Environmentally benign hardness removal using ion-exchange fibers and snowmelt

Many industrial unit operations and unit processes require near-complete removal of hardness to avoid scaling in heat-transfer equipment, fouling in membranes, and high consumption of detergents and sequestering chemicals in cooling and wash water. Lime softening and cation exchange are the most commonly used processes practiced to date for hardness removal. Herein, we report and discuss the results and attributes of a new hardness removal process using ion-exchange fibers (IX-fibers). Most importantly, the process uses harvested snowmelt (or rainwater) as the regenerant chemical along with sparged carbon dioxide. Consequently, the spent regenerant does not contain a high concentration of aggressive chemicals such as sodium chloride or acid like traditional ion-exchange processes nor does the process produce voluminous sludges similar to lime softening. The bulk of carbon dioxide consumed during regeneration remains sequestered in the aqueous phase as alkalinity. IX-fibers form the heart of the process. They are essentially thin cylindrical polymeric strands 10-20 microm in diameter. The weak-acid carboxylate functional groups reside near to the surface of these cylindrical fibers. Low intraparticle diffusional resistance is the underlying reason IX-fibers are amenable to efficient regeneration with snowmelt sparged with carbon dioxide. When the carbon dioxide partial pressure is increased to 6.8 atm, over 90% calcium desorption efficiency is obtained. On the contrary, commercial weak-acid ion-exchange resins in spherical bead forms are ineffective for regeneration with carbon-dioxide-sparged snowmelt due to extremely slow ion-exchange kinetics involving counter-transport of Ca2+ and H+.     

Modeling and optimization of the process parameters in vacuum drying of culinary banana (Musa ABB) slices by application of artificial neural network and genetic algorithm

The influence of drying temperature, sample slice thickness, and pretreatment on quality attributes like rehydration ratio, scavenging activity, color (in terms of nonenzymatic browning), and texture (in terms of hardness) of culinary banana (Musa ABB) has been evaluated in the present study. A comparative approach was made between artificial neural network (ANN) and response surface methodology (RSM) to predict various parameters for vacuum drying of culinary banana. The effect of process variables on responses during dehydration were investigated using general factorial experimental design. This design was used to train feed-forward back-propagation ANN. The predictive capabilities of these two methodologies for optimization of process parameters were compared in terms of relative deviation (R_d). Results revealed that a properly trained ANN model is found to be more accurate in prediction as compared to RSM. The optimum condition selected from ANN/GA responses on the basis of highest fitness value revealed that culinary banana slices of 6 mm thickness pretreated with 1% citric acid and dried at 76°C resulted in a maximum rehydration ratio of 6.20, scavenging activity of 48.63% with minimum nonenzymatic browning of 25%, and hardness of 43.63 N. Results further revealed that, in the case of rehydration ratio, temperature and pretreatment showed a positive effect while thickness had a negative effect. On the contrary, for scavenging activity, temperature showed the highest negative effect followed by slice thickness and positive effect with pretreatment. For nonenzymatic browning, thickness showed the highest negative effect but temperature and pretreatment showed a positive effect. Similarly, for hardness, all three parameters showed a negative effect.     

Exploring interfacial interactions,dielectric, ferroelectric and piezoelectric properties of ultrahigh molecular weight polyethylene/graphene oxide nanocomposites

Graphene oxide (GO) incorporated ultra-high molecular weight polyethylene (UHMWPE) nanocomposites were prepared by encapsulating GO by UHMWPE in an aqueous media via high-shear mixing, which were subsequently dried and compression molded. Morphological characterizations via scanning electron microscopy revealed the intercalation of UHMWPE chains in the graphitic stacks corresponding to GO. Further, dielectric permittivity of UHMWPE/GO nanocomposite of 1 wt% GO showed a drastic increase (~61) as compared to pure UHMWPE (~2) due to an enhanced interfacial polarization. A significantly higher value of remnant polarization (~10 nC/cm²) and coercive field (~3 kV/cm) was observed in UHMWPE/GO nanocomposite of 1 wt% GO, which showed a strong hysteresis loop of polarization versus electric field plot as compared to pure UHMWPE, which displayed a very weak hysteresis loop. The piezoelectric coefficient (d₃₃) of ~9.5 pm/V was estimated in UHMWPE/GO nanocomposite of 1 wt% GO via piezoresponse force microscopy. Nanocomposite sensor devices were also fabricated and piezoelectric output voltage of ~6 V was recorded in UHMWPE/GO nanocomposite of 1 wt% of GO. We report here for the first time the unique ferroelectric and piezoelectric properties displayed by UHMWPE/GO nanocomposites.     

