Remediation of groundwater fluoride using Cu2O nanostructures as an efficient adsorbent

Fluoride is essential but a higher fluoride intake greater than 1.5 mg L-1 poses substantial health risks. This necessitates the fluoride remediation from contaminated water. Herein, we report the synthesis of copper oxide nanostructures by co-precipitation method in the presence of Lantana camara flower (LCF) extract to use as an effective adsorbent for fluoride remediation. These nanostructures are pure and crystalline exhibiting distinct morphologies depending on the concentration of LCF extract. The phytochemicals present in the extract modulate the growth of the nanostructures and thereby not only control the morphology of the formed nanostructures but also convert CuO to Cu2O. The BET surface areas of the as-synthesized CuO and Cu2O nanostructures range between 16.4 and 64.9 m(2) g(-1). The optimal adsorption condition has been attained in batch experiments by varying adsorbent dosage, contact times, initial fluoride concentrations, co-existing ions, and pH of the medium. Cu2O nanostructures can remove 76.6 % fluoride from water in 60 min at pH similar to 7.0 at 303 K while CuO nanostructures are capable of removing 68.4 % fluoride under the same condition. The adsorption process is spontaneous and exothermic following pseudo-second-order kinetics. The maximal adsorption capacities based on Langmuir isotherm and Sips isotherm models at 313 K are 140.43 mg g(-1) and 170.85 mg g(-1), respectively. The adsorbent is very stable and reusable for up to five cycles with a minimal loss in adsorption performance. Further, the adsorbent performs exceptionally well in removing fluoride from contaminated groundwater from 20 mg L-1 to 1.2 mg L-1 in 60 min.