Heavy metal removal by clinoptilolite. An equilibrium study in multi-component systems

Ternary and quaternary ion-exchange equilibria have been studied between heavy metal solution (Pb(2+), Cd(2+), Cu(2+)) and Na-form of clinoptilolite. The value of the ion-exchange equilibrium constant was estimated using the Langmuir, Competitive Langmuir, and thermodynamic sorption models. For each isotherm, calculations were done taking into account the concentration of ions in both phases. Additionally, for the thermodynamic isotherm, two other cases were considered: activity of ions in the liquid phase and concentration in the solid phase; activity of ions in both phases. The activity coefficients of ions in the liquid phase were determined using Pitzer's model; activity coefficients in the solid phase were estimated by Wilson's model. It was found that the exchange capacity for a given M(2+) is not constant and differs in one- or multi-component systems. The results show that the equilibrium model based on the law of mass action, which considers nonideal behavior of both phases, allows one to achieve the best approach to the real multi-component equilibrium data in all studied systems.     

A specific effect of alkali-metal iodides and thiocyanates on the viscosity of solutions of poly(methacrylic acid) in methanol

The solution properties of poly(methacrylic acid) (PMA) in methanol are specifically affected by thiocyanates and iodides of alkali metals. The relative decrease in the reduced specific viscosity of PMA in dilute methanolic solutions due to KSCN depends only on the ratio of concentrations of polymer and salt, and is independent of temperature and polymer molecular weight. With copolymers of methacrylic acid and 2-hydroxyethyl methacrylate, the effect is weaker.     

Kinetics and equilibria of the hydration of propene over a strong acid ion exchange resin as catalyst

The kinetics and equilibria of the direct hydration of propene over a strong acid ion exchange resin (C8P ex AKZO) were studied. The experiments were c     

Supercritical carbon dioxide extraction ofDimorphotheca pluvialis oil seeds

The possibility of extraction ofDimorphotheca oil with supercritical carbon dioxide is demonstrated in this article. Before extraction, the seeds have to be pretreated to improve extraction yield. Experiments showed that the best pretreatment procedure forDimorphotheca was heating the seeds under reduced pressure to 100°C for 60 min, followed by flaking or milling. To give an impression about the efficiency of the supercritical extraction, a mathematical model has been developed to estimate the overall mass transfer coefficient (A _p K). Also, an empirical relation betweenA _p K and the interstitial velocity has been found. The physical properties of the supercriticalDimorphotheca oil are in good agreement with those of conventionally extracted oil, except for a lower phospholipid content. It is expected that further refining of supercriticalDimorphotheca oil will be marginal.     

Fabrication and properties of point structures formed on <Emphasis Type="Italic">n</Emphasis>-InSe single crystals

Point structures based on InSe single crystals were obtained by the method of electric discharge. The steady-state current-voltage characteristics and the photosensitivity of the structures (point contact)/n-InSe were studied. Rectification was found and the first spectra of photosensitivity of the structures obtained by electric discharge were measured. The broadband character and excitonic feature of the photosensitivity spectra of the structures (point contact)/n-InSe were observed and discussed. It is established that the point structures can be used as broadband photoconverters of optical radiation.     

Robust Huber adaptive filter

Classical filtering methods are not optimal when the statistics of the signals violate the underlying assumptions behind the theoretical development. Most of the classical filtering theory like least-squares filtering assumes Gaussianity as its underlying distribution. We present a new adaptive filter that is optimal in the presence of Gaussian noise and robust to outliers. This novel robust adaptive filter minimizes the Huber objective function. An estimator based on the Huber objective function behaves as an L₁ norm estimator for large residual errors and as an L₂ norm estimator for small residual errors. Simulation results show the improved performance of the Huber adaptive filter (configured as a line enhancer) over various nonlinear filters in the presence of impulsive noise and Gaussian noise     

Behavior of functional compounds during freeze concentration of tofu whey

The liquid waste generated from tofu production, denominated as Tofu Whey (TW), contains important amounts of isoflavones that can be evaluated by various separation techniques. In this work TW was concentrated by falling-film freeze concentration from 1.9 to 15.5 °Brix, up to levels of 208 mg of isoflavones per 100 g solids. The levels of isoflavones, proteins, sugars, calcium and magnesium were determined both in the ice and in the concentrate obtained. It was found by rheological characterization that TW shows a Newtonian behavior at concentrations between 1.9 and 15.5 °Brix with freezing points of −0.6 to −2.7 °C.     

Effects of tangential microfiltration and pasteurisation on the rheological,microbiological, physico‐chemical and sensory characteristics of sugar cane juice

The aim of this study was to determine the physico‐chemical, microbiological, rheological and sensory characteristics of sugar cane juice with passion fruit pulp (5% w/w) added and which had been submitted to microfiltration and pasteurisation (90 °C/30 s; 95 °C/30 s) processes. The results showed that the juices obtained after the microfiltration and pasteurisation processes had low microbial counts. The microfiltered juice showed a reduction in the soluble solids, acidity and vitamin C content (P = 0.05), while the pasteurised juice showed no change in these parameters (P > 0.05) in relation to the natural sugar cane juice, with the exception of vitamin C, which was not detected after the thermal treatment. In relation to the rheological properties, Newtonian behaviour was observed for both microfiltered and pasteurised juices. The sensory tests on a hedonic scale showed good acceptance of both juices (microfiltered and pasteurised).     

Heat pretreatment of oilseeds: effect on oil quality

We studied the effect of seed conditioning via a rapid preheating technique to destroy the activity of oil-degrading enzymes. Rape and sunflower seeds were heated via steaming, oven cooking, infrared, and microwave. After the pretreatment the oil was expelled from the seeds by a screw press and its quality was determined via the analysis of oxidative stability, peroxide value, free fatty acid content, phosphorus, and iron. From the results it was concluded that preheating of the seeds leads to the expected decreased activity of lipase, but nevertheless increased levels of phosphorus and free fatty acids were observed. However, increased levels of phenolic antioxidants markedly improved the oxidative stability of rapeseed oil. From the techniques studied for heating of the seeds, microwave and steaming appeared to be the most suitable techniques. Both methods gave markedly improved oxidative stability, whereas steaming seemed to result in less formation of free fatty acids than microwave heating. Infrared heating led to rapidly burnt seeds and off-flavours.