Methyl Red Adsorption on Biochar Obtained by Physical Activation of Caraway Seeds with Carbon Dioxide

In this study carbon adsorbents were produced from caraway (Carum carvi L.) seeds, through direct and physical activation by carbon dioxide. The resulting biochar adsorbents were analyzed using low-temperature nitrogen adsorption-desorption isotherms and Boehm titration. Furthermore, the acid-base properties of the biochar samples obtained were examined, and the pH of their aqueous extracts was determined. The obtained adsorbents had a specific surface area ranging between 10 to 70 m2 /g. Resulting carbon materials exhibited a predominance of basic groups on their surfaces. The sorption capacities of methyl red for the samples varied from 3 to 20 mg/g. Conducted adsorption studies determined, that the adsorption kinetics of the dye on biochar materials followed a pseudo-second order model and the adsorption process was best described by the Freundlich isotherm, indicating the development of a multi-layer adsorbate on their surfaces. The effectiveness of adsorption in aqueous solutions of methyl red increased with the rise in process temperature. Moreover, the adsorption process was found to be spontaneous and endothermic based on thermodynamic investigations.

Optimization Conditions of Malachite Green Adsorption onto Almond Shell Carbon Waste Using Process Design

Almond shell-based biocarbon is a cheap adsorbent for the removal of malachite green, which has been investigated in this work. FT-IR, DRX, and BET were used to characterize almond shell-based biocarbon. The nitrogen adsorption-desorption isotherms analysis results showed a surface area of 120.21 m2/g and a type H4 adsorption isotherm. The parameters of initial dye concentration (5-600 mg.L-1), adsorbent mass (0.1-0.6 mg), and temperature (298-373 K) of adsorption were investigated. The experiments showed that the almond shell could be used in a wide concentration and temperature range. The adsorption study was fitted to the Langmuir isotherm and the pseudo-second-order kinetic model. The results of the FT-IR analysis demonstrated strong agreement with the pseudo-second-order chemisorption process description. The maximum adsorption capacity was calculated from the Langmuir isotherm and evaluated to be 166.66 mg.g-1. The positive ∆H (12.19 J.mol-1) indicates that the adsorption process is endothermic. Almond shell was found to be a stable adsorbent. Three different statistical design sets of experiments were taken out to determine the best conditions for the batch adsorption process. The optimal conditions for MG uptake were found to be adsorbent mass (m = 0.1 g), initial dye concentration (C0 = 600 mg.L-1), and temperature (T = 25 °C). The analysis using the D-optimal design showed that the model obtained was important and significant, with an R2 of 0.998.

Structure-activity relationship of antioxidant prenylated (iso)flavonoid-type compounds: quantum chemistry and molecular docking studies

Prenylated (iso)flavonoid-type compounds are a subclass of natural flavonoids that have been reported to exhibit good antioxidant properties. In the present paper, the structure-activity relationship of three typical prenylated (iso)flavonoids namely 8-prenyldaidzein (Per), Licoflavone (Lic), and erysubin F (Ery) have been determined using DFT (density functional theory)-based calculations and molecular docking studies. As result, the CH bond of the prenyl substituent was found to be the most thermodynamically favorable site for trapping free radicals in the gas phase and lipid physiological environments. While the OH bond of the B-ring seems to be more reactive in water. HAT (hydrogen atom transfer) and SPLET (sequential proton loss electron transfer) play a decisive role in the antiradical activity of the studied compounds in lipid and polar physiological environments, respectively. All of the studied compounds exhibit strong binding affinity to both xanthine oxidase and inducible nitric oxide synthase enzymes by forming several hydrogen bonds and hydrophobic interactions with their respective catalytic sites. These results suggest that (iso)flavonoid-type compounds are promising radical scavengers and antioxidants. Communicated by Ramaswamy H. Sarma.

