Magnetic Carbon Electrode Research Articles

Phosphate selective recovery by magnetic iron oxide impregnated carbon flow-electrode capacitive deionization (FCDI)

The recovery of phosphorus (P) from wastewaters is a worthy goal considering the potential environmental and economic benefits. Flow-electrode capacitive deionization (FCDI), which employs flowable carbon electrodes instead of the static electrodes used in conventional CDI, has been demonstrated to be a promising P recovery technology. FCDI outperforms CDI and other competitive technologies in a number of aspects including (i) large salt adsorption capacity and (ii) extremely high water recovery rate. In this study, magnetic (Fe3O4 impregnated) activated carbon particles were prepared and applied as FCDI electrodes. The magnetic carbon electrodes were found to have a strong affinity towards P, facilitating the selective adsorption of P to the magnetic particles through a ligand exhange mechanism. Continuous operation of the FCDI system could be achieved with only three minutes required to separate the electrode particles from the brine stream on application of an external magnetic field. A P-rich stream was produced on regeneration of the exhausted magnetic electrodes using alkali solution. We envision that the use of magnetic carbon enhanced flow-electrodes will pave the way for efficient operation of FCDI as well as the preferential recovery of P.

Rich heteroatom doping magnetic carbon electrode for flow-capacitive deionization with enhanced salt removal ability

Core-shell nanoparticles were prepared by coating magnetic nanoballs (Fe3O4) with highly cross-linked polymer poly(-cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) to serve as heteroatomic-rich doping electrodes (MZPS). After formation by carbonization, C-MPZS acts like a flowing electrode used for flow-capacitive deionization (FCDI), which has fast ion transfer and diffusion performances because of its rich heteroatom content and the prominent synergistic effect of N, P, S atoms. Moreover, the FCDI performance of C-MPZS is enhanced due to its increased synergistic effect from its excellent available specific surface area, unique porous characteristics with large micro-/mesopores, and favorable conductivity with high graphitization. The optimal carbonization temperature was 500 °C with an optimum specific capacitance of 211.54 F g−1, which was tested in a 1 M sodium chloride solution at a scan rate of 1 mV s−1. Then, the C-MPZS flowing electrode was found to have a high electrosorption capacity (50.07 mg g−1), removal efficiency (68.50%) and removal rate (83.07%) at an applied potential of 1.0 V in a sodium chloride solution with a conductivity of 1200 μS cm−1 at 6 rpm. An additional cyclic test demonstrated good stability performance after 10 cycles due to the magnetic nanoparticles effect. Finally, through the successful application in tail water from printing and dyeing wastewater, the results indicated that the as-prepared C-MPZS flowing electrode has promise for application in high-performance electrochemical deionization.

Electrochemical determination of diethylstilbestrol by using a magnetic nanoparticle/graphene composite film electrode

The magnetic nanoparticle-graphene modified magnetic carbon electrode (MCE) was fabricated and the electrochemical effect of diethylstilbestrol (DES) on this electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The factors that affected the performance of the sensor were also optimized. The experimental results exhibited good electrocatalytic activity and a fast response for the electrochemical oxidation of DES. The linear range for the determination of diethylstilbestrol was 1 to 100 μM and the detection limits were 1.06 × 10−7 M based on S/N = 3.

Electrochemical immunosensor for detection of prostate specific antigen based on an acid cleavable linker into MSN-based controlled release system

A mesoporous silica nanoparticle (MSN)-based controlled release system with acid cleavable linkage was developed to fabricate an electrochemical immunosensor for the quantitative detection of the prostate-specific antigen (PSA). 3,9-Bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane functionalized mesoporous silica nanoparticles (MSN-Acetal) were used to immobilize the electron mediator thionine (Th). The encapsulation of Th molecules was achieved by capping the pores of MSN-Acetal with carboxylic acid modified Au nanoparticles (defined as MSN-Th-Au). Under the acidic conditions, the capped Au nanoparticles were removed from MSN-Th-Au through the hydrolysis of the acid-labile acetal linker, resulting in the release of encapsulated Th. In this work, the pH-responsive cargo release system was firstly used as the label of secondary anti-PSA for developing an electrochemical immunosensor, and amination Fe3O4 was used as the sensing matrix for immobilizing primary anti-PSA on magnetic carbon electrode surfaces. The specific recognition of PSA resulted in the attachment of MSN-Th-Au-secondary anti-PSA (MSN-Th-Au-Ab2) onto the electrode surfaces. Subsequently, the released Th was detected by differential pulse voltammetry under the acidic conditions. The developed cargo release system provided an innovative and reliable method for the detection of PSA because the response signal was correlated with the concentration of PSA. Under the optimal conditions, the electrochemical immunosensor exhibited a wide linear range of 0.001–5.0ng/mL with a low detection limit of 0.31pg/mL. Moreover, the developed immunosensor showed superior reproducibility and long-term stability, which has promising applications in bioassay and biosensing.

Enabling electrochemical studies of chemically-modified carbon nanotubes in non-aqueous electrolytes using superparamagnetic nanoparticle-nanotube composites co-modified by diazirine molecular “tethers”

Multiwalled carbon nanotubes (MWCNTs) were covalently modified with polymer-coated superparamagnetic Fe 3O 4 nanoparticles via amide bond formation to surface oxo-groups located predominantly at the ends of the nanotubes to form “magnetic MWCNTs”. The sidewalls of the magnetic MWCNTs were then selectively covalently modified with ferrocenyl groups via the photolysis of 3-[3-(trifluoromethyl) diazirin-3-yl] phenyl ferrocene monocarboxylate, which uses an aryldiazirine moiety as a molecular “tether”. We demonstrate that the assembly of the chemically-modified magnetic MWCNTs onto the surface of a magnetic carbon electrode enables one to obtain stable voltammetric signals of chemically-modified carbon nanotubes in non-aqueous electrolytes even under vigorous hydrodynamic conditions of stirring at 3000 rpm for up to twenty minutes. In contrast, non-magnetic chemically modified MWCNTs are removed from the electrode surface within the first two minutes of stirring.