Breakthrough of natural organic matter from fixed bed adsorbers: investigations based on size-exclusion HPLC

Abstract

Fixed bed adsorption experiments were performed using four granular activated carbon (GAC) columns designed by packing two size ranges of pulverized and sieved Filtrasorb 400 (d=0.5-0.59 and 1.0-1.19 mm) to two bed depths (L=10 and 20 cm), respectively. Continuous supplying of river water containing a lower content of natural organic matter (NOM) allowed investigation of the breakthrough of aqueous natural organic matrices assessed with lumped quality indices of total dissolved organic carbon (DOC) and ultraviolet absorbance at 260 nm (UV260). The capability of GAC columns in dealing with sudden rise in the load of influent NOM was also displayed by intermittently adding to the influent river water a peaty field groundwater that contained a higher content of NOM. Besides, assisted by the size-exclusion HPLC (SEHPLC), changes in the apparent molecular weight distribution of NOM along the bed depth of GAC columns were evaluated, and an important finding revealing relatively even adsorption for adsorbable NOM constituents within the entire molecular weight range of 1000-5200 g mol−1 as PSS (polystyrene sulfonates) detected for the river and groundwater NOM was obtained. Furthermore, using a previously proposed hypothetical multi-component approach incorporating the ideal adsorbed solution theory and a plug flow homogeneous surface diffusion model, the observed concentration profiles of the river water NOM were predicted.