Guoquan Zhang

PB/PANI-modified electrode used as a novel oxygen reduction cathode in microbial fuel cell

This study focuses on the preparation of a new type of Prussian Blue/polyaniline (PB/PANI)-modified electrode as oxygen reduction cathode, and its availability in microbial fuel cell (MFC) for biological power generation. The PB/PANI-modified electrode was prepared by electrochemical and chemical methods, both of which exhibited good electrocatalytical reactivity for oxygen reduction in acidic electrolyte. The MFC with PB/PANI-modified cathode aerated by either oxygen or air was shown to yield a maximum power density being the same with that of the MFC with liquid-state ferricyanide cathode, and have an excellent duration as indicated by stable cathode potential for more than eight operating circles. This study suggests a promising potential to utilize this novel electrode as an effective alternative to platinum for oxygen reduction in MFC system without losing sustainability.

Hydraulic power and electric field combined antifouling effect of a novel conductive poly(aminoanthraquinone)/reduced graphene oxide nanohybrid blended PVDF ultrafiltration membrane

Membrane fouling is still a bottleneck problem towards the wide-spread applications of membrane bioreactors (MBRs) for wastewater treatment/reclamation. Thus, membrane modification has ever been a hot topic for improving the separation efficiency and antifouling ability of membranes. In this study, a novel conductive and hydrophilic poly(1,5-diaminoanthraquinone)/reduced graphene oxide (PDAAQ/rGO) nanohybrid blended polyvinylidene fluoride (PVDF) membrane was prepared by the phase inversion method. The fabricated PDAAQ/rGO/PVDF membrane was characterized by different characterization techniques. The effect of additive content on the membrane structure and antifouling performance was evaluated. An obvious growth in pore size/porosity and surface roughness was observed for the 1.5 wt% PDAAQ/rGO nanohybrid blended membrane, which caused higher hydrophilicity, pure water flux and fouling resistance than those of the pristine PVDF membrane. By applying an appropriate external electric field of 1.0 V cm−1, the conductive PDAAQ/rGO nanohybrid blended PVDF membrane exhibited an admirable electrocatalytic activity towards the oxygen reduction reaction, and 8.84 mg L−1 H2O2 was accumulated within 30 min electrolysis. Meanwhile, the conductive PDAAQ/rGO/PVDF membrane displayed superior fouling removal ability along with a higher water flux recovery ratio after electric cleaning. Applying bovine serum albumin as the model protein and 1.0 V cm−1 external electric field, the fouling rate of the conductive PDAAQ/rGO/PVDF membrane decreased by about 63.5% when compared with the control test during the long-term continuous-flow membrane filtration process. The cross-flow shear stress induced by aeration scouring, the increased electrostatic repulsion force induced by the external electric field and the in situ electro-generated H2O2 contributed to the prominent fouling mitigation and fouling resistance.

One-step potentiodynamic synthesis of poly(1,5-diaminoanthraquinone)/reduced graphene oxide nanohybrid with improved electrocatalytic activity

In this work, we facilely synthesized poly(1,5-diaminoanthraquinone)/reduced graphene oxide (P(1,5-DAAQ)/RGO) nanohybrid through a one-step potentiodynamic deposition method (by changing the potential scanning range and direction), in which the 1,5-DAAQ monomer and GO acted as the starting materials. RGO was generated by cathodic electro-reduction of GO and P(1,5-DAAQ) polymer was simultaneously produced by in situ anodic electro-oxidative polymerization of the 1,5-DAAQ monomer. The morphology and microstructure of the resultant nanohybrid was fully characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Characterizations indicate that the P(1,5-DAAQ) polymer displays a barleycorn-like structure and is covalently grafted onto the RGO surface. The electrochemical properties and electrocatalytic activity of the P(1,5-DAAQ)/RGO nanohybrid were investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and rotating disk electrode (RDE) techniques. The P(1,5-DAAQ)/RGO nanohybrid shows higher electrical conductivity than that of 1,5-DAAQ/GO, since it has a lower concentration of oxy-functional groups after the potentiodynamic synthesis. The CV and RDE results reflect the fact that the P(1,5-DAAQ)/RGO nanohybrid possesses superior electrocatalytic activity toward the oxygen reduction reaction (ORR) with a long cycle life. The covalently grafted P(1,5-DAAQ) polymer on RGO sheets supplies sufficient electroactive sites (the π-conjugated system and the quinone groups), resulting in more favorable electron-transfer kinetics and greatly enhanced electrocatalytic performance for O2 reduction on the P(1,5-DAAQ)/RGO nanohybrid.

