This study aimed to remove uranium (U(VI)) ions from sulfate-based acidic soil-washing effluent using the ion-exchange method. For effective ion exchange of U(VI) ions under acidic conditions, one chelate resin (Purolite S950) stable under low pH conditions and two anion-exchange resins (Ambersep 400 SO4 and 920U SO4) used in sulfuric acid leaching systems were selected. The exchange performance of the three selected ion-exchange resins for U(VI) ions was evaluated under various experimental conditions, including ion-exchange resin dosages, pH conditions, reaction times, and reaction temperatures. U(VI) ion exchange was consistent with the Langmuir model and followed pseudo-second-order kinetics. Thermodynamic experiments revealed that the U(VI) ion exchange by the ion-exchange resins is an endothermic and spontaneous process. On the other hand, U(VI) ions was effectively desorbed from the ion-exchange resins using 0.5 M H2SO4 or Na2CO3 solution. Overall, on the basis of the results of the present study, we propose that Purolite S950, Ambersep 400 SO4, and Ambersep 920U SO4 are ion-exchange resins that can be practically applied to effectively remove U(VI) ions from sulfate-based acidic soil-washing effluents.

A large amount of acidic wastewater was generated from the soil washing process. This study focuses on the capture for the radionuclide, especially cesium (Cs), in soil washing wastewater. We conducted the two-step process to reduce the amount of radioactive wastewater after soil washing using the coagulants and adsorbents in each step. We synthesized the adsorbent to capture Cs radionuclides in acidic wastewater (pH < 1). Based on the results, we found that the optimum ratio (NiFC:PAN) was 3.5:1 for the removal efficiency and strength of adsorbent. We compare the NiFC powder and NiFC-PAN for removal efficiency and separation of adsorbent after batch test, showing that the removal efficiency and separation of NiFC-PAN was lower and higher than NiFC power, respectively. We conducted the radioactive experiment to evaluate the satisfaction below release criteria (< 10 Bq·L−1, Cs), reporting that NIFC-PAN adsorbent meet the release criteria. These results showed that NiFC-PAN is promising adsorbent for Cs capture in strong acidic wastewater generated from soil washing and separation after capture process.

Aluminum (Al) stress in acidic pH is known to decrease the growth and productivity of alfalfa. However, not much is known about how the application of silicon (Si) affects the Al stress response in alfalfa. This study was conducted to evaluate the effect of exogenous application of Si on the growth of alfalfa seedlings exposed to Al stress in pots. Alfalfa seedlings grown in pots for 2 weeks were treated either Al stress (pH 4.0, 0.2 mM Al) or Al stress + Si (1 mM) for 5 days, lengths and biomass of shoot and root, and chlorophyll and carotenoid contents in leaf tissues were analyzed respectively. Al stress treatment inhibited shoot and root growth, and decreased fresh and dry weights, and chlorophyll content in leaves, but increased carotenoid content. In contrast, when alfalfa seedlings treated with Al stress combined with Si, delayed growth caused by Al stress of shoot and root of alfalfa seedlings was restored, dry weight was increased and chlorophyll content of leaf tissue was increased, but carotenoid content was decreased. These results suggest that Si has a function of alleviating Al toxicity in alfalfa, of which it exhibits a mitigating effect by a function that overlaps with some of the intracellular functions of carotenoids.