Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

Abstract

A series of oxine ligands, 5-X, 8AOHAC 9 H 6 N (X ¼ H, Cl, SO 3 H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP-1) by the Mannich reaction. The resulting modified composites WP-4(X ¼ H), CB-1(X ¼ Cl), and SB-1(X ¼ SO 3 H) were characterized by elemental analysis, FTIR, and solid state CPMAS-13 C-NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP-4 and CB-1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB-1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine as the dominant species at pH ¼ 2 where the sulfonic acid group is ionized, the quinoline nitrogen is protonated and where two sulfonate groups on adjacent oxines bind a trivalent or divalent ion. All the modified composites show a clear selectivity for trivalent over divalent ions and a good selectivity for gallium over aluminum. The substituent groups on the oxine ligand have only a minor influence on these selectivity trends but SB-1 shows slightly better capture kinetics. The selectivity for gallium over aluminum is applied to the separation of gallium from aluminum, ferrous, and zinc in an acid ore leach of solid tailings obtained from a zinc mine using WP-4.

Investigations on the surface structure and properties of silica‐polyamine composites on the nanoscales and microscales

“…This interpretation is consistent with the very low rate constant for the second micro‐BP‐1 run. In our prior work, a particular stability of the imine intermediates of the PAA bound imine has been noted …”

“…Our initial investigations began in the early 1990's and focused on developing a metal remediation technology that was capable of being commercialized using the SPC platform. Eventually, this surface was expanded to a wider range of applications and synthetic approaches . The early years focused on the synthesis and applications of the polyamine‐amorphous silica gel composites to problems in heavy metal ion removal and recovery .…”

“…Later characterization of the polymer‐surface interface and refining the use of polymer modifying ligands to improve metal selectivity was the focus of the research . Most recently, the emphasis has been on the synthesis of these composites by more environmentally benign routes, the development of materials that can capture anions as well as cations and to their applications in catalysis . Several of the SPC have been scaled‐up and are being commercialized by Johnson–Matthey Ltd. for use in metal recovery and remediation in the mining industry .…”

A methods study of immobilization of PONOP pincer transition metal complexes on silica polyamine composites (SPC)

“…The silica polyamine composites (SPC) are organic-inorganic hybrid composite materials that have been commercially developed and have been used industrially for applications in the recovery and removal of transition metals, precious metals, and mercury from diverse waste streams and mining leaches (Scheme 2). [36][37][38][39]…”

“…[43] In addition, a series of luminescent ruthenium complexes with various types of ligands have also been successfully immobilized on SPC. [14] Given the ease of modification of the SPC amine surface with aromatic ligands using the Mannich Reaction without prior parasubstitution, [38,44] and its ability to provide a basic surface for bifunctional catalysis, SPC would appear to be a suitable candidate for the immobilization of metal pincer complexes.…”