Evaluation of Chromate Removal Using Layered Double Hydroxides and Their Calcined Products Derived from Blast Furnace Slag

Abstract

High-volume blast furnace (BF) slag resulting from iron-making activities has long been considered a burden on the environment. Despite a high number of investigations, aspects of the transformation of BF slag into high value-added products for environmental remediation are still challenging. This work presents a feasible solution toward layered double hydroxides [Ca1.89Mg0.89Al1.0(OH)7.5Cl0.83(CO3)0.11·yH2O] and the formation of its oxide derivatives (Ca1.91Mg0.98Al1.0Cl0.12O4.33) by taking advantage of proper cationic composition in BF slag. The adsorption kinetics and isotherms of adsorbents for Cr(VI) removal were investigated in detail. The adsorption kinetic data for layered double hydroxides (S-LDHs) and oxide derivatives (S-LDOs) agreed well with pseudo-second-order kinetic equations. The adsorption activation energies for Cr(VI) adsorption on S-LDHs and S-LDOs were 41.84 and 60.50 kJ/mol, respectively. Thermodynamic studies demonstrated that the adsorption was a spontaneous and endothermic chemical process, and the better-fitted Langmuir model revealed that the adsorption reaction was monolayer adsorption. S-LDOs exhibited good adsorption capacity (55.37 mg/g), which could be attributed to more active sites with increased specific surface area and a memory effect after calcination. This paper provides highlights regarding the utilization of metallurgical wastes for environmental remediation.