Application of polymeric flocculant for enhancing settling of the pond ash particles and water drainage from hydraulically stowed pond ash

Delayed settling of the ash particles and poor drainage of water from the pond ash are the major problems faced during the hydraulic stowing of pond ash. In this study the effect of polymeric flocculant on settling of the ash particles and drainage of water during pond ash stowing are investigated. In addition, the parameters, viz. drainage and absorption of water during pond ash stowing are quantified by stowing a mine goaf model with pond ash slurries of five different concentrations added with and without flocculant. The study revealed that addition of only 5 × 10^?6 of Sodium Carboxymethyl Cellulose (Na-CMC) flocculant with the pond ash slurries during stowing offers best result in terms of quicker settling of the ash particles and enhanced water drainage from the hydraulically stowed pond ash. Besides, it resulted in drainage of more than 85% of the total water used in the initial 45 min of stowing. The improvement in drainage is caused due to coagulation and flocculation of the pond ash particles because of charge neutralization and particle–particle bridging. This study may provide a basis for estimating the drainage and absorption of water during the real pond ash stowing operation in underground mines.     

Application of nanostructured titanium dioxide pigments in paper coating: a comparison between prepared and commercially available ones

Nano-TiO₂ pigments in pure crystallographic anatase and rutile phases have been successfully prepared by hydrothermal at 120°C and hydrolysis methods, respectively. The laboratory-prepared pigments were characterized parallel to two commercial pigments of the same crystal structure. All pigments were applied in paper coating mixtures, and their influence on coated paper properties was systematically investigated. X-ray diffraction investigation showed that the laboratory-prepared pigments using the hydrothermal method at 120°C were pure anatase, whereas hydrolysis method produced pure rutile phase pigment. The application of the prepared nanopigments and the corresponding commercial TiO₂ phases in paper coating revealed that clay/rutile nano-TiO₂ pigments in paper coating mixture decreased coated paper roughness more than blending clay with anatase nano-TiO₂ pigments. Commercial nano-TiO₂ pigments increased porosity of coated paper at both the 30% and 50% addition of nano-TiO₂ pigments to clay, while laboratory-prepared nano-TiO₂ pigments highly decreased it at 30% addition of nano-TiO₂ to clay, compared to clay only. Blending of clay/nano-TiO₂ pigments improved both brightness and opacity of the coated paper where commercial pigments are more effective. Burst, tensile strength, stretching, and TEA were improved in the case of all pigments. The 50% addition of the prepared and commercial nanopigments in conjunction with clay improved the mechanical coated paper properties more than 30% addition (except the cases of stretching and TEA of the commercial pigments). The coated paper samples were offset printed. It was found that blending of clay/nano-TiO₂ pigments improved print density. Commercial nano-TiO₂ pigments improved print gloss more than the laboratory-prepared ones. This result was found consistent with the results of coated paper roughness.     

The pseudo-single-phase,base-catalyzed transmethylation of soybean oil

The base-catalyzed transmethylation of soybean oil has been studied under conditions whereby the reaction starts as a single phase, but later becomes two phases as glycerol separates. Methanol/oil molar ratios of 6∶1 were used at 23°C. The catalysts were sodium hydroxide (0.5, 1.0, and 2.0 wt%), potassium hydroxide (1.0 and 1.4 wt%), and sodium methoxide (0.5, 1.0, and 1.35 wt%), all concentrations being with respect to the oil. Oxolane (tetrahydrofuran) was used to form a single reaction phase. The reactions deviated from homogeneous kinetics as glycerol separated, taking with it most of the catalyst. When 1.0 wt% sodium hydroxide was used, the methyl ester content reached 97.5 wt% after 4 h, compared with 85–90 wt% in the two-phase reaction. Sodium hydroxide (1.0 wt%), sodium methoxide (1.35 wt%), and potassium hydroxide (1.4 wt%) gave similar results, presumably because the same number of moles was used. The ASTM biodiesel specification for chemically bound glycerol was achieved after only 3 min when 2.0 wt% sodium hydroxide was used. However, the standard was not achieved after 4 h when 1.0 wt% sodium hydroxide was used, the MG content being 1.1–1.6 wt%. The use of 2.0 wt% catalyst is commercially impractical.     

