Ligand Interaction in Thorium Adsorption by Pacitan Bentonite

Roza Indra Laksmana; Mohammad Khotib; Zainal Alim Mas'ud; June Mellawati; Afiq Azfar Pratama; Suci Indryati; Dwi Luhur Ibnu Saputra

doi:10.55981/urania.2026.9210

Authors

Roza Indra Laksmana Badan Riset dan Inovasi Nasional
Mohammad Khotib IPB University
Zainal Alim Mas'ud IPB University
June Mellawati Badan Riset dan Inovasi Nasional
Afiq Azfar Pratama Badan Riset dan Inovasi Nasional
Suci Indryati Badan Riset dan Inovasi Nasional
Dwi Luhur Ibnu Saputra Badan Riset dan Inovasi Nasional

DOI:

https://doi.org/10.55981/urania.2026.9210

Keywords:

thorium adsorption, acid activation, ligands, radioactive waste, bentonite, pacitan

Abstract

Many studies have investigated the use of bentonite as an adsorbent; however, questions remain regarding the effects of sulfate and phosphate on thorium (Th) adsorption. Sulfate may reduce adsorption through the formation of Th-sulfate complexes and competition for adsorption sites between SO2-and UO2+, whereas phosphate is an important component of subsurface systems and plays a key role in controlling Thmobility. This study investigated Thadsorption by natural and acid-activated Pacitan bentonite as adsorbents for radioactive waste treatment. Because of its large surface area and porosity, bentonite has a high adsorption capacity, which can be further enhanced by acid activation. The adsorbents were characterized by FTIR and XRD to evaluate structuralchanges after activation. Batch experiments were conducted to examine the effects of pH, contact time, temperature, and complexing ligands, including sulfate, carbonate, and phosphate, on Thadsorption. The results showed that natural bentonite exhibited high Thadsorption efficiency from the beginning of the experiment, whereas acid-activated bentonite showed a gradual increase in adsorption efficiency over time. Thcomplexation with sulfate decreased adsorption efficiency, while phosphate improved Thstability in activated bentonite. These findings indicate that Pacitan bentonite, in both natural and acid-activated forms, is a promising adsorbent for Th-containing radioactive waste, provided that the adsorption conditions are properly optimized.

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