Molecular Dynamics Beyond the Monolayer Adsorption as Derived from Langmuir Curve Fitting

Adsorption mechanism and remediation of heavy metals from soil amended with hyperthermophilic composting products: Exploration of waste utilization

Due to high humification, hyperthermophilic composting products (HP) show potential for remediating heavy metal pollution. However, the interaction between HP and heavy metals remains unclear. This study investigated the adsorption mechanism and soil remediation effect of HP on heavy metals. The results showed that the maximum adsorption capacity of HP increased by an average of 30.74 % compared to conventional composting products. HP transformed 34.87 % of copper, 42.55 % of zinc, and 35.63 % of lead from exchangeable and reducible forms into residual and oxidizable forms, thus reducing the soil risk level. In conclusion, HP significantly enhanced the adsorption of heavy metals and their transformation from unstable to stable forms, primarily due to the higher content of hydroxyl and carboxyl groups. This study aims to demonstrate the effectiveness of HP for remediating heavy metal pollution and to enhance the understanding of the underlying mechanism, which lays a foundation for waste utilization.

Formulations of poly(vinyl alcohol) functionalized silk fibroin nanoparticles for the oral delivery of zwitterionic ciprofloxacin

Fibroin nanoparticles (FNP) have been employed in numerous biomedical applications. However, limited research has focused on the oral delivery of FNP and in-depth molecular interactions between the encapsulated drug and FNP. Therefore, this work developed the FNP, functionalized with poly(vinyl alcohol) (PVA), to orally deliver the zwitterionic ciprofloxacin, focused on the molecular interactions. The particles were formulated using both desolvation (the drug precipitated during the particles formulation) and adsorption (the drug adsorbed on the particles surfaces) methods. The optimal formula possessed a size of ~630 nm with narrow size distribution (measured by DLS method), spherical shape (determined by SEM), and moderate drug loading (confirmed by FT-IR, XRD, and DSC techniques) of ~50% for the desolvation method and ~43% for the adsorption method. More than 80% of the drug molecules resided on the particle surfaces, mainly via electrostatic forces with fibroin. The drug was physically adsorbed onto FNP, which followed Langmuir model and pseudo second-order kinetics. In the in-vitro simulated gastric condition at pH 1.2, the ciprofloxacin bound strongly with FNP via electrostatic forces, thus hindering the drug release (< 40%). Contrastingly, in the simulated intestinal condition at pH 6.8, the particles could control the drug release rates dependent on the PVA amount, with up to ~100% drug release. Lastly, the particles possessed adequate antibacterial activities on Bacillus subtilis, Escherichia coli, and Salmonella enterica, with MIC of 128, 8, and 32 μg/mL, respectively. In summary, the FNP and PVA functionalized FNP could be a potential oral delivery system for zwitterionic drugs.

Development of pH-responsive Eudragit S100-functionalized silk fibroin nanoparticles as a prospective drug delivery system

Silk fibroin nanoparticles (FNP) have been increasingly investigated in biomedical fields due to their biocompatibility and biodegradability properties. To widen the FNP versatility and applications, and to control the drug release from the FNP, this study developed the Eudragit S100-functionalized FNP (ES100-FNP) as a pH-responsive drug delivery system, by two distinct methods of co-condensation and adsorption, employing the zwitterionic furosemide as a model drug. The particles were characterized by sizes and zeta potentials (DLS method), morphology (electron microscopy), drug entrapment efficiency and release profiles (UV-Vis spectroscopy), and chemical structures (FT-IR, XRD, and DSC). The ES100-FNP possessed nano-sizes of ∼200-350 nm, zeta potentials of ∼ -20 mV, silk-II structures, enhanced thermo-stability, non-cytotoxic to the erythrocytes, and drug entrapment efficiencies of 30%-60%, dependent on the formulation processes. Interestingly, the co-condensation method yielded the smooth spherical particles, whereas the adsorption method resulted in durian-shaped ones due to furosemide re-crystallization. The ES100-FNP adsorbed furosemide via physical adsorption, followed Langmuir model and pseudo-second-order kinetics. In the simulated oral condition, the particles could protect the drug in the stomach (pH 1.2), and gradually released the drug in the intestine (pH 6.8). Remarkably, in different pH conditions of 6.8, 9.5, and 12, the ES100-FNP could control the furosemide release rates depending on the formulation methods. The ES100-FNP made by the co-condensation method was mainly controlled by the swelling and corrosion process of ES100, and followed the Korsmeyer-Peppas non-Fickian transport mechanism. Whereas, the ES100-FNP made by the adsorption method showed constant release rates, followed the zero-order kinetics, due to the gradual furosemide dissolution in the media. Conclusively, the ES100-FNP demonstrated high versatility as a pH-responsive drug delivery system for biomedical applications.

