Anthocyanin based agricultural wastes as bio-adsorbents for scavenging radioactive iodide from aqueous environment

[Display omitted] •Fruit waste containing anthocyanin showed potential for removing I− in the water.•Mangosteen pericarps and red onion peels exhibited selective adsorption of I−.•Amount of anthocyanin correlated with the I− adsorption efficiency.•Ion-exchange and electrostatic attraction were the main adsorption mechanisms.•Anthocyanin-based adsorbents are green alternatives for radioactive I− remediation. To provide an alternative solution for radioactive iodine remediation, mangosteen pericarps, red onion peels, red dragon fruit peels, and passion fruit rinds (anthocyanin-based adsorbents) were successfully employed for iodide (I−) removal from aqueous solution with minimal processing. The adsorption results revealed that 0.5 g/L of mangosteen pericarps and red onion peels removed up to 90 % of 10 mg/L I− within 30 min. For both adsorbents, the experimental and the predicted Langmuir isotherms adsorption capacity (qmax) were over 70 mg/g. Anthocyanin quantification revealed that the quantity of vacuole pigments coincided with I− adsorption capacity across different adsorbents. O+, as part of the flavylium cation in anthocyanin, attracted I− via electrostatic force, and the adsorption was controlled by ion-exchange. The computational radial distance was predicted to be ∼3.28 Å. Further characterization by UV–vis spectrometry, FTIR, EDX, XPS, and XAS supported the claim of flavylium cation in anthocyanin as the main I− adsorbing functional group. Thus, the anthocyanin-based materials from agriculture waste can be used sustainably to remove radioactive I− from nuclear power facilities, water treatment plants and for environmental remediation.