Human Hair as Adsorbent of Palladium(II) in Solution: A Precursor of Well-Dispersed Size-Controlled Pd Nanoparticles

Fernanda Mendonça,Walace Do Pim,Humberto Stumpf,Gustavo Do Nascimento,Raquel Mambrini,Thaís Silva

doi:10.21577/0103-5053.20180194

Abstract

This work describes, for the first time, the preparation of palladium nanoparticles supported in thermally-treated human hair. Human hair showed to be an efficient adsorbent of Pd2+ in aqueous media, reaching nearly 100% of adsorption from a 100 ppm solution. The thermal treatment of hair containing Pd2+ at 200 oC under nitrogen atmosphere led to the formation of an N, S-containing material presenting 0.5 wt.% of palladium. The material was extensively characterized by elemental analysis (CHN and inductively coupled plasma optical emission spectroscopy (ICP OES)), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopies, and by thermogravimetry (TG), thermogravimetry coupled to mass spectrometry (TG-MS), scanning electron miscroscopy (SEM), transmission electron microscopy (TEM) and dispersive X-ray spectroscopy (EDS) analyses. It was possible to observe that the surface structure of hair was preserved during thermal treatment, presenting palladium nanoparticles with particle sizes of approximately 4 nm. This material was used as heterogeneous catalyst in a preliminary application in nitrobenzene reduction to aniline in aqueous medium using sodium borohydride.

Highlights

Human hair is a bio-waste or waste biomass composed of lipids and proteins, in which keratin is the main component
A later evaluation through atomic absorption spectroscopy showed that Pd2+ adsorption reached nearly 100% under the experimental conditions, resulting in a material which contains 0.5 wt.% of Pd
A first attempt to understand the interaction of metal ions with hair fibers can be related to the isoelectric point of human hair, which is observed at approximately pH 4.32 As adsorption experiment was performed at pH value ca. 5.5, hair fibers will be deprotonated in this condition, indicating that an electrostatic interaction can initially act as driving force for Pd2+ adsorption by human hair

Summary

Introduction

Human hair is a bio-waste or waste biomass composed of lipids and proteins, in which keratin is the main component. A later evaluation through atomic absorption spectroscopy showed that Pd2+ adsorption reached nearly 100% under the experimental conditions, resulting in a material which contains 0.5 wt.% of Pd. A first attempt to understand the interaction of metal ions with hair fibers can be related to the isoelectric point of human hair, which is observed at approximately pH 4.32 As adsorption experiment was performed at pH value ca.

Results

Conclusion