Cost-effective sorbents for removing phthalate residues from water

Abstract

Biochars are sustainable materials that can be produced by pyrolysis of cost-effective biomass sources, such as agricultural waste. With high carbon content and physicochemical stability, biochars show significant potential for environmental applications. The study focused on the preparation and characterization of biochar obtained from apple waste, activated and functionalized with metal oxides, obtained by green synthesis (Fe3O4 and NiO), as well as on testing the extraction capacity of phthalate residues – di-butyl (DBP) and bis(2-ethylhexyl) phthalate (DEHP) from water. The green synthesis of metal oxides was carried out in the presence of Urtica dioica L. extract, which was previously characterized for its total polyphenolic content and antioxidant capacity. The sorption activity was tested on 11 experimental samples of functionalized biochars, as a result, 3 samples with significant sorption activity towards phthalates were selected. Phthalate solutions were prepared from individual substances - DBP (99.8%) and DEHP (99.7%) PESTANAL from SIGMA-ALDRICH®, which were used for sample contamination. The interaction of the sorbent with the phthalate was carried out in a sealed container with constant stirring, at room temperature. The extraction of the phthalate was carried out with chloroform in the presence of an internal standard. The separated organic extract was dried with anhydrous sodium sulfate. The detection of phthalates was carried out with a GCMS-QP-2010S (IS), on a Restek - Rtx-5MS silica column (30 m/0.25 mm/0.25 μm 5% diphenyl phase 95 % di-methylpolysiloxane). The selected biochars showed the highest adsorption efficiency for DBP (74.98%), which highlights the sustainable of apple waste derivatives fortified with synthesized metal oxides for environmental applications, especially for the removal of plastic-derived pollutants from water. However, the sorption properties of materials on real samples may vary in real systems, which implies the need to test biochars in the presence of competing reactions with cations, anions, dissolved gases, hydrocarbons and other natural water pollutants.