Study On The Preparation Of Modified Multi-walled Carbon Nanotubes And The Treatment Of Sulfamethoxazole By The Adsorption

In recent years, the abuse of antibiotics leads to excessive residues amount in the environment, which results in the resistance increase of microorganisms. Finally, it may cause great problems in the prevention and treatment of diseases. Adsorption method which has many advantages, such as simple operation, low energy and raw material consumption, high removal rate and less further pollution, is widely explored in removal of antibiotics in the water. However, the recovery efficiency of traditional adsorbent is low, which increase the running cost of the treatment. Therefore, it is necessary to find a kind of adsorbent which has high adsorption efficiency and high regeneration ability.Due to the small particle size of multi-walled carbon nanotubes(MWCNTs), it has low recovery rate and easy to cause further pollution after the application of the adsorption to remove pollutants. In this study, chemical co-precipitation method was used to modify the multi-walled carbon nanotubes. We explored adsorption kinetics and adsorption isotherm experiments of three kinds of adsorbents(activated carbon(AC), biochar(BC), multi-walled carbon nanotubes(MWCNTs)) on sulfamethoxazole(SMX), and explored the different adsorption properties of adsorbent. As one adsorbents, modified multi- walled carbon nanotubes adsorbed SMX in water were carried out. We investigated the effect of solution pH and ionic strength on the adsorption, and recycling effects of modified MWCNTs were determined. The results for the application of modified multi-walled carbon nanotubes provided theoretical basis to remove antibiotics from water. Major results are listed as follows:(1) By means of Fourier transform infrared spectroscopy(FT-IR), compared the modified MWCNTs with raw MWCNTs, there is a new peak in the ~590 cm-1 which is the peak of Fe-O. And that indicates that the magnetic particles have successfully loaded onto MWCNTs. By scanning electron microscopy(SEM) characterization, it indicated that there are a lot of nano-particles on the MWCNTs. Then through the determination of EDS, the results confirm that Ag was successfully loaded onto the multi-walled carbon nanotubes. Using the vibrating sample magnetometer(VSM) detection of the modified multi walled carbon nanotubes, the hysteresis curve shape and trend show that FMWCNTs and 1% Ag-FMWCNTs is super paramagnetic, and the saturation magnetization(MS) value are 43.40 emu g-1 and 39.93 emu g-1, respectively, which show that they have a strong magnetic.(2) The results showed that the adsorption kinetic data of the three adsorbents(AC、BC and MWCNTs) fitted the pseudo-second-order kinetics equation well. The adsorption equilibrium time of MWCNTs was 4 h which was shorter than BC and AC(48 h). The adsorption isotherm data of three kinds of adsorbent could be better fitted with the Freundlich and Langmuir. And the order of the maximum adsorption capacity obtained from the Langmuir was AC(126.149 mg g-1) > MWCNTs(73.691 mg g-1) > BC(41.211 mg g-1). MWCNTs showed a faster adsorption rate and adsorption capacity, so the use of MWCNTs as an adsorbent for the removal of SMX is a good choice.(3) The results showed that the adsorption kinetics of the modified adsorbents was in accordance with the pseudo-second-order kinetic equation, and the intra-particle diffusion was not the only rate-limit step. Adsorption isotherms were fitted to Freundlich and Langmuir equation. Comparison of Langmuir maximum adsorption capacity that adsorption capacity declined after magnetic modification, but promoted after modified silver. And the promoting effect increased with the increasing proportion of modified silver. The optimal pH value was 4, and the adsorption efficiency of SMX was better when p H in 2~6. However, when the values of pH are more than 6(p H > 6), the adsorption capacity decreased rapidly. The ionic strength had a certain inhibitory effect on the adsorption. The inhibitory effect is enhanced with the increase of ionic strength. Modified multi-walled carbon nanotubes had better effect of recycling. The recycling rate of the sorbent dosage and adsorption effect of regeneration after regenerating three times could reach more than 90% and 80%, respectively.