Haiou Song

Rapid removal of copper with magnetic poly-acrylic weak acid resin: Quantitative role of bead radius on ion exchange

A novel magnetic weak acid resin NDMC was self-synthesized for the removal of Cu(2+) from aqueous solutions. NDMC showed superior properties on the removal of Cu(2+) compared to commercial resins C106 and IRC-748, which was deeply investigated by adsorption isotherms and kinetic tests. The equilibrium adsorption amount of Cu(2+) onto NDMC (267.2mg/g) was almost twice as large as that onto IRC-748 (120.0mg/g). The adsorption kinetics of Cu(2+) onto the three resins fitted well with the pseudo-second-order equation. The initial adsorption rate h of NDMC was about 4 times that of C106 and nearly 8 times that of IRC-748 at the initial concentration of 500mg/L. External surface area was determined to be the key factor in rate-controlling by further analyzing the adsorption thermodynamics, kinetics parameters and physicochemical properties of the resins. NDMC resin with the smallest bead radius possessed the largest external surface and therefore exhibited the fastest kinetics. The adsorption amount of Cu(2+) onto NDMC was not influenced as the concentration of Na(+) increased from 1.0 to 10.0mM/L. Dilute HCl solution could effectively desorb Cu(2+). NDMC demonstrated high stability during 10 adsorption/desorption cycles, showing great potential in the rapid removal of Cu(2+) from wastewater.

Highly-sensitive electrocatalytic determination for toxic phenols based on coupled cMWCNT/cyclodextrin edge-functionalized graphene composite

Highly-sensitive electrocatalytic determination of toxic phenol compounds is of significance in environmental monitoring due to their low degradation and high toxicity to the environment and humans. In this paper, a rapid and sensitive electrochemical sensor based on coupled carboxyl-multi-walled carbon nanotube (cMWCNT) and cyclodextrin (CD) edge-functionalized graphene composite was successfully employed towards trace detection of three typical phenols (4-aminophenol, 4-AP; 4-chlorophenol, 4-CP; 4-nitrophenol, 4-NP). The morphology studies from scanning electron microscope and transmission electron microscope analysis revealed that cMWCNTs as conductive bridges were successfully incorporated into CD edge-functionalized graphene layers. Further, The electrocatalytic detection performance of the 3D simultaneously reduced and self-assembled sensing architecture (GN-CD-cMWCNT) with trace amounts of CDs was evaluated. The electrochemical studies demonstrated that GN-CD-cMWCNT displays excellent electrocatalytic activity, high sensitivity and stability. Under optimal conditions, the current responses of 4-AP, 4-CP and 4-NP are linear to concentrations over two different ranges, with low detection limit of 0.019, 0.017 and 0.027μM (S/N=3), respectively. And, GN-CD-cMWCNT shows an excellent anti-interference ability against electroactive species and metal ions. In addition, validation of the applicability of the presented sensor was also performed for the determination of three phenols in tap water sample with satisfactory results.

Selective Removal of DOM on Anion-Exchange Resin from Water

In this research, an anion-exchange resin NDP-2 has been successfully prepared and applied on the removal of dissolved organic matter (DOM). The results exhibit that the adsorption capacity toward gallic acid (GA) is higher than tannic acid (TA) or humic acid (HA) utilizing NDP-2 resin. High correlation coefficients indicate that the uptake of GA onto NDP-2 resin can be fitted better by the pseudo-first-order and pseudo-second-order models.

Carbon-nanotube-doped Pd-Ni bimetallic three-dimensional electrode for electrocatalytic hydrodechlorination of 4-chlorophenol: Enhanced activity and stability

A novel composite bimetallic electrode, palladium-nickel/multi-walled carbon nanotubes/graphite felt (Pd-Ni/MWCNTs/GF), was synthesized for the electrocatalytic hydrodechlorination of 4-chlorophenol (4-CP). GF with a three-dimensional structure was used as the electrode substrate, and doped with MWCNTs, which can improve the GF conductivity and serve as a skeleton for metal loading. Ni and Pd were deposited on the electrode surface stepwise to obtain a well-aligned, highly active and stable Pd-Ni/MWCNTs/GF electrode. The Pd-Ni/MWCNTs/GF cathode showed a high reactivity for the electrocatalytic hydrodechlorination of 4-CP; up to 100% removal of 4-CP was achieved within 30 min, and followed pseudo-first-order kinetics with a rate constant of 0.162 min-1. Compared with other cathodes, the Pd-Ni/MWCNTs/GF electrode showed superior performance in 4-CP reduction. Excessive current will lower the reaction efficiency and current efficiency because of hydrogen evolution, and acidic solution conditions are more conducive to electrocatalytic reactions. Experiments confirmed that the Ni had a small amount of loss under acidic conditions but remained stable under neutral and alkaline conditions, whereas the loss of Pd for different pH values was constantly low. In cycle tests, the bimetallic electrode exhibits a better reactivity and stability than the single-metal Pd electrode in the long-term.

Hierarchical Self-Assembly of Cyclodextrin and Dimethylamino-Substituted Arylene–Ethynylene on N-doped Graphene for Synergistically Enhanced Electrochemical Sensing of Dihydroxybenzene Isomers

An electrochemically active sensing nanomaterial (denoted as CD-MPEA-NG) has been successfully constructed by an hierarchical self-assembly of cyclodextrin (CD) and N,N-dimethyl-4-(phenylethynyl)aniline (MPEA) on N-doped graphene (NG) in a low-temperature hydrothermal process. The unique nanostructure of the high-performance CD-MPEA-NG was confirmed by utilizing Fourier transform infrared spectra, an X-ray diffractometer, and differential pulse voltammetry (DPV), etc. In particular, the method of density functional theory with dispersion energy (DFT-D) of wB97XD/LanL2DZ was employed to optimize and describe the face-to-face packing structure of heterodimers of NG and MPEA. The CD-MPEA-NG sensor exhibits highly sensitive performance toward dihydroxybenzene isomers, without relying on expensive noble metal or a complicated preparation process. The experimental results demonstrate that given the synergistic effect of NG and MPEA as a coupled sensing platform, CD as a supramolecular cavity can significantly enhance the electrochemical response. The detection limits (S/N = 3) for catechol (CT), resorcinol (RS), and hydroquinone (HQ) are 0.008, 0.018, and 0.011 μM by DPV, respectively. Besides, the CD-MPEA-NG sensor shows a superb anti-interference, reproducibility, and stability, and satisfactory recovery aimed at detecting isomers in Nanjing River water. The encouraging performance as well as simplified preparation approach strongly support the CD-MPEA-NG sensor is a fascinating electrode to develop as a seamless and sensitive electroanalytical technique.