Theoretical and Practical Evaluation of the Feasibility of Zinc Evaporation from the Bottom Zinc Dross as a Valuable Secondary Material

This study presents a theoretical and practical evaluation of zinc evaporation from bottom zinc dross (hard zinc) as a secondary zinc source (zinc content approximately 94-97%), which originates in the batch hot-dip galvanizing process. The thermodynamics of the zinc evaporation process were studied under the normal pressure (100 kPa) in the inert atmosphere, using argon with flow rate 90 mL/min. Samples were subjected to the evaporation process for 5, 10 and 20 min under the temperature of 700 °C and 800 °C, respectively. For the theoretical thermodynamic study, HSC Chemistry 6.1 software was used and final products, as well as residuals after the evaporation process, were analyzed by SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray). Calculated and experimental argon consumption in the process of zinc evaporation has been compared. A high purity zinc with efficiency over 99% was reached. Due to a dynamic regime, argon consumption at the temperature of 700 °C and 800 °C were 7 times and 3 times, respectively, less than calculated.

Activation of Waste Materials with Carbon(IV) Oxide as an Effective Method of Obtaining Biochars of Attractive Sorption Properties towards Liquid and Gas Pollutants

Biochars that are the subjects of this report have been obtained from the residue of supercritical extraction of common nettle seeds with CO₂. The residue was subjected to direct activation with carbon(IV) oxide as an activator. The obtained biochars were found to have a specific surface area inthe range of 888-1024 m²/g and a basic surface. They were used for the adsorption of a liquid organic pollutant (methylene blue) and a gas inorganic pollutant (NO₂). As follows from the test results, the biochars were able to adsorb 150-239 mg of the dye. The Langmuir model was found to better describe the adsorption experimental data, while the kinetics of the process was better described by the pseudo-second-order model. From the thermodynamic analysis, it was inferred that the adsorption of methylene blue from a water solution was an endothermic and spontaneous reaction. It was established that elevated temperature of activation and the presence of air stream during adsorption had a positive impact on the adsorption of NO₂ by the biochars studied. The greatest sorption capacity of the biochars towards NO₂ was 59.1 mg/g.

Adsorption of Organic Compounds on Adsorbents Obtained with the Use of Microwave Heating

Activated carbons were obtained by physical and chemical activation of the residue of supercritical extraction of green tea leaves. All the adsorbents obtained were characterized by: elemental analysis, low-temperature nitrogen adsorption, and the contents of acidic and basic oxygen functional groups on the surface of activated carbons by the Boehm method. The activated carbons were micro- or micro-mesoporous with well-developed surface area ranging from 520 to 1085 m²/g and total pore volume from 0.62 to 0.64 cm³/g. The physical activation of the precursor led to the strongly basic character of the surface. Chemical activation with 50% solution of H₃PO₄ of the residue of supercritical extraction of green tea leaves promoted the generation of acidic functional groups. All adsorbents were used for methylene blue and methyl red adsorption from the liquid phase. The influence of the activation method, pH of the dye solution, contact time of adsorbent with adsorbate, the temperature of adsorption, and rate of sample agitation on the effectiveness of organic dyes removal was evaluated and optimized. In the process of methylene blue adsorption on adsorbents, an increase in the sorption capacity was observed with increasing pH of the adsorbate, while in the process of methyl red adsorption, the relation was quite the reverse. The adsorption data were analyzed assuming the Langmuir or Freundlich isotherm models. The Langmuir model better described the experimental results, and the maximum sorption capacity calculated for this model varied from 144.93 to 250.00 mg/g. The results of the kinetic analysis showed that the adsorption of organic dyes on activated carbon was following the pseudo-second-order model. The negative values of the Gibbs free energy indicate the spontaneous character of the process.

Predicted Shelf-Life, Thermodynamic Study and Antioxidant Capacity of Breadsticks Fortified with Grape Pomace Powders

Grape pomace (GP), is the main winemaking by-product and could represent a valuable functional food ingredient being a source of bioactive compounds, like polyphenols. Polyphenols prevent many non-communicable diseases and could contrast the oxidation reaction in foods. However, the high content in polyunsaturated fatty acid, the described pro-oxidant potential action of some polyphenols and the complex interactions with other components of matrices during food processing must be considered. Indeed, all these factors could promote oxidative reactions and require focused and specific assay. The aims of this study were to evaluate the effects of GP powder (GPP) addition (at 0%, 5% and 10% concentrations) in breadsticks formulations both on the antioxidant activity at room temperature during storage and on the shelf-life by the OXITEST predictive approach. GPP fortification increased the total polyphenols content and the antioxidant activities of breadsticks. FRAP reduced during the first two days of storage at room temperature, TPC increased during the 75 days, while ABTS showed a slight progressive decrease. However, GP negatively influenced OXITEST estimated shelf-life of breadsticks, incrementing the oxidation rate. In conclusion, even if GP fortification of breadsticks could improve the nutritional value of the products, the increased commercial perishability represents a drawback that must be considered.

