Langmuir Isotherm Research Articles

Sustainable Zn2+ removal using highly efficient, novel, and cost-effective chitosan-magnetic biochar composite.

This study focused on the development of a sustainable and low-cost adsorbent derived from the chitosan-biochar composite for the removal of Zn2+ from an aqueous solution. Biochar was prepared from cotton stalk residue by pyrolysis at 600°C for 2h, modified with FeCl3, and composed with chitosan in various ratios (1:3, 1:1, 3:1), leading to the formation of an efficient, thermally stable, and rich with functional groups chitosan-biochar composite denoted as CHB-Fe-CS. Functional groups (hydroxyl, carboxyl, and amine) were identified as key contributors to the adsorption mechanism. Langmuir isotherm (R2 = 0.99) and Pseudo-Second order (R2 = 0.99) were best fitted models with the experimental results indicating chemisorption-driven monolayer adsorption. The results revealed CHB-Fe-CS (3:1) composite obtained the highest adsorption capacity of 117.50mg/g for Zn2+ under optimal conditions viz., 180min batch time, 500mg/l metal concentration, 4g/l adsorbent dosage, 40°C solution temperature, and 5.0 pH. Regeneration of the used adsorbent was performed using 0.2mol/l HCl and obtained desorption efficiency of 67.48% and 51.48% after the 4th and 8th cycles. The adsorption mechanisms were dominated by ion exchange, surface complexation, and electrostatic attraction compared to intra-particle diffusion and physisorption. The CHB-Fe-CS demonstrated an economical, environment friendly, and good performing adsorbent for water decontamination.

Molecular Dynamics Simulation of the Interaction within the Carboxymethyl Cellulose-Modified Montmorillonite Lamellae at Aggressive CuCl2 Concentrations.

To elucidate the degradation mechanism of the CMC-modified MMT composite at aggressive Cu2+ concentrations, large scale molecular dynamics simulation was conducted for CuCl2 concentrations ranging from 0 to 800 mM. Both CMC and MMT followed the Langmuir isotherm for Cu2+ adsorption, and the adsorption capacity of CMC (8.75 mmol/g) was much higher than that of MMT (0.83 mmol/g). Despite the CMC mass ratio being only 4.1%, it adsorbed up to 34.3% of the total adsorbed Cu2+. The Cu2+ attraction ability hierarchy of oxygen-containing functional groups in the CMC is as follows: carboxylic oxygens > alcoholic oxygens > carbinolic oxygens > bridging oxygens > glucose oxygens. Carboxyls were the most effective in chelating and complexing with Cu2+, and they could be intentionally added in artificially synthesized polymer-MMT composites for Cu2+ containment. Formation of the Cu2+ cation bridge between CMC and MMT at aggressive CuCl2 concentrations contributed to the transition of CMC density distribution from unimodality to bimodality and enhanced resistance of polymer elution. As the CuCl2 concentration increased, the stoichiometric ratio between the chelated Cu2+ and carboxylic oxygens increased from 1:2 to 1:1, suggesting the evolution of the Cu2+ chelation mechanism.

Simultaneous Removal of Cadmium and Disperse Black-9 Dye Using Chemically Modified Rice Husk-Derived Activated Carbon

Heavy metals and organic dyes pose significant environmental concerns due to their persistence, toxicity, and tendency to accumulate in the food chain. These pollutants are often discharged from various industrial sources without proper management, resulting in unacceptable damage to the environment. The use of low-cost agricultural by-products can be a sustainable and green solution for the industrial effluent treatment process. In the present research, the effective removal of Cd2+ and disperse black‒9 (DB‒9) dye simultaneously was planned through the adsorption method utilizing specially activated carbon (AC) derived from rice husk. FTIR, SEM, and XRD were used to characterize the produced AC. The adsorption studies showed that approximately 88% of the dye DB‒9 and 97% of Cd2+ were adsorbed by using optimal dosages of the AC, which were 16 g/L and 12 g/L, respectively. In addition, it was successfully demonstrated that Cd2+ adsorbed AC was capable of binding with DB‒9 and also DB‒9 adsorbed AC is capable of binding with Cd2+. Therefore, a novel strategy for the simultaneous elimination of Cd2+ and DB-9 ideas was successfully implemented in the current study. In addition, equilibrium data were examined to assess the adsorbate-adsorbent system's isotherms. The Langmuir isotherm was determined to be the most well-fitting, with a maximum uptake of 11.48 mg/g. Thermodynamic study (ΔG⁰) showed that the adsorption process was spontaneous, and the adsorption process followed pseudo-second-order kinetics.

