Removal of Paraquat, Diquat, and Amitrole from Aqueous Solution by Chemically Modified Peat1
- Patrick Mac Carthy and
- K. E. Djebbar2
The presence of organic pesticides in aquatic systems has been reported for more than 40 yr. Various methods, such as sorption by clays, activated C, or synthetic resins, have been used to remove these pesticides from water. Certain pesticides, such as the cationic species paraquat (C12H14N2Ch2; 1,1′-dimethyl-4,4′-bipyridinium dichloride), diquat (C12H12N2Br2; 6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazinediium dibromide), and the basic species amitrole (C2H4N4; 3-amino-s-triazole), are sorbed by peat. However, the use of raw peat as a sorption medium for the removal of pesticides is hampered by the relative impermeability of peat, the leaching of organic matter from peat into the effluent, and by the disaggregation of peat at pH values greater than ca. 6.0. Treatment of peat with concentrated sulfuric acid at elevated temperatures yields a granular product that has an enhanced cation exchange capacity, that is resistant to leaching, and is permeable to water flow. The objective of this research was to evaluate the use of such chemically-modified peat for removing paraquat, diquat, and amitrole from aqueous solution under a variety of experimental conditions. Using isotherm and column experiments, it was shown that the treated peat is very effective in removing these pesticides from aqueous solution. Treated peat has a capacity of about 1 mol (+) kg−1 for these three pesticides. The effects of pH, ionic strength, and flow rate on the efficiency of pesticide removal were found to be relatively small. Peats from two different localities behaved similarly in these experiments.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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