Effects of pre, post, and simultaneous loading of natural organic matter on 2-methylisoborneol adsorption on superfine powdered activated carbon: Reversibility and external pore-blocking

• Published in: Water research (Oxford) 2020-09, Vol.182, p.115992-115992, Article 115992
• Main Authors: Nakayama, Akiko, Sakamoto, Asuka, Matsushita, Taku, Matsui, Yoshihiko, Shirasaki, Nobutaka
• Format: Article
• Language: English
• Subjects: Competitive adsorption; Humic substance; PAC; Particle size; Sub-micrometer; Taste and odor
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.115992

Three different natural organic matter (NOM)-loading methods were compared for the adsorptive removal of 2-methylisoborneol (MIB) by superfine powdered activated carbon (SPAC) and conventionally-sized powdered activated carbon (PAC). The three NOM-loading methods were: NOM adsorption followed by MIB (MIB adsorption on NOM-preloaded carbon), MIB adsorption followed by NOM (MIB adsorption on NOM post-loaded carbon), and simultaneous NOM and MIB loading (MIB adsorption on NOM-simultaneously loaded carbon). MIB removals were similar for the smaller-sized carbon (SPAC) at higher AC dosages and at lower initial NOM concentrations. The similar MIB removals indicate direct site competition between MIB and NOM with MIB adsorption reversibility (complete desorption of MIB by NOM). At lower AC doses, especially for PACs, and at higher initial NOM concentrations, the adsorption of MIBs depended on the sequence of MIB or NOM adsorption. MIB removal was lowest for the NOM-preloaded carbon, followed by NOM-simultaneously loaded carbon. The highest MIB removal was achieved by post-loading of NOM, indicating that the adsorption is irreversible. MIB adsorption on SPAC was more reversible than on PAC, although the pore size distributions of the two carbons were similar. The high degree of adsorption irreversibility for PAC compared with SPAC indicated that pore blocking occurs due to NOM loading at the PAC particle surface. Images of the external adsorption were obtained using isotope mapping and 15N-labeled effluent organic matter. [Display omitted] •MIB adsorbed on SPAC was desorbed by NOM up to the adsorption equilibrium.•MIB adsorbed on conventionally sized PAC was partially desorbed.•MIB adsorption on SPAC was more reversible than on PAC.•Irreversible adsorption was caused by pore blockage on the PAC particle surface.•We observed external adsorption on a PAC particle by using 15N-labeled EfOM.