The specialized twin-solution method for selective Pd(II) ions determination and methyl orange removal

The proper determination of Pd(II) ions in the presence of Pt(IV) ions in a waste solution is an intricate analytical issue. Having the knowledge about waste composition, we are able to properly design processes and their selective separation and recovery. Other important aspect is related to the dyes removal coming from textile industry, which is still not resolved. To solve these issues, in this work, we propose the twin solution, which describes a specialized method allowing for both selective Pd(II) ions determination and methyl orange removal. These processes take place in the range of tautomeric equilibrium of methyl orange (pH = 3 - 5). In order to follow the process of cyclopalladated compounds formation, UV-Vis spectra were registered at different conditions, i.e. pH, temperature as well as in the presence of different anions: Cl- and ClO4- and cations: Na+, K+, Pt4+, Pt2+, Ni2+, Zn2+, Cu2+. The developed method of Pd(II) ions determination is distinguished by high sensitivity and selectivity, even in the presence of Pt (IV) ions. Moreover, the palladium content can be determined using UV-Vis spectroscopy at two wavelengths, i.e. at 560 and 702 nm at 50 degrees C. This extends the possibility of metal detection in the presence of cations having spectra in similar wavelength ranges. It is also concluded, that the process of removal of methyl orange is possible only in water: obtained product is unstable and forms an easy-filtratable blue/purple coloured precipitate. (C) 2021 The Authors. Published by Elsevier B.V.