Positive ΔS Research Articles

A new three-dimensional modeling of fluorescence excitation-emission measurements to explore the interaction of hydroxychloroquine and DNA, and to quantify their binding constant

A new three-dimensional chemometric approach was introduced to explore the interaction of hydroxychloroquine (HCQ)-calf thymus deoxyribonucleic acid (DNA) and quantify binding constant using fluorescence excitation and emission measurements. The fluorescence excitation-emission spectra were recorded after gradual titration of HCQ with DNA. Then, the excitation and emission curves and relative concentrations of the drug and drug-DNA complex were quantitatively estimated using a three-dimensional model called Parallel Factor Analysis (PARAFAC) to a cubic fluorescence data array. The interaction of HCQ and DNA was predicted by applying newly modified Stern-Volmer equations to the relationship between the actual DNA concentration, and the HCQ concentration in the relative concentration profile of the PARAFAC model. In the PARAFAC application, the binding constants of the HCQ-DNA complex at 288, 298, and 310 K were found as 6.78 × 103, 5.07 × 103, and 3.74 × 103 L mol−1, respectively. From the temperature studies, the thermodynamic parameters (ΔS0= 3.528 J mol−1 K−1, ΔH0= −20.099 kJ mol−1 and ΔG0=-21.11, −21.12, and −21.19 kJ mol−1 at 288, 298, and 310 K, respectively) were calculated. The drug-DNA interaction is spontaneous due to negative ΔG0 values. The positive ΔS0 and negative ΔH0 values revealed the major role of the electrostatic force on the binding of HCQ to DNA. Assay results obtained from the proposed three-way modeling were compared to those provided by the traditional spectrofluorimetric method.

Removal of hazardous Aniline Blue dye using a potential Biosorbent – Hen feather

In this research we have successfully removed a highly toxic dye, “Aniline Blue”, from its aqueous solution employing an adsorbent, Hen Feathers. The dye adsorption over Hen Feather was comprehensively studied over ranges of contact time, pH, concentration, and adsorbent dosage, and the optimum values were evaluated. In order to understand the behaviour of the adsorption system, various isotherm models were evaluated at temperatures of 30, 40 and 50 °C. The data obtained from contact time studies were used to test pseudo-first and pseudo-second order kinetic models and it was found that the adsorption follows pseudo-second-order kinetics. Using the Langmuir constant, b, thermodynamic parameters including ΔG°, ΔH° and ΔS° were calculated and it was ascertained that the process is endothermic (positive ΔH°), involves an increase in disorder (positive ΔS°) and is spontaneous (negative ΔG°). The values of the separation factor (r) also confirmed a favourable adsorption process at all three temperatures studied. Overall, it is affirmed that the adsorbent, Hen Feather, acts as highly potent scavenger to remove the dye Aniline Blue from its aqueous solutions.

Waste newspaper as cellulose resource of activated carbon by sodium salts for methylene blue and congo red removal

The work was aimed at evaluating the adsorptive properties of waste newspaper (WN) activated carbons chemically produced using sodium salts for methylene blue (MB) and congo red (CR) removal. The activated carbons, designated as AC1, AC2, AC3 and AC4 were prepared through impregnation with NaH2PO4, Na2CO3, NaCl and NaOH, respectively and activation at 500 °C for 1 h. The activated carbons were characterized for surface chemistry, thermal stability, specific area, morphology and composition. The AC1 with a surface area of 917 m2/g exhibits a greater MB capacity of 651 mg/g. Meanwhile, a greater CR capacity was recorded by AC2 at 299 mg/g. The pseudo-second order model fitted well with the kinetic data, while the equilibrium data could be described by Langmuir model. The thermodynamic parameters, i.e.., positive ΔH°, negative ΔG° and positive ΔS° suggest that the adsorption of dyes is endothermic, spontaneous and feasible at high solution temperature. To conclude, WN is a potential cellulose source for producing activated carbon, while NaH2PO4 activation could be employed to convert WN into activated carbon for effective dye wastewater treatment.

