Study the transport properties of anion and cation exchange membranes toward various ions using chronopotentiometry
The transport properties of various anion and cation exchange membranes were studied in different electrolyte solutions using chronopotentiometry technique to get insight about the influence of the counter ion on the transport properties of the membranes. The investigated samples include heterogeneous ion exchange membranes varying in the functionality of fixed charged groups, physical properties of the polymer and the preparation procedure. Chloride and nitrate were investigated as counter-ion in their sodium salts for anion exchange membranes while sodium, calcium, potassium, and magnesium were selected as counter-ion in their chloride salts to study cation exchange membranes transport properties. First, the current – voltage curve of an ion exchange membrane in a given solution was recorded to obtain the limiting current, then a constant current above the limiting current was used for chronopotentiometry measurement. In all the studied membranes the potential across the membrane remained constant for a time interval called the transition time , when a constant current was applied. Then the potential increased rapidly to reach the steady state potential. The permselectivty and the transport number of a membrane were calculated using the corresponding transition time.
Optimization Study for Treatment of Acid Mine Drainage Using Membrane Technology
The use of membrane technology in the treatment of Acid Mine Drainage (AMD) can result in reduction of chemical usage and sludge production making the treatment process more environmentally friendly. This study deals with the optimization of membrane filtration performance in the treatment of AMD using two nanofiltration (NF) membranes (NF99 and DK) and one reverse osmosis (RO). All membranes were used in various tests treating a model solution at two different concentration levels in order to cover the concentration of actual AMD found in the mining industry. The main parameters which were studied to determine the optimal condition for AMD filtration are pressure, pH, temperature, and flow rate. Pressure and temperature were found to have a considerable influence on flux, while rejection was only slightly influenced by pressure. The feed flow rate had no effect on rejection. The highest flux with moderate rejection was determined for NF99 while RO had the lowest flux but highest rejection. Therefore, NF is preferable for AMD treatment due to lowest energy consumption. The treatment has also been tried on a large scale to check its applicability at a commercial scale. Finally, PHREEQC has been used to determine the scaling risk in the prepared AMD.
Conception of a Language Learning Environment Based on the Communicative and Actional Approaches
This paper's aim is to give a conceptual framework about the conception of a Computer Assisted Language Learning environment based on the communicative and actional approaches. In this environment, the learner is implicated in a task that he/she has to complete by interacting with a partner using his/her language competencies. Given a task, different ways exist to accomplish it and the different competencies of the learner can then be solicited with different types of interaction. Works accomplished in human computer dialogue give models to manage this interaction.