Miniaturization of Anthracene-Containing Nonapeptides for Selective Precipitation/Recovery of Metallic Gold from Aqueous Solutions Containing Gold and Platinum Ions

Kin-Ya Tomizaki,Haruka Okazaki,Tatsuki Tonoda,Takahito Imai,Shungo Teramura,Masahiro Asano

doi:10.3390/pr9112010

Abstract

The separation and recovery of noble metals is increasingly of interest, in particular the recovery of gold nanocrystals, which have applications in medicine and industry. Typically, metal recovery is performed using liquid–liquid extraction or electrowinning. However, it is necessary to develop noble metal recovery systems providing high selectivity in conjunction with a one-pot setup, ready product recovery, and the use of dilute aqueous solutions. In prior work, our group developed a selective gold recovery process using peptides. This previous research showed that RU065, a nonapeptide containing an anthracene moiety (at a concentration of 2.0 × 10−4 M), is capable of selective reduction of HAuCl4 to recover gold from a solution of HAuCl4 and H2PtCl6, each at 5.0 × 10−5 M. However, peptide molecules are generally costly to synthesize, and therefore it is important to determine the minimum required structural features to design non-peptide anthracene derivatives that could reduce operational costs. In this study, we used RU065 together with 23 of its fragment peptides and investigated the selective precipitation/recovery of metallic gold. RU0654–8, a fragment peptide comprising five amino acid residues (having two lysine, one L-isoleusine, and one L-alanine residue (representing six amide groups) along with an L-2-anthrylalanine residue) provided an Au/Pt atomic ratio of approximately 8, which was comparable to that for the full-length original RU065. The structural features identified in this study are expected to contribute to the design of non-peptide anthracene derivatives for low-cost, one-pot selective gold recovery.

Highlights

Introduction published maps and institutional affilThe separation and recovery of noble metals from industrial wastewater has recently received significant attention as a component of sustainable chemistry
Based on our prior results on the synthesis of gold nanocrystals using peptides containing aromatic side chains [25,26], we investigated the selective recovery of gold from homogenous aqueous solutions containing a mixture of dilute HAuCl4 and
23 different peptides having smaller structures than the original RU065 were obtained by sequentially removing amino acid residues from both N- and C- termini to the Ant group at the sixth position of the original molecule. These fragment peptides are referred to as RU065x-y, where x and y are the positions on the original RU065 (a) at which these fragments begin and end, respectively (Figure 1C and Figure S1)

Summary

Introduction

Introduction published maps and institutional affilThe separation and recovery of noble metals from industrial wastewater has recently received significant attention as a component of sustainable chemistry. In order to separate metal ions of interest, liquid–liquid extraction is a common technique where metals such as gold and palladium can be extracted from an aqueous phase by employing specific organic solvents [3,4,5,6,7]. This technique is commonly used but is labor intensive and requires organic solvents that can have environmental impacts. New approaches to liquid-based separation of noble metals have been demonstrated These include the use of ionic liquids supported on silica to extract platinum group iations

Methods

Results

Conclusion