Evaluation of the Adsorption of Aquatic Humic Substances in Batch and Column Experiments by Thermally Modified Activated Carbons

Abstract

Two commercially available granular activated carbons (GACs) were thermally modified and evaluated for their adsorption properties in batch and column mode experiments. The widely used and well characterized aquatic humic substances were used as adsorbate. The aim was to relate the adsorption properties of GAC with their physicochemical properties and also evaluate the impact of heat treatment under nitrogen atmosphere on the performance of the adsorbent in both batch and column operation modes. Heat treatment had a qualitatively similar effect on surface basicity and pore volume of both adsorbents. However, in quantitative terms, significant differences were reported. Heat-treatment enhanced batch adsorption capacity only for GAC-A. Surface available in pores within 12-15 Å width was strongly correlated to the NOM adsorption capacity. Benefits of thermal treatment were more evident at high initial solute concentrations. Results from batch adsorption did not have a straightforward relationship with column adsorption performance. Column adsorption capacities at complete breakthrough reached 26% and 79% of batch mode capacities. The highest difference was observed for carbon GAC-A, which corresponds to the more mass transfer limited system. During column operation smaller fractions of NOM were more readily adsorbed compared to batch mode.

Enhanced adsorption of humic acids on ordered mesoporous carbon compared with microporous activated carbon

“…Adsorption of humic acids on activated carbon is highly affected by the source and hydrophobicity of humic acids as well as the surface chemistry of activated carbon [8][9][10][11][12]. Randtke [9] compared the adsorption of different humic acids with varied hydrophobility on activated carbon and concluded that more hydrophobic humic acids exhibited stronger adsorption affinity.…”

“…Randtke [9] compared the adsorption of different humic acids with varied hydrophobility on activated carbon and concluded that more hydrophobic humic acids exhibited stronger adsorption affinity. Moreover, adsorption of humic acids on activated carbon negatively correlates with the surface acidity of adsorbent [11,12]. Pore structure of activated carbon is another important factor controlling humic acid adsorption [13][14][15].…”

Microcolumn adsorption studies of acid/basic dyes related to the physicochemical properties of the adsorbent

“…From Table it is again evident that pore volume in the dp > 2 nm range ( V 4 , V 5 ) had a statistically very significant and high correlation with this parameter ( q b / q s ) and for both solutes. This corresponds, on average, to 1.7 times the solute molecular radius and is in accordance with the value of 1.5 previously reported by the present authors in batch experiments for satisfactory adsorption of natural organic matter, and also in other work reporting ratios of about 1.7 and 1.3–1.8 . These observations suggest that this ratio can be generalised to processes using porous media to remove a solute from liquid phase adequately and independently of the flow configuration, batch, or plug flow mode.…”

Dye adsorption onto activated carbons from tyre rubber waste using surface coverage analysis

“…Some studies also pointed out that the pore width should be approximately 1.7 times the adsorbate molecule width (i.e. 1.7W) [5,[45][46][47]. Therefore, the assumption of a minimum pore opening d min > 1.7W is used for the assessment of surface coverage by the dyes, which is defined as…”