AR (apple residue) was used as an alternative and cheap material for bindin
g metal ions due to the presence of carboxyl and phenolic functional groups
. The binding capacity of copper, lead, and cadmium by AR was pH dependent.
Carboxyl groups of AR were esterified by acidic methanol to determine the
contribution of carboxyl groups to metal ions binding. The extent of esteri
fication was determined by analyzing the amount of methanol released in the
sample hydrolysates by gas chromatography. The effect of esterification on
binding metal ions was investigated in batch experiments by unmodified and
modified AR. All esterified AR showed significant decreases in binding cop
per, lead and cadmium. The loss in the capacity of metal ion binding was pr
oportional to the extent of esterification. The capacity of metal binding d
ecreased with increase in the concentration of methanol in the respective h
ydrolysates or the modified AR. The data indicate that carboxyl groups on A
R play an important role in the metal ion binding.