Mingming Chen,Qinghua Gu,Huiping Shao,Haihong Liu,Jingde Luan,Zheng Yan,Wengang Liu,Xin Ke
In this study, the PPY/CMC aerogels showed rapid removal of norfloxacin (NOR) within 2 h with a maximum adsorption capacity of 845.7 mg/g and excellent adsorption performance in the pH range of 3–10. The exhaustive Density Functional Theory (DFT) calculations revealed that π-π electron-donor–acceptor (EDA) interactions dominated at different pH. Humic acid (HA) mainly competed with NOR for the sites of π-π EDA interactions on the adsorbent, but only slightly inhibited NOR adsorption at high concentrations due to the weak competitiveness and compensation by NOR-bridging interactions. Background ions mainly competed with NOR for electrostatically interacting sites, but ions in the lower valence state were less competitive and preferentially occupied different adsorption sites, thus hardly affecting the adsorption of NOR. The higher valence state with higher concentration of ions had increased competing ability, and although the bridging interaction can compensate some adsorption sites, it still inhibited the adsorption of NOR. The PPY/CMC aerogels had fine affinity for multiple antibiotics, and the differences in adsorption capacity were determined by the charge and structural properties of the antibiotics themselves. Moreover, excellent recyclability of PPY/CMC aerogels was confirmed after five adsorption–desorption cycles as the diminished performance from 96.8% to 83.7%. These results will help us to understand the structure-performance relationship between contaminants and PPY/CMC aerogels, and prefigure the potential of PPY/CMC aerogels as a novel adsorbent for the removal of multiple antibiotics.
Mingming Chen,Zheng Yan,Jingde Luan,Xun Sun,Wengang Liu,Xin Ke
In this work, a hydrophilic polypyrrole carboxymethyl cellulose aerogel (PPY/CMC) with a 3D structure was prepared via in-situ polymerization of pyrrole monomers with carboxymethyl cellulose as the substrate. The adsorption experiments showed that tetracycline can be effectively removed in a wide range of pH (4–10), and the adsorption capacity was 689.39 mg/g when the pH value was 6. The pseudo-second-order kinetic and Langmuir models better fitted the kinetic and isotherm data, which revealed that the adsorption was homogeneous and dominated by chemisorption. The experiment of adsorption thermodynamics showed that the adsorption process was spontaneous and endothermic. Zeta potential, FT-IR and XPS results indicated that the adsorption mechanism included π-π EDA interaction, hydrogen bonding and electrostatic interaction. Through Density Functional Theory (DFT) and Frontier Orbital Theory (FOT) simulation, the microscopic adsorption mechanism was further explored on the molecular and electronic scales. It is confirmed that TC was adsorbed onto PPY/CMC aerogels mainly through π-π EDA interaction in sandwich (S) configuration and parallel-displaced (PD) configuration, thus ensuring high adsorption efficiency. Compared with various adsorbent materials reported recently, the PPY/CMC aerogels have the advantages of higher adsorption capacity, excellent pH buffering capacity, simple preparation process and quickly removal of pollutants.
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