Anchoring nanoscale zero-valent iron within bacterial cellulose particles for boosting efficient adsorption of Co(II) and Sr(II) from seawater: Dual system and varying adsorption mechanisms

Abstract

Increasing attention has been paid to radioactive wastewater to direct discharge in Japan or accidental leaks. Strontium-90 (90Sr) and Cobalt-60 (60Co) are the most hazardous nuclides in waste discharged form nuclear reactors. Because of their high solubility and long half-lives, these radioisotopes can persist for hundreds of years before decaying to negligible levels. Herein, a green and biodegradable material nanoscale zero-valent iron (nZVI) supported by bacterial cellulose particles (BCP-nZVI) is constructed for the first time to adsorb Co2+ and Sr2+ in single and binary systems. BCP-nZVI shows superior adsorption capacities of Co2+ and Sr2+ in a single system within a wide range of pH values from 5 to7, while the coexistence of Co2+ adsorption inhibits the Sr2+ in binary system. Pseudo-second-order dynamics model and Langmuir isothermal model can be indicated the BCP-nZVI adsorption progress with 107.10 mg/g (Co2+) and 64.96 mg/g (Sr2+) maximum adsorption capacity. BCP-nZVI has outstanding stability, allowing it to be stored for more than one month with compromising its performance. More importantly, BCP-nZVI exhibits exceptional removal efficiency of Co2+ (92.53%) and Sr2+ (58.62%) removal in natural seawater systems. The mechanism investigation illustrates the high adsorption capacity of BCP-nZVI for Co2+ is controlled by redox and hydroxyl complexation. While Sr2+ is controlled by hydroxyl complexed adsorption, thus it has weak against interference by cations like Na+, Ca2+, etc. BCP-nZVI exhibits the advantages of high adsorption capacity, wide pH range, strong stability, and good applicability in natural seawater, which has excellent potential for application in radioactive ions removal.