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Abstract
The adsorption of herbicide paraquat (as model adsorbate) in aqueous solution onto
regenerated clay mineral from bleaching earth waste has been studied in a batch reaction
system. The adsorption rate has been investigated under the controlled process parameters
including initial pH, salinity and temperature. Based on the high affinity between
cationic paraquat and clay mineral, a pseudo-second order model has been developed
using experimental data to predict the rate constant of adsorption, and equilibrium
adsorption capacity. The results showed that the adsorption process could be satisfactorily
described with the reaction model and were reasonably explained by assuming a competitive
adsorption mechanism in the ion exchange process. Further, the fitted adsorption capacity
at equilibrium decreased with increasing temperature. It implied that the strong interaction
might play an important role in the paraquat-clay system. Overall, the results from
this study demonstrated that the clay resource regenerated from bleaching earth waste
could be used as a low-cost mineral adsorbent for the removal of environmental cationic
organic pollutants from the aqueous solution.