Molecular insights through computational modeling of methylene blue adsorption onto low-cost adsorbents derived from natural materials: A multi-model's approach

Efficiency of Fe3O4@ZIF-8 for the removal of Doxorubicin from aqueous solutions: equilibrium, kinetics and thermodynamic studies

Due to inadequate pharmaceutical wastewater treatment, anticancer contaminants from the pharmaceutical industry frequently end up in the aquatic environment where they endanger aquatic life and humans. As a result, the appropriate treatment of wastewater that contains anticancer agents is crucial for pollution prevention. The purpose of this work is to assess the effectiveness of a Fe3O4@ZIF-8 nanocomposite as an adsorbent to remove of the chemotherapeutic drugs doxorubicin (DOX) from aqueous solution. SEM, XRD, BET, FT-IR, Zeta potential, and point of zero charge analysis were used to study the surface and structural characteristics of the Fe3O4@ZIF-8 nanocomposite. Via the proposed treatment, 804.84 mg/g elimination was successful under the following circumstances: pH = 6; Fe3O4@ZIF-8 dose = 0.02 g/25 mL; DOX concentration = 1.22x10-3 mol; adsorption time = 100 min; and shaking speed = 200 rpm. A investigation of isotherms shown that the Langmuir equation and experimental data suited each other quite well. The adsorption of DOX on Fe3O4@ZIF-8 was endothermic and spontaneous, in accordance with thermodynamic properties. Furthermore, the elimination of DOX was enhanced by the rise in solution temperature. The kinetic analysis revealed that the pseudo-second order was fitted by the model. The suggested adsorption method could recycle Fe3O4@ZIF-8 nanocomposite six times, with a modest reduction in its ability for adsorption. For all XRD reflection peaks, physical characteristics including strain rates were computed and the dislocation of was 4.7 × 10-6. Investigate the activity of the DOX towards COVID-19, breast and prostate cancer using molecular docking.

Contribution of air-water interface in removing PFAS from drinking water: Adsorption, stability, interaction and machine learning studies

As a class of synthetic persistent organic pollutants, contamination of Per-and poly-fluoroalkyl substances (PFAS) in drinking water has attracted widespread concern. Aeration has been confirmed to enhance the removal of PFAS in drinking water by activated carbon (AC). However, the contribution of the air-water interface in removing PFAS is not yet to be fully understood at the molecular level. In this work, molecular dynamics (MD) simulations were employed to investigate the role of nanobubble in removing PFAS in the aqueous environment. The result suggests that the free energies of the air-water interface are about 3-7 kcal mol^-1 lower than that of the bulk water region, indicating that the transformation of PFAS from the water phase into the air-water interface is favorable from the viewpoint of thermodynamics. The interface-water partition coefficients (P_sur/wat) of PFAS are in the order of PFOS > PFOA > PFHxS > PFBS. On the air-water-AC three-phase interface, PFBS can not only move along the interface region but also leave the interface region into water phase, while PFOS tended to move along the interface region until it was captured by AC. Finally, the ΔG_{water-interface} quantitative structure-activity relationships (QSAR) models were developed to predict the removal efficiencies of PFAS enhanced by aeration in aquatic systems. The proposed mechanism promotes the understanding of the contribution of air-water interface in removing PFAS from drinking water by activated carbon.

The deconstruction and recombination of endogenous active units of carbon@chitosan@montmorillonite nanosheet microsphere adsorbent caused by cadmium and copper cations benefit for high adsorption performance