On the Strategic Impact of the Degenerative Transfer of Xanthates on Synthetic Planning

The present brief account relates synthetic endeavours revolving around a novel chemistry of xanthates (dithiocarbonates) being developed in our group. The degenerative reversible transfer of xanthates has a unique ability to store reactive radicals in a dormant form, and thereby to enhance their lifetime in a concentrated medium, while at the same time, regulating their absolute and relative concentrations. It allows intermolecular radical additions even to unactivated alkenes, and can promote otherwise sluggish radical processes, such as 5-endo, 6-exo, 6-endo, 7-endo, and 8-endo cyclisations, as well as ring closures on (hetero)aromatic structures. This chemistry has proved remarkably versatile and powerful, both for solving synthetic problems and for the industrial production of block copolymers through the RAFT/MADIX technology.     

Experimental study of the burner for FAA fire test: NexGen burner

The NexGen (Sonic) burner is the new burner developed by the Federal Aviation Administration, FAA, to replace old oil burners used for the required fire certification tests on power plant‐related materials, as it provides the capability to control both air and fuel flow rates. During a fire test, the burner is supposed to simulate a certain fire condition, so the flame properties should be robust and repeatable. The NexGen burner can achieve this due to the precise fuel and air controls. However, the current calibration criterion (ISO2685:1998 and AC20‐135) may not be good enough to ensure consistent flame properties. In the presented work, the sensitivity of the burner performance to air and fuel flow rate, as measured by the temperature and heat flux for calibration purposes, was studied. Additionally, the influence of the turbulator and the thermocouple size used for flame calibration was also studied. The impact of varying fuel/air ratio and thermocouple sizes was studied by conducting fire tests on aluminum samples, to show the inadequacies in the current calibration standards.     

A comparative study of new linear and hyperbranched polyurethanes built up from a synthesized isocyanate-terminated polyester/urethane

In the present study, the effects of architecture and structural building blocks of the polyurethane chains on their properties were studied. New linear and hyperbranched polyurethanes (LPU and HPU) were prepared via A2 + B2 and A2 + B3 methodologies, respectively. Polyethylene glycol (PEG-1000) and castor oil (CO) were used as bi- and trifunctional monomers (B2 and B3), respectively. However, A2 monomers were synthesized by the reaction between ethylene glycol (EG) with terephthaloyl chloride (TPC) and reacting the product with excess toluene diisocyanate (TDI) to produce isocyanate-terminated PU (NCO-PU). NCO-PU was reacted with PEG to synthesize LPU; however, its reaction with CO synthesized HPU. NCO-PU, LPU and HPU were characterized by FTIR, H-NMR, GPC, TEM, TGA, DSC and XRD. The prepared PUs were applied as coatings and their physical, chemical and mechanical properties were investigated. The results showed that the degree of branching of HPU was 79%. No phase separation was observed in NCO-PU as indicated by its DSC curve. However, two phases are detected in HPU and LPU that represent to the hard and soft segments. NCO-PU displayed the highest crystallinity index (CrI = 89.26%). However, the high degree of branching in HPU led to lower CrI than LPU. The lack of entanglements in HPU led to its slightly lower solution viscosity than LPU. TEM images showed spherical PU nano-particles. The surface of HPU coating showed the highest gloss which is due to its low degree of crystallinity. HPU and LPU exhibited excellent chemical resistivity.     

