Synthesis and performance evaluation of olive fruit waste resin for removal of fluoride from aqueous solution: batch and column modeling

The excessiveness of fluoride in water triggers severe environmental problems and adversely affects human health. This research is focused on the preparation of novel absorbent through modification of olive fruit waste (OFW) characteristics via hydroxyl radical pre-treatment and quaternization for fluoride adsorption. A remarkable removal performance was achieved with pH ranging between 3 and 9. The highest adsorption capability of quaternized olive fruit waste-based adsorbent could reach 2.35 mg g-1 at pH equalling 6 and 2.01 mg g-1 at neutral pH. The overall size of the anion exchange resin ranging between 0.25 and 0.5 mm was vital in the biosorption mechanism, providing the removal performance up to 5.15 mg g-1 in column study. The performance was evaluated employing the models including Langmuir isotherm and pseudo-second-order model as well as Thomas and Adams-Bohart models. Langmuir isotherm (R2 = 0.985) and pseudo-second-order model (R2 = 0.999) provide better results than Freundlich isotherms and pseudo-first-order models, respectively. The scanning electron microscopy revealed significant variability in morphology with projections and porous surfaces, which were confirmed by Brunauer-Emmett-Teller assessment. Fourier-transform infrared spectroscopy and CHNS analysis also verified the existence of amine group and hydroxyl ions on bio-absorbent and active points. The outcomes of this research advocate that the OFW based absorbent have a notable prospect in engineering application.