As most heavy metals are highly toxic upon accumulation in the human body, it is urgent to develop accurate, low-cost, and on-site methods to detect multiple heavy metal ions in real water samples. Quantum dots (QDs) are an approved choice for use in sensors and exhibit favorable luminescence in aqueous solution, but they often become quenched when isolated from their suspensions due to agglomeration. Therefore, QDs must exist in a solid state in order to be successfully applied to luminescence detection. This work reports the fabrication of a novel luminescence composite based on glutathione-capped Mn-doped ZnS quantum dots (GSH-Mn-ZnS QDs) and layered double hydroxides (LDH). The composite is solid and exhibits enhanced luminescence intensity, as the structure of LDH prevents the aggregation of QDs. Most importantly, it exhibits a similar response when used as a sensor for detecting Pb2+, Cr3+ and Hg2+ with a linear range of 1 × 10−6 M to 1 × 10−3 M for each heavy metal, and a detection limit for the mixed metal ions of 9.3 × 10−7 M. In addition, the composite was successfully applied for detection in lake water with low interference. Therefore, a practical method is presented for the design and fabrication of a QD–LDH composite that can be used for qualitative and quantitative testing of mixed heavy metal ions simultaneously in real water samples.

Diphenhydramine (DPH) is one of the pharmaceuticals commonly found in the effluent stream after wastewater treatment, and the cause of its environmental persistence needs to be addressed urgently. Smectite minerals are common soil components with large surface area, expandable interlayer, and high cation exchange capacity (CEC), thus are capable of adsorbing or intercalating inorganic or organic cations on the surface or in the interlayer. In this study the intercalation of DPH in the interlayer of a Ca-smectite was characterized by X-ray diffraction, infra-red, and thermogravimetric analyses supported by molecular dynamic simulation. At the low (0.2–0.3 CEC) and high (0.6–0.7 CEC) adsorption levels, the intercalated DPH might take a horizontal monolayer or a bilayer configuration, resulting in a d001 expansion to 15 or 17 Å, respectively. As the amount of DPH intercalation increased, a gradual, yet systematic, dehydration due to removal of hydrated inorganic cation Ca2+ from the interlayer was observed. In addition, the intercalated DPH had a slightly higher thermal stability due to the shield effect of the host mineral smectite against heat. The uptake of DPH by the smectite was attributed to both electrostatic interactions between the negatively charged mineral surfaces and the positively charged tertiary amine and cation exchange interactions between DPH+ and hydrated Ca2+. Thus, smectite minerals could serve as a sink to remove dissolved DPH from water on the one hand, and as a carrier to transport intercalated DPH in the environment on the other hand.

•A novel self-assembled materials of ciprofloxacin-montmorillonite was prepared.•The release rate and amount of interlayer ciprofloxacin could be controlled.•The CIP-MMT composite had better effect on antibacterial and disinfection.In developing new generations of coatings for drug and drug controlled release, there is a need for self-assembled materials that provide controlled sequential release of multiple therapeutics, while provide a tunable approach to time dependence and the potential for sequential or staged release. Herein, we demonstrated the ability to develop a self-assembled, in ciprofloxacin intercalated montmorillonite (CIP-Mt), the release rate and amount of interlayer ciprofloxacin (CIP) could be controlled by modifying the layer charge of montmorillonite (Mt). Compared with common sustained release materials, this composite had better effect on antibacterial and disinfection. The CIP-Mt system effectively blocked diffusion-based release, leading to approximately 50% reduction in bolus doses and 10-fold increase in the release timescale. Mt was a non-toxic and non-polluting sustained release material, could be applied to drug release research, and the release rate and time of its interlayer CIP can be controlled by modifying layer charge.

