[Comparative study on adsorption behaviors of natural organic matter by powered activated carbons with different...

The effect of powered activated carbon (PAC) particle size in the range of 10-100 microm on the adsorption of natural organic matter (NOM) in micro-polluted water was investigated, and the adsorption fractionation characteristics in terms of relative molecular mass distribution changes were evaluated. Three PACs with different median particle diameters were obtained through grinding and sieving of a commercial PAC product: PAC-1 (19 microm), PAC-2 (46 microm), and PAC-3 (76 microm). The adsorption results showed that with the decrease of particle size, the adsorption properties (both adsorption capacity and adsorption rate) of PAC for NOM in both simulated and real micro-polluted water were significantly enhanced. The faster adsorption rate of PAC with smaller particles was attributed to its more available adsorption sites and shorter diffusion distance for adsorbate molecules. The larger adsorption capacity of smaller particle PACs was mainly due to their greater specific external surface area per unit mass and higher mesopore volume, as the pore blockage effect from large relative molecular mass NOM was alleviated. For micro-polluted water sample, the decrease of PAC particle size significantly enhanced the adsorption of organic matter fractions with relative molecular mass > 2 000, but had no notable improvement for that with relative molecular mass < 800.