Concentration of acetic acid in sulfite pulp evaporation drain by reverse osmosis

The evaporation drain of sulfite pulp spent liquor contains few volatile fatty acids, most of which is acetic acid. The main objective of this study is to recover acetic acid as the concentrated solution (about 4%), which could be used as a culture medium of the yeast. As acetic acid can easily pass through the cellulose acetate membrane, SP drains neutralized by NaOH, NH₄OH and Ca(OH)₂ were used as the feed solutions. In all cases, concentration by reverse osmosis was successfully carried out provided the appropriate pretreatment was employed. The recovery of acetic acid was 95.6, 90.5 and 98.2% for Na-, NH₄-, and Ca-drain, respectively. In addition, the recovered (permeated) water may be used as an industrial one.     

Recovery of gold from the plating rinse by adsorption with nylon fibers

Taking note of the affinity of some reverse osmosis membranes to Au(CN)^-₂ in the citrate buffered gold plating rinse, we accomplished the recovery of gold by the adsorption to some polymers. Among several polymers, tested nylon fibre had the most excellent characteristics of adsorption. The amount of adsorption of gold on nylon fiber increased with a decrease in pH value of the solution, and 7.5 mg of gold was adsorbed on 1 g of nylon fiber at pH 3, 25°C. The rate of adsorption increased with an increase in temperature. In the case of desorption, the solution containing cyanide ions at a pH as high as 10 was desirable to be employed as an eluant. By passing the simulated plating rinse through a column of nylon fiber, the adsorption and desorption of gold was successfully accomplished. The maximum concentration of gold in the eluant was approximately 600 ppm.     

The permeation behavior of metal complex solutions through cellulose acetate membranes

Transport phenomena of several kinds of metal complexes were investigated with cellulose acetate membranes annealed at 65°–76°C. In reverse osmosis experiments, the rejections of metal complexes involving organic sequestering agents such as EDTA or citric acid were much higher than those of the corresponding metal ions. While, in the case of metal complexes involving small inorganic ligands such as NH₃ or SCN^-, their rejections did not necessarily increase with the increase in the coordination numbers of the metal ions. To more precisely understand such transport behaviors, the distribution and the diffusion coefficients of metal complexes were obtained by desorption-rate measurements with dense cellulose acetate membranes. The results revealed that the distribution of a metal ion to the membrane was largely depended on the coexisting ligands. Attempts were also made to explain the distribution coefficient from the microscopic point of view by using Glueckauf's equation.     

Studies on the treatment of gold plating rinse by reverse osmosis

Studies on the treatment of citrate buffered gold plating rinse were carried out with four types of membranes. For three membranes (NS-200, polybenzimidazolone, aromatic polyamide), the rejections of gold were more than 92% in the initial stage of the concentration process, but they decreased remarkably with the increase in the concentration of the feed. For the cellulose acetate membrane, negative rejection was observed as Golomb pointed out. To understand the phenomena more clearly, the relationship between the state of the species in the solution and their permeation behavior was investigated in detail. It was shown that in multiion solutions such as gold plating rinse, a less permeable ion such as the citrate ion improved the permeability of a more permeable ion of like charge such as Au(CN)^-₂. Therefore the recovery of gold was as low as 85% at most in a five-fold concentration of the rinse.     

A Tabu search algorithm for solving the extended maximal availability location problem

The aim of this study is to develop a Tabu Search (TS) procedure for the Extended Maximal Availability Location Problem (EMALP). This probabilistic location problem consists of locating the servers of the system so that the expected coverage of demand is maximized, in which a demand area is said to be covered if there is at least one server available within a given critical distance with a probability greater than or equal to a given reliability. The results obtained from this procedure are compared with those obtained from the Simulated Annealing (SA) procedure developed by Galvão et al. for the same problem. To the best of our knowledge, we are not aware of other methods proposed in the literature to solve the EMALP. The computational results show that in terms of the quality of the solutions, SA slightly outperforms TS for the smaller networks, while TS outperforms SA for the larger networks.     

On the conditions of fabrication of tubular cellulose acetate membranes

The conditions of fabrication of asymmetric tubular cellulose acetate membranes was investigated. In the fabrication process, the chief determining factor of membrane performance was the amount of evaporation of solvent in the casting solution. To measure the evaporation amount a test sample of a membrane was collected by using a device at each section of the tube.The evaporation amount of acetone and membrane performance were measured with the membranes fabricated by various methods of casting, and the relationship between them studied from their distribution curve. The vapor of acetone evaporated from a membrane caused a downward stream in the tube. Therefore a casting bob was modified to prevent the steam and maintain the atmosphere in the tube constant.In the fabrication process using a modified bob, the rate of evaporation and evaporation time were kept constant over the whole region of a tube to obtain a uniform tubular membrane.     

Isothermal Capacitance Transient Spectroscopy of Grain-Boundary Interfacial States in Beryllium Oxide-Doped Silicon Carbide Ceramics

Grain boundaries of SiC ceramics doped with 2 wt% BeO were investigated using isothermal capacitance transient spectroscopy (ICTS). ICTS signals were observed above 433 K and the resulting capacitance-time curves (under bias and zero bias) were ascribed to interfacial states at the grain boundaries. The signals were sharp compared to those of the SrTiO₃─Bi₂O₃ system, suggesting that the structural disorder of grain boundaries in the SiC─BeO system was relatively small. It was determined that the interfacial state was located 0.92 eV above the valence band.     

Precise measurement of membrane constants of cellulose acetate membranes by direct osmosis tests

A method for the determination of membrane constants by direct osmosis tests was studied using cellulose acetate membranes. A countercurrent type osmosis cell was designed and made for this study, and a method for precise measurements of permeated water and solutes through the membrane was established. Based on the membrane constants derived from direct osmosis tests, membrane performances of cellulose acetate membranes under pressure of 40 atm were predicted. The predicted values were in good agreement with the observed values in reverse osmosis experiments and it was confirmed that membrane performances under pressure could be predicted by the direct osmosis with considerably good accuracy.     

An Optimally Controlled Respirator

An optimally controlled respirator was developed. It has three main features: 1) ventilation is controlled by the patient's metabolic rate from continuously measured C02 output, 2) physiologic dead space approximated as a linear function of tidal volume is used to estimate alveolar ventilation, and 3) respiratory rate is computed to minimize ventilatory work.