Separation of chosen heavy metals from multi-component mixtures and galvanic wastewater in adsorption on unmodified and modified magnetite

Adsorption is often proposed for the separation of heavy metals from aqueous solutions. The composition of the solution and the presence of the competing ions can strongly affect the process efficiency. To improve the effectiveness of adsorbents, various modifications are applied, including the functionalization of adsorbents with appropriate chemical compounds. This work aimed to investigate and compare two nanoadsorbents – unmodified magnetite and magnetite modified with poly(sodium acrylate) (PSA) – in the separation of heavy metal ions from multi-component mixtures and galvanic wastewater. The effect of the type and dose of adsorbent on the separation efficiency of heavy metals from two multi-component mixtures containing Cu(II), Zn(II), Cd(II), Ni(II), Pb(II), Cr(III), and Cr(VI) were investigated. The process effectiveness depends on the type and the dose of the adsorbent and the type of metal ion, and was higher using the PSA-modified magnetite, especially towards Zn(II), Ni(II) and Cd(II) ions. With the adsorbent to metals mass ratio m_NPs/m_Ms = 50, magnetite modified with poly(sodium acrylate) enabled the separation of 93.2%–94.7% of the total amount of metals, while for non-modified magnetite these values were 55.7%–59.9%. In addition, both adsorbents were used to remove heavy metal ions from five types of galvanic wastewater, containing Cu(II), Zn(II), Ni(II), Cr(VI) and a mixture of Zn(II) and Cr(III), respectively. PSA-modified adsorbent was especially effective towards Cu(II) and Cr(III) (over 90% removal) and Ni(II) and Zn(II) (approx. 70% separation). Separation of Cr(III) ions occurred with good efficiency (about 98%) on both types of magnetite.