Concentration Of Copper Ions In Solution Research Articles

Preparation and characterization of microgels sensitive toward copper II ions

An emulsion polymerization technique has been used to prepare chemically crosslinked microgels in aqueous suspension that are sensitive to the presence of copper ions. Poly(N-isopropylacrylamide) (PNIPAM) was copolymerized with different amounts of 1-vinylimidazole (VI), and the resultant microgels exhibited multi-responsive behavior being sensitive to changes in temperature, pH and to the presence of metal ions, particularly copper. These swelling properties of the microgel particles were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effect of temperature showed that the microgel particles shrunk continuously as the temperature was raised, up to a temperature of 50°C, and the volume phase transition temperature, VPTT, has been shifted to higher temperatures (in the range of 35–45°C) compared to pure PNIPAM microgels where the VPTT≈30–35°C. The particle size of these microgels was also investigated as a function of pH; the microgel particles became swollen at low pH and collapsed at high pH, due to the ionization of the VI component of the microgels. Most interesting, however, was the effect of the copper ion concentration in solution. The PNIPAM-co-VI microgels were found to swell with increasing concentration of Cu2+ up to 0.3g/l of Cu2+ due to adsorption of the cations inside the particle, which leads to charging up the internal phase of the microgel. However, at higher concentrations of added copper (II) ions, the binding forces of complexation lead to conformational changes to the microgel resulting in weaker polymer–solvent interaction and consequential shrinkage again of the polymer. In addition, the copper (II) uptake was calculated, and the uptake was found to be well described by the Langmuir adsorption isotherm, with up to 2g of copper II being taken up by 1g of microgel.

Effect of copper content on the properties of Ni–Cu–P plated polyester fabric

The copper content of electroless Ni–Cu–P-plated polyester fabric mainly depends on the copper ion concentration in the plating solution, which in turn has a significant effect on the properties of the coatings. The effects of copper sulphate concentration (CuSO4) on the deposition rate, composition, surface morphology, crystal structure, surface resistance and electromagnetic interference (EMI) shielding effectiveness of electroless Ni–Cu–P deposits were investigated. The results show that the copper content in the deposits increased significantly, whereas nickel content decreased significantly and phosphorus content decreased slightly with a higher copper ion concentration. Compact coating layers were obtained with a nodular morphology. With increase of copper ion concentration in the solution, the crystallinity of the deposits also increased. In addition, the surface resistance decreased and the EMI shielding effectiveness of the Ni–Cu–P deposits increased.