Cefuroxime-impregnated calcium phosphates as an implantable delivery system in experimental osteomyelitis

The study aimed to investigate the effectiveness of porous calcium phosphates viz., hydroxyapatite (HAp) and a bi-phasic calcium phosphate (BCP) with predominately β-tricalcium phosphate (β-TCP) prepared by aqueous solution combustion method impregnated with cefuroxime axetil for the treatment of experimental osteomyelitis and compared with parenteral treatment. In vitro release of the drug was tested for its sustained elution characteristics for 21 days in PBS (pH 7.2) and measured by HPLC. In the in vivo study, bone infection was induced in tibia of rabbits by inoculation of 1 ml (3 × 10⁶) CFU Staphylococcus aureus. On the 21st day, after the development of osteomyelitis, six animals were treated by filling the cavity with cefuroxime-impregnated HAp blocks (Group II), six animals with the same drug-impregnated β-TCP (Group III) and in six others, only cefuroxime (15 mg/kg twice daily) was injected parenterally 6 weeks (Group IV). Group I with six animals was kept untreated. Histologically, the signs of infection were found to subside by 3 and 6 weeks. Radiological evaluation with cefuroxime-impregnated HAp and β-TCP pointed out the disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime in bone and serum as estimated by HPLC showed highest value on day 21 itself which reduced marginally by day 42 in both the groups and these values were higher than minimum inhibitory concentration (MIC) against S. aureus. Our findings suggest that bi-phasic calcium phosphates with predominately β-TCP content is a very efficient carrier material for antibiotic compounds even for refractory infections by S. aureus.     

CFD simulations of the Andersen cascade impactor: Model development and effects of aerosol charge

Cascade impactors are commonly used to assess the size characteristics of aerosols in toxicology and pharmaceutical applications. These aerosol instruments have been developed and refined over decades. However, a number of questions remain related to impactor performance, including the influence of electrostatic charge on measured size distributions. The objective of this study was to develop a validated CFD model of the Mark II Andersen cascade impactor (ACI) and apply this model to evaluate the effects of particle charge on deposition. The flow field was simulated using a commercial CFD code for incompressible laminar and transitional flows. Particle trajectories and deposition were evaluated using a well tested Lagrangian tracking approach that accounts for impaction, sedimentation, diffusion, and electrostatic attraction. Particle charge levels typical of dry powder inhaler (DPI) and metered dose inhaler (MDI) aerosols were considered for a particle size range of 0.3–12 μm. As a model validation, computational predictions of cutoff d₅₀ diameters for each of the eight ACI stages were found to be within 10% difference of existing experimental and manufacturer data. Results indicated that charges consistent with DPI and MDI aerosols increased deposition fraction in Stages 0–3 by up to 30% and increased deposition fraction in Stages 4–7 by up to an order of magnitude. For Stages 0–3, both DPI and MDI charges reduced the d₅₀ value by approximately 10% or less. In contrast, charged aerosols reduced the d₅₀ values in Stages 4 and 5 by 200% and 60%, respectively. All charged submicrometer aerosols considered deposited in Stages 6 and 7. Increasing the particle charge by an order of magnitude from DPI to MDI values had a relatively small effect on further decreasing the cutoff size of each stage. In conclusion, these results can be used to approximate the actual aerodynamic diameter of a charged pharmaceutical aerosol based on measurements in a standard ACI. Future applications of the developed ACI model include evaluating the influence of space charge on deposition and quantifying the effects of aerosol condensation and evaporation on size assessment.     

Effects of dietary casein and soy protein on metabolism of radiolabelled low density apolipoprotein B in rabbits

Rabbits fed semipurified diets containing casein have elevated plasma cholesterol levels compared to those fed soy protein. As part of continuing studies on the mechanism of casein-induced hypercholesterolemia, two groups of six rabbits were fed these diets for 14 to 16 weeks. Animals fed the casein diet were found to have significantly higher plasma concentrations of protein, cholesterol, triacylglycerol, phospholipid and apolipoprotein B (apo B) associated with low density lipoprotein (LDL) than those fed the soy protein diet. Kinetic studies showed that the fractional catabolic rate of LDL-apo B was significantly lower in animals fed casein than in those fed soy protein regardless of whether the tracer LDL was obtained from donors fed casein or soy protein. The production rate of LDL-apo B was higher in casein-fed animals but this was not statistically significant. These results show that the efficiency of removal of LDL is significantly reduced in animals fed casein compared to those fed soy protein, and that the source of LDL did not affect the efficiency of its subsequent removal. The acumulation of LDL in casein-fed animals is consistent with down-regulation of the LDL receptor.