Search

Pursuit of well-dispersed carbon nanotubes (CNTs) is of great significance since agglomeration of CNTs in aqueous solution and poor compatibility between CNTs and the polyamide (PA) layer are considered as the prominent drawbacks for the preparation of defect-free thin-film nanocomposite (TFN) membranes. In the present study, well-dispersed CNT porins (CNTPs) were successfully synthesized and then incorporated in the PA layer of TFN membranes. Raman and static test results showed that CNTPs exhibited better dispersion in aqueous solution than pristine CNTs, which could maintain stability for at least 15 days. Addition of CNTPs provided extra water nanochannels and slowed down the diffusion rate of m-phenylenediamine (MPD) to the organic phase, thereby contributing to the excellent increment in water permeability to 4.12 L/m2·h·bar, 1.93 times higher than that of TFC membranes. All of the TFN membranes exhibited unchanged salt rejection (above 99.1% for NaCl), implying little effect of soluble CNTPs on the membrane selectivity. Besides, TFN membranes exhibited not only satisfactory separation performance for NaF and H3BO3 and better chlorine resistance capacity but also great potential in the practical use of the desalination process. In all, this work presents an avenue for preparing defect-free CNT-based TFN membranes. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2 ) photocatalyst was prepared with a sol-gel method and its characterizations were analyzed TiO 2 photocatalytic reduction of Cr 6+ was investigated in visible light irradiation and reduction mechanisms were calculated. Prepared TiO 2 is anatase with a bandgap of about 2.95 eV. Experimental results display that almost 100% of Cr 6+ is removed by visible light-driven TiO 2 photocatalytic reduction after 120 min when Cr 2 O 7 2- initial concentration is 1.0 mg·L -1 , TiO 2 dosage is 1.0 g·L -1 , and pH value is 3. In acidic aqueous solution, HCrO 4 - is the dominant existing form of Cr 6+ and is adsorbed by TiO 2 , forming a complex catalyst HCrO 4 - /TiO 2 with an increase in wavelength to the visible light zone, demonstrated by UV-Vis diffuse reflection spectroscopy. Based on X-ray photoelectron spectroscopy data, it can be deduced that Cr 6+ is adsorbed on the surface of TiO 2 and then reduced to Cr 3+ in situ by photoelectrons. Self-assembly of HCrO 4 - /TiO 2 complex catalyst and self-reduction of Cr 6+ in situ are the key steps to start the visible light-driven TiO 2 photocatalytic reduction. Furthermore, TiO 2 photocatalytic reduction of Cr 6+ fits well with pseudo-first-order kinetics and has the potential application to treat chemical industrial wastewater.