Recovery of platinum group elements (PGEs) from wastewater : a case for the development of predictive adsorption numerical methods

Abstract

Platinum group elements (PGEs) are very important for the modern world, and they are used in many applications due to their physical and chemical properties that cannot be found in other naturally occurring elements. This means that the availability of PGEs now and in the future is very crucial. However, research has indicated that PGEs are at the edge of becoming scarce due to gradually depleting natural resources. This review reports on the recent techniques for the recovery of PGEs from secondary sources. However, there is still a need for cheap and efficient methods and technologies that can be applied at large scale. The need for PGEs speciation information especially in adsorption and/or recovery studies is discussed. Speciation modelling codes (PHREEQC, Geochemist’s workbench, MINEQL+, MINTEQA2 and WHAM) which can be used for this purpose are also discussed. These models can be used for adequate predictive adsorption of PGEs in order to determine the performance of the adsorbents beyond the available laboratory, pilot or real application data. However, most of the PGEs are not included in the available databases used in the numerical models hence, new databases should be developed, or the modification of the available databases will always be a requirement in order to simulate PGEs accurately and successfully, under various conditions. To automate the calibration of the models including calibration-constrained uncertainty analysis of the models, parameter estimation (PEST) software which can estimate important parameters and compute sensitivities of model outputs to parameters, can be coupled with the modelling codes.