Poly(methacrylic acid)-branched rice husk is prepared
by grafting copolymerization using Fenton’s reagent as a
redox initiator. The grafting percentage declines slightly
as the hydrogen peroxide concentration increases and
increases markedly as MAA monomer is added. Carboxylic
groups grafted to the surface of the rice husk can readily
be adopted to adsorb paraquat ions from aqueous
solution. The rapid uptake and high adsorption capacity
make the PMAA-modified rice husk a very promising
alternative adsorbent of paraquat. The Langmuir isotherm
is more accurate than the Freundlich isotherm. The monolayer
adsorption capacity is 317.7 mg/g-adsorbent, and
exceeds that of currently used absorbents of paraquat.