Composite adsorbents including oxidized graphene: effect of composition on mechanical durability and adsorption of pesticides

A number of multifunctional composite adsorbents based on hydrated zirconium dioxide has been synthesized. The inorganic ion exchanger contained nanosheets of oxidized graphene (GO), the modifier amount was   0.5–7 mass. %. The composites were investigated with methods of transmission electron microscopy and nitrogen adsorption-desorption, macropores were determined using water as a working liquid. It has been found that increasing of GO content depresses microporosity, but meso- and macroporosity grow. Crushing strength reduces exponentially with increase of total pore volume from 0.49 to 0.62 cm 3  g – 1 . Removal of phenol from water containing also inorganic ions was investigated. Adsorption capacity reaches 0.15–0.85 (phenol), 0.5–0.85 (Ca 2+ and Mg 2+ ), 0.005–0.045 (SO 4 2 – ) mmol g – 1 . When the GO content in the composites is 0.5–2 %, this carbon addition improves adsorption of cations and organic molecules comparing with hydrated zirconium dioxide. Further increase in GO amount causes no sufficient effect on adsorption due to decline of specific surface area of the composites. It has been suggested that the optimal content of the modifier, which provides the maximal growth of adsorption capacity, is 2 %. This composite is obtained in a form of large granules (0.3–0.5 mm), their crushing  strength is 9 bar. The material was applied to removal of pesticides (acetomipride, carboxine, epoxyconazole and thiamethoxam) from aqueous multicomponent solution under batch conditions. The residual content of carboxine and epoxyconazole, molecules of which contain benzene rings, is lower than the maximal allowable concentration. No deterioration of pesticide uptake has been found after five cycles of adsorption-regeneration.