Magnetic materials as adsorbent can provide effective remove and quickly separate of pollutant in wastewater treatment. A magnetic CoFe 2 O 4 /MgAl-LDH composite was successfully synthesized through low saturation coprecipitation method. The adsorption behaviors of Cr(VI) from aqueous solution by CoFe 2 O 4 /MgAl-LDH were investigated. The adsorbents were characterized using scanning electron microscope (SEM), N 2 adsorption/desorption isotherms, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Kinetic and equilibrium studies indicated that the experimental data of Cr(VI) adsorption were best described by pseudo-second-order kinetic and Langmuir models. The maximum adsorption capacity of CoFe 2 O 4 /MgAl-LDH for Cr(VI) was found to be 72.4 mg/g at an equilibrium time of 300 min and temperature of 283 K. Evaluation of the thermodynamics parameters ( ∆ H < 0, ∆ S < 0 and ∆ G < 0) revealed the adsorption process was exothermic and spontaneous. The mechanisms study showed that the adsorption of Cr(VI) onto CoFe 2 O 4 /MgAl-LDH likely involved adsorption/surface complexation and ion exchange interaction. This study demonstrated that the magnetic CoFe 2 O 4 /MgAl-LDH composite was an effective adsorbent for Cr(VI) removal with quick separation.
We
herein report the development of a compact and robust optical
emission spectrometry (OES)-based technique for the ultrasensitive
determination of Se and As utilizing hydride generation (HG) as the
sampling technique and direct-current atmospheric pressure glow discharge
in He (APGD) as the radiation source. The emission sensitivities of
50 ng mL–1 Se and As in the newly designed HG-APGD
were enhanced more than 3-fold by constraining the spatial volume
between two hollow-tube APGD electrodes, and the stability was significantly
improved. The developed technique achieved Se and As detection limits
of 0.13 and 0.087 ng mL–1, respectively, with the
corresponding relative standard deviations at analyte concentrations
of 50 ng mL–1 being <0.5% in both cases. Moreover,
the HG-APGD-OES procedure was advantageous in that it exhibited a
low power consumption (<17 W) and a low gas consumption (<100
mL min–1). Its accuracy and practicality were also
demonstrated by the determination of GBW10024 (scallop) and GBW07381
(stream sediments) certified reference materials and mice blood samples.
The results showed good agreement with the certified values and values
obtained using inductively coupled plasma–mass spectrometry.
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