Rhodium recovery from acidic wastewater using radiografted chelating adsorbents

Abstract

This study explores the effectiveness of radiografted chelating adsorbents for the recovery of rhodium (Rh) from acidic wastewater, focusing on functionalized materials with and without loaded silver (Ag). Platinum group metals (PGMs), particularly Rh, are essential yet rare, necessitating efficient recovery methods from industrial waste. Rh exhibits complex chemistry in acidic environments, often complicating its extraction and recovery. Traditional methods such as solvent extraction and ion exchange adsorption have limitations, prompting the development of alternative recovery methods. The adsorption efficiency of these materials was evaluated in a wide range of hydrochloric acid (HCl) concentrations, both in static and dynamic conditions. Radiotracer ¹⁰¹Rh was used to track and quantify Rh adsorption. Results show that the radiografted chelating adsorbents exhibit high distribution coefficients (K_d, LogK_d ≈ 3) and high adsorption capacities (Q_c > 74 mg/g), comparable or superior to commercial resins, particularly under varying pH conditions. Selective recovery of Rh was achieved even in the conditions of extreme competition (with additional 21 metal ions). Therefore, amine and amide-based adsorbents presented in this study could offer a sustainable and inexpensive alternative to standard methods of Rh recovery from industrial waste.