Adsorptive Removal of Trace Concentration of Fluoride Using Orange Waste Treated Using Concentrated Sulfuric Acid

Novel adsorption gel was prepared from orange juice residue by using boiling concentrated sulfuric acid to create a condensation cross-linking reaction. It was then loaded with Zr(IV) ion to create adsorption sites for fluoride ions. This prepared gel was characterized by IR, EDX, XRD, SEM and chemical analysis. Fluoride adsorption was strongly pH dependent and maximum adsorption occurred at pH 3-4. The maximum adsorption capacity was drastically improved by loading Zr(IV) from 0.21 mmol/g up to 0.71mmol/g at 303 K. The thermodynamic parameters evaluated from adsorption isotherms at varying temperature suggested that adsorption of fluoride onto the present adsorbent is spontaneous and endothermic in nature. The adsorbed fluoride was successfully desorbed using dilute alkaline solution. Trace concentrations of fluoride contained in the actual waste plating solution was completely removed by adding small amounts of this adsorbent.