Synthesis and characterization of LIX-84 noncovalently bound silica sorbents for metal-ion recovery

Mesoporous silica particles were modified with LIX-84 (2-hydroxy-5-nonylacetophenome oxime). LIX-84 was attached to the surface of silica via noncovalent forces. The effects of silica particle size, pore size, temperature, and pH on metal-ion-exchange properties were studied to characterize metal ion adsorption properties for chelating groups noncovalently bound to the surface of silica. The adsorbent had a capacity of 0.6 mmol of Cu²⁺/g of adsorbent at room temperature and a capacity of 1.1 mmol of Cu²⁺/g of adsorbent at 60 °C. Depending on the solution pH, the adsorbent had varying capacity for Cu²⁺, Ni²⁺, and Pb²⁺. The adsorbent was found to have good stability and gave high metal recovery when regenerated with 2 vol % nitric acid. An increased ion-exchange rate was achieved and was attributed to the use of larger pore size silica. The silica was found to contain from 5 to 7 wt % LIX-84.