The amino polymer was treated with 2 M HCl, the excess
of HCl was removed by water washing, and suspended in
350 ml of ice-water, and the reaction mixture was treated
with 1 ml portions of 1 M HCl–1 M NaNO2 until a durable
blue color formed on the starch iodide paper. The polymer
was thus converted to the diazonium salt, washed with
cold water, and treated with a solution containing 1 g of
o-aminobenzoic acid in 200 ml water and 100 ml of glacial
acetic acid at 0–3 ◦C, and the final mixture was kept at this
temperature for 24 h until the reaction was complete. The
dark brown grains were filtered off and washed as suggested
by Tewari and Singh [9].
The reaction sequence for various stages of the preparation
of the Amberlite XAD-4 resin functionalized with
o-aminobenzoic acid is shown in Fig. 1.