TY - JOUR
T1 - Calcium and TOC loading
T2 - Effect of hydroxyl and carboxyl substituents
AU - Frederick, Holly T.
AU - Cannon, Fred S.
AU - Dempsey, Brian A.
N1 - Funding Information:
Funding provided by the Women in Engineering Program at Penn State, the American Waterworks Service Company, The Ben Franklin Technology Program, and the Kappe Fund at Penn State is gratefully acknowledged. D. Mazyck and B. Moore of Penn State University performed the GAC surface area analysis.
PY - 2001/10/31
Y1 - 2001/10/31
N2 - Calcium loading onto granular activated carbon (GAC) was evaluated in batch reactor tests for a series of single ring aromatic compounds. In the pH range from 7 to 9 when these aromatic rings contained adjacent carboxyl and hydroxyl groups, the level of calcium loaded was always greater than with compounds that did not contain this arrangement. Also with these compounds, the presence of calcium increased the loading of the organic onto GAC. When rings contained only carboxyls, only hydroxyls or carboxyl and hydroxyl groups not adjacent to one another, the calcium loading was much lower. For the compounds evaluated with only carboxyl groups (benzoic acid and phthalic acid), calcium loading onto GAC at pH greater than 8 was the same as when no organic compound was present in the system. It was noted that there was not a relationship between the ability of a ligand to form aqueous complexes and the effect of that ligand on calcium loading. Specifically phthalate was the strongest complexing ligand evaluated, but it did not cause significant calcium loading onto GAC. Calcium loading was found to increase in relation to the acidity constants of the organic ligands: increasing calcium loading was observed as the value (pKa2-pKa1) increased. These results are consistent with the formation of hydrophobic Ca-ligand assemblages within the GAC.
AB - Calcium loading onto granular activated carbon (GAC) was evaluated in batch reactor tests for a series of single ring aromatic compounds. In the pH range from 7 to 9 when these aromatic rings contained adjacent carboxyl and hydroxyl groups, the level of calcium loaded was always greater than with compounds that did not contain this arrangement. Also with these compounds, the presence of calcium increased the loading of the organic onto GAC. When rings contained only carboxyls, only hydroxyls or carboxyl and hydroxyl groups not adjacent to one another, the calcium loading was much lower. For the compounds evaluated with only carboxyl groups (benzoic acid and phthalic acid), calcium loading onto GAC at pH greater than 8 was the same as when no organic compound was present in the system. It was noted that there was not a relationship between the ability of a ligand to form aqueous complexes and the effect of that ligand on calcium loading. Specifically phthalate was the strongest complexing ligand evaluated, but it did not cause significant calcium loading onto GAC. Calcium loading was found to increase in relation to the acidity constants of the organic ligands: increasing calcium loading was observed as the value (pKa2-pKa1) increased. These results are consistent with the formation of hydrophobic Ca-ligand assemblages within the GAC.
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U2 - 10.1016/S0927-7757(01)00772-5
DO - 10.1016/S0927-7757(01)00772-5
M3 - Article
AN - SCOPUS:0035980602
SN - 0927-7757
VL - 191
SP - 161
EP - 177
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
IS - 1-2
ER -