Anti-fouling performance and mechanism of anthraquinone/polypyrrole composite modified membrane cathode in a novel MFC–aerobic MBR coupled system

In this study, an aerobic membrane bioreactor (MBR) equipped with anthraquinone–disulphonate/polypyrrole (AQDS/PPY) composite modified polyester (PT) flat membrane serving as the cathode of a dual-chamber microbial fuel cell (MFC) was developed for wastewater treatment, energy recovery and membrane fouling mitigation. Various physicochemical characteristic parameters were investigated to determine the surface properties of the AQDS/PPY/PT membrane. During most of the operation period, the chemical oxygen demand and NH4+–N removal efficiencies of this novel MFC–MBR coupled system averaged 92.5% and 70.6%, respectively. Over the hydraulic retention time of 11.58 h and the external resistance of 1000 Ω, a maximum power density of 0.35 W m−3 and a current density of 2.62 A m−3 were obtained, meanwhile, the membrane fouling mitigation achieved the best status the H2O2 concentration in membrane effluent also reached the highest value of 2.1 mg L−1. The effective membrane fouling mitigation was attributed mainly to the continuous self-generated bio-electricity of MFC, which not only accelerates the back-diffusion of negative charged foulants away from the membrane surface through the electrostatic repulsion, but also realizes membrane chemical cleaning through the in situ electrogenerated H2O2 and even ˙OH radicals on the membrane surface and/or inside the membrane pore from the self-sustainable heterogeneous electro-Fenton process. Though the electricity recovery of the MFC–MBR coupled system was much lower than other high-output MFC systems, this study provided a new insight into the membrane anti-fouling mechanism and will arouse extensive interests to explore more high-efficiency catalytic membrane materials to maximize power output and minimize membrane fouling.

Highly antifouling and antibacterial performance of poly (vinylidene fluoride) ultrafiltration membranes blending with copper oxide and graphene oxide nanofillers for effective wastewater treatment

Innovation and effective wastewater treatment technology is still in great demand given the emerging contaminants frequently spotted from the aqueous environment. By blending with poly (vinylidene fluoride) (PVDF), the strong hydrophilic graphene oxide (GO) and antibacterial copper oxide (CuxO) were used as nanofillers to develop the novel, highly antifouling composite membranes via phase inversion process in our latest work. The existence and dispersion of GO and CuxO posed a significant role on morphologies, structures, surface composition and hydrophilicity of the developed composite membranes, confirmed by SEM, TEM, FTIR and XPS in depth characterization. The SEM images showed that the modified membranes presented a lower resistant structure with developed finger-like macrovoids and thin-walled even interconnected sponge-like pores after adding nanofillers, much encouraging membrane permeation. The XPS results revealed that CuxO contained Cu2O and CuO in the developed membrane and the Cu2O nanoparticles were dominant accounting for about 79.3%; thus the modified membrane specifically exhibited an efficient antibacterial capacity. Due to the hydrophilic and bactericidal membrane surface, the composite membranes demonstrated an excellent antifouling performance, including higher flux recovery rate, more resistant against accumulated contaminants and lower filtration resistance, especially lower irreversible resistance. The antifouling property, especially anti-irreversible fouling, was significantly improved, showing a significant engineering potential.

Synergetic adsorption and catalytic oxidation performance originating from leafy graphite nanosheet anchored iron(II) phthalocyanine nanorods for efficient organic dye degradation

Leafy graphite nanosheet anchored iron(II) phthalocyanine nanorods (FePc@LGNS) were facilely synthesized without using a complex covalent anchoring procedure. FE-SEM, XRD, FTIR, and XPS characterizations confirmed the molecular configuration of FePc on the LGNS surface. The interlaced hydrophobic/hydrophilic regions and large specific-surface-area of the FePc@LGNS hybrid not only improved the adsorption capacity, but also promoted the oxidative ability of the FePc@LGNS–H2O2 system due to sufficient FePc catalytic active sites on LGNS surface. The optimal conditions for CR removal were initially pH 6.98, 50 mM H2O2 and 1.0 g L−1 FePc@LGNS hybrid. Different from the classical Fenton process, high-valent iron(IV)–oxo complexes and hydroxyl radicals are responsible for Congo red (CR) oxidative degradation. Liquid chromatography-mass spectrometry (LC-MS) analysis demonstrated the effective cleavage of both azo bonds and C–C bonds of CR molecules. A plausible oxidation mechanism of the FePc@LGNS–H2O2 system and the degradation pathway of CR were proposed. This FePc@LGNS–H2O2 system could be a highly efficient oxidation process for recalcitrant pollutants elimination over a wide pH range.

Exploration of permeability and antifouling performance on modified cellulose acetate ultrafiltration membrane with cellulose nanocrystals

Cellulose nanocrystals (CNCs) were introduced into cellulose diacetate (CDA) matrix via immerged phase-inversion process, aiming to improve the filtration and antifouling performance of CNCs/CDA blending membrane. The effects of CNCs on membrane morphologies, hydrophilicity, permeability and antifouling property were investigated. Results showed that the incorporation of CNCs into CDA membrane could effectively enhance the permeability and antifouling property of CNCs/CDA blending membrane by optimizing membrane microstructure and improving membrane hydrophilicity. A high pure water flux of 173.8L/m2h was achieved for the CNCs/CDA blending membrane at 200KPa, which is 24 times that of the CDA membrane (7.2L/m2h). The bovine serum albumin (BSA) adsorption amount of the CNCs/CDA blending membrane decreased about 48% compared to that of the CDA membrane. Additionally, the CNCs/CDA blending membrane exhibited better antifouling performance with the flux recovery ratio (FRR) of 89.5% after three fouling cycles, compared to 59.7% for the CDA membrane.