Removal of Cu(II) and a PET Glitter Microplastic Surrogate by Alginate, Alginate–Opuntia, and Chitosan-Treated Alginate–Opuntia Beads

The use of alginate-only beads, alginate–Opuntia (AO) beads, and chitosan-treated AO beads for the removal of Cu(II) and a PET glitter (a microplastic surrogate) from water has been investigated. Each bead type was made from the previous one by the addition of one component. Batch experiments were carried out in water containing glitter, Cu(II), or both, and AO beads soaked in dilute acetic acid without chitosan served as a control for the acid. The removal of Cu(II) in copper-only water was 45.71 ± 1.97%, 59.44 ± 2.28%, and 84.19 ± 2.65% for the alginate-only, AO, and chitosan-treated beads, respectively (mean ± SD, n = 12, 6 h, 140 rpm). Opuntia increased the Cu(II) removal by 13.72 percentage points and chitosan by a further 24.75 points (paired t-test, p < 0.001 for both, and p ≤ 0.0013 for the batch means). In the presence of 2.00 g of glitter, the chitosan-treated beads still removed about 84% of the Cu(II). Meanwhile, the glitter removal increased by about 7 points with Opuntia but changed by less than 0.25 points with chitosan (p = 0.648 and 0.231). No significant difference was found between the acid-soaked and the untreated AO beads. It can be concluded that Opuntia was responsible for the increase in glitter capture and chitosan for most of the increase in Cu(II) removal.