The Effect Of Dissolved Organic Matter On Sorption Of Benzotriazole To Black Carbon And Iron Oxide Coated Sand

Dissolved organic matter (DOM) has a significant impact on the sorption ofnutrients, heavy metals and organic pollutions in the environment. But the effectmechanisms of DOM on the sorption of benzotriazole (BTA) are not clearly atpresent. So the effects of DOM on BTA sorption to black carbon (BC), iron oxidecoated sand, the mixture of BC and iron oxide coated sand were studied by batchexperiments. The main conclusions are as follows:(1) The hydrogen bonding and π-π interactions existed in the sorption of DOM to BC.The cations (Ca2+, Na+) were added into solution, which resulted in decreasing ofrepulsion forces between DOM and BC, and the changing of DOM structure. Theelectrolytes (CaCl2, NaCl) facilitated the sorption of DOM to BC. The cationicbridge played an important role on DOM concentration decreased in CaCl2solution. The mechanisms of electrostatic interaction, ligand exchange andhydrophobic effect existed in sorption of DOM to iron oxide coated sand. Theelectrolytes (CaCl2, NaCl) inhibited the sorption of DOM to iron oxide coatedsand by weakening electrostatic attraction between DOM and iron oxide coatedsand.(2) Macromolecular DOM sorption to BC by cationic bridge blocked BC pores forBTA sorption in CaCl2solution. So BTA sorption to BC was inhibited in CaCl2solution. As the DOM concentration increasing, the inhibition was more obvious.DOM sorption to BC which increased the sorption sites, so DOM facilitated BTAsorption to BC in NaCl solution.(3) The hydrogen bonding interaction played an important role on the sorption ofBTA to iron oxide coated sand. The sorption amount of BTA increased to ironoxide coated sand as the increasing of DOM concentration (0-15.68mg/L) in theCaCl2solution. That was because of cumulative sorption effect. When theconcentration of DOM was10.63mg/L in the NaCl solution, the sorption amountof DOM to BC was less，so DOM had no significant effect on BTA sorption to iron oxide coated sand.(4) As the content of BC increased, the BTA sorption increased in the mixture of BCand iron oxide coated sand, and the BC contribution rate to BTA sorptionincreased. The effect of DOM on the sorption of BTA to the mixture of BC andiron oxide coated sand depended on the DOM concentration and BC content. Acritical DOM concentration value was affected by the BC content. When theDOM concentration was more than the DOM critical concentration value, DOMinhibited BTA sorption. Otherwise, DOM promoted BTA sorption to the mixtureof BC and iron oxide coated sand. The critical value of DOM concentration wasnegative correlation with the content of BC.