Novel iminepyridinium -modified silicas as super-adsorbents for metals ions

Abstract

For effective removal of toxic metals from waste water, novel bifunctional iminepyridinium- silicas were fabricated and studied in detail to show their high applicability as adsorbents of Pb(II), Cd(II) and Cu(II). The novel adsorbents were synthesized using two-stage procedure to incorporate sillylpropylpyridinium moieties: co-condensation to obtain chloro- and bromopropyl-functionalised silicas, and next quaternisation with N-decyloxy-1-(pyridin-4-yl)ethaneimine and N-decyloxypyridine-4-carboximidamide (MCl-D4EI, MBr-D4EI, and MCl-D4IA, MBr-D4IA, respectively). The fabricated materials were characterized by Raman, SEM, XPS, zeta potential and IGC techniques. Various batch adsorption parameters were investigated to demonstrate high potential of the novel sorbents. The optimum pH for adsorption of Pb(II), Cd(II) and Cu(II) from aqueous solutions was found to be 4–6 and the maximum loading was obtained after a contact time of 15 min. The process took place on the surface through chemisorption, in which imine and amine groups lead to the strong binding of the metals ions. The spherical MBr-D4IA was found to be the most efficient sorbent of Pb(II) and Cd(II) with the adsorption capacity of 339 mg/g and 173 mg/g, respectively, while Cu(II) was co-extracted from the synthetic waste solution in 79%. Moreover, MBr-D4IA displayed extraordinary tolerance to the presence of coexisting ions, good reusability and stability.