Phytofabrication of silver nanoparticles from Illicium verum fruit extract and its role in Cr+6 removal: a comparative analysis

ABSTRACT Herein, using Illicium verum (IV) aqueous fruit extract, spherical shape silver nanoparticles (IV-AgNPs) of 40 nm average size with typical SPR at 422 nm were synthesised through the one-pot chemical reduction method. In the presence of Cr+6, IV-AgNPs rapidly changed from yellow to pink colour, with immediate SPR quench at 422 nm and new peak appearance at 510 nm, suggesting carboxylate groups involvement in AgNPs synthesis and Cr+6 interaction, respectively. Clusters were formed in Cr+6 presence; as a result, IV-AgNPs’ zeta potentials changed from −24.1 to 14 mV. Moreover, with the lowest limit of detection (22.1 nM), IV-AgNPs displayed higher potential for Cr+6 adsorption in aqueous medium. The Langmuir isotherm predicts monolayer adsorption on a homogeneous surface of both adsorbents via chemisorption kinetics with adsorption capacity of 1511.65 and 720.35 mg/g for IV-AgNPs and IV fruit extract, respectively. Calculated thermodynamic values of -∆G°, +∆H°, and +∆S° indicate spontaneity, randomness, and endothermicity of the adsorbate system(s). Akaike information criterion ranking alignment and kinetics equilibrium for adsorbents showed that the Elovich plot and intra-particle diffusion produced the best output in comparison to other models. These findings indicate adsorption dynamics are controllable for both adsorbents, but the size-dependent properties of IV-AgNPs significantly improve interaction efficiency for Cr+6 adsorption.

Adsorbent Biomaterials Based on Natural Clays and Orange Peel Waste for the Removal of Anionic Dyes from Water

This study demonstrates the efficient removal of Alizarin Yellow R anionic dye (AY) from aqueous solutions using green adsorbents. Natural kaolin clay (A1), acid-modified natural clay (A2), chemically treated orange peel (C1) and biochar produced by the thermal treatment of orange peel (C2) were tested for the adsorption of AY. The characteristics of the sorbents were determined by instrumental methods: SEM, EDS, FTIR, BET and TGA. The adsorption experiments were performed under different conditions, including the initial AY dye concentration, adsorbent weight, pH, temperature and contact time. The maximum adsorption capacities had values between 15.72 and 74.62 mg/g at 298 K and the optimal pH of 6.5 at initial concentrations ranging from 30 to 70 mg/L for all adsorbents. The equilibrium data were used for the adsorption isotherm models: Freundlich, Langmuir and Temkin. The Freundlich model fit best for the adsorbents A2, C1 and C2, and the Langmuir isotherm had the highest regression value for the adsorbent A1 (R2 = 0.9935). Thermodynamic parameters indicated the spontaneous and favorable adsorption process of AY. A study of the adsorption kinetics proved that they best fit the pseudo-second-order model, with the highest coefficients of determination (R2), outperforming the pseudo-first-order model. The results of this study indicate the potential for the valorization of locally available clays and orange peel waste in the purification processes of water.

