Xiushan Yang

Chromium (VI) adsorption from wastewater using porous magnetite nanoparticles prepared from titanium residue by a novel solid-phase reduction method

Porous magnetite nanoparticles were successfully synthesized by reduction of titanium residue with pyrite under nitrogen protection, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometer, X-ray photoelectron spectroscope, zeta potential and Brunauer-Emmett-Teller method. The XRD analysis confirmed the formation of porous magnetite nanoparticles with single spinel structure. The SEM image demonstrated that porous magnetite nanoparticles displayed spherical shape with the average diameter of ~51nm. The surface area of porous magnetite nanoparticles with high magnetic moment (78emu·g-1) was 11.1m2g-1. The experimental results revealed that equilibrium adsorption behavior of Cr(VI) was well described by Langmuir isotherm model with the maximum adsorption capacity of 14.49mgg-1 at 298.15K, and kinetic data was found to fit well with pseudo-second-order model. The adsorption rate for Cr(VI) was controlled by both boundary layer diffusion and intraparticle diffusion. Thermodynamics analysis showed that the adsorption processes of Cr(VI) were endothermic and spontaneous. In addition, the adsorption of Cr(VI) on porous magnetite nanoparticles was classified as chemisorption adsorption, which depended on electrostatic attraction accompanied with reduction of Cr(VI) to Cr(III). Porous magnetite nanoparticles were readily regenerated and used repeatedly for Cr(VI) adsorption at least five cycles. Furthermore, the experimental results indicate that porous magnetite nanoparticles have a promising application for Cr(VI) adsorption from wastewater.

The mechanism study on the cooperative flame resistance effect between HMP and NP in ABS by TG–FTIR

Thermogravimetry (TG) coupled with Fourier transform infrared spectroscopy (FTIR) (TG–FTIR) is an effective tool on studying the mechanism of the flame retardant. The mechanism on the cooperative effect between hydroquinone bis(di-2-methylphenyl phosphate) (HMP), which is an effective flame retardant, and novolac phenol (NP) in acrylonitrile–butadiene–styrene (ABS) is investigated by TG–FTIR under air in this study. The TG–FTIR of ABS/HMP, ABS/HMP/NP and ABS/NP are discussed carefully as well as their semi-quantitative analyses. The semi-quantitative analysis results of TG–FTIR show that ABS/HMP, ABS/HMP/NP and ABS/NP decompose in a two-step process. The first step is mainly the process of thermal degradation, macromolecules being decomposed into micromolecules containing many functional groups such as CAr–H, –CH2–, –OH, P–O–CAr. The second step is mainly the process of combustion, the layer of carbon being further oxidized into carbon dioxide, water and alkyne. The residue of ABS/HMP/NP is the highest as well as its temperature at which the maximum of mass loss rate occurs. Furthermore, the comparison of their semi-quantitative analyses indicates that NP could absorb parts of micromolecules containing the functional groups of –OH, CH2– and CAr–H, contributing to the formation of carbon layer, and HMP slows down the degradation of the carbon layer, achieving the cooperative effect.