Jianhua Cheng

Adsorption of Cu2+, Cd2+ and Ni2+ from aqueous single metal solutions on graphene oxide membranes

Novel, highly ordered layered graphene oxide (GO) membranes with larger interlayer spacing were prepared by induced directional flow and were used as adsorbents for the removal of Cu(2+), Cd(2+) and Ni(2+) from aqueous solutions. The effects of pH, ionic strength, contact time, metal ion concentration and cycle time on Cu(2+), Cd(2+) and Ni(2+) sorption were investigated. The results indicated that the adsorption of Cu(2+), Cd(2+) and Ni(2+) onto GO membranes was greatly influenced by the pH and weakly affected by the ionic strength. The adsorption isotherms for Cu(2+), Cd(2+) and Ni(2+) were well fitted by the Langmuir model. The maximum adsorption capacities of the GO membranes for Cu(2+), Cd(2+) and Ni(2+) were approximately 72.6, 83.8 and 62.3 mg/g, respectively. The adsorption kinetics of Cu(2+), Cd(2+) and Ni(2+) onto GO membranes followed the pseudo-second-order model. The adsorption equilibrium was reached in a shorter time. The GO membranes can be regenerated more than six times based on their adsorption/desorption cycles, with a slight loss in the adsorption capacity. The results demonstrated that the GO membranes can be used as effective adsorbents for heavy metal removal from water.

Sorption/desorption behavior of triclosan in sediment-water-rhamnolipid systems: Effects of pH, ionic strength, and DOM.

Effects of pH, ionic strength and DOM on the sorption and desorption of triclosan (TCS) in sediment-water-rhamnolipid systems were systematically investigated through controlled batch experiments. Results showed that solubilization enhancement of TCS by rhamnolipid was higher in acid pH range than in alkaline pH range and was the highest at the ionic strength of 5×10(-2) M. Sorption of rhamnolipid onto sediment decreased with the increase of pH while the result was contrary to ionic strength. Moreover, the apparent distribution coefficients of TCS (Kd(*)) decreased from 73.35 to 32.30 L/kg with an increase of solution pH, as varying pH had significant influence on sorption of RL onto sediment and degree of ionization of TCS. Rhamnolipid presented the largest distribution capacity of TCS into the aqueous phase at moderate ionic strength (5×10(-2) M) with the Kd(*) of 17.26 L/kg. Further results also indicated that the presence of humic acid in aqueous phase could increase the desorption of TCS from contaminated sediment. The desorption enhancement was much higher in the system containing both rhamnolipid and DOM than in the single system. These findings provide meaningful information for enhanced migration of TCS from sediment to water by rhamnolipid.

Starch nanoparticles prepared in a two ionic liquid based microemulsion system and their drug loading and release properties

In this work, 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br) and 1-octyl-3-methylimidazolium acetate ([C8mim]Ac) were simultaneously used as substitutes for surfactants and the polar phase to prepare [C16mim]Br/butan-1-ol/cyclohexane/[C8mim]Ac ionic liquid microemulsions. Then, the structure of the microemulsion was investigated by pseudo-ternary phase diagram, dynamic light scanning (DLS) and conductivity measurement. Starch nanoparticles with a mean diameter of 80.5 nm were prepared with Octenyl Succinic Anhydride (OSA) starch as raw material through ionic liquid-in-oil (IL/O) microemulsion cross-linking reaction. Scanning electron microscope (SEM) data revealed that starch nanoparticles were spherical granules with small size. In addition, the particles presented homogeneous distribution and no aggregation phenomenon appeared. The results of Fourier transform infrared spectroscopy (FTIR) identified the formation of cross-linking bonds in starch molecules. Finally, the drug loading and releasing properties of starch nanoparticles were investigated with mitoxantrone hydrochloride as a drug model. This work might provide an efficient method to synthesis starch nanoparticles.

