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La-modified vermiculites for efficient adsorption of Congo red

Huang, W-Y, Yu, C. and Li, D. (2017) La-modified vermiculites for efficient adsorption of Congo red. Asia-Pacific Journal of Chemical Engineering, 12 (6). pp. 969-979.

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In this study, we utilized lanthanum to modify vermiculite (RV) targeting at high dye removal and superior reusability. La-modified RV materials were synthesized; followed by detailed characterizations and adsorption studies. Compared with the BET surface area (SBET) of RV (2.98 m2·g−1), those of La-modified RV samples were increased by up to 8 times. Their adsorption performances were investigated by employing Congo red (CR) as the target pollutant in aqueous solution. An increasing loading of La in RV led to enhanced CR removal capacity. The experimental equilibrium data of the La-modified RV were fitted better by using the Freundlich model than the Langmuir model. At the same initial concentration of 100 mg·L−1, the equilibrium capacity of CR was 32.3–80.5 mg·g−1 using the La-modified RV adsorbents, which was 2.5–7.8 times greater than that using RV (9.1 mg·g−1). Meanwhile, the adsorption kinetics was analysed by the pseudo-first-order, pseudo-second-order and intra-particle diffusion models; the kinetics followed the pseudo-second-order model best and the intra-particle diffusion was not the only rate limiting step during adsorption. Superior adsorption capacity of LaRV-0.2, which possessed 29.93 wt% La loading, was observed in the pH range of 3–9; especially the high removal rate (~94%) was observed when pH = 3. The removal rate was increased to ~96.8% in the presence of NaCl compared with 91.6% in the absence of NaCl. The as-synthesized adsorbent maintained a superior adsorption capacity after four adsorption–desorption cycles. The capacity of the regenerated adsorbent in the fourth adsorption–desorption cycle was only 4.2% lower than that of the fresh LaRV-0.2 sample, suggesting great potential in practical wastewater treatment.

Item Type: Journal Article
Murdoch Affiliation(s): School of Engineering and Information Technology
Publisher: Wiley-Blackwell
Copyright: © 2017 Curtin University and John Wiley & Sons, Ltd.
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