Superb Adsorption of Congo Red by Zn-Cr Layered Bimetallic Hydroxides Prepared from Electroplated Sludge

Graphical Here, we used a two-phase solvothermal method to prepare electroplating sludge into LDHs. the conditions for the formation of LDHs were achieved by sodium oleate intercalation and the addition of divalent metal ions to prepare a material with a layered nanostructure. The adsorption of Congo red was mainly realized by surface metal complexation, formation of hydrogen bond and electrostatic attraction. It is a challenge to achieve the harmless treatment and resourceful use of various metal elements in electroplating sludge, and converting them into functional materials has become an important technological direction. Based on the existence of various metal ions in electroplating sludge, sodium oleate intercalated Zn−Cr-LDHs (Zn−Cr-layered double hydroxides) were prepared by two-phase solution heating method. The adsorption process of the prepared LDHs for Congo red (CR) in aqueous solution can be described by Langmuir isotherm model and pseudo-second-order kinetic model and the maximum adsorption capacity is 2750.43 mg/g. The results of TEM and XPS show that the adsorption mechanism is dominated by electrostatic adsorption, ion exchange process, hydrogen bonding interaction and surface complexation. Therefore, this paper provides a strategy for recovering metal elements from electroplating sludge to prepare LDHs adsorption materials with ultra-high adsorption capacity.