Separation of cadmium and copper from phosphorous rich synthetic waters by micellar-enhanced ultrafiltration
2011
Landaburu-Aguirre, Junkal | Pongrácz, Éva | Keiski, Riitta L.
In this study, micellar-enhanced ultrafiltration (MEUF) was proved to be a viable technique for the purification of phosphorous rich waters. The experiments were conducted in order to study the simultaneous removal of heavy metals from phosphorous rich synthetic waters by evaluating the effect of pH (3.5–5) and the feed concentrations of sodium dodecyl sulphate (CSDS, 3.5–20mM), phosphorous (CPₕₒₛₚₕ., 0–1.3g/dm³), zinc (CZₙ, 0.8–2mg/dm³) and nickel (CZₙ, 2–4mg/dm³) on the rejection coefficients of cadmium and copper. Zinc and nickel feed concentrations had no statistically significant effect and the metal competition was negligible. pH, SDS and phosphorous feed concentration did show a significant effect on the MEUF process. Rejection coefficients up to 98% were achieved for both metals when no phosphorous was present and at SDS feed concentration of 20mM. The phosphorous feed concentration showed a bigger negative effect on the rejection coefficient of copper at higher pH levels due to complex formation. At low pH values and in the presence of phosphorous the heavy metals were present as divalent cations and no complex formation was observed. In these conditions, copper rejection coefficients were very similar to cadmium, achieving up to 80% removal of heavy metals. At higher pH levels the presence of Cu₃(PO₄)₂ was more substantial and the rejection coefficients of copper decreased to 65%. The research presented in this manuscript could lead to novel uses of MEUF for the purification of nutrients from wastewater streams prior to their recovery, closing phosphorous cycles in anthropogenic systems.
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