•Fe-doped birnessites could be used as a catalyst for tetracycline degradation under microwave irradiation.•The increase of unpaired electrons in Fe-doped birnessites resulted in higher electron spin magnetic moment.•The dielectric loss was the main factor to improve the microwave absorption performance.•Microwave absorption performance could be improved by controlling the electron spin magnetic moment of the birnessite.Manganese oxides exhibit an excellent microwave absorption performance that could increase the degradation efficiency of organic pollutants in contaminated water. Incorporation of various transition metals into manganese oxides could bring about changes in their crystal structure and improve their physicochemical performance. In this work, a better microwave absorption material was obtained by adjusting and controlling the electron spin magnetic moments of Fe-doped birnessite. The powder X-ray diffraction, inductive coupled plasma emission spectrometer, X-ray photoelectron spectroscopy, and network analyses were performed to characterize the crystal structure, chemical composition, valence and content of the elements, and the microwave absorption performance of the obtained samples. Doping Fe into birnessite resulted in little changes to their crystal structure. The narrow energy spectrum of Fe (2p) revealed that the doped Fe was in the form of Fe (III) in birnessite structure. As the content of Fe (III) increased, the content of Mn (III) decreased accordingly. Substitution of Mn (III) by Fe (III) in the birnessite crystal lattice, confirmed by combining the characterization analyses with structure refinements for each doped sample, increased the overall numbers of unpaired electrons in birnessite structure, resulting in a higher electron spin magnetic moment and better microwave response. Compared with the non-doped sample, Fe-doped birnessite improved the efficiency of tetracycline degradation, which proved that Fe-doped birnessite indeed had better response towards the microwave, and thus, could be utilized for better removal of organic pollutants under microwave irradiation.Download high-res image (149KB)Download full-size image

Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn2+ and Mn3+ for Mg2+ and Al3+, especially the replacement of Mn2+ for Mg2+ and Al3+, and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn7+), and promoted the replacement of Mn2+ for Mg2+ and Al3+. XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO32− was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis.

Microwave-induced oxidation is an effective method for degradation of organic pollutants with high concentrations in wastewater. In this study, manganese oxide (MO), a mixture of 74% akhtenskite and 26% ramsdellite was used as an oxidant for the microwave-induced oxidation of methylene blue (MB). With 0.1 g of MO and 2.5 mg of MB, the MB removal efficiency was about 99% under 10 min microwave irradiation (MI). The oxidative capacity of MO in this study was closely related to the concentration of H+. A strong acidic condition was optimal for MB degradation in the presence or absence of MI. The intermediates of MB degradation from C16H18N3S to C14H13N2OS, C13H11N2OS, and C12H9N2OS were identified by LC-MS. Network analysis described the excellent microwave adsorption property of MO which was mainly attributed to its dielectric loss. The maximal microwave reflection loss was about −21.23 dB for a sample that is made of 70% MO and 30% paraffin with a thickness of 6 mm. DOS calculation showed that the unit cell of akhtenskite with two manganese ions had the natural spin magnetic moment (2*Integrated Spin Density) of 6.0 which is in accordance with the theoretical calculation of two Mn4+ which could help the hysteresis loss under microwave irradiation. Considering the variable valence of MO and its zero electric dipole moment, it was deduced that charge transfer was the main mechanism for causing the dielectric loss.

Luminous properties of organic fluorescent dyes could be effectively enhanced by adjusting the layer charge of the inorganic host. In this study, we constructed a novel inorganic/organic composite whose layer charge is tunable. This composite material greatly enhanced the luminous efficiency of lucigenin. Compared to the crystalline lucigenin, the fluorescence lifetime of lucigenin increased by 26 folds and luminous intensity was 14 times higher after being intercalated into the interlayer of the saponite host. In addition, the thermal stability was greatly improved. The tunable layer charge can provide a static confinement to the fluorescence dyes and better distribute the lucigenin molecules to prevent fluorescence quenching due to aggregation. The inhibition of fluorescence quenching by intercalating the fluorescence dye into the interlayer of the host inorganic substrate reveals a theoretical significance for the development of high performance organic luminous materials.

With more and more emerging organic contaminants (EOCs) detected in the soil and groundwater, researches on interactions between these pollutants and soils or aquifer materials have attracted greater concerns. In this study, the removal of chlorpheniramine maleate (CP), an antihistamine drug used to treat rhinitis and urticaria, by birnessite, which is a common layered manganese oxide, in aqueous solution was investigated by batch studies, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses, and molecular simulations. The quantum mechanics simulation showed that the final energy of the interaction between CP and the (010) edge surfaces under a strong alkaline condition was much smaller than that under a neutral to slightly alkaline condition. A higher CP adsorption were achieved from neutral to weak alkaline solution, as the broken bond effect of birnessite was strongly influenced by solution pH by protonation and deprotonation of birnessite edges.

