Publications by authors named "Zhenxun Yu"

3 Publications

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New insights into interaction of proteins in extracellular polymeric substances of activated sludge with ciprofloxacin using quartz crystal microbalance with dissipation.

Chemosphere 2021 Jan 25;263:128044. Epub 2020 Aug 25.

Department of Civil and Environmental Engineering, Ningbo University, Ningbo, 315211, China.

Proteins in extracellular polymeric substances play a vital role in adsorbing organic contaminants in biological wastewater treatment processes, but there is still lack of a fast and effective approach to monitor their interaction. Quartz crystal microbalance with dissipation (QCM-D) was used to investigate the binding and viscoelastic properties of ciprofloxacin (CIP) on extracellular proteins from activated sludge by a two-step sequential deposition method. A saturated viscoelastic monolayer of proteins was formed on the crystal by injecting 500 mg L extracellular proteins. Binding of CIP with the extracellular proteins film followed the pseudo-first-order kinetic equation and Langmuir model, with the maximum binding capacity of 172.4 mg g. The binding mass, energy dissipation, and reaction rate constant increased with increasing CIP concentration. A strong binding was obtained at pH 5, suggesting electrostatic interactions as the dominating binding mechanism. Cations inhibited CIP binding with extracellular proteins, probably due to cations competition. Two binding periods were distinguished according to the viscoelastic properties of CIP layer: viscous binding in the initial period and elastic towards binding saturation. Results highlighted QCM-D as an effective and real-time technique to evaluate the role of extracellular proteins in contaminants removal.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128044DOI Listing
January 2021

Has the formation of disinfection by-products been overestimated? Membrane leakage from syringe filter heads serves as unexpected precursors.

Chemosphere 2020 Nov 3;258:127278. Epub 2020 Jun 3.

State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China. Electronic address:

Syringe filters are widely used for sample pretreatments in laboratories. This study found that, surprisingly, these filters can leak dissolved organic carbon (DOC) that can potentially serve as precursors of disinfection by-products (DBPs). Nine common types of syringe filters were assessed. The results showed that the DOC of ultrapure water increased after syringe filtration. The DOC shed from filter membranes was characterized, whose spectra showed that the main compounds exhibited a low apparent molecular weight. Five classes of DBPs were investigated including trihalomethanes, haloacetaldehydes, haloacetonitriles, haloacetamides and halonitromethanes, among which trichloromethane (TCM), dichloroacetaldehyde (DCAL), trichloroacetaldehyde (TCAL), dichloroacetonitrile (DCAN), and trichloronitromethane (TCNM) were principally detected. The DBP formation was affected by chlorination time and membrane types. In general, the use of the poly vinylidene fluoride membrane resulted in the highest formation of TCM and TCAL, whereas nylon and mixed cellulose esters membranes contributed significantly to the formation of DCAN and TCNM, respectively. The shedding DOC and the formation of TCM, DCAL and TCAL from filter membranes were mitigated effectively by pre-washing; however, the contribution of membrane leakage to DCAN and TCNM formation was still notable, even with a pre-wash volume of 50 mL. When unwashed syringe filters were used for a real water sample, the DBP formation increased by up to 73.2% compared to the pre-washed ones; particularly for TCNM it was always over 15%. Therefore, for better quality control in laboratories, more attention should be paid to the syringe filters during sample pre-treatments, particularly when DBP formation is being investigated.
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http://dx.doi.org/10.1016/j.chemosphere.2020.127278DOI Listing
November 2020

Interaction of ciprofloxacin with the activated sludge of the sewage treatment plant.

Environ Sci Pollut Res Int 2018 Dec 16;25(35):35064-35073. Epub 2018 Oct 16.

Faculty of Architectural, Civil Engineering and Environment, Ningbo University, Ningbo, 315211, China.

Interaction of ciprofloxacin with the activated sludge of the sewage treatment plant is of importance for the ciprofloxacin migration and risk control. More than 96.0% ciprofloxacin was removed through the sludge adsorption. The sludge surface charge varied little with ciprofloxacin since most ciprofloxacin was dissociated into the neutral one. No obvious shift was observed for the soluble carbohydrate concentration and composition with the addition of ciprofloxacin, indicating the weak interaction between the carbohydrates and ciprofloxacin. The introduction of ciprofloxacin resulted in a reduction of the soluble protein concentration, a marked increase of the extracellular protein fluorescence intensities, and a dramatic emergence of new extracellular proteins. The alteration of the proteins highlights the strong interaction between the extracellular proteins and ciprofloxacin, and the consequent integration of certain soluble proteins and original unextractable inner layer extracellular proteins into the extractable extracellular proteins. Different types of interactions are suggested to dominate between the extracellular proteins and the differently dissociated ciprofloxacin.
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http://dx.doi.org/10.1007/s11356-018-3413-0DOI Listing
December 2018