Removal of carbol fuchsin from aqueous solution by using three-dimensional porous, economic, and eco-friendly polymer

In this study, a three-dimensional (3D) porous polydimethylsiloxane (PDMS) was prepared using a cheap material with a highly simple and different method. PDMS was firstly applied for the removal of carbol fuchsin (CF) cationic organic dye pollution in this study. Besides, the adsorption capacity of 3D PDMS for removal of the CF was found quite high compared to other materials in already published results. The synthesized PDMS was characterized using several spectroscopic and imaging techniques such as FTIR, Raman, SEM, stereomicroscope, EDX, UV/Vis, and TGA. The optimal conditions were found as 10 mg L^-1 initial concentration, 20 mg of adsorbent dose, 2 h contact time, pH 10, and 25°C temperature. The removal % of CF and the maximum adsorption capacity were calculated at approximately 89% and 88.8 mg g^-1 , respectively. Furthermore, the equilibrium studies showed that the Langmuir isotherm model fitted well with the removal of CF. Moreover, according to the kinetic results, the second-order kinetic model was found suitable (q_e,cal 89.3 mg g^-1 and q_e,exp 88.8 mg g^-1 close to each other) for the adsorption of CF. Also, the thermodynamic studies indicated that adsorption occurs spontaneously, and the adsorption process was physical adsorption. Besides, the reusability of the adsorbent was studied. PRACTITIONER POINTS: Water treatment technology should be low cost, economically viable and in the meantime, eco-friendly. The 3D porous PDMS was prepared by using cheap material with a highly simple method and eco-friendly This unique material was firstly applied for the removal of organic dye in water in this study.

α-Mangostin/γ-Cyclodextrin Inclusion Complex: Formation and Thermodynamic Study

α-Mangostin (α-M) has various biological activities, such as anti-cancer, antibacterial, anti-fungal, anti-tyrosin, anti-tuberculosis, anti-inflammatory, and antioxidant. However, it has very low solubility in water. The formulation of this compound requires high amounts of solubilizers, which limits its clinical application. In addition, its low solubility in water is a barrier to the distribution of this drug, thus affecting its potency. Cyclodextrin (CD) is widely used as a solubility enhancer of poorly soluble drugs. This study aimed to increase the solubility of α-M in water through complex formation with CD. The complex of α-Mangostin and γ-Cyclodextrin (α-M/γ-CD CX) was prepared by the solubilization method, resulting in a solubility improvement of α-M in water. Characterization of α-M/γ-CD CX by using FTIR-Spectrometry, XRD, H-, C-, and HMBC-NMR showed that α-M was able to form an inclusion complex with γ-CD. The complex yielded an entrapment efficiency of 84.25 and the thermodynamic study showed that the α-M/γ-CD CX was formed spontaneously, based on the negative values of Gibbs energy and ΔH. Interestingly, the solubility of α-M/γ-CD CX significantly increased by 31.74-fold compared with α-M. These results suggest that α-M/γ-CD CX has the potential in the formulation of water-based preparation for clinical applications.

Use of Different Types of Biosorbents to Remove Cr (VI) from Aqueous Solution

This article summarizes the results of a research study that was focused on the possibility of removing Cr (VI) from aqueous solution, using low-cost waste biomaterial in a batch mode. A set of seven biosorbents was used: Fomitopsis pinicola, a mixture of cones, peach stones, apricot stones, Juglans regia shells, orange peels, and Merino sheep wool. Three grain fractions (fr. 1/2, fr. 0.5/1.0, and fr. 0/0.5 mm) of biosorbents were studied. The aim was to find the most suitable biosorbent that can be tested with real samples. The influence of other factors on the course of biosorption was studied as well (chemical activation of the biosorbent, pH value, rotation speed during mixing, temperature, and the influence of biosorbent concentration). The use of chemical activation and adjustment of the pH to 1.1 to 2.0 make it possible to increase their sorption capacity and, for some biosorbents, to shorten the exposure times. Two kinetic models were used for the analysis of the experimental data, to explain the mechanism of adsorption and its possible speed control steps: pseudo-first and pseudo-second-order. The pseudo-second-order kinetic model seems to be the most suitable for the description of the experimental data. The thermodynamic parameters suggest that the biosorption was endothermic and spontaneous. In the biosorption equilibrium study, the adsorption data were described by using Langmuir and Freundlich adsorption isotherms. The Langmuir model was applicable to describe the adsorption data of all biosorbents. Both models are suitable for chemically treated sheep fleece and peach stones.

