Aqueous Boron Removal by Using Electrospun Poly(vinyl alcohol) (PVA) Mats: A Combined Study of IR/Raman Spectroscopy and Computational Chemistry.

We report the use of a novel and efficient method to remove aqueous boron by using electrospun, water-resistant poly(vinyl alcohol) (PVA) mats stabilized in methanol. The removal of the primary aqueous boron species as (B(OH)3), was accomplished by chemical adsorption in reactions with -OH (hydroxyl) groups on the PVA mat surface. The chemical adsorption of B(OH)3 was qualitatively confirmed by the analysis of IR and Raman spectra. The bands, corresponding to the molecular vibration modes of chemically bonded boron in PVA, were identified by using the frequency calculation from the computational chemistry for the first time. The adsorption capacities of PVA mats for aqueous boron were then quantitated at a low boron concentration (range: 0.0010 to 0.0025 g of aqueous boron per g of PVA mats) by the Carmine method. The PVA mats were prepared by a well-established electrospinning technique, which make these substrates promising potential candidates for use as boron-selective sorbent media in applications such as reverse osmosis desalination processes.

Modification of Vermiculite for the Preparation of Floating Adsorbent for Phosphate in Wastewater.

Floating adsorbents made from exfoliated vermiculite (EV) were tested for their ability to remove phosphate in aqueous solution. The modified vermiculites (MEV) were prepared with EV/glycerol ratio of 1/4 where glycerol contained 4 mol% H2SO4 and heated until designated temperatures. The highest specific surface area of 58.6 m(2)/g and carbon content of 62.2% were obtained for MEV heated at 580 °C and 380 °C, respectively. The dry density of MEV was decreased from 1.78 g/cm(3) (EV) to 0.25 g/cm(3), indicating these adsorbent floating characteristic. The MEV heated at 380 °C showed the highest Freundlich partition coefficient of 45.7 L/kg and the highest Langmuir sorption capacity of 714.3 mg/kg among other MEVs (476.2 mg/kg for MEV-580 and 181.8 mg/kg for MEV-780). Removal of phosphate using MEV heated at 380 °C was well explained by pseudo-second-order model and model parameters were comparable to other phosphate adsorption tests.

Preparation of anatase/rutile mixed-phase titania nanoparticles for dye-sensitized solar cells.

Acid-labile high surface mesoporous ZnO/Zn(OH)2 composite material is used as a novel hard template for the preparation of mesoporous amorphous TiO2. The template-free amorphous TiO2 material is then thermally crystallized at suitable temperature to control the relative ratio of anatase and rutile phases in a particle. Four different anatase/rutile (AR) mixed-phase TiO2 nanoparticles (AR-3, AR-15, AR-20, and AR-23 denoted for the samples of 3%, 15%, 20%, and 23% rutile phase, respectively) are prepared and characterized by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The coexistence of anatase and rutile phases in a TiO2 nanoparticle is visually confirmed by HRTEM analysis. These mixed-phase TiO2 nanoparticles are examined as candidates for photoelectrodes of dye-sensitized solar cells (DSSCs). The J-V curves and IPCE spectra for the DSSCs prepared from the mixed-phase TiO2 nanoparticles are obtained, and their photovoltaic properties are investigated. The photo-conversion efficiency (eta) indicates the highest value of 5.07% for AR-20. The synergistic effect of coexisting anatase and rutile phases with an optimal ratio in a TiO2 nanoparticle of AR-20 for an efficient interfacial transfer of photo-generated electrons is likely to lead to the highest efficiency among the AR-n samples.