Chemistry 244

Experiment 4 – Ion exchange: Determination of Fe3+ and Ni2+ content

Dian Page

15533670

21 September 2010


Abstract

The separation of a Fe3+ and Ni2+ mixture was firstly investigated; followed by the determination of the Fe3+ and Ni2+ content (concentration) in the original mixture. It was found that iron was a yellow solution and nickel respectively had a greenish colour. Their original concentrations respectively were 0.0392M for iron and 0.00225M for nickel.

Introduction

Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex.1This term can be used to denote the process of separation of aqueous and other ion-containing solutions with solid polymeric or mineral ion exchangers. Typical ion exchangers are ion exchange resins, zeolites and soil humus. Ion exchangers are either cation exchangers that exchange positively charged ions or anion exchangers that exchange negatively charged ions. Amphoteric exchangers exchange both cations and anions simultaneously.2 

An ion-exchange resin (refer to figure 1) is an insoluble matrix normally in the form of small beads, yellowish in colour, fabricated from an organic polymer substrate. They are capable of exchanging particular ions within the polymer with ions in a solution that is passed through them. Synthetic resins are used in various applications including separating out some elements.3

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Most typical ion-exchange resins are based on cross linked polystyrene.1 

The aim of this experiment was to separate a mixture of Fe3+ and Ni2+ using the anion exchange resin, Amberlite IRA-400. We then had to determine the Ni2+ and Fe3+ content of the two solutions from experiment 2a. Nickel was determined by complexometric titration with standard EDTA and iron was determined by titration with potassium dichromate in HCl medium.

Method

The method was followed as per the practical manual (page 21-30). As this is a practical, perfect results can’t always be obtained; therefore we had to work ...

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