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Boron nitride nanotubes (BNNT) were synthesized over both Fe 3+ impregnated MCM-41 (mobil composition of matter no. 41) and Fe 2 O 3 /MCM-41 complex catalyst systems at relatively low temperatures for 1 h by the chemical vapor deposition technique in large quantities. The formation of BNNT was tailored at different reaction temperatures by changing catalyst type. The use of Fe 3+ -MCM-41 and Fe 2 O 3 as a complex catalyst system led to thin and thick tube formations. The diameters of BNNTs were in the range of 2.5−4.0 nm for thin tubes and 20−60 nm for thick tubes. The thin tube formation originated from the growth of BNNT over Fe 3+ -MCM-41 due to its average pore size of 4 nm. Higher reaction temperatures caused both BNNT and iron-based side product formations. The hydrogen uptake capacity measurements by the Intelligent Gravimetric Analyzer at room temperature showed that BNNTs could adsorb 0.85 wt % hydrogen which was two times larger than that for commercial carbon nanotubes.

A laboratory study was conducted to investigate the ability of ferric ion loaded red mud (FRM) for the removal of arsenic species from water. The adsorbent material was characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. For an initial arsenic concentration lower than 0.3 mg/L, the FRM with a dosage of 1 g/L was able to reduce As(III) at pH 7 below 10 lg=L, the maximum contaminant level (MCL) of arsenic in drinking water set by the World Health Organization. In the case of As(V) removal, FRM was also particularly effective in reducing the initial arsenic concentration value of 1 mg=L at pH 2, below the MCL requirement of arsenic for drinking water. According to kinetic sorption data, the initial stage of adsorptions of As(III) and As(V) onto FRM were mainly governed by the external diffusion mechanism; however, upon saturation of the external adsorbent surface, the arsenic species were eventually adsorbed by intraparticle diffusion mechanism. The present results are promising for using the very inexpensive FRM as a low-cost material that is effective in remediating drinking waters contaminated with low concentrations of arsenic species. We report here the sorption kinetics and adsorption mechanisms of As(III) and As(V) on the FRM that has not been decsribed previously.

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Novel nanocomposite materials where titanium dioxide nanoparticles were inserted into the walls of a macroporous activated carbon were produced and their efficiency for the removal of As(III) from water was compared with pure activated carbon and titanium dioxide nanoparticles. The nanocomposites were synthesized with different molar ratios by using sol-gel method and were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The nanocomposite system showed excellent capability for the removal of As(III) ions from water by considering feasibility, efficiency and cost. The maximum As(III) removal percentages were ∼4.7% at pH 8 for activated carbon, ∼38 % for titanium dioxide at pH 6, and ∼98 % at pH 7 for activated carbon/titanium dioxide (AC/TiO2) nanocomposite, respectively. According to kinetic sorption data, the higher regression coefficients (R2) were obtained after the application of pseudo-second order to the experimental adsorption data for all adsorbent materials. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The maximum arsenic uptake (qmax) value computed from slope of the linearized Langmuir plot was 26.62 mg/g for the adsorption of As(III) onto AC/TiO2 nanocomposite.