The synergy of BN and SiO2 can be explained by the CLFT theory. As shown in Figure , AFFF can be dispersed on SiO2 particles because of their hydrophilic surfaces. The SiO2 (∅ 250 μm) mainly served as dispersants to provide an extra 453 cm 2 collision area (Text S2). When amended with 5 g SiO2, the Z0 for treating 100 and 200 μL of AFFF are 1.4 and 2.8 μm, smaller than or close to the CLFT. Therefore, efficient PFAS destruction and defluorination were facilitated since the beginning of [BN+SiO2]-BM treatment, which explains the elimination of the incubation period compared with the BN-BM process (Figure vs. Figure ). As for treating 300 and 500 μL AFFF with Z0 of 4.2 and 6.9 μm, the Z's were reduced to 1.0 and 1.7 μm, respectively, after 8 h of reaction. Thus, the high DeF observed at this treatment time can also be attributed to Z < CLFT.