Purification of high–toxicity beryllium–containing water resources using carbon dot–enhanced phosphoric acid/chitosan composite gels

Abstract

• The adsorption can be completed within 20–min. • PCH@CDs has excellent adsorption capacity (59.84 mg/g). • PCH@CDs can reduce the concentration (≤2.5 mg/L) of beryllium to below 5 µg/L. With the sensitization of carbon neutrality, the efficient removal of beryllium from beryllium-containing wastewater has gained increasing research interest in the environmental field. In this study, carbon dots (CDs)/phosphonated chitosan hydrogel (PCH@CDs) are prepared by cross-linking nanometer CDs with phosphoric acid, calcium hydroxide, and chitosan. The doping with CDs increases the number of adsorption active sites (AAS) on PCH@CDs, thereby improving the removal rates of small molecular pollutants. The adsorption isotherm results show that the maximum amount of Be(II) adsorbed by PCH@CDs in neutral water is approximately 59.84 mg/g. The excellent adsorption of Be(II) by PCH@CDs can be attributed to the homogeneous dispersion of CDs in PCH@CDs, which results in significant exposure of CDs binding sites to Be(II). In addition, the surface of PCH@CDs contains many phosphate groups, including N–H and O–H, which have strong synergistic adsorption capacity for Be(II). In simulated wastewater, the Be(II) distribution coefficient of PCH@CDs is 6.56 × 10 5 mL/g, which is significantly higher than that of other coexisting ions. Furthermore, PCH@CDs can reduce the Be(II) concentration to less than 5 µg/L when treating Be(II)-containing solutions with an initial Be(II) concentration of less than 5 mg/L.