Application of supercritical fluid chromatography for separation and quantitation of 15 co-formulated binary anti-hypertensive medications using a single elution protocol

A facile supercritical fluid chromatography method is proposed to analyse 15 co-formulated binary anti-hypertensive drug combinations using a customized elution procedure. The effect of mobile phase composition, column back pressure and temperature was suitably optimized for adequate retention, analyte response and resolution. The chromatographic separation of the different drug combinations was performed on a DCPak poly(4-vinylpyridine) column (250 × 4.6 mm, 5 μm) at 125-bar pressure and 40°C using a photodiode array detector. A linear gradient of CO₂ and 0.1% formic acid in methanol provided the best elution conditions for all drug combinations. Baseline separation of the drugs was possible with resolution factor R_s ranging from 1.42 to 12.58. The method was validated for specificity, sensitivity, accuracy and precision, recovery and robustness. The limit of detection and limit of quantitation for aliskiren, amlodipine, atenolol, candesartan, hydrochlorothiazide, lisinopril, losartan, metoprolol, olmesartan, telmisartan and valsartan were in the range of 0.26-2.56 and 0.77-7.75 μg/mL, respectively. The thermodynamic study revealed that interactions of the drugs with the stationary phase were spontaneous as evident from the negative free energy values, and the separation process was enthalpy driven. The developed method was successfully employed to analyse these drugs in their co-formulated tablet formulations.

Preparation and Characterization of Graphene Oxide for Pb(II) and Zn(II) Ions Adsorption from Aqueous Solution: Experimental, Thermodynamic and Kinetic Study

A thermodynamic and kinetic study of the adsorption process of Zn (II) and Pb (II) ions from aqueous solution on the surface of graphene oxide (GO) to establish the mechanisms of adsorbate–adsorbent interaction on this surface. The effect of pH on the retention capacity was studied and adsorption isotherms were determined from aqueous solution of the ions; once the experimental data was obtained, the kinetic and thermodynamic study of the sorption process was carried out. The data were fitted to the Langmuir, Freundlich, Dubinin-Raduskevich and Temkin isotherm models. The results showed that Zn(II) and Pb(II) on the GO adsorbing surface fitted the Langmuir model with correlation coefficients (R²) of 0.996. Kinetic models studied showed that a pseudo-second-order model was followed and thermodynamically, the process was spontaneous according to the values of Gibbs free energy (ΔG^o). N₂ adsorption isotherms were determined and modeled with the NLDFT (nonlocal density functional theory) and QSDFT (quenched solid density functional theory) kernels.

Determination of panthenol enantiomers in cosmetic preparations using an achiral-chiral-coupled column HPLC system

A new high-performance liquid chromatography (HPLC) method for separation and determination of panthenol enantiomers in hair care products was developed. Two types of detectors, low-wavelength ultraviolet (UV) and polarimetric, were used. Optimized conditions consisted of coupled achiral, amino type, and chiral, amylose tris(3,5-dimethylphenylcarbamate), stationary phases, mixture of n-hexane/ethanol (60:40, v/v) as mobile phase under isocratic conditions and flow rate 0.8 cm³ min^-1 . The effect of column temperature on retention and resolution of enantiomers was studied. The analysis runtime was 10 minutes, and the average retention times for d- and l-panthenol were 7.10 ±0.1 minutes and 8.21 ±0.2 minutes, respectively. The resolution of enantiomers on coupled achiral-chiral columns was R_s = 2.7. The solid-phase extraction method was employed for extraction and purification of analytes. The validated method was selective, accurate, and linear (R² > .998) over the concentration range of 0.001 to 1.0 mg cm^-3 for both enantiomeric forms. The limits of detection (LOD) and quantitation (LOQ) of each enantiomer were 0.3 and 1.0 μg cm^-3 , respectively. The results demonstrated the occurrence of d-panthenol in hair care products.