Quan Chen,Peng Yi,Wei Dong,Yihui Chen,Liping He,Bo Pan
The discharge and consequent occurrence of antibiotics in the environment has led to increasing concerns because their presence can promote the development of resistance genes, which in turn pose a significant health risk. A key process to control the transport and risk of antibiotics is adsorption. Thus, we investigated the adsorption mechanisms of six typical antibiotics onto a MnFe 2 O 4 @cellulose activated carbon (CAC) hybrid combining batch adsorption experiments and quantum chemical calculations. In the single-adsorbate adsorption systems, the solid-phase concentrations of the adsorbates varied from 152.8 to 395.7 mg/g, which were dependent on the adsorption affinity and molecular structures or sizes of the antibiotics. Chemisorption was the main adsorption mechanism, and it was driven by p-d electronic conjugation and cation-π interactions. In the competitive adsorption systems, the solid-phase concentrations of both primary (sulfamethazine, SMT) and secondary (the other five antibiotics) adsorbates decreased significantly. The decrease ratio of SMT varied from 15.42% to 67.28% while that of the secondary adsorbates varied from 14.13% to 52.74%. The “competition” strength was depended on the adsorption energy and the overlapping of adsorption sites. We believe that these findings will provide a better understanding of the adsorption characteristics of typical antibiotics and facilitate the strategy developing for the removal of antibiotics from the aqueous phase.
Quan Chen,Zhenya Tang,Hao Li,Min Wu,Qing Zhao,Bo Pan
Heavy metal is a serious environmental issue mostly because of their toxicity and bioaccumulation. The recovering and recycling of the adsorbents became a bottleneck in heavy metal removal through adsorption. A hybrid adsorbent MnFe 2 O 4 @CAC showed great application potential because of its easy regeneration. However, as for other commonly used adsorbents, the removal performance of different types of heavy metals are distinctively different, but the mechanism is still unclear. To address this knowledge gap, the electron-scale behavior and adsorption mechanism of six divalent cations (Cu(II), Cd(II), Pb(II), Co(II), Ni(II), Hg(II)) on MnFe 2 O 4 @CAC were investigated in-depth combining experimental analysis and density functional theory (DFT) calculations. The experimental results showed the order of adsorption: Ni(II) > Cu(II) > Co(II) > Pb(II) > Cd(II) > Hg(II). The reaction from transition state to the final product was the rate-determining step for the Cu(II), Pb(II), Co(II) and Ni(II) adsorption, while the reaction from reactant to intermediate controlled the adsorption rate of Cd(II) and Hg(II). The main adsorption mechanisms were surface complexation and ionic exchange, which were further confirmed by the spectroscopic (Fourier Transform infrared spectroscopy, FT-IR and X-ray photoelectron spectroscopy, XPS) characterizations and DFT calculations. In addition, the electron density of state (DOS) results indicated the 4s orbit of the cations most easily to be occupied by the d electrons of MnFe 2 O 4 . The order of adsorption affinity agreed well with the apparent adsorption, and was decided by the electronic empty orbit and ionic electron cloud size of the cations. The results of the current study provide an in-depth understanding on the adsorption mechanism of heavy metals and offer a theoretical guidance for improving their removal efficiency.
危险品化学品经营许可证（带存储）