Adsorptive removal of trace concentration of fluoride ion from water by using dried orange juice residue

Dried orange juice residue (DOJR) marketed as cattle food in Japan was converted into a promising adsorbent for fluoride as a result of chemical loading with Zr(IV), Ce(IV) and Al(III). The effectiveness of the metal loaded DOJR in adsorbing trace fluoride concentrations from synthetic and actual waste water were investigated. Energy dispersive X-ray (EDX) and infra red (IR) spectroscopic analysis confirmed the effective adsorption of Zr(IV) ions on DOJR in addition to fluoride ion on Zr(IV)-loaded DOJR. The amount of Zr(IV), Ce(IV) and Al(III) loaded on the DOJR were evaluated as 0.90, 0.85 and 0.97 mmol/g, respectively, while the maximum adsorption capacity of fluoride on the Zr(IV), Ce(IV) and Al(III) loaded DOJR were evaluated as 1.43, 1.22 and 0.67 mmol/g, respectively. Application of Zr(IV) loaded DOJR using actual waste plating solutions exhibited effective removal of trace concentration of fluoride to acceptable level. The negligible interference of coexisting anions such as nitrates, carbonates and chlorides makes the Zr(IV) loaded DOJR a promising sorbent for waste water treatment. The adsorbed fluoride was effectively desorbed using an alkali (NaOH) solution for its regeneration. Thus, this work shed light on the potential application of metal loaded DOJR to remediate aquatic environment polluted with fluoride.