The highly efficient removal of heavy metals is one of the important factors to evaluate adsorbents. In our study, carbon@chitosan@montmorillonite nanosheet (C@CS@MTN) was successfully prepared via layer-by-layer assembly for the removal of Cu2+ and Cd2+ from solution. High-intensity ultrasound peeling technology was used to release Si-O tetrahedron and Al-O octahedron from montmorillonite in order to exert their optimal adsorption potential. Fourier transform infrared spectroscopy, an X-ray diffractometer, BET surface area measurement, and the inductively coupled plasma emission spectrometry were adopted to investigate the morphology, functional groups, and adsorption capacity of C@CS@MTN. Batch experiment results indicated that both Cu2+ and Cd2+ were effectively removed from solution with the range of pH from 2 to 6. The removal ratio of Cu2+ and Cd2+ onto C@CS@MTN increased with the rise of reaction temperature and their maximum adsorption capacities reached 1108.8 mg·g-1 and 237.4 mg·g-1, respectively, under the condition of the reaction temperature 40 °C, the reaction time 4 h, and the pH = 6. The molecular simulation calculation indicated that there was an obvious electron transfer between Si-O tetrahedron and metal cations, but not for Al-O octahedron. In comparison to Al-O octahedron, the bonding of Cu-O and Cd-O caused the Si-O bond to be broken, resulting in the deconstruction of Si-O tetrahedron and their recombination via the junction of O atoms. It was exactly the deconstruction and recombination of endogenous active units that provide more sites for metal ion adsorption.

Enhanced adsorption of 3,4-methylenedioxymethamphetamine by magnetic graphene oxide-polydopamine nanohybrid modified zeolitic imidazolate framework-67 and its micro-mechanism: Experiments and calculations

Exploring the structure-dependent adsorption mechanism of contaminants in wastewater is beneficial to high-efficiency adsorbents design and environmental remediation. In this study, emerging porous material of zeolitic imidazolate framework-67 (ZIF-67) has been modified by the magnetic graphene oxide-polydopamine nanohybrid (mGOP) to obtain three-dimensional ZIF-67/mGOP through an in-situ growth strategy, which was applied to adsorb 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") in wastewater. A combination of characterizations, experiments (pH, humic acid and ion strength effect) and quantum chemical calculations revealed the microscopic adsorption mechanism involves each single component, of which the hydrogen bond (O/N…HO) and π-π electron donor acceptor (π-π EDA) interactions of mGOP endowed favourable adsorption of ZIF-67/mGOP, and mechanisms of the pore filling and Co-O chelation of ZIF-67 played synergistic effect. Such nanocomposite as a ZIFs-based adsorbent exhibited ultra-high porosity (total pore volume = 0.4033 cm³/g) and specific surface area (995.22 m²/g), revealed the heterogeneity and multilayer adsorption properties, and obtained a theoretical maximum adsorption capacity of 159.845 μg/g which higher than that of mZIF-67 alone. Overall, this work provided an effective strategy for rationally modulate ZIFs-based composites and exploration of adsorption mechanism.

Synthesis, spectroscopic characterization, molecular docking and in vitro cytotoxicity investigations on 8-Amino-6-Methoxy Quinolinium Picrate: a novel breast cancer drug

Density Functional Theory (DFT) studies of the 8-Amino-6-Methoxy Quinolinium Picrate (8A6MQP) molecule have been carried out with extensive and accurate investigations of detailed vibrational and spectroscopic investigations as well as validated experimentally. The 8A6MQP sample was synthesized and characterized using FT-IR, FT-Raman, FT-NMR and UV-Vis spectroscopic techniques. Subsequently, the optimized molecular structure and harmonic resonance frequencies of the molecule were computed based on DFT/B3LYP method with a 6-311G++(d,p) basis set using the Gaussian 09 program. The experimental and calculated vibrational wavenumbers were assigned. The absorption spectrum of the molecule was computed in the liquid phase (ethanol), which exhibits n to л* electronic transition and compared with the observed UV-Vis spectrum. Frontier molecular orbital analysis shows the molecular reactivity and kinetic stability of the molecule. The Mulliken atomic charge distribution and molecular electrostatic potential surface analysis of the molecule validate the reactive site of the molecule. The natural bond orbital analysis proves the bioactivity of the molecule. Molecular docking analysis indicates that the 8A6MQP molecule inhibits the action of DNA topoisomerase 2-alpha protein, which is associated with breast cancer. In addition, the in vitro cytotoxicity analysis of the 8A6MQP molecule against human cervical cancer cell lines (ME180) and human breast cancer cell lines (MDA MB 231) were determined by MTT assay, which evidences that the title molecule exhibits higher inhibition against the breast cancer cell lines compared to that of cervical cancer cell lines. Hence, the present study paves the way for the development of novel drugs in the treatment of breast cancer.Communicated by Ramaswamy H. Sarma.

