On copper removal from aquatic media using simultaneous and sequential iron-perlite composites

The use of reusable, affordable, and inert adsorbents as a means to mitigate copper pollution, with a lesser burden on the environment, has been attracting some attention. However, aiding the adsorption process of a promising adsorbent, such as expanded volcanic glass (perlite), with a reducing companion, such as solid iron, that can displace and dispose of copper from polluted water has never been tested before. In this laboratory study, we investigated the removal of Cu2+, resulting from contaminating freshwater with copper sulphate pentahydrate, using simultaneous or non-simultaneous (sequential) mixes of expanded perlite and iron coarse powder over 23 hours. The percentage of copper removed was calculated at 15 min, 40 min, 120 min, 300 min, and 1380 min using induced coupled plasma (ICP-OES). A rapid removal of 71% at 120 min was achieved when the perlite and iron were added simultaneously in separate permeable pouches; the application of the iron after the perlite led to 78% of removal at 1380 min that was almost identical to what was accrued via perlite alone (77%). This, therefore, suggests that the presence of iron is most advantageous in the short run as it leads to fast uptake of Cu2+, attributable to the combined action of the reduction of Cu2+ by iron and Cu2+ adsorption by perlite. Further investigation in support of the results was carried out using Energy-Dispersive X-Ray Spectroscopy (EDAX), X-Ray Diffraction (XRD), Brunauer, Emmett and Teller (BET), and Fourier-Transform Infrared Spectroscopy (FTIR). The findings of this multidisciplinary work provide insights and mechanisms for heavy metal removal from water in a relatively short time using a novel time-specific combination of iron and perlite and thus merit wider testing across different classes of adsorbents, pollutants, and water systems.