AN EXPERIMENTAL EVALUATION OF THE GOVERNING MOISTURE MOVEMENT PHENOMENA IN THE PAPER COATING PROCESS. II. EXPERIMENTAL

This paper investigates the moisture movement in the paper coating process experimentally and theoretically. The experimental data is obtained by coating a base paper with a laboratory coater and by scraping off some of the coating color after a certain amount of time. The moisture content of the material, which has been scraped off, is measured and the amount of liquid absorbed from the coating color by the base paper is determined. The laboratory results are similar to measurements made on a pilot-coating machine. The mathematical solution is based on the diffusion of water vapor in air and taken the vapor partial pressure in a hygroscopic material, i.e. paper. The measurements and a theory based on vapor diffusion show that the moisture content of the base paper is an important parameter when trying to determine the loss of water from the coating color to the base paper. This kind of dependency cannot be explained by theories based on water movement in the liquid phase by capillary suction, as is discussed in Berg et al., 2000, Part I: Theoretical Aspects.     

Electrokinetic removal of 2,6-dichlorophenol and diuron from kaolinite and humic acid-clay system

This paper presents the results of a study on the electrokinetic treatment of kaolinite and humic acid kaolinite complexes spiked with 2,6-dichlorophenol or 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron). In particular, the attention was paid to the interaction between solid surface and dissolved organics: the effects of contaminant sorption as well as the physicochemical reactions on the efficiency of electrokinetic remediation were investigated. Using a 3V/cm voltage gradient, approximately 90% of diuron was removed from kaolinite after one water pore volume was collected in the cathode reservoir, but much lower efficiency was obtained in the electrokinetic removal of this compound from humic acid-coated kaolinite. The results also showed that partial degradation of the contaminant occurred during electrokinetic treatment of kaolinite clay spiked with 2,6-dichlorophenol: the contamination in the clay could be remediated by the combination of electrokinetic extraction and electrochemical reactions.     

Moisture sorption study on Nigerian foods: Kuka

Kuka is an important vegetable in the Nigerian food chain. The moisture sorption characteristics of the vegetable studied at 34, 37 and 45°C between a_w 0.10–0.96, revealed a BET type II behaviour. The Kuka exhibited hysteresis and an increase in EMC with increase in a_w and decrease in temperature. Four sorption models (Oswin, Halsey, Kuhn, and GAB) were studied and the Oswin model was the most suitable. The constants in the Oswin model and GAB monolayer moisture contents were obtained and found to be temperature-dependent. Heats of sorption were greater for desorption than adsorption and in either mode, they reduced with an increase in moisture content. An exponential equation was obtained to relate heat of sorption with moisture content.     

The Effect of Drying Temperature on Physical Properties of Thin Gelatin Films

The molecular morphology of thin gelatin films, controlled through the casting temperature, was monitored by wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Gelatin films dried at lower temperatures had a markedly higher crystalline or helical structure with a slightly higher T_g and lower ΔC_p compared with hot dried films, which had a more coiled structure. The relationship between molecular morphology and gelatin-water interaction in terms of hydration behavior and water diffusivity was assessed using dynamic vapor sorption (DVS). The sorption capacity increased and the level of hysteresis decreased with increasing the degree of crystallinity. The difference in the aging behavior of the films was explained in terms of the difference between the glass transition and aging temperatures, (Tg – Ta).     

裂片核素在岩石中的迁移研究 Ⅰ.核素~(75)Se在花岗岩和石灰岩中的扩散行为

高水平放射性废物处置的主要方法是深埋在地质岩石中。在研究放射性核素随地下水穿过岩石缝隙网的迁移中,扩散法起着重要的作用。本文测定了~(75)SeO_3~(2-)在花岗岩和石灰岩(取自北京郊区)中的扩散系数,并详细叙述了实验技术和分析方法。     

Effects of process variables on kinetics of methylene blue sorption onto untreated guava (Psidium guajava) leaf powder: Statistical analysis

The sorption of methylene blue onto untreated guava leaf powder has been studied. The kinetics of sorption of methylene blue is described by pseudo-second-order model. Effects of initial dye concentration, solution temperature, and adsorbent dosage have been studied. The pseudo-second-order rate constant has been correlated as a function of the system variables. Statistical tools like Student's t-test, F-test, ANOVA and lack of fit have been employed to determine the significance of each coefficient that appeared in the model. Model adequacy has been checked by residual distribution. The proposed model explains 95.1% of the total variation in the response.     