Explaining the adsorption mechanism of the herbicide 2,4-D and the drug ketoprofen onto wheat husks Fagopyrum esculentum treated with H2SO4

In this paper, the adsorption of the herbicide 2,4-D and the drug ketoprofen on wheat husks Fagopyrum esculentum treated with H₂SO₄ is experimentally and analytically analyzed. The adsorbent is fully characterized through some techniques such as FT-IR, SEM, and XRD. Adsorption tests are carried out to optimize the performances in terms of adsorbent dosage and solution pH. Subsequently, the impact of temperature is determined through the realization of adsorption isotherms. A multilayer model is employed to microscopically interpret the adsorption mechanism of both the investigated compounds. The modelling analysis shows that the number of molecules bound per adsorption site varied from 0.68 to 2.77 and from 2.23 to 3.59 for ketoprofen and herbicide 2,4-D, respectively. These estimated values testify that an aggregation process occurs during adsorption. The global number of formed layers of each adsorbate is also determined, showing a significant reduction from 5.73 to 2.61 for ketoprofen and from 1.79 to 1.5 for herbicide 2,4-D with the temperature. For a complete understanding of the adsorption mechanism, the saturation adsorption capacity and adsorption energy were calculated and interpreted. Overall, it may be inferred that physical interactions govern how these contaminants adsorb on the tested adsorbent.

Releasing SiO tetrahedron and AlO octahedron from montmorillonite to enhance the adsorption performance of carbon@chitosan@montmorillonite nanosheet for cationic dyes: Coupling quantum chemistry simulations with experiments

A novel adsorbent of carbon@chitosan@montmorillonite nanosheet (C@CS@ MTN) was successfully fabricated layer-by-layer assembly method to deal with cationic dye wastewater. Batch adsorption experiments showed that the adsorption capacities of MB and RhB were higher than 325 mg·g^-1 and 236 mg·g^-1, respectively, indicating that C@CS@MTN exhibited an excellent adsorption performance. Through quantum chemistry simulations, the molecular electrostatic potential, electron density, differential charge density, molecular orbital distribution and adsorption binding energy were analyzed to reveal the adsorption reaction mechanism between C@CS@MTN and cationic dyes. The results indicated that SiO tetrahedron ring and AlO octahedron ring released from montmorillonite with inherent periodic structure was beneficial to electrostatic attraction, while cation-π interaction benefitted from the interaction between Al atoms of AlO octahedron ring and benzene ring. It was noteworthy that the electron transfer direction of electrostatic attraction was from O atoms of SiO tetrahedron ring to the benzene ring of dye molecules, but the electron transfer direction of cation-π interaction was from benzene ring of dye molecules to Al atoms of AlO octahedron ring. These results provide fundamental theoretical support for the functional design of mineral-based adsorbents and the efficient removal of cationic dyes.

Removal of Dye (Methylene Blue) from Wastewater Using Bio-Char Derived from Agricultural Residues in Palestine: Performance and Isotherm Analysis

The main aim of this study was to perform a parametric study for treating a model dye containing wastewater (i.e., methylene blue, MB) using locally available biomass wastes in Palestine as the adsorbent. Eight different types of biomasses were investigated in batch adsorption tests, including coffee grains, almond shells, pistachio shells, date pits, jute sticks, sunflower shells, peanut shells, and grapevine sticks. The experiments were conducted on three different phases of processing for these materials: as natural adsorbents, biochar, and activated carbon. The biochar was prepared by pyrolysis, while ZnCl2 was used to chemically activate the materials for obtaining activated carbon. The influences of pH, initial MB concentration, and adsorbent dosage on the adsorption capacity and kinetics were investigated for activated carbon obtained from sunflower shells. The results indicate that the adsorption efficiency of natural adsorbents and biochar is highly dependent on the biomass type. As a natural adsorbent, peanut hulls demonstrated the maximum efficiency (>95%) for removing MB, whereas date pits showed the lowest efficiency (20%). In terms of biochar, jute sticks provide the highest removal efficiency. After activation with ZnCl2, a considerable increase in their adsorption efficiency (>95%) was obtained for most of the adsorbents, with sunflower shells being the most efficient adsorbent. The results confirm the technical feasibility of the adsorption technology to treat dye containing wastewater using locally available biomass wastes.