Adsorption of Cd and Mn from neutral mine effluents using bentonite, zeolite, and stabilized dewatered sludge

This study aimed to investigate the adsorption efficiency of Cd and Mn using natural sorbents—bentonite, zeolite and stabilized digested dewatered waste sludge. The main contributions of the scientific article are in adding to the scientific knowledge of the use of natural and waste sorbents in the removal of heavy metals from neutral mine effluents. Current studies mainly focus on metal removal by sorption using natural sorbents from acid mine drainage. This study investigates sorption in neutral mine drainage. The efficiency of the sorption process was evaluated using the following parameters: efficiency (%) of metal ion removal, Freudlich and Langmuir adsorption isotherm constant. The AES–ICP method (atomic emission spectrometry with inductively coupled plasma) was used for the initial metal analysis of the materials used. The atomic absorption spectrometry (AAS) method was used for the analysis of Cd and Mn in the sorption process. The maximum efficiency of Mn removal by bentonite at the end of the test was approximately 90%. The removal of Mn by zeolite was considerably lower—about 20% compared to the use of sludge—80%. Based on the sorption efficiency, the sludge was suitable for sorption. Much higher levels of Cd sorption were achieved using sludge compared to using natural bentonite and zeolite. The main novelty of the work lies in the sorption of metals using dewatered digested sludge. Previous studies have focused on metal sorption using activated sludge. Most previous studies focused on sorption from acid mine drainage. The novelty of this study is that we focused on the sorption of neutral mine drainages, which are typical for the location we are monitoring.

Chemical, electrochemical, and quantum investigation into the use of an organophosphorus derivative to inhibit copper corrosion in acidic environments

In order to protect the copper against corrosion, a novel corrosion inhibitor known as diphenyl ((2-aminoethyl) amino) (4-methoxyphenyl) methyl) phosphonate (DAMP) was developed. Acid solutions of HCl and H2SO4 were the aggressive solutions employed in this study. Analysis using the FT-IR, 1H-NMR, 31P-NMR, 13C-NMR and BET confirmed that the DAMP was successfully synthesized. The anti-corrosion capabilities of DAMP are evaluated using a combination of chemical, electrochemical and quantum studies. The DAMP has been found to be crucial in preventing the corrosion of copper in both HCl and H2SO4 acid. This was obviously implied by the observation that the corrosion rate of copper in acid solutions decreased when DAMP was added. It is significant to note that 180 ppm produced the highest levels of inhibiting efficiency (96.6% for HCl and 95.2% for H2SO4). The tendency of DAMP to adsorb on the surface of copper through its hetero-atoms (O, N, and P) is the main factor for the anti-corrosion capabilities of DAMP. Results from SEM/EDX tests supported this. The actual adsorption takes place via various active centers, physical and chemical mechanisms that are coordinated with the estimated quantum parameters. Additionally, the adsorption of DAMP adheres to the Langmuir isotherm.

Application of Three-Dimensional Porous Aerogel as Adsorbent for Removal of Textile Dyes from Water

The textile industry is one of the most important industries in the European Union. The main environmental problems of the textile industry are the high water consumption, the generated pollution, the variety of chemicals used and the high energy demand. Recently, adsorbents with a large specific surface area and low weight, such as aerogels, have attracted great interest as promising materials for removing dyes from polluted water. Cellulose aerogels are inexpensive and non-toxic. Langmuir and Freundlich isotherms were chosen as the best method to describe the performance of the adsorbent. In this study, the adsorption efficiency of Congo red, Naphthol green B, Rhodamine B and Methylene blue were determined by using an adsorbent synthesized from paper and cardboard waste. The total organic carbon concentration was chosen as an indicator of the concentration of the dyes in the solutions. The aerogel capsules had 5% cellulose content. It was found that the adsorption capacity of the aerogel in the solutions of Congo red varied from 0.028 mg/g to 14.483 mg/g; in the solutions of Naphthol green B, from 0.013 mg/g to 7.698 mg/g; in the solutions of Rhodamine B, from 0.020 mg/g to 8.768 mg/g; and in the solutions of Methylene blue, from 0.024 mg/g to 13.538 mg/g.

