Adsorptive Removal of Strontium from Water by using Chemically Modified Orange Juice Residue

Adsorbent for strontium (Sr2+) ion removal was prepared from orange waste generated in an orange juice factory. The orange juice residue (OJR) was treated with lime water to prepare saponified orange juice residue (SOJR). The energy dispersive X-ray (EDX) spectroscopic analysis revealed that substitution of Ca2+ ions in SOJR by Sr2+ ions takes place during the adsorption process. The adsorption of Sr2+ ions onto SOJR was fast and strongly pH dependent. Maximum adsorption occurred at pH higher than 5. The adsorption isotherm study showed maximum adsorption capacity of SOJR for Sr2+ ion was 833.4mmol/kg. Equimolar amount of Ca2+ was found to be released from SOJR during Sr2+ adsorption also indicating that adsorption of Sr2+ on SOJR takes place according to the Ca2+ substitution reaction by cation exchange mechanism. Thus, the adsorption gel prepared in this study can be a promising adsorbent to remove Sr2+ from aqueous solution.