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.
Transport properties of lithium-ion in green nonaqueous solutions and polymer ionic exchange membranes: an attempt to elaboration of ecological Li-ion battery
Organic solutions are considered as good electrolytes yielding higher lithium-ion (Li-ion or Li+) transference numbers for lithium-ion batteries during charge and discharge processes. However, owing to ecological reasons, the transference numbers of this metal ion in green viscous solvent such as glycerol at various concentrations and temperatures have been measured by means of the concentration cell and Bruce–Vincent techniques. An average value of the transport number less than 0.5 was obtained at 298.15 K, suggesting that the solvated Li+ carries less electric charges than the larger size chloride anion. The results were then compared to a recent study utilizing molecular dynamics simulation where it was confirmed the smallness values of the Li+ transference number. Besides, Hittorf’s method using the polymer cation exchange membrane (nafion 117) has been also investigated and shows the highest transport, suggesting its advantageous utilization in ecological lithium-ion batteries. Furthermore, the concentration polarization of membrane equilibrated with the electrolyte solution of lithium was carried out by means of voltamperometry that allowed recording the current–voltage characteristic. It yielded, however, low limiting current density, indicating that the polarization is more pronounced with such light metal, in contrast to larger diffusion constant and average transport number.
Interaction of Diclofop-Methyl and MCPA on Wild Oats (Avena fatua)
Diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate} loses part of its activity on wild oats (Avena fatua L.) when it is applied in combination with ester or amine formulations of MCPA {[4-chloro-o-tolyl)oxy] acetic acid.} Uptake of diclofop-methyl is reduced in the presence of commercial formulations of MCPA, particularly amine formulations, which are only partly compatible with the diclofop-methyl formulation. With added MCPA, regardless of formulation, hydrolysis of diclofop-methyl to the acid diclofop is slowed down, both in intact wild oat plants and in a crude leaf extract. At the same time, conversion of any acid formed to inactive conjugates is accelerated in the presence of MCPA. It is concluded that the loss of activity of diclofop-methyl by MCPA can be accounted for by the effects of MCPA on uptake and metabolic conversion of diclofop-methyl.