Investigation of Interactions of Cationic and Anionic Polyacrylamaides with Modified Nanoclays by Potentiometric Sensors
A new ion-selective membrane electrode based on Calix  arene-18-Crown-6 was prepared and applied as a sensor for determination of traces of cationic (PAM + and anionic (PAM – polyacrylamaides (PAM) in their aqueous sulutions by potentiometric technique. The prepared sensor was then used to study the affinity of PAM + and PAM – to surfaces of various modified bentonite nanoclays. Surface modifications of the nanoclays were carried out by grafting of different copolymers including poly(1-vinyl pyrrolidone-co-styrene), P(VP-S), poly(methyl methacrylate-co-methacrylic acid), P(MM-MA), and poly(acrylamide-co-diallyl dimethyl amoniom chloride), P(AM-D). It was shown based on FTIR, XRD and TGA results that P(VP-S) as well as P(AM-D) copolymers had been grafted successfully on the nanoclay surface, while most of the P(MM-MA) molecules had entered the galleries and grafted on the inner surfaces of the nanoclay. The optimum membrane composition of the electrode was found to be 10 w/w% ionophore, 10 w/w% sodium tetraphenylborate (NaTPB), 28 w/w% poly vinyl chloride (PVC) and 52 w/w% dioctylphtalate (DOP) for PAM + tracing and 10 w/w% ionophore, 10 w/w% sodium tridodecylmethylammonium chloride (TDDMACl), 28 w/w% poly vinyl chloride (PVC) and 52 w/w% dioctylphtalate (DOP) for PAM – tracing. The electrodes exhibited Nernstian slope over wide concentration ranges of 0.5–100.0 g/L (1.1 × 10–6–2.2 × 10–3 M) and 0.1–10.0 g/L (1.2 × 10–8–1.2 × 10–6 M) for PAM+ and PAM–, respectively. Determination of the free energy, ΔG, of the interactions of the modified nanoclays with PAM+ and PAM–, using the data derived from the sensors, revealed the higher affinity of the cationic PAM over the anionic one towards the modified nanoclay surfaces.
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Document Type: Research Article
Publication date: 01 October 2011
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