| This study investigated the adsorption characteristics of the MWNTs & MWNTs/TiO2 on TCB removal from water. And we discussed the effect of diameter of carbon nanotube, pH, metal ions, non-ionic surfactant on the adsorption of MWNTs, in addition the kinetic and thermodynamic properties of the TCB adsorbed on MWNTs & MWNTs/TiO2 and the regeneration of two adsorbents were also investigated.Using the batch experiments, this study investigated the effect of MWNTs & MWNTs/TiO2's adsorption on TCB under different conditions. The results showed: The diameter of MWNTs had great influence on the adsorption, when the diameter decreased,the surface curvature and surface area would increase, and the adsorption would be stronger. The variation of pH had little influence on the TCB adsorption on the MWNTs & MWNTs/TiO2. The metal ions in solution (Cu2+, Fe2+) had little effect on the dynamic process adsorption to the MWNTs. However, the surfactants in solution had a great effect on the adsorption process. When the surfactant concentration was 0.04g/L, Brij35 had the greatest influence on the adsorption, the adsorption capacity was only 57.3% of which without surfactant under the same conditions. Adding DBS and SDS, the adsorption capacities were 90.5% and 84.7% of which without surfactant respectively. The greater surfactant concentration in solution would increase adsorption resistance. With the surfactant concentration increased, the molecules covered on the external surface of MWNTs hindered the adsorption for the TCB on MWNTs. Compared by kinetic experiments, when the SDS concentration in solution was 0.2g/L, the adsorption rate constant reduced to 0.00597g/(mg·min) in the adsorption for the 1,2,3-TCB on MWNTs, it was 71.4% of which without adding SDS under the same experimental conditions.Kinetic studies demonstrated that the adsorption equilibrium curves of the TCB on MWNTs were consistent with ones on MWNTs/TiO2. The adsorption was fast in the first 30min, and then slowed down, after 80min it reached equilibrium. The adsorption of the two adsorbents conformed to pseudo-second-order kinetics. The adsorption rate constants were 0.00836g/(mg·min) and 0.04159g/(mg·min) respectively.The adsorption isotherm on MWNTs could be well described using Freundlich isotherm, and the adsorption isotherm on MWNTs/TiO2 could use either Freundlich isotherm or Langmuir isotherm, which indicated that compared with MWNTs, the adsorption characteristics had been altered after adding TiO2. The thermodynamic parameters, such as equilibrium constant(K0), standard free energy changes(ΔG0), standard enthalpy change(ΔH0)and standard entropy change(ΔS0), showed that the adsorption of the TCB on the MWNT was spontaneous and endothermic.MWNTs can be reused by thermal regeneration. The rate of absorption ability reached as high as 97.65% of the raw MWNTs after the first regeneration; the rate decreased slightly to 96.29% after the second regeneration, which explained that the reuse of MWNTs was promising. It took 60min to well regenerate the MWNTs/TiO2 via photocatalytic regeneration. The absorption ability reached 94.3% after the first regeneration; the efficiency was essentially the same as the former after the second regeneration, which was 94.2%. MWNTs/TiO2 can be employed in in-situ remediation of contaminated water, so it has a great potential in the future.There were a lot of defects on the surface of MWNTs treated by nitric acid oxidation, so the surface had some surplus areas withπelectron. The benzene-ring between the TCB molecules can be considered as a six-ring with single bond and double bonds alternation, so that is 6πelectrons. The influence of the strong interaction between MWNTs and the TCB was mainly onπ-πinteraction between the benzene ring and MWNTs. In addition, hydrophobic interactions between the MWNTs and the TCB also affect the adsorption. Thus, this study usedπ-πinteraction and hydrophobic interactions to explain the strong interaction between organic chemicals and CNTs.
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