Constructing FeS/MgAl-carboxylate layered double hydroxide functional materials using steel slag for Cr(VI) removal

Vast progress in recycling steel slag has been witnessed, while advanced approaches for minimizing the metal element-abundant residues are seldomly exploited. In this work, we present a facile strategy to tailor steel slag surface and use various metal components of steel slag to first construct MgAl-carbonate layered double hydroxide supported iron sulfide nanocomposites (FeS-LDH-CO₃) using a filtrate rich in Fe³⁺, Mg²⁺, and Al³⁺ ions after steel slag dissolution. 2D intercalated FeS-LDH-RCOO nanosheets are then obtained via carboxylate anion (acetic acid, chloroacetic acid, dichloroacetic acid, n-propionic acid, acrylic acid) exchange with FeS-LDH-CO₃. FeS-LDH-RCOO nanocomposites are characterized by XRD, Raman, FT-IR, TG–DSC, BET, TEM and XPS. Characterizations revealed the uniformly dispersion of poorly crystalline FeS on LDH nanosheets, and they present high specific surface area and special composite structure. Besides, FeS-LDH-RCOO show superior performances for Cr(VI) detoxification in designed case studies. The acetate intercalated FeS-LDH, FeS-LDH-CH₃COO, shows well Cr(VI) adsorption capacity of 36.1 mg/g via synergy in simultaneously immobilize Cr(VI) on LDH nanosheets and reduce Cr(VI) to Cr(III) on FeS. The fabricated FeS-LDH-RCOO composite not only exploits various components of steel slag while minimizing the metal element-abundant residues, but also possesses well Cr(VI) cleaning ability due the integration of FeS and MgAl-carboxylate LDH. This study thus provides a new toolbox for a reasonable and deep utilization of steel slag which may shift the waste material into things of value in environment cleaning applications.