Enhanced adsorption performance of MoS2 nanosheet-coated MIL-101 hybrids for the removal of aqueous rhodamine B

A MoS2 nanosheet-coated chromium terephthalate MIL-101 octahedron hybrid (denoted as MoS2/MIL-101) was prepared via a simple hydrothermal reaction. The obtained MoS2/MIL-101 hybrid exhibited a significantly enhanced adsorption ability toward rhodamine B (RhB) as compared with pure MoS2, MIL-101, and the physical mixture of the two. The results demonstrate that the MoS2/MIL-101 hybrid had a high uptake capacity (Qm ≈ 344.8mgg-1) and fast adsorption rate for the removal of aqueous RhB. The excellent adsorption performance is likely related to the synergism of hydrogen bonding, π-π stacking interactions, and direct coordination between the MIL-101 substrate and RhB, as well as electrostatic interactions between MoS2 nanosheets and RhB. In particular, the uniform distribution of MoS2 nanosheets along with the negative charges on MIL-101 could have a strong interaction with the positively charged RhB, thus leading to an improvement in adsorption performance as observed for the MoS2/MIL-101 hybrid. Furthermore, MoS2/MIL-101 displayed good regenerability and reusability, making it attractive for the adsorption removal of aqueous RhB.

The Effects of Physicochemical Properties of Sludge on Dewaterability Under Chemical Conditioning with Amphoteric Polymer

This study investigated the effects of chemical conditioning with amphoteric terpolymer poly (acrylamide-’acryloyloxyethyl trimethyl ammonium chloride -2-acrylamido-2-methyl-propane sulfonate) (PADA) on sludge dewaterability. Particle size, fractal dimension, surface charge, extracellular polymeric substances (EPS) and trivalent metal ions (Al3+ and Fe3+) of sludge were monitored and Pearson statistical analysis was used to understand the correlation of dewaterability and physicochemical properties of sludge. The results revealed that: (1) Sludge dewaterability was significantly enhanced by amphoteric polymer PADA. (2) Particle, fractal dimension and surface charge of sludge were associated with anionic degrees and molecular weights of polymer. (3) PADA had apparent effects on removal of EPS and enrichment of metal ions in sludge system. (4) Content of water and specific resistance to filtration had statistically strong correlations with the values of particle size, fractal dimension and EPS, but had weak correlations with values of surface charge and metal ions.

Adsorption behavior of methyl orange onto an aluminum-based metal organic framework, MIL-68(Al)

MIL-68(Al), a powdered aluminum-based metal organic framework (MOF), was synthesized and used to explore its adsorption behavior toward methyl orange (MO). The adsorption isotherm, thermodynamics, kinetics, and some key operating factors as well as changes in the materials structure were investigated. The adsorption isotherm conformed to the Langmuir isotherm model and the maximum equilibrium adsorption capacity was 341.30 mg g-1. Thermodynamic data demonstrated that the adsorption process was spontaneous, endothermic and showed positive entropy. For kinetics, the process of MO adsorption onto MIL-68(Al) was more suitably described by a pseudo-second-order model. Electrostatic and hydrogen-bonding interactions contributed to dye adsorption, with electrostatic interactions considered to be the principal binding force between adsorbent and adsorbate. Furthermore, MIL-68(Al) maintained a stable structure after adsorption. From these results, MIL-68(Al) was suggested here to be a stable MOF adsorbent for removing MO from aqueous solution.

Simultaneous degradation of tetracycline and denitrification by a novel bacterium, Klebsiella sp. SQY5

Polluted waters with a high residue of tetracycline also have a high concentration of nitrate. Thus, screening for both, highly efficient tetracycline biodegradation and nitrate transformation, is a key technical strategy. In this study, a novel tetracycline degrading strain, SQY5, which was identified as Klebsiella sp., was isolated from municipal sludge. Biodegradation characteristics of tetracycline were studied under various environmental conditions; including inoculation dose (v/v), initial tetracycline concentration, temperature, and pH. Response surface methodology (RSM) analysis demonstrated that the maximum degradation ratio of tetracycline can be obtained under the condition with an initial tetracycline concentration of 61.27u202fmgu202fL-1, temperature of 34.96u202f°C, pH of 7.17, and inoculation dose of 29.89%. Furthermore, this was the first report on the relationship between the degradation of tetracycline and the denitrification effect, showing that a maximum tetracycline reduction rate of 0.113u202fmgu202fL-1·h-1 and denitrification rate of 4.64u202fmgu202fL-1·h-1 were observed within 32u202fh and 92u202fh of SQY5 inoculation, respectively. The data of this study has the potential for use in engineering processes designed for the simultaneous biological removal of nitrates while degrading antibiotics.