Synthesis of Pyridine Dicarboxylic Acid Functionalized and Crosslinked to Polyvinyl Alcohol/polyamide for Thorium Capturing From Aqueous Solution

AbstractThorium harms humans and the environment. Mining can release thorium‐containing waste. This study aims to simplify the production of a novel poly‐adsorbent by mixing pyridine dicarboxylic acid, polyvinyl alcohol, and polyamide and first removing thorium from the solution. Various analytical methods were used to characterize the produced dicarboxylic acid/polyvinyl alcohol/polyamide poly‐adsorbent. The practical conditions on adsorption effectiveness evaluated to pH 3.5, 60 mg poly‐adsorbent, 60 min. Th(IV) uptake for poly‐adsorbent is 107.3 mg/g. The linear and nonlinear uptake for the pseudo‐second‐order is closer to the practical uptake (107.71 mg/g). Hence, the kinetic analysis verified the sorption mechanism. Also, the uptake of linear (107.64 mg/g) and nonlinear (108.63 mg/g) types for the Langmuir isotherm is closer to the practical uptake (107.71 mg/g); thus, the sorption isotherm was suitably utilizing Langmuir modeling. Thermodynamic studies proved that the sorption is spontaneous, exothermic, and random due to the negative ΔG°, negative ΔH°, and positive ΔS° during the thorium adsorption process on poly‐adsorbent. In addition, the regeneration ability of poly‐adsorbent was tested utilizing 1.5 M H2SO4. After six cycles, the poly‐adsorbent showed about 83 % regeneration efficacy. The results confirmed that the dicarboxylic acid/polyvinyl alcohol/polyamide poly‐adsorbent might be effective in removing Th(IV) from the watery solution.

Disodium terephthalate as a multifunctional additive for simultaneous enhancing the energy release performance and weakening the water reactivity of aluminum

In this study, disodium terephthalate (Na2TP) has been successfully introduced as a novel multifunctional additive for simultaneous enhancing the energy release performance and weakening the water reactivity of micro-aluminum (μ-Al). Seven μ-Al/Na2TP composites with different contents of Na2TP (R-100 to R-700) and four comparison samples have been prepared to investigate the thermochemical behaviors, combustion performances and water reactivity. Importantly, structure characterizations as well as kinetic parameters (e.g., Ea, ΔS‡) have been performed to reveal the impacts of Na2TP on μ-Al oxidation. Moreover, incorporating Na2TP into μ-Al shows the enhancement of energy release, with R-400 exhibiting the highest heat release (4970 J/g) in the main oxidation stage, compared to μ-Al (1696 J/g). Interestingly, μ-Al shows an increased Ea while R-400 exhibits a decreased Ea as the oxidation proceeds. The decomposition of Na2TP generates both heat and CO2 gases, which are beneficial for destroying alumina shell and increasing oxidation kinetics, in consistent with higher positive ΔS‡ value, rougher surface, and higher surface O content for oxidation of R-400 compared to μ-Al. As a result, the enhanced combustion performances of higher peak pressure, pressurization rate and characteristic shock velocity as well as brighter/larger flame images have been achieved by μ-Al/Na2TP composites. On the other hand, water reactivity of μ-Al has been significantly suppressed by introducing Na2TP in terms of the 85.4 % decrease in heat release, elevated Ea, and alteration of reaction mechanism. Consequently, taking organic Na2TP as a multifunctional additive, two birds of enhancing the energy release and weakening the water reactivity is harvested, showing great potentials in improving the performances of metal-based energy systems.

Eco-Engineered Low-Cost Carbosorbent Derived from Biodegradable Domestic Waste for Efficient Total Chromium Removal from Aqueous Environment: Spectroscopic and Adsorption Study

Chromium contamination in water bodies poses severe risks to both the environment and human health. This research introduces an innovative solution to this challenge by creating a vapor-activated carbosorbent from biodegradable household waste. The efficacy of this adsorbent in removing total chromium through batch methods from aqueous solutions was investigated. Surface analysis using scanning electron microscopy (SEM) exhibited a porous structure, while Fourier-transform infrared spectroscopy (FTIR) identified distinct functional groups on the surface. The point of zero charge (PZC), determined at 6.95, revealed the adsorbent’s surface chemistry. Impressively, the synthesized carbosorbent exhibited significant adsorption capacities of 23.08 mg.g-1 for Cr(III) and 24.84 mg.g-1 for Cr(VI) under optimal conditions. The Langmuir isotherm model illustrated a monolayer adsorption mechanism aligned with the pseudo-second-order kinetic model, confirming chemisorption. Thermodynamic analysis disclosed favorable and spontaneous chromium adsorption. Negative ΔG° values affirmed the spontaneity, while the exothermic nature of the process was signified by the positive ΔH° value, indicating heat release. Increased randomness at the solid-liquid interface, indicated by the positive ΔS° value, underscored the enhanced affinity between the adsorbent and adsorbate. This study exemplifies the potential of the vapor-activated carbosorbent as an efficient and sustainable remedy for chromium-contaminated water bodies.

