Synthesis of monolith silica anchored graphene oxide composite with enhanced adsorption capacities for carbofuran and imidacloprid.

ABSTRACT

Highly efficient adsorbent was prepared for the removal of carbofuran and imidacloprid pesticides from wastewater. The silica monolith anchored graphene oxide composite was synthesized by the modified Fischer esterification protocol. The composite showed improved adsorption capacity for the removal of pesticides from wastewater. Graphene oxide was synthesized using the modified Hummer's method, while the silica monolith was prepared via sol-gel method. The composite was characterized via X-ray diffraction, Fourier transform infra-red, Brunauer Emmett and Teller (BET/BJH) analysis, zeta potential, and FESEM imaging. Different adsorption parameters such as pH, contact time, adsorbate and adsorbent concentration, and temperature were optimized for the adsorption of pesticides. The equilibrium and kinetic models were applied to the adsorption process of the pesticides. Qe of the composite as found to be 342.46 mg g-1 for imidacloprid and 37.15 mg g-1 for carbofuran. The adsorption process followed the pseudo 2nd order kinetic model for carbofuran (R2~0.9971) and imidacloprid (R2~0.9967). The Freundlich isotherm best fitted to the adsorption data of the pesticides with R2 value of 0.9956 for carbofuran and 0.95 for imidacloprid. The resultant adsorbent/composite material came out with very good results for the removal of pesticides.