Semi-quantitative extraction and separation of palladium (II) by the “poly-dibenzo-18-crown ether” polymer. Crown-6

Abstract

This study included the extraction and separation of palladium(II) from its aqueous solutions, by
using swelled polymer crown ether (PDB18C6), and included the following:
After studying the factors that affect the extraction process for palladium ion in order to
find the ideal conditions, it was found that; the palladium ion (II) is extracted when (pH=7), and the
extraction percentage reaches its highest value (E%=91). It was noticed that, the extraction of
palladium ion was impossible from high concentration [0.5M-3.0M] of the acidic medium (HCl ,
H2SO4 , HNO3), but gave extraction percentage (E%=63-64) at the concentration [0.01M] of the
same acid. The percentage extraction of palladium from the alkaline medium (KOH , NaOH) was
very low at [1.0M-3.0M], and it became (E%=51-48) at the concentration [0.01M]. It was found
from experiments that the best shaking time was (60) minutes. It was also found that when adding
ethanol, the best extraction percentage for palladium II was (E%=92), when the volume of ethanol
(20±1Co )in the aqueous phase was (40%V/V) at a temperature The extraction of palladium from natural medium salts (KCl , NaCl) and medium salt (NH4Cl)
has reached highest (E%-69), (E%=80), at the (1.5M) concentration of both NaCl and KCl,
respectively, and (E%=80) at the (0.01M) concentration of NH4Cl. The selectivity of saturated solid
crown ether polymer towards the extraction of palladium(II) ion, in the present of positive ions
(Li+ ,Na+ ,K+ ,Rb+ ,Ba+2 ,Sr+2 ,Ca +2 ,Cd+2 ,Ni+2 ,Mg+2 ) and presence negative ions
(F− ,Br− ,Cl− ,I− ) , was also studied.
The effect of temperature and thermodynamics functions on the process of extraction of
palladium(II) ions was studied, and it appeared that the extraction enthalpy ΔHex , has a positive
value, which means that the extraction process is endothermic. The free energy for extraction
ΔGex showed a negative value while its entropy ΔSex showed a positive value at all temperature
degrees, which means that the reaction is instantaneous.