Citric acid-crosslinked β-cyclodextrin for simultaneous removal of bisphenol A, methylene blue and copper: The roles of cavity and surface functional groups

The increasing worldwide pollution of nature waters with endocrine disrupting chemicals (EDCs), heavy metals and dyes has highlighted the need for versatile and effective removal approaches. In this study, a citric acid-crosslinked β-cyclodextrin polymer (CA-β-CD) was applied for simultaneous adsorption of bisphenol A (BPA), methylene blue (MB) and Cu2+, typical pollutants of EDCs, dyes and heavy metals, respectively. In a monocomponent system, the adsorption behaviors exhibited a monolayer maximum adsorption capacity (qm) of 0.3636 mmol/g for BPA, and a heterogeneous qm of 0.9229 and 0.9155 mmol/g for MB and Cu2+, respectively. The multicomponent experiment indicated that BPA and MB adsorptions onto CA-β-CD were independent from each other, whereas MB and Cu2+ competed over the same sites. An adsorption mechanism was proposed: each component of CA-β-CD played an essential role, the cyclodextrin cavities contributed to entrapment of non-polar BPA, and the surface carboxyl groups provided binding sites for polar MB and Cu2+. Adsorption performance of the polymer was unaffected by humic acid, a major component of natural organic matter. Overall, due to its green synthetic procedure, versatile and good adsorption performance, excellent recyclability and anti-jamming capacity, CA-β-CD has great potentials for practical applications in water purification.