Mechanism of uranium adsorption from groundwater using heated aluminum oxide particles in combination with micro-granular adsorptive filtration

초록

This study investigated the mechanism of uranium adsorption from groundwater using heated aluminum oxide particles (HAOPs) and the characteristics of continuous uranium adsorption with a micro-granular adsorptive filtration (mu-GAF) system. Batch tests showed that uranium adsorption by HAOPs followed the Langmuir model, with a maximum adsorption density (qmax) of 0.428 mg U/mg Al at pH 7.5. It was confirmed that uranium was directly adsorbed onto HAOPs in the form of UO22+ ions. The effects of calcium and sulfate on uranium adsorption in groundwater depended on the energy required for UO2-CO3, Ca-UO2-CO3, and UO2-SO4 complexes to dissociate into UO22+ ions. Uranium adsorption with the mu-GAF system initially achieved nearly 100% uranium removal, which gradually decreased. Adsorption breakthrough occurred with a high correlation with the adsorbent concentration (20-100 g-Al/m2) or uranium concentration (0.268-2.158 mg U/L). This indicates that continuous adsorption characteristics can predict the time for adsorbent replacement, optimizing water quality management. The impact of feed flux (150-500 LMH) and pressure loss was minimal, reducing the need for stringent operational controls. Uranium adsorption efficiency varied with pH and sulfate concentration, but remained stable under typical groundwater conditions (pH 7.5-8.5, sulfate <= 5 mM). Additionally, HAOPs adsorbed other groundwater components (As, Zn, Fe, B, KMnO4 consumption, and F), and adsorbent loss during & micro;-GAF operation was low (1.85%), ensuring stability against dissolution.

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