Wen Yao

Macroscopic, Spectroscopic, and Theoretical Investigation for the Interaction of Phenol and Naphthol on Reduced Graphene Oxide

Interaction of phenol and naphthol with reduced graphene oxide (rGO), and their competitive behavior on rGO were examined by batch experiments, spectroscopic analysis and theoretical calculations. The batch sorption showed that the removal percentage of phenol or naphthol on rGO in bisolute systems was significantly lower than those of phenol or naphthol in single-solute systems. However, the overall sorption capacity of rGO in bisolute system was higher than single-solute system, indicating that the rGO was a very suitable material for the simultaneous elimination of organic pollutants from aqueous solutions. The interaction mechanism was mainly π-π interactions and hydrogen bonds, which was evidenced by FTIR, Raman and theoretical calculation. FTIR and Raman showed that a blue shift of C═C and -OH stretching modes and the enhanced intensity ratios of ID/IG after phenols sorption. The theoretical calculation indicated that the total hydrogen bond numbers, diffusion constant and solvent accessible surface area of naphthol were higher than those of phenol, indicating higher sorption affinity of rGO for naphthol as compared to phenol. These findings were valuable for elucidating the interaction mechanisms between phenols and graphene-based materials, and provided an essential start in simultaneous removal of organics from wastewater.

Decorating of Ag and CuO on Cu Nanoparticles for Enhanced High Catalytic Activity to the Degradation of Organic Pollutants

Metal/semiconductor composites are promising catalysts with superior catalytic activity. In this work, a Cu/CuO-Ag composite with structure that consisted of Ag and CuO nanoparticles (NPs) decorated on the surface of Cu were fabricated via a facile in situ method. With characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and inductively coupled plasma atomic emission spectrometry (ICP-AES), the structure and components of the Cu/CuO-Ag composite were well-defined. The Cu/CuO-Ag composite exhibited superior catalytic activities for the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4 with just a trace amount of Ag NPs (1.28 wt %). The reduction reaction is completed in 75 s with an apparent rate constant kapp of 4.60 × 10-2 s-1. The Cu/CuO-Ag composite also showed excellent durable catalytic stability, as no significant activity loss was detected in the consecutive five reaction runs. With the aid of the Sabatier principle and volcano plot, the opportune chemical adsorption energy of the reagent 4-NP on the Cu/CuO-Ag composite was inferred to be the key to its high reaction rate. The CuO NPs as a semiconductor with narrow band gap also could help the Cu/CuO-Ag composite to capture the electrons/hydride ions and increase opportunities for 4-NP to be reduced. Furthermore, the Cu/CuO-Ag composite exhibited outstanding activity on the oxidative degradation of methylene blue (MB). This work enriched the bimetal/semiconductor catalyst system and supplied new insight into the catalysis mechanism.

In-situ reduction synthesis of manganese dioxide@polypyrrole core/shell nanomaterial for highly efficient enrichment of U(VI) and Eu(III)

Radionuclides with long half-life are toxic, and thereby result in serious threat to human beings and ecological balance. Herein, a simple two-step synthesis method was used to prepare manganese dioxide@polypyrrole (MnO2@PPy) core/shell structures for efficient removal of U(VI) and Eu(III) from aqueous solutions. The adsorption of U(VI) and Eu(III) were investigated under different kinds of experimental conditions. The experimental results suggested that the adsorption of U(VI) and Eu(III) on MnO2@PPy were greatly affected by pH. U(VI) adsorption on MnO2@PPy was independent of ionic strength at pH<6.0, and dependent on ionic strength at pH>6.0. However, Eu(III) adsorption on MnO2@PPy was independent of ionic strength at the whole pH range of experimental conditions. The maximum adsorption capacities (qmax) of U(VI) and Eu(III) were 63.04 and 54.74 mg g−1 at T=298 K, respectively. The BET, XRD, FTIR and XPS analysis evidenced that high adsorption capacities of U (VI) and Eu(III) on MnO2@PPy were mainly due to high surface area and rich metal oxygen-containing group (i.e., Mn–OH and Mn–O), and the interaction was mainly attributed to strong surface complexation and electrostatic interaction. This study highlighted the excellent adsorption performance of U(VI) and Eu(III) on MnO2@PPy and could provide the reference for the elimination of radionuclides in real wastewater management.

Citrate-modified Mg–Al layered double hydroxides for efficient removal of lead from water

Lead contamination is a threat for the environment and human health due to lead non-degradability and non-detoxification. Therefore, methods for efficient removal of lead from contaminated waters are needed. Here, a novel material has been synthesised by surface functionalization of magnesium–aluminum layered double hydroxide with citrate (citric-LDH) and applied to the efficient removal of lead from aqueous solutions. Effects of ionic strength and temperature on the adsorption have been evaluated. Results show that lead adsorption by citric-LDH can be used for lead pollution cleanup. Adsorption kinetics were simulated using a revised model. Simulation results show that citric-LDH adsorb lead ions through a more efficient and time-dependent pathway, leading to the rapid and efficient removal of lead ions.