Industrial activities that utilize nuclear technology can cause radioactive contamination in the ecosystems. In particular, cesium (Cs) has problems, such as neurological diseases, when it is exposed and accumulated in the bodies of animals, plants, and humans for a long time. Therefore, the development of simple and economical adsorbents for Cs removal is required. In this study, the surface of petroleum residue pitch was modified using NaClO and it was used to remove Cs from an aqueous solution. Batch experiments and characterization of the modified adsorbent were performed to determine the adsorption mechanism between the adsorbent and Cs. From these results, chemical and monolayer adsorption were found to occur at the carboxyl groups on the adsorbent surface, along with a cation exchange reaction occurred due to the sodium ions on the surface. Through this modification process, the total acidity, including phenolic, lactonic and carboxylic functional groups, was improved to 1.563 mmol/g and the maximum adsorption capacity of Cs for the modified adsorbent was 65.8 mg/g.

Adsorptive removal of cesium using surface-modified petroleum residue pitch with NaClO
    Abstract
        Graphical abstract
    1 Introduction
    2 Materials and methods
        2.1 Modification of pitch-NaClO
        2.2 Batch adsorption experiments
        2.3 Characterization of pitch-NaClO
        2.4 Adsorption models
    3 Results and discussion
        3.1 Adsorption studies in batch process
        3.2 Characterization of pitch-NaClO
        3.3 Adsorption mechanism
    4 Conclusions
    Acknowledgements 
    References

• Jong‑Soo Choi(Department of Biological and Environmental Engineering, Semyung University, Jecheon 27136, Republic of Korea)
• Suk Soon Choi(Department of Biological and Environmental Engineering, Semyung University, Jecheon 27136, Republic of Korea) Corresponding author
• Choong Jeon(Department of Biochemical Engineering, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea)