Investigation of zinc binding properties onto natural and synthetic zeolites: Implications for soil remediation

Although the potential of natural zeolites for water and soil remediation has been widely studied, the use of synthetic zeolites, especially from by-product/waste materials, is still rather scarce. Therefore, we present a complex study investigating the adsorption mechanisms of Zn(II) on natural (ZC), synthetic (13X), and perlite by-product (ZP) zeolites under different conditions including laboratory solutions, extracted soil solutions and real metal-rich soils. Adsorption mechanisms in laboratory solutions were studied by a combination of adsorption modeling, including a non-electrostatic modeling with two surface sites corresponding to cation exchange and surface complexation (NEM-CE/SC); desorption experiments and comprehensive solid-state analyses. Based on the obtained results, the adsorbed amount and strength of binding decreased in the order of synthetic > perlite by-product > natural zeolite. In the case of natural zeolite, the prevailing effect of CE is expected. Contrarily, the influence of both CE and SC is expected for synthetic zeolites. The experiments in soil solutions showed sufficient sorption efficiency and chemical stability of all materials with a slight pH increase after the application of both synthetic zeolites. Soil incubation experiments showed reversible binding of Zn on natural zeolite and a significant influence of irreversible binding on both synthetic zeolites. Based on the obtained results, zeolites prepared from a perlite by-product material are promising soil amendments. However, their application to real soils needs to be thoroughly evaluated according to specific properties of the given soil due to a potential pH increase and elevated salinity levels caused by leaching of exchangeable cations.