Utilization of rarasaponin natural surfactant for organo-bentonite preparation: Application for methylene blue removal from aqueous effluent

Rarasaponin that belongs to the natural surfactant was used as modifying agent for preparation of organo-bentonite. This surfactant was extracted from wild plant Sapindus rarak DC. The modifying process was conducted by microwave thermal irradiation. The characterization of bentonite and its modified form was carried out using FTIR, nitrogen sorption and XRD analysis. In order to test the adsorption capability of organo-bentonite, batch adsorption experiments of methylene blue from aqueous solution using this adsorbent were conducted under several operating conditions. The highest adsorption capacity (qm) of organo-bentonite obtained in this study was 256 mg/g while for raw bentonite was 194 mg/g at 60 °C. The adsorption isotherm and kinetic data were modeled using several well known models. Freundlich isotherm model represented the adsorption equilibrium data better than the Langmuir isotherm model. For the kinetic model, the pseudo-second order gave reasonable parameters and could correlate the kinetic data well. New mechanisms of organo-bentonite formation as well as adsorption of methylene blue on the surface of organo-bentonite were also proposed in this paper.

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► The use of natural surfactant for organo-bentonite preparation.
► Natural chemical as modifying agent.
► New mechanism on the reaction between rarasaponin and silanol group of bentonite.