Ian D. Potter

Theoretical and experimental study of palladium(II) extraction from hydrochloric acid solutions into Aliquat 336/PVC membranes

Abstract The extraction of palladium(II) from its hydrochloric acid solutions into poly(vinyl chloride) (PVC)-based membranes containing Aliquat 336 chloride as both the extractant and the plasticizer was experimentally studied. The results showed that these membranes extracted palladium(II) rapidly and to a very high degree. This property can be used either for the analytical determination of trace levels of palladium(II) or for the recovery of this precious metal from industrial wastewaters and hydrometallurgical solutions. A mathematical model for the palladium(II) extraction into an Aliquat 336/PVC membrane which takes into account the interfacial palladium(II)–Aliquat 336 chloride reaction and the diffusion mass transport through the membrane was developed. The model was fitted to the experimental extraction data to determine the values of the relevant physicochemical constants (i.e. diffusion coefficients and kinetic rate constants).

Electrochemical Impedance Spectroscopy—A Simple Method for the Characterization of Polymer Inclusion Membranes Containing Aliquat 336

Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon.

Transport of Thiourea through an Aliquat 336/Polyvinyl Chloride Membrane

The transport of thiourea in acidic or neutral chloride solutions through a polyvinyl chloride (PVC) membrane containing immobilized Aliquat 336 was studied experimentally. No chemical interaction between thiourea and Aliquat 336 was observed. The acidity constant of thiourea at 1.0 ionic strength was 13.7 and its distribution constant for acidic solutions and neat Aliquat 336 was 4.20. A mathematical model assuming ideal mixing in the solutions on both sides of the membrane and Fickian diffusion in the membrane was developed and used for the determination of the diffusion coefficient of thiourea in membranes with 30, 40, and 50 wt% Aliquat 336 content. The corresponding values are estimated to be 5.5 × 10−13 m2s−1, 1.2×10−12m2s−1 and 3.5 ×10−12m2s−1, respectively. The transport properties of PVC membranes with other plasticizers [bis(1-butylpentyl) adipate, dioctylphenyl phosphonate, and n–decanol] were compared to the Aliquat 336/PVC membrane.

Phosphine displacement reactions by some alkyl-substituted 1,10-phenanthrolines with bis(triphenylphosphine)copper(I)tetrahydroborate

Abstract The displacement reactions of various alkyl-substituted 1,10-phenanthrolines with bis(triphenylphosphine)-copper( I )tetrahydroborate [(Ph 3 P) 2 Cu(BH 4 )] have been investigated. Two series of products from these displacement reactions: (phen)Cu(BH 4 ) (series 1) and (phen)(Ph 3 P)Cu(BH 4 ) (series 2) have been identified via their spectroscopic properties. Both series 1 and 2 products contain the bidentate tetrahydroborate (η 2 -BH 4 ) group, while the series 2 products also involve the coordination of triphenylphosphine [PPh 3 ] to the copper( I ) centre. In some instances, both series of products may be observed for the same phenanthroline ligand employed. Some series 1 products in the presence of PPh 3 can be converted to their conjugate series 2 products. Both series of displacement products have been characterised by spectroscopic methods: 1 H, 13 C, 11 B and 31 P NMR and FT-IR.

Bovine pancreatic trypsin inhibitor is a new antifungal peptide that inhibits cellular magnesium uptake

Antimicrobial peptides (AMPs) are promising agents for control of bacterial and fungal infections. Traditionally, AMPs were thought to act through membrane disruption but recent experiments have revealed a diversity of mechanisms. Here we describe a novel antifungal activity for bovine pancreatic trypsin inhibitor (BPTI). BPTI has several features in common with a subset of antimicrobial proteins in that it is small, cationic and stabilized by disulphide bonds. BPTI inhibits growth of Saccharomyces cerevisiae and the human pathogen Candida albicans. Screening of the yeast heterozygous essential deletion collection identified the magnesium transporter Alr1p as a potential BPTI target. BPTI treatment of wild type cells resulted in a lowering of cellular Mg2+ levels. Populations treated with BPTI had fewer cells in S‐phase of the cell cycle and a corresponding increase of cells in G0/G1 and G2 phases. The same patterns of cell cycle arrest obtained with BPTI were also obtained with the magnesium channel inhibitor hexamine(III)cobalt chloride. Analysis of the growth inhibition of C. albicans revealed that BPTI is inhibiting growth via the same mechanism in the two yeast species. Inhibition of magnesium uptake by BPTI represents a novel mechanism of action for AMPs.

The interactions of added phenanthroline and triphenylphosphine ligands with the copper(I) tetrahydroborates (phen)Cu(BH4) and (phen)(PPh3)Cu(BH4): Probing the character of species in solution

Abstract Added free ligand, i.e. phenanthroline for (phen)CuBH 4 and either phenanthroline or triphenylphosphine for (phen)PPh 3 CuBH 4 , causes a progressive change in the mode of attachment of the η 2 –BH 4 moiety from that in the initial complexes to the formation in solution of ionic species of the type [(phen) 2 Cu] + BH 4 − and [(phen)(PPh 3 ) 2 Cu] + BH 4 − , respectively. These changes were indicated by: (i) infrared spectroscopy, which showed both a gradual loss of signals attributed to ν (B–H b ) and δ (BH 2 ) and their replacement with spectra typical of ionic BH 4 − ion; (ii) an increase in the conductance measured that was consistent with a 1:1 electrolyte; (iii) chemical shift changes in the 11 B- and 31 P-NMR signals associated with the BH 4 − and PPh 3 moieties, respectively and (iv) a relative increase in signal intensities of the ions detected by electrospray mass spectrometry.