Cellulose acetate membranes fabricated by a combined vapor-induced/wet phase separation method: morphology and performance evaluation

Iranian Polymer Journal - Cellulose acetate (CA) microfiltration membranes were fabricated by a combined vapor-induced and wet phase separation technique. A systematic morphology study was...     

Free vibration and buckling analysis of composite laminated plates using layerwise models based on isogeometric approach and Carrera unified formulation

In this paper, layerwise (LW) theory has been utilized along with that of equivalent single layer (ESL) for free vibration and linearized buckling analysis of composite laminated plates. To this end, the isogeometric approach and Carrera unified formulation (CUF) have been combined. In particular, Taylor-like and Legendre-like polynomial expansions have been utilized in the framework of CUF to approximate the solution field in ESL and LW models, respectively. Indeed, CUF provides an ideal tool that facilitates the implementation of higher orders of the solution field expansion. As ESL model cannot inherently provide interlaminar continuity, they are not suitable for analyzing thick laminated plates. However, the LW model not only presents a three-dimensional (3D)-like accurate mathematical model using two-dimensionalplate theories but also considers interlaminar continuity requirements and obviates the need for the use of shear correction factor. In addition, the nonuniform rational B-spline basis functions have been employed to approximate the solution field, due to their interesting attributes in the analysis. These functions are able to describe the exact geometry of the structure and make it technically feasible to provide refinement process during analysis. The presented numerical results confirm the validity of the proposed methodology.     

Effect of synthesis conditions on performance of a hydrogen selective nano-composite ceramic membrane

A hydrogen-selective nano-composite ceramic membrane was prepared by depositing a dense layer composed of SiO₂ and Al₂O₃ on top of a graded multilayer substrate using co-current chemical vapor deposition (CVD) method. The multilayer substrate was made by dip-coating a macroporous α-alumina tubular support by a series of boehmite solutions to get a graded structure. Using DLS analysis, it was concluded that decreasing hydrolysis time and increasing acid concentration lead to smaller particle size of boehmite sols. XRD analysis was carried out to investigate the structure of intermediate layer and an optimized calcination temperature of 973 K was obtained. SEM images indicated the formation of a graded membrane with a porous intermediate layer having a thickness of about 2 μm and a dense top selective layer with a thickness of 80–100 nm. Permeation tests showed that H₂ permeance flux decreased from 5 × 10⁻⁵ mol m⁻² s⁻¹ Pa⁻¹ for a fresh substrate to 6.30 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ after 6 h of deposition, but H₂ selectivity over N₂ increased considerably from 5.6 to 203.     

Microbial community analysis of mixed anaerobic microflora in suspended sludge of ASBR producing hydrogen from palm oil mill effluent

This study investigated the microbial community of an anaerobic sequencing batch reactor (ASBR) operating at mesophilic temperature under varying hydraulic retention times (HRTs) for evaluating optimal hydrogen production conditions, using palm oil mill effluent (POME) as substrate. POME sludge enriched by heat treatment with hydrogen-producing bacteria was used as inoculum and acclimated with the POME. The microbial community was determined by first isolating cultivable bacteria at each operating HRT and then using polymerase chain reaction (PCR). The PCR products were sequenced and sequence identification was performed using the BLAST algorithm and Genbank database. The findings revealed that about 50% of the isolates present were members of the genus Streptococcus, about 30% were Lactobacillus species and around 20% were identified as species of genus Clostridium. Scanning electron microscopy (SEM) analysis also confirmed the presence of spherical and rod-shaped microbial morphologies in the sludge samples of bioreactor during prolonged cultivation.     

Concentrated O/W emulsions formulated by binary and ternary mixtures of sodium caseinate,xanthan and guar gums: rheological properties,microstructure, and stability

Food Science and Biotechnology - The effects of xanthan gum (XG) (0, 0.3, 0.6 wt%), guar gum (GG) (0, 0.3, 0.6 wt%) and XG:GG mixtures (0.3–0.3, 0.3–0.6, 0.6–0.3 and 0.6–0.6...     

Effects of orbital shaking on settling velocity of mineral particles in aqueous solutions using split‐plot designs

This study aimed to experimentally investigate and statistically test changes in the settling velocity of particles falling in an aqueous solution due to an orbital shaking of the container. A series of settling experiments were conducted on coal samples under different combinations of shaking speed and initial concentration of the particles. First, a generalized version of the factorial design (a split‐plot design) was utilized to obtain the acquired data. Then, an appropriate statistical model was fitted to experimental data using settling velocity as a response while shaking speed and initial coal concentration were defined as factors. Graphic patterns confirmed our hypotheses that settling velocity is affected by the shaking speed, initial coal concentration and the interaction of these two factors. Results of the analysis indicated that the main effects of both initial coal concentration (F‐statistic = 775.75) and shaking speed (F‐statistic = 11.96) on the settling velocity are strongly significant (both with a P‐value near zero). Moreover, a strong interaction of the effects of these factors on the response variable was also observed (F‐statistic is 10.57 with a P‐value of near zero). Based on the results, combination of 4% coal concentration and 50 rpm shaking speed resulted in the highest settling velocity of 1.21 cm/s. In contract, a combination of 10% coal concentration and 100 rpm shaking speed led to a settling velocity of only 0.55 cm/s. Findings of this study may have invaluable benefits to the mineral and water treatment industries where design and construction of thickeners and sedimentation tanks equipped with orbital shakers can significantly accelerate the sedimentation of mineral particles as well as water contaminants.     

Effect of surfactants in synthesis of CsH<Subscript>2</Subscript>PO<Subscript>4</Subscript> as protonic conductive membrane

Cesium dihydrogen phosphate (CDP) powders were synthesized by cetyltrimethylammoniumbromide (CTAB), polyoxyethylene-polyoxypropylene (F-68) and mixture of both surfactants F-68: CTAB with two molar ratios 0.06 and 0.12 as surfactant solutions at room temperature. The synthesized CsH₂PO₄ is characterized by ICP, XRD, TEM, SEM, FT-IR, BET and IS techniques. Based on the width of the (011) XRD diffraction peak and BET measurement, the average size of nanoparticles was ∼ 10 nm in diameter, while the TEM images indicate smaller size than both techniques. The analysis reveals existence of P and Cs with mole ratio 1.02 ± 0.03 which is compatible to molar ratio CsH₂PO₄ formula. The experimental results show that the conductivities increase in the order of CDP_CTAB > CDP_{(F-68: CTAB)0.12} > CDP_{(F-68:CTAB)0.06} > CDP_F-68. The sequence of increasing conductivity is in accordance with the ion exchange capacities of the samples that has direct proportional effect on the proton mobility of samples. Indeed CTAB as cationic surfactant shows the highest proton mobility in the as-obtained samples.