Jozef Hodyl PhD Thesis - Theses - Flinders University

ions by Si-GPS-Trac, 43 is in most cases rapid, for example, Cd(II) occupies 99% ofthe available macrocyclic coordination sites after 15 minutes. This translates to 0.31mmol Cd(II) ions per gram of the silica immobilised macrocycles which, itself has ameasured loading of 0.31 mmol of macrocycle moieties per gram of the silicaimmobilised material, Table 4.2. Loading of the metal(II) ions with Si-GPS-Trac,43, after 15 and 30 minutes of the uptake time are shown in Table 5.1.Table 5.1Percent uptake and loading capacity of Cd(II), Pb(II), Zn(II), Cu(II) and Ca(II) ionswith Si-GPS-Trac, 43, at t = 15 min. and t = 30 min.15 min. 30 min.% Uptake a mmol g -1b % Uptake a mmol g -1bCd(II) 99 0.31 101 0.32Pb(II) 91 0.29 101 0.32Zn(II) 83 0.26 91 0.29Cu(II) 84 0.26 101 0.32Ca(II) 0 0.00 60 0.19a Error = ±3% b Error = ±10%It can be seen from the above table that within 30 minutes the uptake of Cd(II),Pb(II) (eight coordinate) and Cu(II) (five or six coordinate) with Si-GPS-Trac, 43,has reached maximum capacity. However, Zn(II) (five or six coordinate) takes anhour to attain maximum capacity whereas Ca(II) (eight coordinate) coordinatespoorly after 15 minutes and takes three hours to reach full capacity.5.1.2 Metal uptake studies with other related silica based materialsAfter establishing that the time needed to ensure full loading capacity with metal(II)ions it was of interest to ascertain whether precursor materials or residual silanolgroups on the silica surface were also involved with metal complexation and shouldbe taken into account. Therefore, dried silica gel, SiO 2 ; silica gel modified with GPS90