Optimization of ilmenite flotation process in the presence of microwave irradiation

In the present study, the effect of parameters, including microwave irradiation power, pH, dosage of chemical reagents (collector, depressant and activator) were studied by microflotation (in Hallimond tube) process. The mechanical flotation tests were carried out on optimum parameters obtained from microflotation tests. The software based on experimental design method (DX7) with the two-level full factorial design was applied to determine the parameter effects and to optimize the microflotation recovery. The optimum conditions were determined by analysis of variance (ANOVA), indicating that the irradiation power was the most effective parameter. The optimum values of parameters in the microflotation process are as follows: power of microwave (1000 W), pH (6.3), dosage of chemical reagents (sodium oleate 3.65 × 10^-4 M as a collector, acidified sodium silicate 2 g L^–1 as a depressant, and lead(II) nitrate 2.1 × 10^–5 M as an activator). By applying these optimized parameters, a product with ilmenite recovery of 83.26% was predicted by the software. The results of microflotation tests indicated that an ilmenite recovery of 82.35% was achieved being very close to the predicted value. The results of mechanical flotation based on optimized condition showed that the recovery and separation efficiency of irradiated ilmenite were improved up to 86.03% and 48.61%, respectively, indicating the positive effect of irradiation on ilmenite floatability.     

Polymeric Nanoparticles Amenable to Simultaneous Installation of Exterior Targeting and Interior Therapeutic Proteins

Effective delivery of therapeutic proteins is a formidable challenge. Herein, using a unique polymer family with a wide‐ranging set of cationic and hydrophobic features, we developed a novel nanoparticle (NP) platform capable of installing protein ligands on the particle surface and simultaneously carrying therapeutic proteins inside by a self‐assembly procedure. The loaded therapeutic proteins (e.g., insulin) within the NPs exhibited sustained and tunable release, while the surface‐coated protein ligands (e.g., transferrin) were demonstrated to alter the NP cellular behaviors. In vivo results revealed that the transferrin‐coated NPs can effectively be transported across the intestinal epithelium for oral insulin delivery, leading to a notable hypoglycemic response.     

Functionalized analogues of an unnatural amino acid that mimics a tripeptide beta-strand

This paper introduces polar and hydrophobic variants of the unnatural amino acid Hao, which mimics the hydrogen-bonding functionality of one edge of a beta-strand. In these variants, the methyl side chain of Hao is replaced with acidic, basic, and hydrophobic groups. These modifications can impart improved solubility and additional side-chain interactions to peptides containing Hao.     

A model for supersonic and hypersonic impactors for nanoparticles

In this study the performance of supersonic and hypersonic impactors for collection efficiency of nanoparticles (in the size range of 2–100 nm) under various operating conditions is analyzed. Axisymmetric forms of the compressible Navier–Stokes and energy equations are solved and the airflow and thermal condition in the impactor are evaluated. A Lagrangian particle trajectory analysis procedure is used and the deposition rates of different size particles under various operating conditions are studied. For dilute particle concentrations, the assumption of one-way interaction is used and the effect of particles on gas flow field is ignored. The importance of drag, lift and Brownian forces on particle motions in supersonic impactors is discussed. Sensitivity of the simulation results to the use of different assumptions for the Cunningham correction coefficient is studied. It is shown that accurate evaluation of the gas mean free path and the Cunningham correction factor is important for accurate simulation of nano-particle transport and deposition in supersonic/hypersonic impactors. The computer simulation results are compared favorably with the available experimental data.     

Photoluminescence and electrochemical investigation of curcumin-reduced graphene oxide sheets

This paper reports on a novel low-temperature method for preparing curcumin-reduced graphene oxide (Cur-rGO) from graphene oxide (GO) and investigates their cyclic voltammetry (CV) and photoluminescence (PL) properties. GO sheets were synthesized using modified Hummers’ method and then were chemically reduced using polyphenol curcumin into graphene sheets. Atomic force microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy were used to confirm the formation of Cur-rGO and revealed their functionalization with polyphenol curcumin. The electrochemical and optical properties of the Cur-rGO sheets were investigated using CV and PL spectroscopy. According to the PL and CV characterization for the Cur-rGO sheets, charges and resonant energy were transferred from curcumin molecules to the GO sheets’ surfaces. This arises from the bonding of the fluorescence curcumin molecules to the Cur-rGO surfaces, through π–π stacking of their aromatic rings. It should be noted that curcumin molecules act as electron donors, suppressing the fluorescence of the GO sheets while improving their electrochemical activities.     

