Full description of copper uptake by algal biomass combining an equilibrium NICA model with a kinetic intraparticle diffusion driving force approach

In this work kinetic and equilibrium studies related to copper binding to the protonated macroalga Sargassum muticum are reported. An intraparticle-diffusion linear driving force (LDF) model has been chosen for the quantitative description of the kinetics at several initial metal concentrations. Copper intraparticle homogeneous diffusion coefficient (Dh) obtained is in the range 0.2–0.9 × 10−10 m2 s−1. NICA isotherm is demonstrated to constitute a substantial improvement with respect to a simpler Langmuir competitive equation. The binding parameters were chosen to provide the best simultaneous description of the equilibrium experiments. Values of log K ∼ Cu (4.3), nCu (1) and p (0.31) in NICA isotherm, and log KCu (3.5–5) in Langmuir competitive model, have been obtained. These parameters have been also used to predict the competition between copper and cadmium for binding sites. Two acids, HNO3 and HCl, have been tested to evaluate their effectiveness to release copper from the metal-laden biomass.