Inert Center Immobilization of Bromopyrogallol Red on Diazo-Enriched Silica Gel Support via Multipoint Mode: Attune pH Extractor for Sequential Separation of Nd(III), Th(IV), Ce(IV), and Zr(IV) from Aqueous Admixtures

In surface functionalization, picric acid was coupled with SG using dimethyldichlorosilane, an efficient silane coupling reagent, resulting in a highly enriched nitro compound. Subsequently, we developed the diazo compound of a densely populated diazo surface to diazo-couple the Bromopyrogallol Red (BPR) using BPR's inert center via multipoint mode: {Si(OSi)₄(H₂O)_<i>x</i>}_<i>n</i>{OSi(CH₃)₂-O-C₆H₂(<i>N</i>═N⁺)₃(C₁₉H₁₀Br₂O₈S)_1.5}₄.<i>y</i>H₂O. The parameters <i>x</i>, <i>n</i>, and <i>y</i> have been precisely determined as 0.5, 45, and 20, respectively. The synthesized material is an attune pH extractor comprising appreciable BPR content (40 μmol g^-1); BPR's phenolic -OH is involved in extracting Nd(III) as a dimer, while Ce(IV), Th(IV), and Zr(IV) are used as a monomer to attain the respective BTC values of 156, 79, 84, and 88 μmol.g^-1. The extractor enhances the solution concentration with enrichment factors 49, 44, 46, and 53 for the respective metal ions Nd(III), Ce(IV), Th(IV), and Zr(IV), respectively, and sequentially separates them from aqueous admixtures. The synthesized material was durable for up to 18 months and may be recycled 200 times without losing extraction capacity.