Polypyrrole coated molybdenum disulfide composites as adsorbent for enhanced removal of Cr(VI) in aqueous solutions by adsorption combined with reduction

By L. Xiang, C. Niu, Ning Tang, Xiao-Xiao Lv, Hai Guo, Zhong-Wu Li, Hui-Yun Liu, Li-Shen Lin, Ya-Ya Yang, Chao Liang. 2020

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Abstract In this study, polypyrrole coated molybdenum disulfide organic–inorganic composites (PPy/MoS2) were fabricated by a simple in-situ oxidative polymerization, and used as a novel adsorbent for removal Cr(VI). The sorption of Cr(VI) was consumingly pH-reliant behavior, which the optimal elimination efficiency was attained at pH 2. Meanwhile, the adsorption of Cr(VI) on PPy and PPy/MoS2 followed the pseudo-second-order kinetic model and Langmuir isotherm model. Compared with PPy, PPy/MoS2 exhibited better elimination ability for Cr(VI) because of its well-dispersion and massive surface active sites. The maximum sorption capacity of Cr(VI) by PPy/MoS2 reached 257.73 mg/g at 298 K, which was obviously higher than that of Cr(VI) by PPy (151.29 mg/g). The thermodynamic parameters demonstrated that the sorption process was endothermic and spontaneous. The coexisting ions like K+, Na+, Ca2+, Mg2+, NO3–, Cl- and SO42- had no significant influence for Cr(VI) elimination, whereas H2PO4- was main competitors. Mechanism investigation indicated that the ion exchange, electrostatic interactions, chemical reduction (Cr(VI) to Cr(III)) and surface chelation played a crucial role in the elimination of Cr(VI). In addition, the PPy/MoS2 composites could be employed for three continuous cycles without significantly reducing the sorption capacity of Cr(VI). This work demonstrated that PPy/MoS2 composites were a promising sorbent for efficient treatment Cr(VI) in polluted water.

Subfields: Inorganic Chemistry, Materials Chemistry, Water Science and Technology

View Paper: https://www.semanticscholar.org/paper/8b2a5911d9ea7c150b726bcf62cce9564aafb209