Phosphorus can effectively reduce selenium adsorption in selenium-rich lateritic red soil

Phosphorus (P) application can improve the availability of selenium (Se) in soil, which benefits the output of Se-rich agricultural products. However, the mechanism by which P affects the adsorption of Se in Se-rich soil is still unclear. Therefore, this study took Se-rich lateritic red soil as the research object and studied the adsorption behavior of P and Se in the soil through batch adsorption tests and soil characterization technology. The results showed that the adsorption of P or Se in lateritic red soil increased with an increase in equilibrium concentration. The P or Se adsorption process was explained using the Langmuir and Freundlich isotherm models. After adding P, the adsorption of Se decreased from 276-423 mg/kg to 52-201 mg/kg at different initial Se concentrations. The scanning electron microscope and energy dispersive spectrometry (SEM-EDS) results showed that the lateritic red soil was rich in C, O, Fe, Al, and other elements, and the free oxidation states of these elements could efficiently facilitate the adsorption of P and Se. Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses indicated that both Se and P could react with ferrite groups in the soil to form iron-containing complexes, and there was a competitive adsorption phenomenon, which was the main reason for the decrease in Se adsorption. This study provides theoretical support for further exploring the effect of P on Se behavior in the geochemical cycle. Furthermore, it promotes the efficient use of Se-rich soil resources.

Sustainable remediation of dye-contaminated wastewater using novel cross-linked Hex-CCP-co-PPT microspheres

The presence of dyes in contaminated water poses substantial dangers to the health of both humans and aquatic life. A process called precipitation polymerization was used to create unique cross-linked hexa-chlorocyclotriphosphazene-co-phenolphthalein (Hex-CCP-co-PPT) microspheres for the purpose of this research. Advanced methods such as X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermogravimetry (DTG) were used to characterise these microspheres. In a simulated solution, the performance of Hex-CCP-co-PPTs as a sorbent for removing MB dye was investigated, and the results showed an unprecedentedly high removal rate of 88.4% for MB. Temperature of 25 °C, a Hex-CCP-co-PPTs dose of 40 mg, an MB concentration of 20 ppm, an MB solution volume of 20 mL, a contact time of 40 min, and a pH of 9 were found to be the optimal experimental conditions. According to the results of the kinetic and adsorption analyses, the PSO and Langmuir adsorption models are the best ones to use. These models favour the chemi-sorption nature and mono-layered adsorption of MB in comparison to Hex-CCP-co-PPTs. Importantly, the thermodynamic analysis demonstrated that the process of removing MB by utilizing Hex-CCP-co-PPTs was endothermic and occurred spontaneously. These findings highlight the potential application of Hex-CCP-co-PPT microspheres in Algal Membrane Bioreactors (AMBRs) for the efficient and sustainable removal of dye from wastewater. This would contribute to the protection of ecosystems as well as the public's health.

Naphthenic Acids Removal from Model Transformer Oil by Diethylamine Modified Resins

Resins have enormous potential in the removal of naphthenic acids (NAs) from transformer oil due to their rich porosity and high mechanical and diversified functionality, whereas their poor adsorption capacity limits application. In this work, the polystyrene–diethylamine resin (PS−DEA−x) was prepared by grafting diethylamine (DEA) onto chloromethylated polystyrene (PS−Cl) resin to efficiently adsorb cyclopentane carboxylic acid from transformer oil for the first time. The characterization analysis results indicated that amine contents were significantly enhanced with the increase in DEA. Particularly, resin with a molar ratio of 1:5 depending on chloromethyl to DEA (PS−DEA−5) exhibited the highest amine contents and efficient adsorption of cyclopentane carboxylic acid (static adsorption capacity up to 110.0 mg/g), which was about 5 times higher than that of the pristine PS−Cl. The thermodynamic and kinetic studies showed that the adsorption behaviors could be well fitted to the Langmuir isotherm equation and pseudo−second−order rate equation. Moreover, it was found that 1 g of the PS−DEA−5 can decontaminate about 760 mL transformer oil to meet reuse standards by a continuous stream, indicating its potential application in industry.

Interfacial Coordination Bonding-Assisted Redox Mechanism-Driven Highly Selective Precious Metal Recovery on Covalent-Functionalized Ultrathin 1T-MoS2

Rational design of functional material interfaces with well-defined physico-chemical-driven forces is crucial for achieving highly efficient interfacial chemical reaction dynamics for resource recovery. Herein, via an interfacial structure engineering strategy, precious metal (PM) coordination-active pyridine groups have been successfully covalently integrated into ultrathin 1T-MoS2 (Py-MoS2). The constructed Py-MoS2 shows highly selective interfacial coordination bonding-assisted redox (ICBAR) functionality toward PM recycling. Py-MoS2 shows state-of-the-art high recovery selectivity toward Au3+ and Pd4+ within 13 metal cation mixture solutions. The related recycling capacity reaches up to 3343.00 and 2330.74 mg/g for Au3+ and Pd4+, respectively. More importantly, above 90% recovery efficiencies have been achieved in representative PMs containing electronic solid waste leachate, such as computer processing units (CPU) and spent catalysts. The ICBAR mechanism developed here paves the way for interface engineering of the well-documented functional materials toward highly efficient PM recovery.