Microwave-assisted decolorization and decomposition of methylene blue with persulfate

This work experimentally determined the effect of a combination of microwave irradiation (MWI) and sodium persulfate (Na2S2O8, SPS) on decolorization and decomposition of methylene blue (C16H18N3SCI, MB). The effects of treatment temperature (70-100 degrees C, T) and SPS concentration (1-5 g l(-1)) at 8-min MWI time were characterized. The conversion rate of MB (50 mg l(-1)) was increased and accelerated by MWI, reaching 99.9% after heating for 8 min at 90 degrees C and 600-W MW power in the presence of 5 g l(-1) of SPS; this is higher than the conversion rate (98.3%) of treatment by conventional heating for 30 min. The MB decolorization increased with T (p = 0.002) and initial SPS (p = 0.006). The total organic carbon (TOC) removal also increased with T (p = 0.004). Within the design boundaries, full decolorization was achieved at T >= 93 degrees C and SPS >= 3.5 g l(-1). The TOC removal level reached 100% at T >= 95 degrees C and SPS = 5 g l(-1). The results show that MWI combined with SPS is effective in decolorization and degradation of MB due to advantages of fast and effective processing. (C) 2014 Elsevier Ltd. All rights reserved.