Removal of cobalt(Ⅱ) ion from aqueous solution by chitosan-montmorillonite

Montmorillonite （MMT） modified with chitosan （CTS, molecular weight = S x 104） was applied to remove heavy metal cations by using Co2＋ as a model ion. An increase in MMT interlayer distance observed from X-ray diffraction indicates the intercalation of CTS into MMT. Together with the results of scanning electron microscopy and Fourier transform infrared spectroscopy, it was concluded that the composite material of CTS and MMT （CTS-- MMT） was prepared successfully. The mass ratio of CTS to MMT had a strong influence on the adsorption performance of CTS-MMT. The highest adsorption value of 150 mg/g was obtained over the composite material with CTS to MMT mass ratio of 0.25, which is much higher than those reported in other studies. The adsorption isotherms and kinetic results indicated that Co2＋ was adsorbed over CTS-MMT in a multilayer model, and the chemical sorption of Co2＋ was determined to be the rate-limiting step.     

Debromination of decabromodiphenyl ether by organo-montmorillonite-supported nanoscale zero-valent iron：Preparation, characterization and influence factors

An organo-montmorillonite-supported nanoscale zero-valent iron material(M-NZVI) was synthesized to degrade decabromodiphenyl ether(BDE-209). The results showed that nanoscale zero-valent iron had good dispersion on organo-montmorillonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30–90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased.     

Removal of arsenate with hydrous ferric oxide coprecipitation：Effect of humic acid

Insights from the adverse effect of humic acid(HA) on arsenate removal with hydrous ferric oxide(HFO) coprecipitation can further our understanding of the fate of As(V) in water treatment process. The motivation of our study is to explore the competitive adsorption mechanisms of humic acid and As(V) on HFO on the molecular scale. Multiple complementary techniques were used including macroscopic adsorption experiments, surface enhanced Raman scattering(SERS), extended X-ray absorption fine structure(EXAFS) spectroscopy, flow-cell attenuated total reflectance Fourier transform infrared(ATR-FTIR) measurement, and charge distribution multisite complexation(CDMUSIC) modeling. The As(V) removal efficiency was reduced from over 95% to about 10% with the increasing HA concentration to 25 times of As(V) mass concentration. The SERS analysis excluded the HA-As(V) complex formation. The EXAFS results indicate that As(V) formed bidentate binuclear surface complexes in the presence of HA as evidenced by an As-Fe distance of 3.26–3.31 ?. The in situ ATR-FTIR measurements show that As(V) replaces surface hydroxyl groups and forms innersphere complex. High concentrations of HA may physically block the surface sites and inhibit the As(V) access. The adsorption of As(V) and HA decreased the point of zero charge of HFO from 7.8 to 5.8 and 6.3, respectively. The CD-MUSIC model described the zeta potential curves and adsorption edges of As(V) and HA reasonably well.     

Photocatalytic degradation of Rhodamine B bymicrowave-assisted hydrothermal synthesized N-doped titanate nanotubes

Microwave-induced nitrogen-doped titanate nanotubes（NTNTs） were characterized by transmission electron microscopy（TEM）, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, Fourier transform infrared spectroscopy（FT-IR）, Zeta potential analysis,specific surface area（SBET）, and UV-Visible spectroscopy. TEM results indicate that NTNTs retain a tubular structure with a crystalline multiwall and have a length of several hundred nanometers after nitrogen doping. XRD findings demonstrate that the crystalline structure of NTNTs was dominated by anatase, which is favored for photocatalytic application. The Ti-O-N linkage observed in the XPS N 1s spectrum is mainly responsible for narrowing the band gap and eventually enhancing the visible light photoactivity. FT-IR results demonstrated the existence of H3O＋, which could be excited by photo-generated holes to form hydroxyl radicals and degrade environmental pollutants. After sintering at 350°C, the UV-Vis absorbance edges of NTNTs significantly shift to the visible-light region, which indicates N atom doping into the nanotubes. Photocatalytic degradation of Rhodamine B（RhB） via NTNTs show good efficiency, with pseudo first-order kinetic model rate constants of 3.7 × 10-3, 2.4 × 10-3and 8.0 × 10-4sec-1at pH 3, 7, and 11, respectively.