Exploring bioenergy prospects from malt bagasse: Insights through pyrolysis with multi-component kinetic analysis and thermodynamic parameter estimation

Malt bagasse is a by-product of little commercial value in the brewing industry. Under this scenario, the current study represents the first investigation aiming to determine the kinetic triplet and thermodynamic parameters for malt bagasse pyrolysis using a multi-component kinetic approach to elucidate its bioenergy prospects. The pyrolysis progress profiles of malt bagasse were obtained through slow pyrolysis experiments on a thermogravimetric scale in an inert atmosphere, employing four distinct heating rates (10, 15, 25, and 40 °C min−1). This investigation also used the Frazer-Suzuki deconvolution function to elucidate the relative contributions of hemicellulose, cellulose, and lignin to malt bagasse pyrolysis. Activation energies for devolatilization reactions were determined by the isoconversional methods of Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink, and revealed the lowest and highest mean values for pseudo-hemicelluloses (158.3−215.3 kJ mol−1) and pseudo-lignin (279.5−294.8 kJ mol−1), respectively. Frequency factors in malt bagasse pyrolysis ranging from 8.9 × 1016 and 2.2 × 1023 min−1 offer evidence of a simplified reaction chemistry pathway in the conversion towards bioenergy production. The integral master plot indicates the involvement of order-based and geometrical contraction-based mechanisms in malt bagasse pyrolysis. After defining multiple kinetic triplets, a differential equation encompassing contributions from all pseudo-components was formulated, and the simulated results aligned closely with experimental data, accurately describing pyrolysis progress profiles with at least 92.8% precision. The thermodynamic analysis reveals positive ΔH and ΔG values, indicating the non-spontaneous nature of malt bagasse pyrolysis. Higher disorder in the resultant products is attributed to volatile release and molecular rearrangement and is signified by positive ΔS values compared to the initial reactants. This study provided valuable insights into the valorization of malt bagasse, offering crucial information for optimizing pyrolysis reactors, scaling, and designing malt bagasse conversion into valuable biofuels, constituting an effort towards bio-circular economy principles based on the zero-waste concept.

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.

Insight to the batch reactor design and sorption potential profiling of polymer grafted chitosan embedded silanated halloysite for Th(IV) recovery from aqueous system

The removal of Th(IV) from wastewater stands as a pivotal step towards advancing cleaner energy, mitigating radioactive contamination, and fostering sustainable nuclear fuel practices. In this research endeavor, a pioneering adsorbent, polymethacrylic acid-grafted-chitosan embedded silanated halloysite (PMAA-g-CT/sHNT), has been synthesized to effectively remove Th(IV) from aqueous solutions. The study meticulously optimized process parameters for the adsorption of Th(IV) onto PMAA-g-CT/sHNT, employing both pseudo-second-order and intra-particle diffusion models. Remarkably, the Langmuir isotherm model exhibited exceptional fitting, revealing a remarkable Th(IV) uptake capacity of 320.99 mg/g at 30 ℃. Thermodynamic analyses underscored the spontaneous and endothermic nature of Th(IV) sorption, as evidenced by the negative ΔG° (-43.73 kJ/mol), positive ΔH° (398.71 kJ/mol), and positive ΔS° (0.0123 kJ/mol/K) values. The desorption process exhibited significant promise, with over 90% Th(IV) recovery even after four cycles of use. In a stride towards practical applicability, a two-stage batch reactor has been devised for commercial implementation of the adsorbent, with operating lines delineated. The efficacy and practicality of the sorbent were further corroborated through investigations conducted using simulated seawater, where a dosage of 2.5 g/L proved optimal for treating 1 L of water. This groundbreaking research not only elucidates the potential of PMAA-g-CT/sHNT as a potent Th(IV) adsorbent but also heralds a promising avenue for addressing critical challenges in wastewater treatment and nuclear waste management.

