Development of ion exchangers for the removal of health-hazardous perchlorate ions from aqueous systems

Abstract

In order to investigate diffusion models and adsorption mechanism of polymeric ligand exchangers (PLE) for the removal of perchlorate from tap water Lewatit MonoPlus TP 220-Cu, Lewatit MonoPlus TP 220-CuEDDS, Dowex 4195-Cu and M 4195-CuEDDS were prepared and compared with commercial Lewatit TP 220 and Dowex M 4195. Based on the adsorption experiments, diffusion mechanisms were studied using the intraparticle diffusion, film diffusion, Boyd, Dumwald-Wagner models. The pore diffusion coefficient (Dp), film diffusion coefficient (Df) as well as well-known kinetic models like the pseudo first and the pseudo second order were also applied to fit the experimental data. The adsorption study was carried out at pH equal 7.0 and different contact time. The kinetics of adsorption was based on the pseudo second order model. The adsorption studies show that the adsorption rate controlling step is realized mainly by intraparticle diffusion. The basic surface structural changes before and after the perchlorate sorption on each sorbent were investigated using ATR-FTIR. After sorption the band at 1085 cm−1 appeared which showed efficiency of the sorption process. The adsorbents were also characterized by the nitrogen adsorption/desorption isotherms, thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis. The study proved efficiency of Lewatit MonoPlus TP 220-Cu and Lewatit MonoPlus TP 220-CuEDDS, Dowex 4195-Cu and M 4195-CuEDDS for perchlorate removal from water.