4.7 Article

Efficient removal of Cr(VI) from aqueous solutions by polypyrrole/natural pyrite composites

Journal

JOURNAL OF MOLECULAR LIQUIDS
Volume 365, Issue -, Pages -

Publisher

ELSEVIER
DOI: 10.1016/j.molliq.2022.120041

Keywords

Hexavalent chromium; Polypyrrole; Natural pyrite; Adsorption and reduction; Mechanism

Funding

  1. National Natural Science Foundation of China [51708561]
  2. Fundamental Research Funds for the Central Universities, South-Central Minzu University [CPT22028]
  3. Major Innovation Projects of Hubei Province of China [2019ACA156]

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In this study, a novel composite of PPy/NP was synthesized and applied for the efficient removal of hexavalent chromium from aqueous solutions. The results showed that the PPy/NP composites exhibited better Cr(VI) removal performance than PPy alone, and could be used as recyclable absorbents for multiple cycles.
Easily agglomeration of polypyrrole (PPy) significantly limits its practical applications. In this study, nat-ural pyrite (NP) was applied to disperse PPy and overcome this agglomeration; a novel composite of PPy/ NP was synthesized and applied for the efficient removal of hexavalent chromium [Cr(VI)] from aqueous solutions. Results showed that the PPy/NP composites exhibited better Cr(VI) removal performance than PPy alone. This enhanced removal capacity is attributed to the addition of NP, which prevents PPy agglomeration and reduces Cr(VI) to trivalent chromium[Cr(III)]; Cr(VI) removal was significantly dependent on the solution's pH. The sorption kinetics of Cr(VI) with PPy/NP was described by the pseudo-second-order model and Elovich models, which highlight the chemicalsorption process. The sorp-tion isotherm was well simulated by Langmuir model and the maximum adsorption capacity of Cr(VI) on PPy/NP was 261.78-395.26 mg/g at 303 - 323 K, which is significantly higher than that of PPy alone (124. 84-194.17 mg/g). Thermodynamic analyses confirmed that this adsorption process was spontaneous and endothermic. PPy/NP composites could be used as a recyclable absorbents for four Cr(VI) reduction cycles without any evident loss in adsorption performance. The mechanism Cr(VI) removal by PPy/NP compos-ites is attributed to ion exchange (9.47 %), adsorption (31.03 %), and reduction (59.50 %).(c) 2022 Elsevier B.V. All rights reserved.

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