COMPARATIVE ADSORPTION OF MAJOR CATIONS FROM BRINES BYION EXCHANGE PROCESSING USING AMBERLITE 252-RFH RESINS AND AMIDOXIME FIBRES

摘要

The Amberlite 252 RFH resin and poly(amidoxime) fibre containing the amidoxime group were used to investigate the adsorption of Na(I) in brine waste water as a function of contact time, metal ion concentration, and initial solution pH. Brines are problematic effluents created by water desalination processes, oil and gas production, coal and gold mine drainage and evaporative cooling in power stations and process industries. The poly(amidoxime) was synthesized by conversion of the nitrile groups of polyacrylonitrile (PAN) copolymers into amidoxime groups by a reaction with hydroxylamine under alkaline conditions. Characterization was carried out in terms of elemental composition, surface functionality, FT-IR, exchange capacity, and the effects of pH. Amberlite resin showed a higher metal ion adsorption capacity for the Na(I) ion (25.03 mg/g) than poly(amidoxime) fibre (16.40 mg/g) due to its higher exchange capacity. The adsorption capacity of Ca(II), Mg(II), and Na(I) in the adsorbent increased with an increase in poly(amidoxime) alkali treatment reaction time. The uptake of the alkali or alkaline earth metals was shown to be independent of pH, hence the amidoxime functionalized fibres do not exhibit any pH dependent selectivity for Na(I) ions and Amberlite being a strong acid cation exchange resin is not affected by pH. The kinetics of the fibrecation ion interaction, however, was found to be sufficiently rapid reaching equilibrium in 10-20 mins as compared to the resin which reaches equilibrium in 30-40 min. The advantage of a faster rate of equilibrium is achieved because of the fibrous configuration of the polymer backbone which allows for more rapid kinetics than resin bead type backbones.