Limnetica 34
Single-ion interferences when using magnetic microparticles for phosphorus removal in aquatic ecosystems
The specific adsorption of phosphate (P) on strongly magnetisable carbonyl iron (Fe) particles and their subsequent removal by in-flow High Gradient Magnetic Separation (HGMS) is considered a promising tool for restoring eutrophied waters. A previous study showed the existence of chemical interferences in natural waters without considering the influence of specific major ions on the P removal efficiency (de Vicente et al., 2011). Therefore, in this manuscript, we assess the single-effect of some of the major ions present in natural waters, including sulphate (SO42-), calcium (Ca2+), humic acid (HA, as an indicator of Dissolved Organic Carbon, DOC), and reactive silicate (Si), on P adsorption to magnetic Fe particles in artificial lake water. The results showed that HA and Si significantly decreased the effectiveness of P adsorption by magnetic Fe particles. In particular, P removal efficiency decreased to 12 % and 22 % when HA and Si concentrations were 35.5 mg HA L-1 and 10 mg Si L-1, respectively. By contrast, SO42- and Ca2+ did not significantly reduce P removal. We recommend chemically analysing the lake water and determining the Fe dosage that obtains the highest P removal before using magnetic particles for the restoration of aquatic ecosystems in a whole-lake application.
