Abstract:

Sulfate radical (SO₄^－ · )，a kind of radical with low selectivity and high oxidation reduction potential,can be applied to the removal of nondegradable organics,just like hydroxyl radical (OH·).In this paper,the deg-radation of a typical pesticide diuron by the sulfate radical produced by heat- activated persulfate was investigated,and the effects of temperature,diuron concentration,sodium persulfate dosage,initial pH value and some commonanions (CO₃^2－,HCO₃^－ and Cl^－) in groundwater on diuron degradation were analyzed by experiments.The resultsshow that (1) the degradation of duiron by heat- activated persulfate follows a pseudo first- order kinetic model (r² ＞0.95); (2) the effect of temperature on duiron degradation rate well accords with the Arrhenius model (r²＞0. 95); (3) the apparent activation energy achieves (166.7 ±0.8)kJ/mol when the temperature ranges from 50 to70℃; (4) the pseudo first- order degradation rate increases with the increase of persulfate dosage but with the decreaseof the initial diuron concentration; (5) the observed rate constant achieves the maximum (k_obs =0.003min－1 ) atpH 6/3; and (6) the degradation inhibition by anions follows the order of CO₃^2－＞HCO₃^－＞Cl^－.It is thus concludedthat the heat- activated persulfate oxidation is suitable for the degradation of organic pollutants such as diuron ingroundwater.

Key words: diuron, heat- activated persulfate, kinetics, impact factor