Nitrilotris(methylenephosphonic) acid as a complexing agent in sorption of heavy metal ions on ion exchangers

In this work the strongly basic anion exchanger Amberlite IRA 402, the weakly basic anion exchangers Purolite A 100 and Purolite A 103 as well as the chelating ion exchangers Purolite S 920 and Purolite S 930 were used to investigate the influence of phase contact time, pH and metal(II) concentration on the sorption of the heavy metal complexes of Cd(II), Pb(II), Cu(II) and Zn(II) with nitrilotris(methylenephosphonic acid), NTMP. These types of complexes are often found in industry where NTMP is used. The studies were carried out in the M(II):NTMP = 1:2 system. The sorption capacity of the studied ion exchangers increases with the increase of the initial M(II) ions concentration and the sorbate/ion exchanger ratio. It was found that sorption capacity increases with the increasing temperature and initial pH of metal solution. Equilibrium sorption tests show that chelating ion exchangers as well as the strongly basic anion exchanger have a larger capacity and affinity for sorption of Cd(II), Pb(II), Cu(II) and Zn(II) complexes with NTMP than weakly basic anion exchangers. It was found that the Langmuir and Hill models were more representative to describe complexes sorption than the Freundlich, and Dubinin–Radushkevich ones whereas the kinetic process followed the pseudo second-order pattern.

• Different ion exchangers were used in removal of heavy metals from solutions.
• The different factors affecting the metal ions loading in the presence of NTMP.
• The pH, contact time and system composition were studied.