The polymer-surfactant aggregate process has been developed to remove metallic ions from aqueous solutions for which the ions are typically at the mg/l (parts per million) concentration level. In some cases, such as extremely valuable or highly toxic metals, the concentration of metals may exist at the μg/l (parts per billion) level. It is, nevertheless, essential to be able to apply such a process to treat them cost-effectively. In this paper, cadmium ions are removed from a 560 ppb aqueous solution down to a concentration of 17 ppb using 2 ppm polyethylenimine (PEI) and 0.02 mM sodium dodecyl sulphate (SDS). At such a low optimum dosage of polymer and surfactant (the removal agent), the loading percentage on the removal agent increases with the concentration of Cd(II) to as high as 39%. However, at this low optimum dosage of the removal agent, the removal efficiency of Cd(II) and the usage efficiency of the removal agent both have a lower tolerance toward salinity effects. This contrasts with the higher salinity tolerance corresponding to the higher optimum dosages commensurate with higher metallic ion concentrations
