Ph-Regulated Differential Selective Extraction of Sb(V) and Cr(Vi) Enabled by Guanidine-Bridged Β-Cyclodextrin

Abstract

High-value recovery of Sb/Cr-containing waste is crucial for both environmental conservation and resource sustainability, yet their selective extraction remains a significant challenge. In this contribution, we design and fabricate guanidine-bridged cyclodextrin (CD-G) that exhibit a selective extraction of Sb(V) and Cr(VI) from wastewater. Notably, the Sb(V)/Cr(VI) are capable of being selectively separated through regulating solution acidity, due to the inherent guanidine and hydrophobic cavities on CD-G with manipulated binding ability for them. At the neutral condition, CD-G shows an excellent selectivity for Cr(VI) with a striking separation factor SFCr/Sb of 45.55, whereas in the acidic condition, CD-G displays a reverse selectivity with the SFSb/Cr reaching 30.03. More importantly, the differential extraction of Sb(V) and Cr(VI) can be modulated by pH-controlled protonation process of the guanidinium groups and the specific host-guest interaction between cyclodextrins and Sb(V). FT-IR, XPS and in-situ NMR confirmed the pH-regulated selective extraction. In addition, CD-G-filled column can achieve the on-demand recovery of Sb(V)/Cr(VI) from simulated Sb and Cr-containing waste through smartly regulating pH. This work provides a new avenue for the selective separation of metal resource, contributing to the treatment of industrial wastewater and metal resource sustainability.

Keywords: Co-adsorption, pH regulation, Recovery, Selective extraction, Sb(V)/Cr(VI)