Evaluation of Kinetic and Isotherm Models for Adsorption of Boron Under Different Soil Orders in Oil Palm Plantations of India

ABSTRACT Adsorption isotherm and kinetic models are essential in predicting the adsorption mechanisms, which helps in boron (B) recommendation at appropriate doses. This study is formulated with the objective of assessing different kinetic and adsorption models for the adsorption of B in different soil orders (Entisol, Alfisol, Inceptisol and Vertisol) in Oil Palm plantations in India. The B adsorption in soils followed the order: Vertisol > Alfisol > Inceptisol > Entisol. The results revealed that, the Langmuir adsorption model fitted well for alfisol (part1 R2 = 0.9912 & part2 R2 = 0.9678), entisol (R2 = 0.9862) and inceptisol (R2 = 0.9924), while the Freundlich model fitted well for vertisol (R2 = 0.9943). The soils under entisol and inceptisol showed linear isotherms whereas, the vertisol and alfisol had curvilinear isotherms and the split Langmuir isotherm was worked out. High bonding energy at the lower part of split isotherm represented stronger retention of B at lower B concentrations. The B equilibrium was attained in 24 h in alfisol and inceptisol, and 12 h in entisol, whereas in vertisol, the equilibrium was not completed until 72 h. From the correlation coefficients obtained from all models, the pseudo-second-order kinetic model explained the B sorption in a better way followed by elovich and power function kinetic models in different soil types. Desorption of B is higher in entisol in most of the added B concentrations. The study suggests a higher rate of B fertilizer application than the recommended in soils having high B adsorption capacity for optimum crop growth and yield.

Artificial neural network-based modeling of Malachite green adsorption onto baru fruit endocarp: insights into equilibrium, kinetic, and thermodynamic behavior

In this study, artificial neural network (ANN) tools were employed to forecast the adsorption capacity of Malachite green (MG) by baru fruit endocarp waste (B@FE) under diverse conditions, including pH, adsorbent dosage, initial dye concentration, contact time, and temperature. Enhanced adsorption efficiency was notably observed under alkaline pH conditions (pH 10). Kinetic analysis indicated that the adsorption process closely followed a pseudo-second-order model, while equilibrium studies revealed the Langmuir isotherm as the most suitable model, estimating a maximum adsorption capacity of 57.85 mg g−1. Furthermore, the chemical adsorption of MG by B@FE was confirmed using the Dubinin–Radushkevich isotherm. Thermodynamic analysis suggested that the adsorption is spontaneous and endothermic. Various ANN architectures were explored, employing different activation functions such as identity, logistic, tanh, and exponential. Based on evaluation metrics like the coefficient of determination (R 2) and root mean square error (RMSE), the optimal network configuration was identified as a 5–11-1 architecture, consisting of five input neurons, eleven hidden neurons, and one output neuron. Notably, the logistic activation function was applied in both the hidden and output layers for this configuration. This study highlights the efficacy of B@FE as an efficient adsorbent for MG removal from aqueous solutions and demonstrates the potential of ANN models in predicting adsorption behavior across varying environmental conditions, emphasizing their utility in this field.

Sulfonated Azocalix[4]arene-Modified Metal–Organic Framework Nanosheets for Doxorubicin Removal from Serum

Chemotherapy is one of the most commonly used methods for treating cancer, but its side effects severely limit its application and impair treatment effectiveness. Removing off-target chemotherapy drugs from the serum promptly through adsorption is the most direct approach to minimize their side effects. In this study, we synthesized a series of adsorption materials to remove the chemotherapy drug doxorubicin by modifying MOF nanosheets with sulfonated azocalix[4]arenes. The strong affinity of sulfonated azocalix[4]arenes for doxorubicin results in high adsorption strength (Langmuir adsorption constant = 2.45–5.73 L mg−1) and more complete removal of the drug. The extensive external surface area of the 2D nanosheets facilitates the exposure of a large number of accessible adsorption sites, which capture DOX molecules without internal diffusion, leading to a high adsorption rate (pseudo-second-order rate constant = 0.0058–0.0065 g mg−1 min−1). These adsorbents perform effectively in physiological environments and exhibit low cytotoxicity and good hemocompatibility. These features make them suitable for removing doxorubicin from serum during “drug capture” procedures. The optimal adsorbent can remove 91% of the clinical concentration of doxorubicin within 5 min.

