| 研究実績の概要 |
This research studies the adsorption and desorption of target pollutants occurred on powdered activated carbon (PAC). We used a submerged-membrane hybrid system (SMHS) with conventionally-sized PAC or superfine PAC (SPAC) to remove 2-methylisoborneol (MIB), a representative micropollutant, instead of perfluoroalkyl substance (PFAS) which requires more sensitive technique for analysis.
We found that 20-40% of the MIB that adsorbed on PAC and SPAC while the influent was contaminated with MIB (6 h, contamination period) desorbed to the liquid phase within 6 h from the time that the MIB-containing influent was replaced by MIB-free influent (no-contamination period). SPAC is fast in removal by adsorption, but it is also fast in release by desorption. SPAC (median diameter: 0.94 um) showed almost the same adsorption-desorption kinetics as PAC (12.1 um) of a double dose. A two-component branched pore diffusion model combined with an IAST (ideal adsorbed solution theory) and Freundlich isotherm was used to describe and analyze the adsorption and desorption of MIB. The diffusivity of MIB molecules in the pores of the activated carbon particles decreased markedly in a short period of time. This decrease, which was attributed to fouling of the activated carbon in the SMHS by coagulant-treated water containing NOM, not only reduced the rate of MIB removal during the contamination period but also hindered the rate of MIB desorption during the no-contamination period and thus prevented the effluent MIB concentration from becoming high.
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