Lignosulfonate-Based Conducting Flexible Polymeric Membranes for Liquid Sensing Applications.

Sandra Magina,Sílvia Soreto,Ana Barros-Timmons,Luís Cadillon Costa,Alisa Rudnitskaya,Dmitry V Evtuguin

doi:10.3390/ma14185331

Abstract

In this study, lignosulfonate (LS) from the acid sulfite pulping of eucalypt wood was used to synthesize LS-based polyurethanes (PUs) doped with multiwalled carbon nanotubes (MWCNTs) within the range of 0.1–1.4% w/w, yielding a unique conducting copolymer composite, which was employed as a sensitive material for all-solid-state potentiometric chemical sensors. LS-based PUs doped with 1.0% w/w MWCNTs exhibited relevant electrical conductivity suitable for sensor applications. The LS-based potentiometric sensor displayed a near-Nernstian or super-Nernstian response to a wide range of transition metals, including Cu(II), Zn(II), Cd(II), Cr(III), Cr(VI), Hg(II), and Ag(I) at pH 7 and Cr(VI) at pH 2. It also exhibited a redox response to the Fe(II)/(III) redox pair at pH 2. Unlike other lignin-based potentiometric sensors in similar composite materials, this LS-based flexible polymeric membrane did not show irreversible complexation with Hg(II). Only a weak response toward ionic liquids, [C2mim]Cl and ChCl, was registered. Unlike LS-based composites comprising MWCNTs, those doped with graphene oxide (GO), reduced GO (rGO), and graphite (Gr) did not reveal the same electrical conductivity, even with loads up to 10% (w/w), in the polymer composite. This fact is associated, at least partially, with the different filler dispersion abilities within the polymeric matrix.

Highlights

Due to an increase in industrial and human activities, the presence of heavy metal salts such as lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), zinc (Zn), and copper (Cu), among others, in wastewater has led to an increasing accumulation of these chemicals in the environment
All solvents and other reagents, namely, 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris), potassium dichromate, chromium(III) chloride hexahydrate, zinc(II) chloride, lead(II) nitrate, ammonia, sodium nitrate, cadmium(II) nitrate, copper(II) chloride, silver(I) nitrate, potassium ferrocyanide(II), potassium ferricyanide(III), mercury(II) chloride, 1-ethyl-3-methylimidazolium chloride, and choline chloride were of analytical grade and were purchased from either
Unlike PU composites based on kraft or organosolv lignins, multiwalled carbon nanotubes (MWCNTs)-doped LS4

Summary

Introduction

Due to an increase in industrial and human activities, the presence of heavy metal salts such as lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), zinc (Zn), and copper (Cu), among others, in wastewater has led to an increasing accumulation of these chemicals in the environment. Considering environmental and health concerns, their removal from wastewaters is imperative [1] Their detection in aqueous systems is crucial. Electrochemical sensors, such as potentiometric, amperometric, and conductometric sensors, are interesting for environmental water monitoring as they are suitable for the determination of chemical species such as heavy metals, among others. They are user-friendly, wellsuited for miniaturization, have short response times, a wide dynamic range, low energy consumption, low cost, ease of preparation, good sensitivity, and high selectivity [2,3,4]

Methods

Results

Conclusion