Synthesis, characterization and ion-exchange properties of a fibrous type ‘polymeric-inorganic’ composite cation-exchanger Nylon-6,6 Sn(IV) phosphate: Its application in making Hg(II) selective membrane electrode

doi:10.1016/j.electacta.2008.12.038

Electrochimica Acta

Volume 54, Issue 12, 30 April 2009, Pages 3320-3329

https://doi.org/10.1016/j.electacta.2008.12.038 Get rights and content

Abstract

A polymeric-inorganic composite cation-exchanger, i.e. Nylon-6,6 Sn(IV) phosphate was synthesized via mixing of polymer Nylon-6,6 into the matrices of inorganic precipitate of Sn(IV) phosphate to form composite cation-exchanger. Ion-exchange capacity (IEC), ion-exchange properties, thermal stability and distribution behavior, etc. were also carried out to understand the cation-exchange behavior of the material. The physico-chemical properties of the material were determined using AAS, CHN elemental analysis, FTIR, TGA-DTA, XRD, and SEM studies. On the basis of distribution studies, the material was found to be highly selective for Hg(II), a highly toxic environmental pollutant. Using this electroactive composite material, a new heterogeneous precipitate based selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The membrane electrode is mechanically stable, with a quick response time, and can be operated within a wide pH range. The selectivity coefficients for different cations determined by mixed solution method were found to be less than unity. The electrode was also found to be satisfactory in potentiometric titrations.

Introduction

Synthetic organic–inorganic composite cation-exchange materials have received a great deal of attention because of their stability and reproducible analytical and electroanalytical applications [1], [2], [3], [4], [5], [6], [7], [8], [9]. Organic polymers of composite material provide the mechanical strength and increase the surface area for more available exchangeable sites of the inorganic part. Nano composites of organic–inorganic cation-exchange materials prepared by sol–gel method are advance class of materials that are expected to provide many possibilities [10], [11]. Development of fibrous type organic–inorganic composite can also open more opportunities in their environmental application as they exhibit high efficiency in the process of sorption from liquid and gaseous media [12], [13], [14], [15], [16], [17], [18]. Paper like strips fabricated from such materials can be used as indicator in identification of various ions in polluted water. Such paper like strips may provide a new material in paper chromatographic techniques in separation and identification of different chemical species in a given sample.

Precipitate based ion-selective membrane electrodes are well known as they are successfully employed for determination of several anions and cations. The ion-selective membranes obtained by embedding ion-exchangers as electroactive materials in a polymer binder, i.e. epoxy resin (Araldite) or polystyrene or PVC, have been extensively studied as potentiometric sensors, i.e. ion sensors, chemical sensors or more commonly ion-selective electrodes.

In view of the above application of fibrous type material, Nylon-6,6 Sn(IV) phosphate composite material is developed in the present research work. The material is characterized and used in making Hg(II) ion-selective membrane electrode.

Section snippets

Reagents and instruments

Reagents used for the synthesis of the material were obtained from CDH, GSC, E-merck (India). All other reagents and chemicals were of analytical reagent grade. A digital pH meter (Elico LI-10, India), a double beam atomic absorption spectrophotometer (GBC 902, Australia), a digital flame photometer (Elico CL 22D, India), a UV/Vis spectrophotometer (Elico EI 301E, India), a water bath incubator shaker were used.

Preparation of reagent solutions

0.10 mol dm⁻³ Stannic chloride (SnCl₄·5H₂O) solution was prepared in 4.0 mol dm⁻³ HCl,

Preparation of Nylon-6,6 Sn(IV) phosphate membrane electrode

The ion-exchange membrane was prepared by following the procedure of Coetzee and Benson [22]. Nylon-6,6 Sn(IV) phosphate cation-exchanger (100 mg) as electroactive material was ground to fine powder, and was mixed thoroughly with Araldite (Ciba-Geigy, India Ltd.) (100 mg) in 1:1 (w/w) ratio to make a homogeneous paste, which was then spread between the folds of Whatman's filter paper No. 42. Glass plates were kept below and above the filter paper folds as support. The phase of the exchanger and

Preparation of PAN indicator strips

About 0.5 g fibrous composite material (Nylon-6,6 Sn(IV) phosphate) was dipped in PAN indicator for 24 h. The excess indicator was washed with DMW and the material was dried at 40 °C in an oven. The material was placed under hydraulic pressure machine at 25 KN pressure to obtain fibrous strip as shown in photograph of Fig. 13b. A drop of different concentration of some heavy metals such as Cu(II), Pb(II), Hg(II), Fe(II) was placed on strip. The color change was observed from the yellowish strip as

Results and discussion

A fibrous composite Nylon-6,6 Sn(IV) phosphate was prepared by mixing inorganic precipitate of Sn(IV) phosphate and Nylon-6,6 developed in formic acid in different (w/v) ratio's as given in Table 1. The ion-exchange capacity of this composite material for alkali and alkaline earth metal ions was determined as shown in Table 2. It is noticed that ion-exchange capacity increases as hydrated radii decreases. The maximum ion-exchange capacity of the composite was found to be 2.1 meq/g for Na⁺ ions.

Acknowledgements

The authors are thankful to Department of Applied Chemistry, Z.H. College of Engineering and Technology, A.M.U. (Aligarh) and Ministry of Environment and Forest (India) for providing research facilities. Assistance provided by the R.S.I.C. Bombay, I.I.T. Delhi and I.I.T. Roorkee to carry some instrumental analysis.

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Synthesis, characterization and ion-exchange properties of a fibrous type ‘polymeric-inorganic’ composite cation-exchanger Nylon-6,6 Sn(IV) phosphate: Its application in making Hg(II) selective membrane electrode

Abstract

Introduction

Section snippets

Reagents and instruments

Preparation of reagent solutions

Preparation of Nylon-6,6 Sn(IV) phosphate membrane electrode

Preparation of PAN indicator strips

Results and discussion

Acknowledgements

Coll. Surf. A: Physicochem. Eng. Aspects

Mater. Res. Bull.

React. Funct. Polym.

Anal. Chim. Acta

React. Funct. Polym.

React. Funct. Polym.

Sens. Actuat. B: Chem.

Electrochim. Acta

Talanta

React. Polym.

Anal. Chim. Acta

Talanta

J. Inorg. Nucl. Chem.

Talanta

Sens. Actuat. B

Talanta

Talanta

Sens. Actuators B

Sens. Actuat. B

J. Anal. Chem.

Langmuir

Indian J. Chem.

Res. J. Chem. Environ.

Chemosorptive Fibres