Novel AgNWs-PAN/TPU membrane for point-of-use drinking water electrochemical disinfection

The safety of drinking water remains a major challenge in developing countries and point-of-use (POU) drinking water treatment device plays an important role in decentralised drinking water safety. In this study, a novel material, i.e. a silver nanowires-polyacrylonitrile/thermoplastic polyurethane (AgNWs-PAN/TPU) composite membrane, was fabricated via electrospinning and vacuum filtration deposition. Morphological and structural characterisation showed that the PAN/TPU fibres had uniform diameters and enhanced mechanical properties. When added to these fibres, the AgNWs formed a highly conductive network with good physical stability and low silver ion leaching (<100u202fppb). A POU device equipped with a AgNWs-PAN/TPU membrane displayed complete removal of 105u202fCFU/mL bacteria, which were inactivated by silver ions released from the AgNWs within 6u202fh. Furthermore, under a voltage of 1.5u202fV, the bacteria were completely inactivated within 20-25u202fmin. Inactivation efficiency in 5u202fmM NaCl solution was higher than those in Na2SO4 and NaNO3 solutions. We concluded that a strong electric field was formed at the AgNW tips. Additionally, silver ions and chlorine compounds worked synergistically in the disinfection process. This study provides a scientific basis for research and development of silver nanocomposite membranes, with high mechanical strength and high conductivity, for POU drinking water disinfection.

Removal of tetracycline from aqueous solution by MOF/graphite oxide pellets: Preparation, characteristic, adsorption performance and mechanism

Tetracycline (TC) as a typical antibiotic has been used extensively and detected in soil, surface water, ground water and drinking water, which results in toxic effect and bacterial resistance. In this study, aluminum-based metal organic framework/graphite oxide (MIL-68(Al)/GO) pellets were prepared through the addition of sodium alginate (SA), a natural crosslinking agent, and applied as a novel adsorbent for aqueous TC removal. The adsorption materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption-desorption analysis and X-ray photoelectron spectroscopy (XPS). Results demonstrated that the pellets maintained similar chemical structure with parent MIL-68(Al)/GO powder. It is noted that the surface area and total volume of the pellets decreased obviously due to the disappearance of micropores. Besides, the efficiency of MIL-68(Al)/GO pellets for TC removal was evaluated by adsorption properties compared with parent powder, including key influential parameters, and adsorption isotherms, kinetics and mechanisms. It is found that the adsorption process was conformed to pseudo-first-order kinetics model and more suitably described through Langmuir isotherm model, with 228u202fmgu202fg-1 of the maximum adsorption capacity. Moreover, these pellets which were separated easily and quickly presented high adsorption capacity and good stability in a wide pH range. The adsorption mechanism of the pellets may be ascribed to the complex interactions of hydrogen bonding, π-π stacking as well as Al-N covalent bonding. Overall, the MIL-68(Al)/GO pellets might be a promising adsorbent and show great potential for the removal of aqueous TC.

Research progress on distribution, migration, transformation of antibiotics and antibiotic resistance genes (ARGs) in aquatic environment

Abstract Antimicrobial and antibiotics resistance caused by misuse or overuse of antibiotics exposure is a growing and significant threat to global public health. The spread and horizontal transfer of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) by the selective pressure of antibiotics in an aquatic environment is a major public health issue. To develop a better understanding of potential ecological risks die to antibiotics and ARGs, this study mainly summarizes research progress about: (i) the occurrence, concentration, fate, and potential ecological effects of antibiotics and ARGs in various aquatic environments, (ii) the threat, spread, and horizontal gene transfer (HGT) of ARGs, and (iii) the relationship between antibiotics, ARGs, and ARB. Finally, this review also proposes future research direction on antibiotics and ARGs. Graphical Abstract