Sorption kinetics of sulphate ions on quaternary ammonium-modified rice straw

Batch sorption experiments with variable concentration of sulphate and temperature were conducted to investigate sorption kinetics of sulphate ions on quaternary ammonium-modified rice straw (QMRS). Kinetic data were discussed with pseudo first- and second-order rate equations and diffusion models. The results showed the sorption equilibrium time is about 20 min and the activated energy Ea is 19.3 kJ/mol. Increase of temperature and initial sulphate concentration favored sorption process. The sorption kinetics followed pseudo second-order rate equation, and the overall rate was determined by film diffusion. Additionally, characterization by 13C NMR and EDS confirmed the presence of quaternary ammonium groups in QMRS.