Adsorption of s-Triazines by Soil Organic Matter

The adsorption of seven s-triazines from aqueous solutions by organic soil colloids was determined at pH levels from 1.0 to 5.2. Maximum adsorption occurred at pH levels in the vicinity of the pKA values of the respective compounds. The amounts adsorbed were dependent upon the molecular structures of the compounds and the pH of the suspension and were, in order of decreasing adsorption, as follows: 2-methoxy-4,6-bis(diethylamino)-s-triazine (hereafter referred to as tetraetatone) = 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) = 2-hydroxy-4,6-bis(isopropylamino)-s-triazine (hereafter referred to as hydroxypropazine) > 2-methoxy-4-diethylamino-6-ethylamino-s-triazine (hereafter referred to as trietatone) > 2-methoxy-4,6-bis(isopropylamino)-s-triazine (prometone) > 2-methoxy-4,6-bis(ethylamino-s-triazine (simetone) > 2-chloro-4,6-bis(isopropylamino-s-triazine (propazine). Approximately 52% of the prometone adsorbed by the organic matter was desorbed with two extractions of 0.1N NaCl. It was concluded that the adsorption of the s-triazines was due to complexing of the triazine molecules with functional groups on the organic colloids and/or adsorption of s-triazine cations by ion exchange forces.