An efficient modified zeolite for simultaneous removal of Pb(II) and Hg(II) from aqueous solution

An Iranian natural clinoptilolite was mechanically prepared to prepare micronized (MC) and nanoparticles (NC). MC and NC particles were modified by Hexadecyltrimethylammonium bromide (HDTMABr) and the obtained surfactant modified zeolites (MSMZ and NSMZ), as good anion or organic compounds adsorbents, were then modified by Dithizone (MSMZ-DT, and NSMZ-DT). Samples were characterized by XRD, FTIR, SEM-EDAX, BET and TG. The raw and modified samples were used for simultaneous removal of Hg(II)and Pb(II) from aqueous solution. The modified samples, especially nanoparticles one; NSMZ-DT, significantly removed Hg(II) and Pb(II) with respect to the corresponding raw samples, because in the modified samples both ion-exchange and complexation processes are responsible for removing of cations. Adsorption isotherms well fitted to Langmuir equation, that indicates monolayer sorption of Hg(II)/Pb(II) while the adsorption kinetic obeyed the pseudo-second-order rate equation indicates that a chemical reaction is responsible for the rate limiting step. The process is exothermic and spontaneous based on negative ∆ H and ∆ G values.