Composite electrospun membranes based on PET-PAN modified with LDH-hybrid as promising adsorbent for pollutants removal from wastewater

<p>The current work reveals the fabrication of a novel nanofiber composite membrane of PET-PAN modified with Mg-Al-LDH-PVA through electrospinning process. The nanocomposite membranes characterization was conducted with different techniques i.e. SEM, EDS, FTIR, XRD, and water contact angle to evaluate the structure and surface morphology. The optimized nanomembrane was utilized as a useful adsorbent for removal of toxic anionic dye Eriochrome Black T (EBT) and cationic dye Methylene blue (MB) from wastewater. Experimental results identified that PPLP3 membrane has a potential for the removal of EBT (83%) and MB (52%) at pH 3 and 7, respectively, from aqueous solution. The optimum adsorption capacity of PPLP3 nanocomposite membrane was identified and calculated as 7.3 mg.g-1 followed by the pseudo 2nd order kinetics and Langmuir adsorption isotherm fit well with R2 values of 0.964 and 0.997, respectively. The synthesized nanocomposite membrane could be utilized for effective adsorption of contaminations from different wastewaters.</p>

Adsorption of Cu(II) and Ni(II) from Aqueous Solutions Using Synthesized Alkali-Activated Foamed Zeolite Adsorbent: Isotherm, Kinetic, and Regeneration Study

Water pollution, particularly from heavy metals, poses a significant threat to global health, necessitating efficient and environmentally friendly removal methods. This study introduces novel zeolite-based adsorbents, specifically alkali-activated foamed zeolite (AAFZ), for the effective adsorption of Cu(II) and Ni(II) ions from aqueous solutions. The adsorbents’ capabilities were comprehensively characterized through kinetic and isotherm analyses. Alkaline activation induced changes in chemical composition and crystalline structure, as observed via XRF and XRD analyses. AAFZ exhibited a significantly larger pore volume (1.29 times), higher Si/Al ratio (1.15 times), and lower crystallinity compared to ZZ50, thus demonstrating substantially higher adsorption capacity for Cu(II) and Ni(II) compared to ZZ50. The maximum monolayer adsorption capacities of ZZ50 and AAFZ for Cu(II) were determined to be 69.28 mg/g and 99.54 mg/g, respectively. In the case of Ni(II), the maximum monolayer adsorption capacities for ZZ50 and AAFZ were observed at 48.53 mg/g and 88.99 mg/g, respectively. For both adsorbents, the optimum pH for adsorption of Cu(II) and Ni(II) was found to be 5 and 6, respectively. Equilibrium was reached around 120 min, and the pseudo-second-order kinetics accurately depicted the chemisorption process. The Langmuir isotherm model effectively described monolayer adsorption for both adsorbents. Furthermore, the regeneration experiment demonstrated that AAFZ could be regenerated for a minimum of two cycles using hydrochloric acid (HCl). These findings highlight the potential of the developed adsorbents as promising tools for effective and practical adsorption applications.

