Rapid synthesis and characterization of silver-loaded graphene oxide nanomaterials and their antibacterial applications.

With the promising potential application of Ag/graphene-based nanomaterials in medicine and engineering materials, the large-scale production has attracted great interest of researchers on the basis of green synthesis. In this study, water-soluble silver/graphene oxide (Ag/GO) nanomaterials were synthesized under ultrasound-assisted conditions. The structural characteristics of Ag/GO were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and energy dispersion spectroscopy, respectively. The results showed the silver particles (AgNPs) obtained by reduction were attached to the surface of GO, and there was a strong interaction between AgNPs and GO. The antibacterial activity was primarily evaluated by the plate method and hole punching method. Antibacterial tests indicated that Ag/GO could inhibit the growth of Gram-negative and Gram-positive bacteria, special for the Staphylococcus aureus.

Cellulose nanocrystal assisted trace silver nitrate to synthesize green silver nanocomposites with antibacterial activity.

Cellulose nanocrystals (CNCs) with silver nanoparticles (AgNPs) are used for applications ranging from chemical catalysis to environmental remediation, and generation of smart electronics and biological medicine such as antibacterial agents. To reduce the synthesis cost of AgNPs and environmental pollution, microwave-assisted generation of AgNPs on the CNC surface (AgNPs@CNC) has been found to be useful, because microwave reaction has the advantages of simple reaction conditions, short reaction time and high reaction efficiency. The silver ions (Ag+) could be added to the CNC suspension and placed in the microwave reactor for a few minutes to produce AgNPs. AgNP generation was affected by factors such as the concentrations of Ag+ and CNC, and the power of the microwave, as well as the time of reaction. In this study, we used trace amounts of AgNO3 to rapidly synthesize AgNPs using a green microwave-based method instead of Tollen's reagent, and the antibacterial activity of the T1 sample showed that only using 0.03 mM (∼0.01 wt%) AgNO3 to synthesize AgNPs@CNC could achieve good antibacterial properties.

Combined application of modified corn-core powder and sludge-based biochar for sewage sludge pretreatment: Dewatering performance and dissipative particle dynamics simulation.

Sludge is an inevitable by-product of municipal wastewater treatment processes, and its high moisture content poses a major challenge for its subsequent treatment and disposal. Previous studies have explored the effects of applying modified corn-core powder (MCCP) on dewatering sludge. Here, we characterized the effects of applying both MCCP and sludge-based biochar (SBB) on dewatering sludge. Analysis of the anti-shear ability of SBB revealed that SBB was a skeleton builder with high compressive strength, demonstrating that SBB could maintain the permeability of sludge under high-pressure filtration processes and facilitate the flow of bound water. Dissipative particle dynamics (DPD) was used to simulated the sludge flocculating process and verify the feasibility of the experiment. As the simulation progressed, the reaction in the sludge network reached equilibrium and the simulated structure of the sludge became loose. The dewatering performance and physicochemical properties of the treated sludge were studied to further characterize the effect of this combined technology. Compared with MCCP-sludge, MCCP&SBB-sludge, which was treated by 20% DS (mass of dry solids in sludge) of SBB and 20% DS of MCCP, achieved superior dewaterability. This combined method reduced the specific resistance of filtration by 76% and enlarged the net sludge solids yield by 138%. Further study of the properties of MCCP&SBB-sludge revealed a loose structure that resembled the structure recovered by the simulation, suggesting that the DPD simulation method simulated the sludge flocculating process successfully. Therefore, the combined application of MCCP and SBB was superior for sludge dewatering because of the synergistic effects of MCCP and SBB.

Role of extracellular polymeric substances in sludge dewatering under modified corn-core powder and sludge-based biochar pretreatments.

Extracellular polymeric substances (EPS) which wrapped on sludge particles were deemed to hinder the outflowing of combined water in sludge system. The complex composition of EPS was the bottleneck for revealing its relationship with sludge dewaterability. In this study, a combined modified corn-core powder (MCCP) and sludge-based biochar (SBB) condition was executed to treat sludge for enhancing dehydration performance, and the concentration and the form distribution of organics in EPS, the variances of protein secondary structures were investigated. Correlation between the sludge dewaterability and EPS components were performed, found strong correlations among the net sludge solids yield (YN) and the specific resistance of filtration (SRF) (R = -0.923), Zeta potential (R = -0.971). Furthermore, the relationship between the secondary structures of protein and dehydration performance were strong related. With the optimal dosage of SBB and MCCP, aggregated strands and α -helix were released, indicated that the unfolding and despiralization in soluble EPS (S-EPS) were improved, disordered the sludge network, reduced the flowing resistance of bound water, finally enhancing sludge dewaterability.

