Zilin Meng

Layered Double Hydroxide Assemblies with Controllable Drug Loading Capacity and Release Behavior as well as Stabilized Layer-by-Layer Polymer Multilayers

A stable drug release system with magnetic targeting is essential in a drug delivery system. In the present work, layered double hydroxide assemblies stabilized by layer-by-layer polymer multilayers were prepared by alternative deposition of poly(allylamine hydrochloride) and poly(acrylic acid) species on composite particles of Fe3O4 and ZnAl-LDH and then covalent cross-linkage of the polymer multilayers by photosensitive cross-linker. The successful fabrication was recorded by Zeta potential and Fourier transform infrared spectrum measurements. The formed assemblies were stable in high pH solutions (pH > 7). The drug loading capacity and release behavior of the assemblies could be controlled by treatment with appropriate acidic solution, and were confirmed by loading and release of a simulated drug, methylene blue. The formed assemblies possessed enough saturated magnetic strength and were sensitive to external magnetic field which was essential for targeting drug delivery. The formed assemblies were multifunctional assemblies with great potential as drug delivery system.

Structure, molecular simulation, and release of a spirin from intercalated Zn-Al-layered double hydroxides

Aspirin or acetylsalicylic acid (AA), a non-steroidal anti-inflammatory drug, is intercalated into Zn-Al-layered double hydroxides (ZnAl-LDHs) by co-precipitation and reconstruction methods. The composition, structure, and morphology of the intercalated products as well as their release behavior are determined experimentally and theoretically by Material Studio 5.5. Experimental results disclose the strong interaction between the LDHs sheets and AA in the intercalated ZnAl-LDHs produced by co-precipitation and slow release of AA from the intercalated ZnAl-LDHs in both phosphate buffered saline (PBS) and borate buffered saline (BBS) solutions. The percentage of AA released from the ZnAl-LDHs prepared by both methods in PBS (96.87% and 98.12%) are much more than those in BBS (68.59% and 81.22%) implying that both H4BO4(-) and H2PO4(-) can exchange with AA in the ZnAl-LDHs. After AA is released to PBS, ZnAl-LDHs break into small pieces. The experimental results are explained theoretically based on the calculation of the bonding energy between the anions and LDHs sheets as well as the AlO bond length change in the LDHs sheets.

Anomalous but massive removal of two organic dye pollutants simultaneously.

A one-pot method to remove two organic dye contaminants and alkali simultaneously from alkaline wastewater was developed by forming Zn-Al layered double hydroxide (ZnAl-LDH). Using this process, not only alkali but also methyl orange (MO), an anionic contaminant was totally removed from wastewater. In addition, cationic contaminant, methylene blue (MB) was also removed effectively while maintaining the high removal efficiency of MO. The removal efficiency of MO was almost 100% and the pH of the treated wastewater decreased from 12 to 7.38. The charge-limited removal process, molecular arrangement of the contaminants in LDHs, and the anomalous removal mechanism were analyzed experimentally and through simulation. After MO accumulated in the interlayers of LDH by electrostatic interaction, MB entered and trapped by hydrophobic interaction.

Modification of a Na-montmorillonite with quaternary ammonium salts and its application for organics removal from TNT red water

Na-montmorillonite (Na-Mont) and organic montmorillonite modified by cetyltrimethylammonium bromide (CTAB-Mont) and tetramethylammonium bromide (TMAB-Mont) were prepared as adsorbents to remove organic contaminants from 2,4,6-trinitrotoluene (TNT) red water. The characterizations of the samples were performed with X-ray diffraction and Fourier transform infrared spectroscopy. The adsorption capacity of CTAB-Mont (15.9 mg/g) was much larger than Na-Mont (0.26 mg/g) and TMAB-Mont (1.7 mg/g). Langmuir isotherm and the pseudo-second-order kinetic models fitted the experimental results well. The main factor in the adsorption promotion was the distribution phase in the interlayer of CTAB-Mont. The arrangement of molecules analyzed by molecular simulation corresponded to the experimental data and supported the adsorption mechanism.

