Adsorption experiments were conducted in duplicate
and the relative standard deviation was under 2.5%. The
adsorption solution comprised 0.2 g of adsorbent (RH-gPMANa),
sieved from 0.625 to 2.54 mm in 1000 ml paraquat
aqueous solution at an agitation rate of 600 rpm for
2 h at 37.5 C, except when otherwise stated. Samples
(0.2 ml) were removed using a micropipette at various
times. The collected samples were then added to sodium
dithionite/saturated ammonium chloride solution and analyzed
using a spectrophotometer.