Carminic acid modified anion exchanger for the removal and preconcentration of Mo(VI) from wastewater

Removal and preconcentration of Mo(VI) from water and wastewater solutions was investigated using carminic acid modified anion exchanger (IRA743). Various factors influencing the adsorption of Mo(VI), e.g. pH, initial concentration, and coexisting oxyanions were studied. Adsorption reached equilibrium within <10 min and was independent of initial concentration of Mo(VI). Studies were performed at different pH values to find the pH at which maximum adsorption occurred and was determined to be at a pH between 4.0 and 6.0. The Langmuir adsorption capacity (q(max)) was found to be 13.5mg Mo(VI)/g of the adsorbent. The results showed that modification of IRA743 with carminic acid is suitable for the removal of Mo(VI), as molybdate, from water and wastewater samples. The concentration of Mo(VI) was determined spectrophotometrically using bromopyrogallol red as a complexation reagent. This allows the determination of Mo(VI) in the range 1.0-100.0 μg/mL. The obtained material was subjected to efficient regeneration.     

Genome‐wide expression profiling of the osmoadaptation response of Debaryomyces hansenii

The euryhaline marine yeast Debaromyces hansenii is a model system for the study of processes related to osmoadaptation. In this study, microarray‐based gene expression analyses of the entire genome of D. hansenii was used to study its response to osmotic stress. Differential gene expression, compared to control, was examined at three time points (0.5, 3 and 6 h) after exposure of D. hansenii cultures to high salt concentration. Among the 1.72% of genes showing statistically significant differences in expression, only 65 genes displayed at least three‐fold increases in mRNA levels after treatment with 2 M NaCl. On the other hand, 44 genes showed three‐fold repression. Upregulated as well as the downregulated genes were grouped into functional categories to identify biochemical processes possibly affected by osmotic stress and involved in osmoadaptation. The observation that only a limited number of genes are upregulated in D. hansenii in response to osmotic stress supports the notion that D. hansenii is pre‐adapted to survive in extreme saline environments. In addition, since more than one‐half of the upregulated genes encode for ribosomal proteins, it is possible that a translational gene regulatory mechanism plays a key role in D. hansenii's osmoregulatory response. Validation studies for ENA1 and for hyphal wall/cell elongation protein genes, using real‐time PCR, confirmed patterns of gene expression observed in our microarray experiments. To our knowledge, this study is the first of its kind in this organism and provides the foundation for future molecular studies assessing the significance of the genes identified here in D. hansenii's osmoadaptation. Copyright © 2009 John Wiley & Sons, Ltd.     

A sustainable approach to enhance fruit shelf-life: Edible coating from pineapple fruit waste biomass

The quality and commercial value of fruits largely depend on color, texture, appearance, nutritional value, and other factors that cease the growth of the microbes causing food spoilage. Coating with suitable edible material would keep fruits fresh for a considerable time after their harvest till it reaches to the demanding consumers. The nonedible portions (peel, crown) of pineapple are identified as an inexpensive source for the production of such edible coating material. The present work is focused on the extraction and physicochemical analysis of cellulose prepared from waste bio-mass of pineapple fruit. Physicochemical characterization of the cellulose is performed using X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. The extracted cellulose is converted to carboxymethyl cellulose and formulated as a coating film in conjugation with other suitable substances. The formulated coating is applied on banana fruit to check the performance of protection against the natural degradation of the fruit. FTIR analysis of the extracted cellulose has confirmed the removal of lignin and hemicelluloses molecules from the waste biomass of pineapple. X-ray diffraction analysis has shown the crystal size of extracted cellulose was 3.23 nm with 35.62% crystallinity. Degree of substitution (DS) is estimated 0.523 for carboxymethyl cellulose prepared from the extracted cellulose. Application of coating has shown the increment in shelf-life period of banana in comparison with control up to 8 days of storage at ambient condition. This study has demonstrated a sustainable process to transform waste biomass into carboxymethyl cellulose based coating for improving storage capacity of banana fruit.     

