Selective adsorption of azine group containing pesticides on carbon-based materials

Abstract

Adsorption of atrazine (ATR) and diquat (DIQ) pesticides were studied on two carbon-based adsorbent materials, graphene oxide (GO) and activated carbon (AC). A modified synthesis of graphene oxide has also been developed using phosphoric acid in reduced amounts instead of nitric acid in order to reduce the formation of poisonous by-products such as nitrogen oxides which are harmful environmental contaminants. High selectivity in DIQ and ATR removal studies was observed with GO and AC. The GO showed more adsorption efficiency for DIQ (97.99 %) whereas AC was more selective for ATR removal (99.99 %). The selectivity of pesticides was accredited to the interplay of surface area and surface charge. The Langmuir adsorption isotherm was followed by all the adsorption studies and the BET isotherm was also obeyed in the case of selective adsorption of DIQ by GO and ATR by AC. The pseudo second-order kinetics was observed in all adsorption studies and the value of the amount adsorbed at equilibrium (qe) was found to be similar theoretically and experimentally.