A modified zeolite (Na₂SO₄ @zeolite NaA) as a novel adsorbent for radium-226,228 from acidic radioactive wastewater: Synthesis, characterization and testing

The radiological contamination with radium in oil and gas production is challenging environmental and health concerns. This study investigated the synthesis of zeolite NaA modified with Na2SO4 (Na2SO4@zeolite NaA) hydrothermal method and subsequent use as an adsorbent along with manganese dioxide (MnO2) for removing radium isotopes (226Ra and 228Ra) from acidic radioactive wastewater (ARW). ARW was generated through acidic sequential leaching of petroleum-based organic soils collected from the South Rumaila fields in the Basra Governorate, Iraq. The optimum adsorption parameters were MnO2: Na2SO4@zeolite NaA mass ratio of 1:0.5 g. g-1 and a pH of 6.3 resulting in maximum removal of 78.7% and 66.7% for 226Ra and 228Ra, respectively. Higher levels of removal were not attainable due to co-elements effect. The adsorption was endothermic with cation exchange of Na+ with Ra2+ being the main mechanism. The incorporation of Na2SO4 increased the exchange sites available for Ra2+ and the surface area and pore size available for facilitating such reactions. The exhausted column was regenerated and subsequently used for five cycles with a small drop in the removal of 226Ra and 228Ra by 11% and 9.5%, respectively highlighting the propitious application of Na2SO4@zeolite NaA and MnO for treating contaminated wastewater in oil fields.