Facile Fabrication of Porous Adsorbent with Multiple Amine Groups for Efficient and Selective Removal of Amaranth and Tartrazine Dyes from Water

The development of an advanced dye adsorbent that possesses a range of beneficial characteristics, such as high adsorption capacity, swift adsorption kinetics, selective adsorption capability, and robust reusability, remains a challenge. This study introduces a facile method for fabricating an amine-rich porous adsorbent (ARPA), which is specifically engineered for the adsorptive removal of anionic dyes from aqueous solutions. Through a comprehensive assessment, we have evaluated the adsorption performance of ARPA using two benchmark dyes: amaranth (ART) and tartrazine (TTZ). Our findings indicate that the adsorption process reaches equilibrium in a remarkably short timeframe of just 20 min, and it exhibits an excellent correlation with both the Langmuir isotherm model and the pseudo-second-order kinetic model. Furthermore, ARPA has demonstrated an exceptional maximum adsorption capacity, with values of 675.68 mg g−1 for ART and 534.76 mg g−1 for TTZ. In addition to its high adsorption capacity, ARPA has also shown remarkable selectivity, as evidenced by its ability to selectively adsorb TTZ from a mixed dye solution, a feature that is highly desirable for practical applications. Beyond its impressive adsorption capabilities, ARPA can be efficiently regenerated and recycled. It maintains a high level of original removal efficiency for both ART (76.8%) and TTZ (78.9%) even after five consecutive cycles of adsorption and desorption. Considering the simplicity of its synthesis and its outstanding adsorption performance, ARPA emerges as a highly promising material for use in dye removal applications. Consequently, this paper presents a straightforward and feasible method for the production of an effective dye adsorbent for environmental remediation.

Thermodynamic and structural investigation of oily wastewater treatment using peach kernel and walnut shell based activated carbon.

Despite the many articles about activated carbon with different precursors in adsorption process, no in-depth research has been carried out to understand the causes of the difference in surface adsorption characteristics of activated carbon with different precursors and different activation processes. In this work, the ability of two active carbon adsorbents made of walnut shell and peach kernel by two chemical and physical methods (totally 4 different types of activated carbon) in treatment of oily wastewater including diesel, gasoline, used oil or engine lubricant has been compared. The results show that the chemical activated peach carbon active with 97% hardness has provided the highest hardness and physical activated walnut carbon active has obtained the lowest hardness value (87%). It is also found that peach activated carbon has a higher iodine number than walnut activated carbon, and this amount can be increased using chemical methods; Therefore, the highest amount of Iodine Number is related to Peach activated carbon that is made by chemical method (1230 mg/g), and the lowest amount of iodine number is seen in walnut activated carbon that is made by physical method (1020 mg/g). moreover, the pore diameter of physical activated carbon is lower than chemical activated carbon in all cases. So that the pore diameter of chemical activated peach carbon active is equal to 22.08 μm and the measured pore diameter of physical activated peach carbon active is equal to 20.42 μm. These values for walnut are obtained as 22.74 μm and 21.86 μm, respectively. Furthermore, the temperature and pH effects on the adsorption of different synthesized oily wastewater was studied and it was found that a decrease in adsorption can be seen with an increase in temperature or decreasing the pH value, which can be referred to this fact that the process of adsorption is an exothermic process. Finally, to analyze the compatibility of adsorption isotherms with experimental data and to predict the adsorption process, three different isotherms named Langmuir, Temkin, and Freundlich isotherms were applied and their parameters were correlated. The correlation results show that the Langmuir isotherm had the best correlation in all cases compared to the Freundlich and Temkin isotherms, based on the correlation coefficient, and the calculated R2 values which was greater than 0.99 in all the studied cases.

Chemical Modification of Birch Bark (Betula L.) for the Improved Bioprocessing of Cadmium(II), Chromium(VI), and Manganese(II) from Aqueous Solutions

