperature
stirred reactor to extract polyphenols from grape skins. Extraction time (15–330 min) and
temperature (30–150 C) were selected as independent variables, and their effects were studied. A preliminary
kinetic study on polyphenols extraction revealed that the second-order model fitted satisfactorily the
experimental results (R2 ‡ 0.9798). Total polyphenol yield and total flavonoid (TF) yield, as well as the
antiradical power (ARP) of the extracts, were analysed. The use of high-pressure high-temperature
technology resulted in obtaining extracts rich in polyphenols with high ARP. The highest total polyphenol
(60.7 mgGAE g1
DS) and TF (15.1 mgCE g1
DS) yields were obtained at 150 C for 270 min and 150 C for
15 min, respectively. HPLC was employed to analyse phenolic compounds. Considerable quantities of single
phenolic compounds were extracted. The highest yields of gallic acid, 5-hydroxymethylfurfural, protocatechuic
acid, catechin, vanillic acid, syringic acid, cumaric acid, trans-resveratrol and quercetin (163.2,
20.0, 69.9, 420.0, 20.6, 603.0, 20.1, 42.4 and 117.1 mg per 100 gDS, respectively) were found. ARP values
were found between 8.45 and 52.17 lgDPPH lL1
extract
Valorization of olive oil solid waste using high pressure–high temperature reactor
No full textResponse surface methodology was used to optimise the combined effects of malaxation time (t) and
aqueous citric acid solution (CA) added at the beginning of the malaxation step on total polyphenols
(TP) and o-diphenols (OD) content and the antiradical power (ARP) of the olive oil extracted from the Italian
olive fruits of Coratina cultivar. Different tests were performed according to a 32 full factorial design,
varying t from 30 to 90 min and the CA from 5 to 15 ml/kgpaste. Overall optimal conditions identified by a
numerical optimisation for the three responses were found to be at t = 30 min and CA = 13.79 ml/kgpaste
under which the model predicted TP = 604.52 lgCAE/goil, OD = 80.44 lgCAE/goil and ARP = 28.73
lgDPPH/llextract. There were also linear correlations between TP (R2 = 0.8176) and OD (R2 = 0.8633) values
of olive oil and waste water. The results of this study demonstrate that considerably short malaxation
time and relatively small amounts of citric acid were required to enhance the quality of olive oil. The outcome
of our study will therefore be of great value for the commercial production of olive oil with high
level of polyphenols and o-diphenols
Recovery of phenolic compounds from grape seeds: effect of extraction time and solid–liquid ratio
No full textThe aim of this research was to study the recovery of phenolic compounds
from grape seeds, by-products from winemaking industries, using ethanolic
solid–liquid extraction. For such a purpose, the combined effects of the
extraction time (9, 19 and 29 h) and the solid–liquid ratio (0.10, 0.20 and
0.30 gdwmL1), were investigated (where dw1⁄4dry waste). Results demonstrated
that Pinot Noir seeds had high levels of both total polyphenols
(73.66 mgGallic Acid Equivalent gdw1) and flavonoids (30.90 mgCatechin
Equivalent gdw1), being the optimum extraction time 19 h approximately.
The main phenolic compounds analysed with high performance liquid
chromatography were catechin and quercetin with a maximum extraction
yield obtained at 29 h (362.23 and 339.35 mg/100 gdw, respectively).
Concentration of the polyphenols and their antiradical powers are
demonstrated to have a significant linear correlation
- …
