Dynamic Removal of Hexavalent Chromium in a Fixed‐Bed Column Using Refining Steel Slag: Experimental and Modeling Analysis

Abstract

ABSTRACT This study explores the use of a slag issued from refining steel (RSS), a by‐product, as a low‐cost, high‐efficiency adsorbent to remove Cr(VI) from aqueous solutions using a fixed‐bed column. Characterization of RSS revealed a porous, heterogeneous structure rich in mineral phases such as silicates, and metal oxides, providing active adsorption sites. The RSS exhibited a basic surface character with a pHPCZ of 8.3 which favors the adsorption of anionic Cr(VI) species under acidic conditions. Parametric studies showed that Cr(VI) removal efficiency decreased with the increasing of flow rate and initial concentration, but improved with bed height. The maximum removal efficiency reached 79.12% with an adsorption capacity of 9.93 mg.g −1 Breakthrough curves were modeled using Thomas, Yoon–Nelson, Modified Dose–Response (MDR), and Logistic models. The MDR model showed the best fit ( R 2 = 0.94–0.99), describing the asymmetric breakthrough profiles related to intraparticle diffusion and noninstantaneous kinetics. The adsorption mechanism combines electrostatic attraction, surface complexation, and partial reduction of Cr(VI) to Cr(III) on oxidized Fe/Mn sites. Overall, the study demonstrated the potential of steel slag as an efficient and sustainable adsorbent for chromium removal.