Selective and Efficient Platinum Group Metal Adsorption from Wastewater by Localized Triethylamine-Based Poly(Ionic Liquid)

With environmental problems and resource
scarcity, it is urgent
to recover Platinum Group Metals (PGMs) from wastewater. In this study,
poly(styrene-triethylammonium cation) (PIL-TEA) was synthesized, characterized,
and used as adsorbent for Pt(II), Pt(IV), and Ir(IV) in both synthetic
and real wastewater. Various isotherm and kinetic models were employed
to analyze the adsorption process, revealing that it involves chemisorption,
with internal diffusion being the crucial step. The different adsorption
performances of PGMs can be attributed to factors such as electrostatic
interaction, weak bonding, configuration, and electrostatic potential
(ESP) between anions and cations. Notably, ESP complementarity dictates
the actual adsorption performance order: Pt(II) > Pt(IV) > Ir(IV).
The higher the degree of ESP complementarity, the stronger the adsorption
tendency. Furthermore, the study reveals that localized triethylammonium
exhibits remarkable adsorption efficiency for trace PGMs in wastewater,
with adsorption capacities reaching 1.615, 1.354, and 1.010 mmol/g
for Pt(II), Pt(IV), and Ir(IV) respectively. Overall, this research
demonstrates the excellent adsorption performance of PIL-TEA for recovering
PGMs from wastewater thanks to its exceptional ability to resist miscellaneous
ion interference. It also provides valuable insights into the relationship
between the adsorption performance and the structure–property
interplay in wastewater.