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Adsorption kinetics of herbicide paraquat in aqueous solution onto a low-cost adsorbent, swine-manure-derived biochar
Tsai, W.-T. & Chen, H.-R.
Abstract
Biochars have received increasing attention in
recent years because of their significant properties such
as carbon sequestration, soil fertility, and contaminant
immobilization. In this work, the adsorptive removal of
paraquat (1,1'-dimethyl-4,4'-dipyridinium chloride, one of
the most widely used herbicides) from aqueous solution
onto the swine-manure-derived biochar has been studied at
25°C in a batch adsorption system. The adsorption rate has
been investigated under the controlled process parameters
including initial pH (i.e., 4.5, 6.0, 7.5, and 9.0), paraquat
concentration (i.e., 0.5, 1.0, 2.0, 4.0, and 6.0 mg/L), and
biochar dosage (i.e., 0.10, 0.15, 0.20, 0.25, and 0.30 g/L).
Based on the adsorption affinity between cationic paraquat
and carbon-like adsorbent, a pseudo-second order model
has been developed using experimental data to predict the
adsorption kinetic constant 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 an adsorption
mechanism in the ion exchange process. Overall, the
results from this study demonstrated that the biomass-
derived char can be used as a low-cost adsorbent for the
removal of environmental cationic organic pollutants from
the water environment.
Keywords
Liquid-phase adsorption; Paraquat; Swine manure; Biochar; Kinetic modeling
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