This study aimed to assess the sorption capacity of a natural sorbent, specifically birch bark (BB), and its modification using chemical reagents, including nitric and hydrochloric acid, sodium hydroxide, and chloride. The objective of the chemical modification was to enhance the sorption capacity of the heavy metals cadmium(II), chromium(VI), and manganese(II). The most effective modification for adsorbing cadmium and manganese from aqueous solutions was achieved by treating the sorbent with a 0.1 M sodium hydroxide solution (BBNa). Conversely, in the case of chromium, each modification adversely affected its adsorption by the sorbent. Concentrations of the solutions were analyzed using atomic absorption spectrometry at appropriate time intervals. The adsorption process was described using Langmuir, Freundlich, and Temkin isotherms. The Freundlich isotherm provided the best fit for cadmium and chromium (R2 = 0.988 and 0.986, respectively), while the Langmuir isotherm was most suitable for manganese (R2 = 0.996). The sorption capacity varied for each metal ion: Cd (II)—33.13 mg/g, Cr (VI)—35.98 mg/g, and Mn (II)—24 mg/g for the highest concentration tested. This study employed pseudo–first-rate order, pseudo–second-rate order model kinetics, and the Weber–Morris model to examine the adsorption kinetics. The pseudo–second-rate order kinetics demonstrated the best fit (R2 > 0.94) for each heavy metal, which underlines the process’s chemical nature.

Prediction of adsorption performance of ZIF-67 for malachite green based on artificial neural network using L-BFGS algorithm

Given the necessity and urgency in removing organic pollutants such as malachite green (MG) from the environment, it is vital to screen high-capacity adsorbents using artificial neural network (ANN) methods quickly and accurately. In this study, a series of ZIF-67 were synthesized, which adsorption properties for organic pollutants, especially MG, were systematically evaluated and determined as 241.720 mg g−1 (25 ℃, 2 h). The adsorption process was more consistent with pseudo-second-order kinetics and Langmuir adsorption isotherm, which correlation coefficients were 0.995 and 0.997, respectively. The chemisorption mechanism was considered to be π-π stacking interaction between imidazole and aromatic ring. Then, a Python-based neural network model using the Limited-memory BFGS algorithm was constructed by collecting the crucial structural parameters of ZIF-67 and the experimental data of batch adsorption. The model, optimized extensively, outperformed similar Matlab-based ANN with a coefficient of determination of 0.9882 and mean square error of 0.0009 in predicting ZIF-67 adsorption of MG. Furthermore, the model demonstrated a good generalization ability in the predictive training of other organic pollutants. In brief, ANN was successfully separated from the Matlab platform, providing a robust framework for high-precision prediction of organic pollutants and guiding the synthesis of adsorbents.

Characterization of melanin from Exophiala mesophila with the prospect of potential biotechnological applications

IntroducionFungal melanin is an underexplored natural biomaterial of great biotechnological interest in different areas. This study investigated the physical, chemical, electrochemical, and metal-binding properties of melanin extracted from the metallotolerant black fungus Exophiala mesophila strain IRTA-M2-F10.Materials and methodsSpecific inhibitory studies with tricyclazole and biochemical profiling of whole cells by synchrotron radiation-based Fourier-transform infrared spectral microscopy (SR-FTIRM) were performed. An optimized extraction protocol was implemented, and purified fungal melanin was characterized using an array of spectrophotometric techniques (UV-Vis, FTIR, and EPR) and by cyclic voltammetry (CV) experiments. The metal-binding capacity of melanin extracts was also assessed by using Cr(VI) as a model heavy metal.ResultsInhibitory studies indicated that 1,8-dihydroxynaphthalene may be the main precursor molecule of E. mesophila melanin (DHN-melanin). The biochemical characterization of fungal melanin extracts were benchmarked against those from two melanins comprising the precursor molecule L-3,4-dihydroxiphenylalanine (DOPA-melanin): extracts from the ink of the cephalopod Sepia officinalis and DOPA-melanin synthesized in the laboratory. The CV results of melanin extracts incubated with and without cell suspensions of the electroconductive bacterium Geobacter sulfurreducens were indicative of novel semiquinone/hydroquinone redox transformations specific for each melanin type. These interactions may play an important role in cation exchange for the adsorption of metals and in microbial interspecies electron transfer processes.DiscussionThe obtained results provided further evidence for the DHN-nature of E. mesophila melanin. The FTIR profiling of melanin extracts exposed to Cr(VI), compared to unexposed melanin, resulted in useful information on the distinct surface-binding properties of fungal melanin. The parameters of the Langmuir and Freundlicht isotherms for the adsorption of Cr(VI) were determined and compared to bibliographic data. Altogether, the inherent properties of fungal melanin suggest its promising potential as a biomaterial for environmental applications.