•A novel composite of nanoscale zero-valent iron/montmorillonite was prepared•The intercalation makes NZVI well dispersed and more stable in the interlayer•The reduction rate of Cr(VI) was 16 times higher than traditional reaction•NZVI/Cr (VI) redox reaction occurred in the interlayer of MMT.Composite of nano-zero-valent iron and montmorillonite (NZVI/MMT) was prepared by inserting NZVI into the interlayer of montmorillonite. The unique structure montmorillonite with isolated exchangeable Fe(III) cations residing near the sites of structural negative charges inhibited the agglomeration of ZVI and result in the formation of ZVI particles in the montmorillonite interlayer regions. NZVI/MMT was demonstrated to possess large specific surface area and outstanding reducibility that encourage rapid and stable reaction with Cr (VI). Besides, the intercalation also makes NZVI well dispersed and more stable in the interlayer, thereby improving the reaction capacity by 16 times. The effects of pH value, initial concentration of Cr (VI) and reaction time on Cr (VI) removal have also been investigated in detail. According to PXRD and XPS characterization, NZVI/Cr (VI) redox reaction occurred in the interlayer of MMT. The study of NZVI/MMT is instrumental to the development of remediation technologies for persistent environmental contaminants.

Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and water contact angle measurements were used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on copper substrates, respectively. Results show that the super hydrophobic surface is composed of micro structure of Cu7S4. The films present a high water contact angle larger than 150°, a low sliding angle less than 3°, good abrasion resistance and storage stability. The molecular dynamics simulation confirms that N-dodecyl mercaptan molecules link up with Cu7S4 admirably, compared with Cu, which contributes to the stable super hydrophobic surface.

In this study, spent activated carbon (AC) saturated with caramel was regenerated by using yeast and NaOH. The efficiency of regeneration was evaluated under parameters such as amount, treatment time, temperature, pH value, stirring temperature of yeast and NaOH concentration. The optimum condition for AC regeneration was 8 h for yeast treatment time, 35°C for 0.075% yeast culture temperature, a pH value of 6 for the yeast dealing with the spent AC, 90°C for NaOH stirring temperature of AC and 6% NaOH for washing after the spent AC was treated by yeast. Under these conditions, methylene blue (MB) adsorption was 213 mg·g−1 in comparison with 60 mg·g−1 of spent AC. The micro structure and surface area of the regenerated AC were characterized by scanning electron microscope (SEM) and N2 sorption, respectively. The pore size distributions of virgin and regenerated AC were analyzed by means of H-K equation, resulting in a mean pore diameter of 1.28 nm and a pore volume of 1.13 cm3·g−1. This study provides data for theoretical support of the AC regeneration technology.

As most heavy metals are highly toxic upon accumulation in the human body, it is urgent to develop accurate, low-cost, and on-site methods to detect multiple heavy metal ions in real water samples. Quantum dots (QDs) are an approved choice for use in sensors and exhibit favorable luminescence in aqueous solution, but they often become quenched when isolated from their suspensions due to agglomeration. Therefore, QDs must exist in a solid state in order to be successfully applied to luminescence detection. This work reports the fabrication of a novel luminescence composite based on glutathione-capped Mn-doped ZnS quantum dots (GSH-Mn-ZnS QDs) and layered double hydroxides (LDH). The composite is solid and exhibits enhanced luminescence intensity, as the structure of LDH prevents the aggregation of QDs. Most importantly, it exhibits a similar response when used as a sensor for detecting Pb2+, Cr3+ and Hg2+ with a linear range of 1 × 10−6 M to 1 × 10−3 M for each heavy metal, and a detection limit for the mixed metal ions of 9.3 × 10−7 M. In addition, the composite was successfully applied for detection in lake water with low interference. Therefore, a practical method is presented for the design and fabrication of a QD–LDH composite that can be used for qualitative and quantitative testing of mixed heavy metal ions simultaneously in real water samples.