Sorption Properties Of The Activated Carbon-zeolite Composite Prepared From Coal Fly Ash For Ni~(2+), Cu~(2+), Cd~(2+) And Pb~(2+)

摘要

Composite materials of activated carbon and zeolite have been prepared successfully by activating coal fly ash (CFA) by fusion with NaOH at 750 C in N_2 followed by hydrothermal treatments under various conditions. Uptake experiments for Ni~(2+), Cu~(2+), Cd~(2+) and Pb~(2+) were performed with the materials thus obtained from CFA. Of the various composite materials, that were obtained by hydrothermal treatment with NaOH solution (ca. 4M)at 80℃ (a composite of activated carbon and zeolite X/faujasite) proved to be the most suitable for the uptake of toxic metal ions. The relative selectivity of the present sorbents for the various ions was Pb~(2+) > Cu(2+) > Cd(2+) >Ni(2+), with equilibrium uptake capacities of 2.65, 1.72, 1.44 and 1.20 mmol/g, respectively. The sorption isotherm was a good fit to the Langmuir isotherm and the sorption is thought to progress mainly by ion exchange with Na~+. The overall reaction is pseudo-second order with rate constants of 0.14, 0.17,0.21 and 0.20 Lg/mmol min for the uptake of Pb~(2+), Cu~(2+), Cd~(2+) and Ni~(2+), respectively.