Adsorption of water on C sites vacancy defected graphene/h-BN: First-principles study

Heterostructures (HS), vacancy defects in HS, and molecular adsorption on defected HS of 2D materials are fervently inspected for a profusion of applications because of their aptness to form stacked layers that confer approach to an amalgamation of favorable electronic and magnetic properties. In this context, graphene (Gr), hexagonal boron nitride (h-BN), HS of graphene/h-BN (Gr/h-BN), and molecular adsorption on Gr/h-BN offer promising prospects for electronic, spintonic, and optoelectronic devices. In this study, we investigated the structural, electronic, and magnetic properties of C sites vacancy defects in Gr/h-BN HS and adsorption of water molecule on defected Gr/h-BN HS materials by using first-principles calculations based on spin-polarized density functional theory method within van der Waals (vdW) corrections DFT-D2 approach. We found that these considered materials are stable 2D vdW HS. Based on band structure calculations, they are semimetallic, and on density of states and partial density of states analysis, they are magnetic materials. The magnetic moment developed in these defected systems is due to the unpaired up-spin and down-spin states in the orbitals of atoms present in the materials created by the vacancy defects.

Electron-Scale Insights into the Single and Coadsorption Cd(II) Behaviors of a Metal-Nonmetal-Modified Titanium Dioxide

Metal (Fe) and nonmetal (P) were used to modify TiO2, and then, several functional groups such as P-O, P=O, Fe-O, and -OH were introduced on its surface to enhance the adsorption capacity for Cd(II), which could reach 121 mg/g. According to the experimental analysis of adsorption performance, chemical adsorption dominates the adsorption process, and the adsorption capacity increases with increasing temperature within a certain range. The results of competitive adsorption experiments showed that both Pb(II) and Cu(II) affect the adsorption of Cd(II) and that the adsorption order of P-Fe-TiO2 for heavy metal ions is $\text{Pb}\left(\text{II}\right)>\text{Cd}\left(\text{II}\right)>\text{Cu}\left(\text{II}\right)$ . We further investigated the adsorption mechanism of P-Fe-TiO2 for Cd(II) and the reasons for the difference in competitive adsorption and used DFT calculations to confirm the experimental results. In the analysis of binding energy and frontier molecular orbitals (FMOs), we confirmed that charge transfer occurred during the adsorption process, so chemical reactions occurred. The binding energy of P-Fe-TiO2 and Pb(II) is the largest. The results of the competitive adsorption experiment also confirmed that the adsorbent has the greatest effect on Pb. Mulliken analysis was used to identify the best binding site on the adsorbent. The results of electrostatic potential, total potential, and differential charge analysis further prove the conclusions described above.

Adsorption mechanism of Zn2+, Ni2+, Cd2+, and Cu2+ ions by carbon-based adsorbents: interpretation of the adsorption isotherms via physical modelling

A theoretical physicochemical and thermodynamic investigation of the adsorption of heavy metals Zn2+, Cd2+, Ni2+, and Cu2+on carbon-based adsorbents was performed with statistical physics fundaments. Particularly, the experimental adsorption isotherms of heavy metal removal, at 30°C and pH 5, using adsorbents obtained from the pyrolysis of three biomasses (cauliflower cores, broccoli stalks, and coconut shell) were modelled and interpreted with a homogeneous statistical physics adsorption model. Calculations indicated that the heavy metal adsorption with these carbon-based materials was a multi-ionic process where several ions interact simultaneously with the same carboxylic functional group on the adsorbent surface. Adsorption capacities for these metal ions and adsorbents were correlated with electronegativity theory, which established that the adsorbate with the highest electronegativity was more readily adsorbed by the carboxylic functional groups available on the adsorbent surfaces. Also, the chemical compositions of biomass precursors explained achieved adsorption capacities for these metallic ions. The best adsorbent for heavy metal removal was obtained from CC biomass pyrolysis. Calculated adsorption energies for heavy metal removal could be associated with physisorption-type forces. Finally, the adsorption mechanism analysis was complemented with the determination of adsorption thermodynamic functions using the statistical physics.