Modeling of heat and mass transfer coupling with gas-solid reaction in a sorption heat pump cooled by a two-phase closed thermosyphon

A model for the global dynamics of a sorption heat pump is presented in this work. It involves a model of a reactor where gas-solid reaction takes place coupled with a model of a two-phase closed thermosyphon cooling exchanger. Simulations of the whole discontinuous cold production process have been performed. The good agreement between experimental and simulation data shows the ability of the present model to accurately represent the dynamics of such systems. An analysis of the physical mechanisms governing the dynamics of each process stage is made. It was shown that mass limitation strongly slowed down the synthesis when the other phases of the process are mainly dependent on the thermal behavior of the transformer. This model can be used as a powerful tool for the optimization of sorption systems and for the intensification of such processes.     

Application of the concentration-dependent surface diffusion model on the multicomponent fixed-bed adsorption systems

The ability of bone char to adsorb three metal ions, namely, cadmium, copper and zinc, from effluents in fixed beds has been studied. Two binary metal ion sorption systems, Cd+Cu and Cu+Zn, have been investigated. The variables studied include metal ion solution flowrate, initial metal ion concentration, and bone char particle size bed height. The experimental breakthrough curves for each binary system were measured at five bed heights.A multicomponent film-surface diffusion model has been developed to predict the breakthrough curves by incorporating the IAS for both the Langmuir and the Sips equations, since they both correlate the single component equilibrium isotherm data well. A novel development is the modification of the solution methodology, previously restricted to a constant diffusivity, to incorporate a variable diffusivity correlated with adsorbent coverage by the constant self-diffusivity. The self-diffusivities for the metal ions have been evaluated.     

Influence of sorption kinetics for zirconia sensitization in solid oxide fuel cell functional anode prepared by electroless technique

For preparation of solid oxide fuel cell functional anode (Ni-YSZ) by electroless deposition technique, surface adsorption of metallic palladium (Pd⁰) on zirconia is the most important step during the sensitization process. For the sensitization process, the initial reaction kinetics are based on external mass transfer followed by intra-particle mass transfer phenomena. A kinetic model for the reversible sorption of Pd⁰ on zirconia is developed that incorporates an effectiveness factor (η) which estimates the extent of intra-particle mass transfer. Based on the proposed model, an expression for Pd⁰ uptake at equilibrium (p), an important property of YSZ, is developed. The theoretical kinetic model proposed is verified with experimental parameters like electrical properties of these functional anodes prepared under various sensitization conditions, e.g., agitation frequencies, equilibration time etc. Due to intra-particle mass transfer, the concentration gradient of Pd⁰ from the surface of YSZ to bulk is minimized which favours uniform deposition of Ni on YSZ. Consequently, during subsequent electroless deposition of metallic Ni, the concentration gradient of the same is reduced from the bulk to the YSZ surface and results in enhanced functionality in the cermet anode. The validation is correlated with the electrical properties and surface morphologies of these functional cermets.     

Wool powders used as sorbents to remove Co ions from aqueous solution

The Co²⁺ sorption of two wool powders was investigated using its radioisotope ⁵⁷Co (T_1/2 = 271.8 days and γ = 122.1 and 136.5 keV) as a tracer. The effects of the type of buffer, the pH value, the contact time and the initial concentration of Co²⁺ on the sorption behaviour of wool powders were studied. The Co²⁺ releasing ability of wool powders and the re-use of wool powders to sorb Co²⁺ were also examined. The optimum sorption of Co²⁺ by the powders occurred at pH 8 in phosphate buffer and pH 10 in ammonium sulphate buffer. Fourier-transform infrared spectroscopy (FTIR) was used to study the changes in chemical structure of the wool after exposure to both buffer solutions. Compared to the untreated wool fibre, the fine wool powders showed rapid sorption rates and high sorption capacities for Co²⁺. Co²⁺ ions were recovered after exposing the Co²⁺ loaded wool to HCl (0.1 M) and buffer at pH 3 (glycine/sodium chloride). After releasing Co²⁺ ions from wool powders, the efficiency of wool powders re-used to sorb Co²⁺ was 80% of that of the fresh wool powders. It is concluded from this study that wool powder can be used as an efficient sorbent to remove and release Co²⁺ from solution.