EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Selective recovery of Pd from complex aqueous industrial waste and process streams is of increasing interest due to its high economic value and supply disruptions. Given the low pH and high anion concentrations encountered in these streams, the development of hydrolytic stable Pd scavenging materials with tailored surface chemistry is envisaged. In this project, titania surfaces are grafted with mercaptopropylphosphonic acid (MPPA). The impact of the MPPA concentration on the obtained surface properties of titania powder is provided via a combination of complementary analysis techniques such as elemental analysis, Diffuse-Reflectance Infrared Fourier Transform (DRIFT) measurements, XPS and solid-state 31P NMR. In parallel, sorption experiments with single-Pd solutions revealed important correlations between the surface properties and adsorption performance. In addition, the knowledge on surface modified powdered sorbents has been transferred to macroporous 3D printed titania structures with mesoporous features in the composing titania fibers. 3D structured metal scavengers offer many advantages over free flowing powder such as an improved mass transport and significantly reduced backpressure under dynamic conditions (i.e. column set-up). The impact of the porosity, fiber diameter and inter-fiber distance on the homogeneity and intrusion depth of grafted MPPA groups has been studied. Due to the complexity imposed by the 3D structure, advanced sample preparation and spectroscopic techniques with high lateral resolution (XPS and TOF SIMS mapping) have been applied to gain insights into the intrusion depth of the MPPA groups in the fibers with varying diameter and in the entire 3D structure. The sorption performance of these materials has been evaluated in dynamic sorption tests, simulating industrial relevant conditions.