Chemical behavior of fluorine and phosphorus in chemical looping gasification using phosphogypsum as an oxygen carrier.

In China, the amount of phosphogypsum (PG) has exceeded 250 million tons with more than 55 million tons of growth rates each year. As the micro constituent, fluorine and phosphorus restrict the resourceful disposal of PG. This paper focused on chemical looping gasification (CLG) which used PG as an oxygen carrier, systematically investigated the gasification performance and chemical behavior of fluorine and phosphorus contained in PG during CLG process. Main conclusions are as follows. The main pollutant of chemical looping gasification process was HF, which was transformed from NaF. Phosphorus transformed from water-soluble phosphorus (Ca(H2PO4)2, Ca(HPO4)) into insoluble Ca3(PO4)2.20 reducing-oxidizing cycles were investigated, and a less and less fluorine content in oxygen carrier was found because its phase transformation from solid NaF to gaseous HF, and the phosphorus content in oxygen carrier changed slightly under the current conditions. The Ca3(PO4)2 particle layers existed in both the middle of the reduced solid particles and the middle of the cycled oxygen carrier particles, confirmed to actually act as a glue between the particles. Furthermore, transformation routes of fluorine and phosphorus during the CLG process were discussed and the generation of syngas in CLG process needed to be purified.

Highly efficient and selective membrane separation of copper from nickel in ammoniacal solution using mixtures of M5640 and BESO as membrane carriers.

Separation of copper from nickel in ammoniacal/ammonium chloride solution using a flat-sheet supported liquid membrane impregnated with mixtures of Acorga M5640 and bis(2-ethylhexyl)sulfoxide (BESO) was investigated. The crucial parameters influencing copper transport and separation abilities of copper and nickel, such as carrier concentration of M5640 and BESO in the membrane phase, initial concentration of ions in the feed phase, H2SO4 concentration in the strip phase and membrane stability, were discussed. The results show that the mixtures of carriers (20 vol% M5640 + 20 vol% BESO) in the membrane have a considerable antagonistic effect on membrane transport of nickel, but favor copper transport. Nearly all of the copper was transferred from the feed phase to the strip phase after 12 hours with a flux of 2.05 × 10-5 mol m-2 s-1 under the following conditions: 100 mg L-1 each of the copper and nickel dissolved in 1.0 mol L-1 each of ammonia and ammonium chloride solution as the feed phase, 60 g L-1 H2SO4 as the strip phase, and stirring speed of 800 rpm in two aqueous phases. Meanwhile less than 3.8% of the nickel was transported into the strip phase over the same time. Copper and nickel were efficiently separated with a calculated factor of 26.3. Furthermore, satisfactory membrane stability was obtained with at least ten cycle runs in this separation system.

Chemical looping gasification of phosphogypsum as an oxygen carrier: The Ca and S migration mechanism using the DFT method.

Chemical-looping gasification (CLG) is a novel process for syngas generation from solid fuels that shares the same basic principles as chemical-looping combustion (CLC). This method also uses oxygen carriers (mainly metal oxides and calcium sulfate) to transfer heat and oxygen to the fuel. In this work, we used phosphogypsum (PG) as the oxygen carrier in CLG with lignite fuel. Based on experimental and density functional theory (DFT) theoretical calculation analysis, the Ca and S migration characteristics in PG and the reaction mechanism between lignite fuel molecules and the oxygen carrier PG in CLG were explored. The results show that there is a series of tandem and competitive reactions during this process, and the optimal temperature range of the fuel reactor in the chemical looping gasification of PG oxygen carriers is 1173 K-1223 K. The only gaseous sulfide detected is H2S, and the solid sulfide CaS and a small amount of unreacted CaSO4 are detected at a temperature of 1173 K. DFT calculation shows that the presence of S+6 atoms from SO42- on the top of the CaSO4 surface is more favourable than Ca2+ for C, CO, and H2 oxidation at a temperature of 1173 K. During oxidation, lattice O consumption mainly occurs around the S+6 atoms stepwise from S+6 → S-2 at a temperature of 1173 K. In addition, CO and H2 oxidation occur more easily than that of C at a temperature of 1173 K. The experimental results and the calculated results show good consistency, providing valuable information regarding the reactivity of the oxygen carrier PG and the C, CO, and H2 oxidation over the CaSO4 surface at an atomic level.