Deciphering the intriguing molecular recognition of a novel indene-phloroglucinol tethered compound with human serum albumin using multi-spectroscopy and molecular docking studies

A new indene-phloroglucinol tethered compound IPC1 was synthesized in our laboratory in three steps. The interaction of the final compound IPC1 with human serum albumin (HSA) was studied using multi-spectroscopic and molecular docking methods. UV–vis and fluorescence studies confirmed the spontaneous formation of ground state complex and the values of the binding constants were found to be in the order of 104 M−1 (4.727×104 M−1 at 290.15 K). Positive ΔS° (+112.797 J K−1 mol−1) and ΔH° (+6.756 KJ mol−1) indicate the involvement of hydrophobic interaction as the major contributing force in the complex formation process. Site marker studies suggested that the compound IPC1 binds near the subdomain IIIA of HSA, which was further supported by fluorescence spectroscopic and molecular docking analysis.

Physicochemical Characterization, Thermal Behavior, and Pyrolysis Kinetics of Sewage Sludge

Pyrolysis is an energy recovery technique with significant potential for managing wastewater treatment plant byproducts. This research aims to investigate the physicochemical and thermal properties of Moroccan sludge, as well as the behavior of its decomposition during pyrolysis at three different heating speeds (5, 10, and 20 K/min). Characterization of the sludge before pyrolysis through ultimate analysis, proximate analysis, FTIR spectroscopy, and XRD revealed that the sludge consists predominantly of organic matter, with a volatile matter rate of 48%, an ash rate of 37%, and a higher heating value (HHV) of 15 MJ/kg. The TGA-DTG curves identified four distinct stages in the sludge decomposition process: drying, decomposition of organic matter, degradation of calcium carbonate, and decomposition of inorganic matter. Using TG-MS analysis, the principal gases identified during pyrolysis were H2O, H2, CH4, CO2, CO, NO, and SO. The average activation energies (Ea) determined through kinetics models were found to be 413.4 kJ/mol for the Kissinger–Akahira–Sunose (KAS) model, 419.6 kJ/mol for the Flynn–Wall–Ozawa (FWO) model, and 416.3 kJ/mol for the Starink model. The values of Ea and the pre-exponential coefficient (A) obtained through the KAS, FWO, and Starink techniques are consistent with ΔG values ranging between 152 and 155 KJ/mol. The positive ΔS values range from 0.003 to 1.415 kJ/mol.K, indicating the complexity of the sludge response during pyrolysis and the spontaneity of the chemical reaction at high temperatures. The kinetic data obtained serves as a pillar for the development and improvement of sewage sludge pyrolysis systems, reinforcing their role in sustainable energy production.

Alginate-Moroccan Clay, New Bio-Nanocomposite for Removal of H2PO4-, HPO42-, and NO3- Ions from Aqueous Solutions.

The aim of this work is to synthesize and characterize alginate-Moroccan clay bio-composite in order to improve our understanding of the adsorption of inorganic pollutants found in textile effluents. Characterization of the bio-composite used was carried out using a variety of techniques (IR-TF, SEM, DRX, and pHZPC). The influence of the medium's physico-chemical parameters (temperature, pH, initial concentration, etc.) on the retention of inorganic pollutants was also studied. Studies of adsorption and inorganic pollutants such as orthophosphate (H2PO4- and HPO42-) and nitrate (NO3-) ions were carried out, using simple solutions from the laboratory, in a batch system. This study explored the impact of adsorbent dose, contact time, solution pH, and temperature on the adsorption process. Various kinetic models, including pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich models, were tested and evaluated, to illustrate the adsorption kinetics. This study's findings demonstrated that the adsorption process follows second-order kinetics, with associated rate constants successfully determined. The correlation coefficient for the pseudo-second-order kinetic model is nearly equal to 1 (>0.98), and the value of theoretical adsorption capacity (qe,the) is comparable to the experimental one (qe,the = 58.14 mg/g for H2PO4-, qe,the = 54.64 mg/g for HPO42-, and qe,the = 52.63 mg/g for NO3-). Additionally, the adsorption equilibrium was investigated through the application of various mathematical models, including the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, to assess the mechanistic parameters associated with the adsorption process. Among these models, the Langmuir isotherm emerged as the most suitable one for characterizing the adsorption of H2PO4-, HPO42-, and NO3- ions using bio-nanocomposite beads. The maximum adsorbed amounts of metal ions by the bio-nanocomposite used were 625 mg/g for H2PO4-, 909.09 mg/g for HPO42-, and 588.23 mg/g for NO3- from the batch system. The endothermic and physical nature of the adsorption is suggested by the positive values of ΔH°, which is consistent with experimental findings. The adsorption process is spontaneous, as evidenced by the negative ΔG° values. Positive ΔS° values indicate increased randomness at the solid/liquid interface during adsorption of ion-organic ions onto the engineered bio-nanocomposite. The obtained results demonstrated that, from a scientific perspective, alginate-Moroccan clay bio-nanocomposites exhibit a highly significant adsorption capability for the removal of oxyanions in aqueous environments.