Oxide-ion conductivity in CuxCe1−xO2−δ (0 ≤ x ≤ 0.10)

Up to 10 at.% of copper readily substitutes for cerium in ceria. It is found that at oxygen partial pressures between 0.21 atm and 10⁻⁵ atm, Cu_xCe_1−xO_2−δ (0 ≤ x ≤ 0.10) solid solution behave as an oxide-ion electrolyte. Interestingly, Cu_0.10Ce_0.90O_2−δ exhibits the oxide-ion conductivity of ca. 10⁻⁴ Ω⁻¹ cm⁻¹ at 600 °C at an oxygen partial pressure of 10⁻⁵ atm.     

A study of magneto-thermoelastic problems with thermal relaxation and heat sources in a three-dimensional infinite rotating elastic medium

This paper is concerned with a study of magneto-thermoelastic problems with thermal relaxation and heat sources in a three-dimensional infinite rotating elastic medium. The medium under consideration is assumed to be homogeneous, orthotropic, electrically as well as thermally conducting. The fundamental equations of the three-dimensional problem of generalized thermoelasticity with one relaxation parameter including heat source in an infinite rotating elastic medium under the influence of magnetic field are obtained as a vector-matrix differential equation form in the Laplace–Fourier transform domain which is then solved by the eigenvalue approach. A closed form solution of the problem is derived in the Laplace–Fourier domain. Finally, the inversion of the transform solution is obtained numerically in the space–time domain. Results of this paper presented graphically and then compared with previous results available in the literature. Two short appendices are included in this paper in order to make the work self-contained.     

A density functional theory study of the effects of metal cations on the Brøsted acidity of H-ZSM-5

Density functional theory calculations have been carried out to establish the influence of mono- and polyvalent cations on the Brønsted acidity of H-ZSM-5. The zeolite was modeled as a cluster containing 41-45 atoms, in the center of which is an Al⁽¹⁾(OH)SiOAl⁽²⁾(OM)unit, where M⁺ = H⁺, Li⁺, Na⁺, K⁺, Ca(OH)⁺, AlO⁺, Al(OH)⁺ ₂. The local geometry of the Brønsted acid site is affected by the nature of M⁺ and this in turn causes a change in the value of the proton affinity (PA) for the site. The highest value of PA is 330 kcal/mol for M⁺ = H⁺ and the lowest value of PA is 305 kcal/mol for M⁺ = AlO⁺. No correlation was found between the value of PA and the Mulliken charge on Al⁽¹⁾. With the exception of the case where M⁺ = AlO⁺ the binding energy of CO with the Brøsted acid proton is approximately 8.8 kcal/mol, independent of the nature of M⁺. When M⁺ = AlO⁺, the binding energy for CO is 11.1 kcal/mol. The present calculations suggest that different factors affect proton affinity and the binding energy for CO adsorption.     

Numerical Understanding of Free Surface Vortex Driven by Rotational Field Inside Viscous Liquid

Abstract

The present study established the genesis of free surface vortex inside a viscous liquid using a rotating cylindrical disc immersed in the liquid. The longitudinal axis of the disc is kept normal to the nominal interfacial plane and its rotation is characterized in terms of Froude number (1.50–4.49). This configuration is simulated using a grid-based volume of fluid technique in the air and high viscous polybutene pair. A dip in nominal interface profile is observed at low disc rotations (Froude number ≈ 1.50), however, the gradual progress of the rotational inertia (Froude number > 1.50) has resulted in elongation of the interface in the form of a free surface vortex progressing inside the liquid. The transient progress of vortex depicts bullet nose like interface tip during the early stages, which grows in the outward radial direction along with its downward motion due to the centrifugal effect of the surrounding liquid. The initial submergence ratio of the disc and its radius are shown as the important parameters governing the entrainment rate and shape of the vortex profiles. The physical understanding behind the formation of the vortex is revealed using axial and crosswise circulations of the surrounding liquid.