Novel polyaluminum ferric chloride composite coagulant from Bayer red mud for wastewater treatment

AbstractA novel composite inorganic polyaluminum ferric chloride (PAFC) coagulant was prepared from Bayer red mud and was usable for wastewater treatment. The reaction parameters affecting the PAFC coagulant performance such as the type of alkali used as the polymerization adjuster, pH, reaction temperature, and reaction time were examined in this study. The structure and morphology of the product were characterized by infrared spectra (FTIR), X-ray diffraction, and scanning electron microscopy. The optimized conditions for preparation were decided as using Ca(AlO2)2 and NaOH together as the polymerization adjuster to reach a pH value of 2.47 with the mixture being kept at 80°C for 6 h. Furthermore, the coagulation performance of the PAFC coagulant was tested in real wastewater samples of pretreated oily sewage and printing and dyeing wastewater. The prepared PAFC coagulant outperformed commercially available PAC coagulant.

Constructing the magnetic bifunctional graphene/titania nanosheet-based composite photocatalysts for enhanced visible-light photodegradation of MB and electrochemical ORR from polluted water

Photocatalysis is a promising strategy to address the global environmental and energy challenges. However, the studies on the application of the photocatalytically degraded dye-polluted water and the multi-purpose use of one type of catalyst have remained sparse. In this report, we try to demonstrate a concept of multiple and cyclic application of materials and resources in environmentally relevant catalyst reactions. A magnetic composite catalyst prepared from exfoliated titania nanosheets, graphene, the magnetic iron oxide nanoparticles, and a polyelectrolyte enabled such a cyclic application. The composite catalyst decomposed a methylene blue-polluted water under visible light, and then the catalyst was collected and removed from the treated water using a magnet. The photocatalytically treated water was then used to prepare the electrolyte in electrochemical reductive reactions and presented superior electrochemical performance compared with the dye-polluted water. The composite catalyst was once again used as the cathode catalyst in the electrochemical reaction. Each component in the composite catalyst was indispensable in its catalytic activity, but each component played different roles in the photochemical, magnetic recycling, and electrochemical processes. We expect the report inspire the study on the multi-functional catalyst and cyclic use of the catalytically cleaned water, which should contribute for the environmental and energy remedy from a novel perspective.

Novel multiple coagulant from Bayer red mud for oily sewage treatment

AbstractMultiple coagulants for the treatment of wastewater were prepared. To obtain the optimum synthetic conditions of coagulants, response surface methodology was used to establish the relationship between parameters and the treatment efficiency. In addition, parameters affecting the coagulation–flocculation process, such as the dosage of attapulgite (ATP), the dosage of poly-dimethyl-diallyl-ammonium chloride (PDMDAAC), and the reaction temperature, were investigated. The optimized parameters to prepare multiple coagulant were determined as the dosage of ATP and PDMDAAC being 4 and 2%, respectively, and the reaction temperature being 60°C. The coagulation performance for oily sewage showed that the optimum dosage of coagulant for the maximum treatment was 100 mg/L and the sedimentation time was 30 min at 60°C. In the coagulation–flocculation process, the COD of the oily water decreased from 534 to 246 mg/L and its turbidity decreased from 124 to 2.0 NTU.

Electrostriction tensor components of alkaline-earth fluoride single crystals

Abstract The separated electrostriction tensor components for alkaline-earth fluoride single crystals have been measured by the converse method using the uniaxial stress dependence of the dielectric permittivity. Values obtained for the individual components of the electrostrictive voltage coefficients were M 11 = −0.116, M 12 = 0.109 and M 44 = 0.538 for SrF 2 and M 11 = −0.107, M 12 = 0.123 and M 44 = 0.594 for BaF 2 , respectively, in units of 10 −20 m 2 /V 2 . The corresponding values for CaF 2 have been reported elsewhere.

Contribution of sodium dodecyl sulphate and sodium lauric acid in the one-pot synthesis of intercalated ZnAl-layered double hydroxides

Anion surfactants, sodium dodecyl sulphate (SDS) and sodium lauric acid (SLA), with almost the same chain length but different anion groups were used together as intercalates to prepare intercalated ZnAl–layered double hydroxides (ZnAl–LDHs). Their composition, structure and morphology were characterized by Fourier transform infrared, X-ray fluorescence, thermogravimetric and X-ray diffraction (XRD). The results indicated SDS intended to maintain the lamellae structure of LDHs, but SLA was more likely to expand the basal spacings of LDHs in the present system. The arrangement of the surfactants in the interlayer of ZnAl–LDHs was also simulated by Materials Studio. The basal spacings of the LDHs calculated based on simulated structure consisted with that from XRD.