Fabrication of Activated Carbon Derived from Glycerin Pitch for Desulfurization of Model Fuel Oil and Electrode Application.

One of the world's challenging energy issues is introducing practical and affordable technology for organosulfur removal in fuel. Adsorptive desulfurization (ADS) can address this issue if highly effective activated carbon (AC) derived from industrial waste with excellent textural properties is used. In this study, the derived ACs from glycerin pitch loaded with P and Fe (AC/P and AC/Fe) were used as adsorbents for the ADS of model fuel oils, such as dibenzothiophene (DBT) at mild operating conditions. Under the optimized experimental conditions, 0.3 g of adsorbent dosage, 60 min reaction time, 30 °C temperature, and pH 4, the maximal DBT removal of 96.28 and 43.64%, respectively, for AC/P and AC/Fe was realized. The results indicated that the phosphorus-doped AC/P increases the selectivity of the ADS mechanism for DBT removal. Kinetic investigations disclosed that the adsorption process follows second-pseudo-order kinetics and the Langmuir adsorption isotherm model. The adsorbents remained active for five successive reuses, indicating their robust real-world applications. The electrochemical properties of the fabricated carbon electrodes were analyzed via cyclic voltammetry by coating the ACs with polytetrafluoroethylene (PTFE) as a binder. The transition-metal-doped AC/Fe, though exhibiting 5 times lower surface area, showed the highest specific capacitance at a scan rate of 5 mVs-1 (0.65 μF cm-2). Similarly, the extended AC:PTFE capacitor at a 10% binder ratio offered the maximum capacitance value (1.13 μF cm-2). The synthesized ACs demonstrated potential application as an electrode material, and hence glycerin pitch could be a low-cost precursor to improve the feasibility of commercial production of AC.

Synthesis and Characterization of a Magnetic Molecular Imprinted Polymer for Tetracycline Quantification in Food Samples

AbstractIn the present work, we synthesized and tested a magnetic molecularly imprinted polymer (mag‐MIP) sensor for the detection of tetracycline in food samples. High‐performance liquid chromatography (HPLC) and spectrofluorometry were employed for tetracycline determination. The mag‐MIP was polymerized on the surface of Fe3O4@SiO2 magnetic nanoparticles using the following substances: 4 mmol of methacrylic acid as the functional monomer, 20 mmol of ethylene glycol dimethacrylate (EGDMA) as the cross‐linking agent, 82.5 mg of benzoyl peroxide as the radical initiator, and 30 ml of acetonitrile as the solvent. The physicochemical characteristics of the proposed mag‐MIP, including adsorption capabilities and selectivity, were studied and compared with those of a magnetic non‐molecularly imprinted polymer (mag‐NIP). The analytical curve was constructed in the range of 1.0×10−5–8.0×10−5 mol L−1, LOD: 3.3×10−6, LOQ: 1.1×10−5 mol L−1. The results obtained from the adsorption analysis showed that the highest adsorption capacity of the mag‐MIP at equilibrium was 8.247 mg g−1 and that the tetracycline adsorption process followed the Langmuir adsorption isotherm model and pseudo‐second‐order reaction kinetics. The proposed mag‐MIP also exhibited good results when subjected to fluorescence analysis; an increase in tetracycline concentration resulted in an increase in the adsorption capacity, and this led to the effective removal of tetracycline with the reduction of fluorescence intensity. The applicability of the proposed mag‐MIP was evaluated in honey, cow milk, and egg samples through recovery tests conducted using samples containing spiked tetracycline concentration at two different concentration levels (1.7×10−5 and 2.5×10−5 mol L−1), where we obtained recovery percentages in the range of 73.2–87.2 % (HPLC) and 90.5–103.7 % (spectrofluorometry).