Synthesis and characterization of activated carbon from biomass for the sorption of radioactive iodine

Abstract

Due to the increasing demand for electricity, building a nuclear power plant in Kazakhstan presents an effective solution. However, this development will lead to the generation of additional radioactive waste. Consequently, managing nuclear waste and synthesizing efficient sorbents becomes crucial. Carbon sorbents are commonly used in water treatment systems because they can adapt to various pollutants. Removing radionuclides, including radioactive iodine, poses challenges due to the presence of anions and molecular iodine in water and air. This study investigates the ability of biomass-based carbon sorbents to absorb iodide ions from an aqueous medium. We produced a series of activated carbons using walnut shells (WN KOH), rice husks (RH KOH), and buckwheat husks (BH KOH). The activation with KOH significantly enhanced the textural and adsorption characteristics of the sorbents. The BET method showed an increase in both specific surface area and pore volume, with values reaching 1881.83 m²/g for RH KOH, 2192.67 m²/g for WN KOH, and 1579.43 m²/g for BH KOH. Infrared (IR) spectroscopy indicated a decrease in the intensity of the -OH group peaks and the emergence of new peaks corresponding to O-H and C-O bonds. Scanning electron microscopy (SEM) images displayed a well-developed porous structure in the activated samples, and energy dispersive X-ray spectroscopy (EDX) analysis confirmed an increased oxygen content following KOH activation. A comparative analysis of sorption capacity revealed that RH KOH (q_e 217 mg/g, t_eq 10 h) and BH KOH (q_e 215 mg/g, t_eq 10 h) were the most effective sorbents. In contrast, the WN KOH samples required more time to reach their maximum sorption capacity (q_e 190 mg/g, t_eq 30 h). Therefore, the KOH activation of carbon sorbents enhances their adsorption characteristics, making them promising candidates for water purification systems targeting radioactive pollutants.