Silk Fibroin/Orange Peel Foam: An Efficient Biocomposite for Water Remediation

A novel approach for the valorization of orange peel waste for the removal of aqueous organic pollutants is presented herein. The orange peel is combined with silk fibroin in order to obtain alcogels, which are successfully converted into highly porous biocomposite foams upon supercritical CO2 drying. The biocomposite shows a Brunauer-Emmett-Teller specific surface area of 174.45 m(2) g(-1) and can absorb three times its weight in water. The resulting adsorbents can adsorb methylene blue from water with a maximum adsorption capacity of 113.8 +/- 12.5 mg g(-1), with the orange peel activity well preserved in the polymeric matrix. The spectroscopic studies performed show that the methylene blue molecules are adsorbed in the form of monomers on the surface of the biocomposite foams, forming a monolayer as suggested by the Langmuir isotherm model. Although the agrowaste powders are already confirmed to be promising biosorbents for the removal of pollutants from water, the difficulties caused by their recovery after the water treatment may limit their manageability and applicability. With this study, such limitations can be overcome thanks to the incorporation of the powder in a solid porous system, without significantly compromising the dye adsorption capacity of the incorporated orange peel.