In this study, carbon nanotube (CNT) purification results were compared between the conventional wet process using strong acids and the dry process using chlorine gas at high temperatures. To evaluate the effect of catalyst support in both methods, purification experiments were conducted using Tuball SWCNT from OCSiAl (without support) and CVD CNT synthesized with supported catalysts (Fe-Mo/MgO). Before and after treatment, the CNT samples were analyzed using scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA) to compare the morphology of CNT bundles, the distribution and content of impurities, and crystallinity. The results confirm that the dry process exhibited superior characteristics for both Tuball SWCNT and CVD CNT. In particular, changes in the IG/ID ratio observed in Raman spectroscopy and the reduction of residue in TGA clearly demonstrate high crystallinity and high-purity purification without damaging the CNTs. TGA reveals a reduction in ash content from 20.2 % to 3.2 % for Tuball SWCNT and from 63.1 % to 5.4 % for CVD CNT, while Raman spectroscopy confirms the preservation of the IG/ID ratio (~50) in Tuball SWCNT and its increase from 6.86 to 9.05 in CVD CNT. The purification method proposed in this study is expected to be effectively applied in fields requiring high-purity SWCNTs, such as electronics, sensors, and energy storage devices.

Optimal processes to remove chromaticity at E water treatment plant(WTP) mainly caused by algae of E lake in Jeju island were investigated based on lab-tests of chlorine and ozone oxidation. 42.9% of chromaticity of filtered water was removed by chlorine oxidation under pH 7.0∼8.0, dose of 1.0 mg/L with contact time of 30∼60 min. On the other hand, chromaticity removal was 71.4% when post-ozone dose of 0.9∼1.9 mg/L and pH 9.0, while it was increased to 86.7% under post-ozone dose of 3.1∼7.3 mg/L and pH 9.0. However, there was no significant chromaticity removal efficiency increase when ozone doses were higher than 5.0 mg/L regardless of feeding point(i.e., pre-ozonation and post-ozonation) and pHs(i.e., 7.0 and 9.0.) under the experimental conditions. Based on the results, chlorine oxidation using existing chlorination facilities at the WTP is recommended for lower chromaticity while ozone oxidation is recommended for higher chromaticity by installing new ozone feeding facilities.