Adsorption of Sunscreen Compounds from Wastewater Using Commercial Activated Carbon: Detailed Kinetic and Thermodynamic Analyses

Sunscreen compounds are one of the most toxic substances detected in the aqueous environment. However, these molecules are continuously utilized in a various range of products to provide protection against UV radiation. The removal of three sunscreen compounds, 4-hydroxybenzophenone (4-HBP), 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3), by commercial activated carbon (AC) was investigated using batch adsorption experiments. Different operational characteristics, such as adsorbent dosing, interaction time, solution pH and starting sunscreen compound concentration, were studied. The adsorption capacity of the AC material was assessed using a liquid chromatograph associated with a mass spectrometer detector (LC–MS/MS). Two isotherm models were utilized to explained the target compound adsorption phenomenon (Langmuir and Freundlich), while pseudo-first and -second kinetic orders and thermodynamics were utilized to examine the adsorption mechanism. The maximum adsorption capacities determined from the Langmuir isotherms were established as 43.8 mg/g for 4-HBP, 48.8 mg/g for BP-3 and 41.1 mg/g for BP-1. The thermodynamic parameters revealed the following: a negative ΔG° (<20 KJ/mol) and ΔH° and a positive ΔS° of the targeted sunscreen compounds adsorbed onto AC suggest a spontaneous and exothermic adsorption process, favored by lower temperature, proving that the physical sorption mechanism prevailed. Effective adsorption of 4-HBP, BP-3 and BP-1 from real wastewater samples proved the viability of sunscreen compound removal using commercial AC material. This paper offers promising results on a sustainable, economical and environmentally friendly method for removal of ubiquitous sunscreen compounds from wastewater, as a possible enhancement of treatment processes.

Loading of Silver (I) Ion in L-Cysteine-Functionalized Silica Gel Material for Aquatic Purification.

The L-cysteine-functionalized silica (SG-Cys-Na+) matrix was effectively loaded with silver (I) ions using the batch sorption technique. Optimal Ag(I) loading into SG-Cys-Na+ reached 98% at pHi = 6, 80 rpm, 1 mg L-1, and a temperature of 55 °C. The Langmuir isotherm was found to be suitable for Ag(I) binding onto SG-Cys-Na+ active sites, forming a homogeneous monolayer (R2 = 0.999), as confirmed by FTIR spectroscopy. XRD analysis indicated matrix stability and the absence of Ag2O and Ag(0) phases, observed from diffraction peaks. The pseudo-second-order model (R2 > 0.999) suggested chemisorption-controlled adsorption, involving chemical bonding between silver ions and SG-Cys-Na+ surface. Thermodynamic parameters were calculated, indicating higher initial concentrations leading to increased equilibrium constants, negative ΔG values, positive ΔS values, and negative ΔH. This study aimed to explore silver ion saturation on silica surfaces and the underlying association mechanisms. The capability to capture and load silver (I) ions onto functionalized silica gel materials holds promise for environmental and water purification applications.

Epichlorohydrin and triethylenetetramine functionalized electrosprayed Fe3O4/Chitosan magnetic microspheres for removal and separation of Congo red