Synthesis of molecular imprinted polymer nanoparticles followed by application of response surface methodology for optimization of metribuzin extraction from urine samples

A molecular imprinted polymer was prepared with precipitation polymerization technique and applied as a sorbent for selective extraction and enrichment of metribuzin herbicide prior to high performance liquid chromatography. Optimization of critical variables affecting the efficiency of molecularly imprinted solid-phase extraction (MISPE), such as sorbent mass, sample pH and flow rate of sample, volume, concentration, and flow rate of elution solvent was done by employing central composite design (CCD) of the response surface methodology. Two separate models were developed for the adsorption and recycling steps. The analysis of variance (ANOVA) demonstrated that, experimental data were excellently fitted to the proposed response models. The optimum operating conditions were: a sorbent mass of 25 mg, sample pH 6.19, sample flow rate of 2.15 mL/min, and a 5 mL portion of methanol/acetic acid with 92.7:7.3 (v/v) ratio and flow rate of 2.1 mL/min for the extraction process. Under the optimized conditions, the linear range was obtained from 20 to 120 µg/L (R²?=?0.999) and the lowest detectable concentration (LOD) and the lowest quantitative concentration (LOQ) were calculated as 5.75 and 19.86 µg/L, respectively. Finally, the designed MISPE method was successfully applied to determine trace amount of metribuzin in real samples. The diluted urine samples were spiked with metribuzin at 4 levels and extracted with recoveries ranging from 93.82 to 97.84% and the relative standard deviation (RSD) less than 4.8%.     

Pyrrole adsorption on aluminum nitride nanotubes on DFT data

The adsorption behavior of pyrrole molecule with external surface of (5.0) on zigzag aluminum nitride nanotube (AlNNT) was studied using density functional theory calculations. It was found that the adsorption energy (E_ad) of pyrrole on the surface of pristine nanotubes is about–11.99 kcal/mol. However, when nanotubes have been doped with P atom, the adsorption energy of pyrrole was increased. Calculation showed that for the phosphorus-doped nanotube the adsorption energy range is about–9.04 to?12.80 kcal/mol. AlNNT is a suitable adsorbent for pyrrole, so it can be used in adsorption and separation processes involving pyrrole. The doped AlNNT can potentially be used for pyrrole sensors for detection in environmental systems.     

Enhanced photocatalytic activities of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> nanohybrids immobilized on cement-based materials for dye degradation

Using cement-based material as a matrix for photocatalytic hybrids is an important development for the large-scale application of photocatalytic technologies. In this work, photocatalytic activity of nanosized hybrids of TiO₂/SiO₂ (nano-TiO₂–SiO₂) for degradation of some organic dyes on cementitious materials was highlighted. For this purpose, an optimal inorganic sol–gel precursor was firstly applied to prepare the composites of nano-TiO₂–SiO₂ which was characterized by XRD, SEM and UV–Vis. Then, a thin layer was successfully coated on white Portland cement (WPC) blocks using a dipping process in a nano-TiO₂–SiO₂ solution. The effect of nano-TiO₂–SiO₂-coated WPC blocks on photocatalytic decomposition of three dyes, including Malachite green oxalate (MG), Methylene blue (MB) and Methyl orange (MO) were studied under UV irradiation and monitored by chemical oxygen demand tests. The results showed an increase in photocatalytic effects which depends on the structure and pH of the applied cement.     

Poly(vinylpyrrolidonium) perchlorate catalyzed one-pot synthesis of tricyclic dihydropyrimidine derivatives

A simple and efficient procedure for the synthesis of benzo[4,5]imidazo[1,2-α]pyrimidine and 2-amino-4-substituted-1,4-dihydrobenzo[4,5]imidazolo[1,2-α]pyrimidine-3-carbonitrile derivatives using poly(vinylpyrrolidonium) perchlorate {[PVPH]ClO₄} as a newly reported, modified polymeric catalyst is reported. Some of the advantages of this novel synthetic method are: easy preparation of the catalyst, simple and easy work-up procedure, short reaction times, high to excellent yields of the products and reusability of the catalyst.