Sharif Digital Repository

An indirect colorimetric method is presented for spectrophotometric determination of hydrazine, phenylhydrazine, and isoniazid. Reduction of silver ions to silver nanoparticles (AgNPs) by these analytes as active reducing agents in the presence of polyvinylpyrrolidone (PVP) and also cetyltrimethylammonium chloride (CTAC) as a stabilizer is the basis of the proposed method. The changes in plasmon absorbance of the AgNPs at λ = 415 nm in the presence of PVP were proportional to concentration of hydrazine, phenylhydrazine, and isoniazid in the ranges of 4.0-150.0 μM, 1.0-55.0 μM, and 2.0-30.0 μM, respectively, and the detection limit obtained was 0.79 μM. In the presence of CTAC, the linear... 

Ultrafiltration (UF) membranes were prepared from blends of poly(vinylidene fluoride) (PVDF)/polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. Polyvinylpyrrolidone (PVP) was used as pore former and hydrophilic polymeric additive. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of different concentrations of PVP on the morphology and performance of the prepared membranes was investigated. Performance of the membranes was evaluated based on pure water flux and filtration of buffered bovine serum albumin (BSA) solution. The contact angle measurements indicated that the hydrophilicity of... 

In this study, ethanol gas sensing of PVP fiber membranes based on Quartz Crystal Microbalance (QCM) was investigated. The fibers were deposited on the QCM's electrodes by electrospinning the viscous blend solutions of PVP. The effects of PVP concentration on morphology of the fibers and their permeability when exposed to ethanol were investigated. Membranes which were prepared using low concentration solutions, contained beads and high packing fibers and showed low permeability. Increase of the PVP concentration to 12 wt% resulted in continuous fine fibers with good permeability. Furthermore, higher PVP concentrations were found to decrease ethanol permeability due to larger fiber radius... 

Ultrafiltration (UF) membranes were prepared from poly(vinyl chloride) (PVC) as main polymer, poly(vinyl pyrrolidone) (PVP) as additive, and 1-methyl-2-pyrrolidone (NMP) as solvent using Design Expert software for designing the experiments. The membranes were characterized by SEM, contact angle measurement, and atomic force microscopy. The performance of UF membranes was evaluated by pure water flux (PWF) and blue indigo dye particle rejection. In addition, the molecular weight cutoff of UF membranes was determined by poly(ethylene glycol) (PEG) rejection. The UF membranes were used as substrates for fabrication of polyamide thin film composite (TFC) reverse osmosis (RO) membranes. The... 

Polyvinylpyrrolidone coated nano zero valent iron-copper (PVP-nZVI-Cu) bimetallic nanoparticles were successfully synthesized for dechlorination of trichloroethylene (TCE) into non-toxic byproducts in the presence of persulfate oxidant. The average size of PVP-nZVI-Cu nanoparticles (3-25 nm) was smaller than PVP-nZVI (25-60 nm) and nZVI (50-90 nm) particles due to PVP role in the prevention of iron aggregation and agglomerations. The synthesized PVP-nZVI-Cu nanoparticles were used as an efficient persulfate (PS) activator to generate reactive oxygen species (ROSs) for the degradation of TCE. The complete removal of TCE (99.6%) was achieved in the presence of 0.4 g/L of PVP-nZVI-Cu...