Aquatic ecosystem contaminated by organic dyes is one of the most crucial issues plaguing people worldwide, while water remediation through adsorption technology is the most sustainable option. Herein, two chitosan-based adsorbents were successfully fabricated by a facile one-step method under alkaline condition via electrospraying technology, then the above two materials were cross-linked with epichlorohydrin and grafted triethylenetetramine to prepare two kinds magnetic Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres for remediation of anion dyes namely Congo red (CR) in wastewater respectively. The morphology features, structure, composition, thermal stability, and pore diameter of the two adsorbents were acquired by SEM coupled with EDX, XRD, FTIR, TGA, and BET. The adsorption behavior of Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres towards CR from water was systematically evaluated. The determined isoelectric points (pHpzc) of Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 are orderly 7.4 and 7.8. The results confirmed that the CR remediation process can be simulated by PSO kinetic model (R2 > 0.995) along with Langmuir isotherm (R2 > 0.998) with maximal CR adsorption amounts by Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres of 1145.42 and 617.28 mg g−1 at pH = 7 and T = 25 °C, respectively. The negative ΔG0, positive ΔH0 (28.65 and 8.02 kJ mol−1), and positive ΔS0 (112.29 and 62.71 J mol−1 K−1) signified that the adsorption of CR onto Fe3O4/CS-ET-1 and Fe3O4/CS-ET-2 microspheres surface was spontaneous and endothermic in nature. After four consecutive cycles, both magnetic microspheres remained a superior CR removal performance, indicative of the stability and recyclability of the adsorbents.

Effective Dye Adsorption with Cross-linked Hexagonal Boron Nitride Spheres

In this study, cross-linked spheres (CS) were synthesized with chitosan and hexagonal boron nitride (h-BN) to be used in Reactive Blue 3R (RB3R) and Red P4BN (RP4BN) dye adsorption from wastewater. Surface characteristics of the CS were investigated by Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis. The behavior of the adsorption processes with varying effective parameters were investigated. The highest removals were obtained at pH 3 for the RB3R and RP4BN removal processes as 62.8 and 74.2%, respectively. The equilibrium time of the processes was determined as 150 min. The pseudo-first-order kinetic model best explained the adsorption rates of the processes. The Freundlich isotherm model was fitted to define the adsorption mechanisms for both dyes. The positive ΔH values obtained as 24.27 and 16.59 kJ mol−1 for the RB3R and RP4BN adsorption processes, respectively, showed that the processes were endothermic. For the RB3R and RP4BN dye removal processes, ΔS values were calculated as 93.38 and 72.23 J mol−1K−1, respectively. Positive ΔS value indicates the processes that occur with an increase in disorder at the interface. The results described that the CS can be used in the adsorption of RB3R and RP4BN dyes from wastewater.

Comparison of structural properties and removal behavior of composites containing chitosan and hexagonal boron nitride in different compositions

ABSTRACT This study aims to prepare different possible composites using hBN and chitosan in varying ratios and compare them with each other. Composites c/hBN:100/0, c/hBN:75/25 and c/hBN:50/50 were prepared in varying mass ratios. Depending on the changing mass composition, the characterization results are presented in comparison with each other. The surface structures were observed by SEM analysis. FTIR analysis was used for functional group determination. Surface and pore identification was carried out by BET analysis. Crystalline formations were revealed by XRD analysis. True density values were determined by pycnometric analysis. Also, the RB 49 dye removal behavior of the composites was examined and compared with each other. c/hBN:100/0 and c/hBN:75/25 showed the highest removals at pH 4 and as 86.53 and 90.2%, respectively, while c/hBN:50/50 showed it at pH 3 and as 86.59%. The highest adsorption capacities were determined as 105.28, 160.71 and 159.01 mg/g for c/hBN:100/0, c/hBN:75/25 and c/hBN:50/50, respectively at 0.3 g/L dosage. The pseudo-second-order kinetic model and intraparticle diffusion model fitted well with the processes over time. The Freundlich isotherm model was found to be compatible with the processes. The positive ΔH and ΔS values and negative ΔG values of each process were presented.

Synthesis of High-Crystallinity Mg-Al Hydrotalcite with a Nanoflake Morphology and Its Adsorption Properties for Cu2+ from an Aqueous Solution

A magnesium–aluminum-layered double hydroxide (Mg-Al LDH) with a nano-lamellar morphology was prepared by using a homogeneous precipitation and hydrothermal method, and a calcination product (Mg-Al LDO) of the Mg-Al LDH was also obtained in this work. The XRD, TEM, SEM, FTIR, N2 ad/desorption, and TG-DTG techniques were employed to characterize the microstructures, morphologies, and thermostability levels of these two materials in detail. The results showed that both the Mg-Al LDH and Mg-Al LDO had mesoporous structures and nanoplate morphologies, with diameters of 50~200 nm. The Mg-Al LDH was transformed into Mg-Al LDO at 773 K in an air atmosphere. The adsorption properties of the Mg-Al LDH were investigated systematically with a copper chloride solution as a simulated waste. The experimental results demonstrated that the pH value of the solution had an obvious influence on its Cu2+ adsorption capacity, and the optimal pH value was approximately 5.0. The adsorption kinetics results showed that the Mg-Al LDH had a rapid adsorption rate, and the equilibrium adsorption capacity was 62.11 mg/g. Additionally, the Cu2+ adsorption could be commendably described using a pseudo-second-order model, demonstrating that the adsorption behavior is regulated by chemical sorption. The adsorption thermodynamic results indicated that the adsorption process was spontaneous at temperatures above 318 K. Moreover, the ΔG0 values decreased as the temperature was raised, which indicated that a higher temperature can cause a greater impetus for Cu2+adsorption. In addition, the positive values of the ΔH0 indicated that the Cu2+ adsorption was endothermic, and the positive ΔS0 values revealed an increase in the confusion at the solid–liquid interface of the adsorbent.

