Pb(II) Uptake by Alginate Beads Containing Saccharomyces Cerevisiae, Activated Nanocarbon, and Their Combination: Single-Replicate Screen

Calcium alginate beads loaded with heat-inactivated Saccharomyces cerevisiae or activated nanocarbon (multi-walled carbon nanotubes) were compared for Pb(II) removal. The objective was to test whether these two sorbents, which bind metals by different routes, give different uptake when prepared and tested in the same way. The novelty lies in this side-by-side comparison within one matrix, evaluated against propagated analytical uncertainty and a mass balance of the bead solids. Beads were made at two sorbent loadings (0.6 and 0.8 g per 4.0 g of alginate), and 1.0 g of wet beads was contacted with 500 mL of Pb(II) solution at 58–496 mg/L for 60 min. Concentrations were measured by atomic absorption spectroscopy, and each condition was run once. Beads carrying both sorbents were also tested at three ratios as an exploratory observation. Removal ranged from 3 to 35%, with an analytical uncertainty of 2–3 percentage points. At 58 mg/L the 0.8 g yeast beads removed 34.6 ± 2.1%, more than any other bead type, whereas at 323 mg/L the four bead types could not be distinguished. Nonlinear fitting gave similar errors for pseudo-first-order and pseudo-second-order kinetics and for the Langmuir and Freundlich isotherms, so neither a rate-controlling step nor an isotherm model could be identified. A mass balance showed that alginate makes up 83–87% of the bead solids and accounts for most of the uptake. The apparent capacity of 45.8 mg/g for the 0.8 g nanocarbon beads at 496 mg/L exceeds what these solids can bind and is not considered reliable.