Scavanging nitrophenol from aquatic effluents with triethyl amine catalyzed ambient pressure dried carbon aerogel

Abstract

Removal of 4-Nitophenol from aquatic effluents through adsorption effected by ambient pressure dried carbon aerogel, was explored in the present investigation. Carbon aerogel was derived from thermal carbonization of Resorcinol-formaldehyde (RF) aerogel at 1050 °C under inert atmosphere. RF aerogel was obtained through sol-gel poly-condensation reaction between resorcinol and formaldehyde catalyzed by a non-conventional organic tertiary amine catalyst (triethyl amine). Gel drying was accomplished through cost effective ambient pressure drying process. Ambient pressure drying technique yielded RF aerogels with almost zero volume shrinkage. Carbon aerogel so obtained, had a very large population of sub-micro, micro and meso pores which were found to be highly conducive to adsorption engineered removal of 4-nitrophenol from aquatic effluent system. The organic amine catalyst was employed at various resorcinol-catalyst mole ratios (R/C), viz.: 100, 250, 500, 1000, 2000 and 3000. The carbon aerogels used in this study showed substantially high affinity for 4-nitrophenol (∼350 mgg−1). Carbon aerogel based adsorption was studied through various models, such as Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and John-Sivanandan Achari (JSA). Specific surface areas of carbon aerogel were calculated from the adsorption data which are very close to those obtained with the BET parameters. Carbon aerogel corresponding to R/C ratio of 2000, is found to be more effective towards adsorption of 4-nitrophenol among the various aerogels considered for the present study. It is further observed that adsorption takes place in multiple stages.