Sorption of transient metal ions into clinoptilolite from waste water and recycling the used zeolite into a composite fertilizer

摘要

The natural clinoptilolite of Marsid (Romania) is suitable for the treatment of certain waste waters to retain some metal cations. For the improvement of ion exchange capacity, the chemical activation by various methods was studied. The ion exchange process equilibrium for a series of cations in the clinoptilolite was studied. The exchange isotherm shape, as well as the value of the standard free enthalpy which characterizes the exchange with NH_4~+ ion, indicated the clinoptilolite hgih affinity for this ion. For the exchange processes where Cu~(2+) and Zn~(2+) ions were involved, isotherms of the same type were obtained, which indicated the impossibility of reaching the exchange maximum degree because of the "ionic sieve" effect. The clinoptilolite low affinity towards Mn~(2+) ion was explained by the high hydration capacity of Mn~(2+), owing to the fact that "d" orbitals on level 3 are semioccupied with electrons.