ABSTRACT
This chapter discusses the absorption and desorption of atrazine on three different purified humic substances before and after acidic hydrolysis. Humic substances were extracted from: a volcanic soil; a North Dakota leonardite; and an oxidized coal. A charge-transfer interaction may arise between electron-poor groups in humic acids and in electron-rich groups in the atrazine molecule. Ion exchange and hydrogen-bonding mechanisms, though they may play a role, do not appear to command the adsorbing capacity of humic substances. Despite the increase for all samples in total carboxyl, and phenolic acidities observed after hydrolysis that should have driven towards a general higher atrazine adsorption, had protonation been the predominant mechanism. The resulting humic acids were purified by an HCl-HF treatment, dialyzed against water, and freeze-dried.
