Cadmium ions sequestration and transformation on confined magnesium hydroxide gel beads

Powdered magnesium hydroxide (MH) has the advantages of high activity, low cost and environmental friendliness, while it faces difficulties in recovery and solid-liquid separation after being used in an aqueous solution. In this study, magnesium hydroxide confined in millimeter-sized chitosan xerogel beads (CXB@MH) were constructed for the first time via facile sol-gel process. High loading (47.7 wt%) and uniform dispersion of MH nanosheets inside CXB@MH endowed it with excellent removal capacity (234.0 mg/g). The macroscopic property of the CXB@MH allowed it easy to recycle from aqueous solution and can be filled in a fixed bed for dynamic Cd2+ removal. Cd2+ ions were removed on the surface of CXB@MH by two-step ion exchange process: first an intermediate Cd(OH)2 were formed, followed by conversion to CdCO3 under ambient air. This work provides a reference for the preparation of analogous support-based nanocomposites for water treatment.

Automated summary

By loading magnesium hydroxide nanosheets into chitosan xerogel beads, a new material with excellent removal capacity was constructed. This material is easy to recycle and suitable for dynamic Cd2+ removal in fixed beds.