Nano-aggregates of furan-2-carbohydrazide derivatives displaying enhanced emission with a bathochromic shift.

The non-fluorescent Schiff base compound C1 (N'-((4'-ethyl-3-hydroxy-[1,1'-biphenyl]-4-yl)methylene)furan-2-carbohydrazide) in organic solvent (e.g., THF) was found to produce yellow-green fluorescence emission upon addition of H2O, and granular-shaped aggregates in a THF/H2O mixed solution formed and exhibited obvious aggregation-induced emission (AIE). Especially its keto fluorescence band intensified dramatically, while the enol emission band remained almost unchanged. Hence, a change in fluorescence from no emission of light to emission of bright yellow-green light under a UV lamp was observed with the naked eye. In contrast, the reference compound C2 (N'-((4'-ethyl-3-methoxy-[1,1'-biphenyl]-4-yl)methylene)furan-2-carbohydrazide) showed no intensified fluorescence emission under the same experimental conditions. These results indicated the significant role played by intramolecular H-bonding in the formation of the C1 aggregates and the AIE process.

Nanoparticle delivery and combination therapy of gambogic acid and all-trans retinoic acid.

In order to enhance the in vivo codelivery efficiency of gambogic acid (GA) and all-trans retinoic acid (ATRA), our strategy was to entrap GA in the self-assembled nanoparticles based on amphiphilic hyaluronic acid (HA)-ATRA (HRA) conjugate. In this way, GA and ATRA were loaded simultaneously in a nanocarrier and codelivered into the tumor cell through HA receptor-mediated endocytosis. GA-loaded HRA nanoparticles (GA-HRA) were prepared by a dialysis method, and their physicochemical characteristics were investigated as well. GA-HRA exhibited a high drug loading capacity (31.1%), had a particle size in the range of 100-150 nm, and good biocompatibility. HRA nanoparticles were effectively internalized by MCF-7 cells and translocated into the nucleus in a time-dependent manner. The in vivo imaging analysis demonstrated that the fluorescent signals in the tumor were markedly increased with DiR-loaded nanoparticles after intravenous administration compared to free DiR solution, suggesting it has excellent tumor targeting properties. More importantly, GA-HRA exhibited excellent in vivo efficacy with dramatically reduced toxicity. In conclusion, with the assistance of HRA nanoparticles, GA and ATRA can successfully realize an effective combination chemotherapy as well as tumor-targeted delivery.

Efficient simultaneous tumor targeting delivery of all-trans retinoid acid and Paclitaxel based on hyaluronic acid-based multifunctional nanocarrier.

An amphiphilic hyaluronic acid (HA)-g-all-trans retinoid acid (HRA) conjugate was successfully developed as a tumor-targeting nanocarrier for potentially synergistic combination chemotherapy of all-trans retinoid acid (ATRA) and paclitaxel (PTX). The HRA conjugate was synthesized by an imine reaction between HA-COOH and ATRA-NH2. PTX-loaded HRA nanoparticles possessed a high loading capacity, nanoscale particle sizes, and good biocompatible characteristics. Cell viability assays indicated that PTX-loaded HRA nanoparticles exhibited concentration- and time-dependent cytotoxicity. Moreover, they displayed obvious superiority in inducing the apoptosis of tumor cells. Cellular uptake analysis suggested that HRA nanoparticles could be efficiently taken up by cells via endocytic pathway and transport into the nucleus, contributing to HA receptor-mediated endocytosis and ATRA-induced nuclear translocation, respectively. Moreover, in vivo imaging analysis indicated that the accumulation of DiR-loaded HRA nanoparticles in tumor was increased obviously after intravenous administration as compared to free DiR solution, which confirmed that the HRA nanoparticles could assist the drugs targeting to the tumor. Furthermore, PTX-loaded HRA nanoparticles exhibited greater tumor growth inhibition effect in vivo with reducing the toxicity. Therefore, HRA nanoparticles can be considered as a promising targeted codelivery system for combination cancer chemotherapy.