Release behavior of fertilizers and heavy metals from iron-loaded sludge biochar in the aqueous environment

In this study, the release behavior of fertilizers (NH4+-N, PO43− and K) and heavy metals (Mn, Zn, Ni, Cu, Pb and Cr) from iron-loaded sludge biochar (ISBC) was investigated to evaluated the feasibility and risks of ISBC as a slow release fertilizer. Their release capacity was significantly enhanced with decreasing initial pH, increasing solid-liquid ratio (RS-L) and rising temperature (p < 0.05). When the initial pH, RS-L and temperature were separately 5 (fertilizers)/1 (heavy metals), 1:5 and 298 K, the final concentrations of NH4+-N, PO43−, K, Mn, Zn and Ni were 6.60, 14.13, 149.4, 53.69, 72.56, and 1.01 mg L−1, while the maximum concentrations of Cu, Pb and Cr were 0.94, 0.77, and 0.22 mg L−1, respectively. Due to the tiny difference between the R2 values, revised pseudo-first-order and pseudo-second-order kinetics models described their release behavior well, suggesting that physical and chemical interactions played an important role. Activation energies greater than 40 kJ mol−1 indicated that the rate-controlling steps of the release of NH4+-N, PO43− and Ni were chemical reactions, while chemical reactions and diffusion together determined the release rates of K, Mn, Zn, Cu, Pb and Cr because their activation energies were in the range of 20–40 kJ mol−1. The increasingly negative ΔG and positive ΔH and ΔS suggested that their release was a spontaneous (except Cr) and endothermic process with an increase of randomness between the solid-liquid interface. The release efficiency of NH4+-N, PO43− and K were in the ranges of 28.21%–53.97%, 2.09%–18.06% and 39.46%–66.14%, respectively. Meanwhile, the pollution index and evaluation index of heavy metals were in the ranges of 33.31–227.4 and 4.64–29.24, respectively. In summary, ISBC could be used as a slow-release fertilizer with low risk when the RS-L was less than 1:40.

Interaction studies of cannabidiol with human serum albumin by surface plasmon resonance, spectroscopy, and molecular docking

The binding interaction of cannabidiol (CBD) and human serum albumin (HSA) under physiological blood pH conditions (pH 7.4) was conducted by surface plasmon resonance (SPR), fluorescence spectroscopy, UV-Visible spectrophotometry, and molecular docking. The responses from SPR measurement increased with the increase in CBD concentration until equilibrium was reached at the equilibrium dissociation constant (KD) of 9.8 × 10−4 M. The results from fluorescence and UV-Visible spectroscopy showed that CBD bound to HSA at one site in a spontaneous manner to form protein-CBD complexes. The quenching process involved both static and dynamic mechanisms while the static mechanism contributed predominantly to the binding between CBD and albumin. The binding constants estimated from the fluorescence studies were from 0.16 × 103 to 8.10 × 103 M−1, which were calculated at different temperature conditions using Stern-Volmer plots. The thermodynamic parameters demonstrated that the binding interaction was a spontaneous reaction as Gibbs free energy had negative values (ΔG = −12.57 to −23.20 kJ.mol−1). Positive ΔH and ΔS values (ΔH = 2.46 × 105 J.mol−1 and ΔS = 869.81 J.mol−1K−1) indicated that the hydrophobic force was the major binding interaction. Finally, confirmation of the type and extent of interaction was provided using UV-spectroscopy and molecular docking studies. The outcomes of this study are expected to serve as a platform to conduct future studies on binding interactions and toxicological research of CBD. Communicated by Ramaswamy H. Sarma