Fast and efficient capture of iodide ions by silver-modified GO nanosheets: From adsorption to membrane filtration

The treatment of radioactive contaminated water is highly valued all over the world nowadays. In this article, an easy-operated strategy with clear principle for the efficient purification of radioactive iodide wastewater was proposed. Silver nanoparticles (Ag NPs) were grown in-situ at the oxygen-containing defect sites on the edge of GO nanosheets, and the nanocomposites were tested for both adsorption and membrane filtration. HRTEM and XRD results confirmed the crystalline structure of Ag and AgI before and after the adsorption. Fast adsorption equilibrium of iodides was observed within 15 min, and theoretical maximum equilibrium capacity was calculated as high as 150.17 mg g-1. Dead-end filtration performances of this Ag-GO stacked membranes were further studied from the view of avoiding secondary radionuclides pollution caused by the difficult recovery of nano powders. The rejection ratio of iodides kept constant which was higher than 90 % during the first thirty minutes. AgI precipitation adsorption and size sieving of confined GO interlayers by the stacked Ag-GO membranes happened simultaneously. Suitable concentration of NaOH can wash out most of the iodide ions entrapped between the confined GO interlayers, and desorb part of the AgI meanwhile. All these results elucidated the application of these Ag-GO NPs for the fast and efficient adsorption of iodides are the most prominent advantage, and the adsorbents exhibited desired adsorption irreversibility. Ag-GO filtration membranes could help these nano powders get an easy solid-liquid separation step.