Low carbon footprint biochar composite electrodes for point of need environmental analysis. A promising material to manufacture flexible electrodes

MOSQUERA ORTEGA, MÓNICA; FIGUEREDO, FEDERICO; ARVA, ALEJANDRO; GONZALES, MARIA JESUS; SAAVEDRA, ALBERT; LONG, LEONEL; ARNAL, PABLO; CORTÓN, EDUARDO; SUSMEL, SABINA

Roma

Workshop; GS 2023 - Workshop del Gruppo Interdivisionale Sensori; 2023

Società Chimica Italiana - Gruppo Interdivisionale Sensori

In recent years, several studies have been showing the presence of heavy metals in sediments and water of the Adriatic Sea, with up to 4 ug/g of Pb+2 being detected. The gold-standard analytical technique to detect traces of Pb+2 is atomic absorption spectrometry (AAS). However, its high cost and non-portable characteristics make it a poor election for point-of-need analysis. Electrochemistry has been successfully applied in the detection of environmental contaminants including heavy metals, proving to be selective, portable, and cost-efficient; to have robust, economic, and simple disposable electrodes reveals as the bottleneck for this method. Carbonized vegetal organic waste retains the porosity of the original materials, having porous (macro, micro and mesoporous) structure, the high surface area the mass transfer facilitates. Likewise, its characteristics and physicochemical properties will depend on the type of raw material, on the pyrolysis conditions, and the preparation of the material before and after of pyrolysis process (size reduction, cleaning, exfoliation, etc.). In this work, we report for the first time, the manufacture of plastic electrodes that contain biochar, from peanut shell, prepared by means of a home-built kiln4 (yield 43%, 86 g final mass) that produce large amount of material in a sustainable way (i.e., gas noble not required, process not energy-intensive, use of low coast equipment). The SEM and BET analysis demonstrated the presence of pores between 1 to 10 um. In the same way elemental analysis showed the C is the principal component (94.13%), followed by O (4.99%), N (0.67%) and S (0.20%). Moreover, a new material is obtained by using chitosan and NaOH 1% (stirring at room temperature, and drying at 60°C overnight) to liquid-exfoliate biochar, which combined with graphite (75%), provide of an interesting blend to manufacture of flexible electrodes. The plastic electrodes prepared with the blend of organic materials here optimized is tested for the environmental detection of lead (Fig. 1). The electrochemical behaviour was studied using the cyclic voltammetry (K3Fe(CN)6 1 mM, KCl 100 mM as support electrolyte), and Pb2+ detection was studied using stripping wave voltammetry (0.1 M acetate buffer, pH 4.5), finding, as preliminary results, a limited of detection of 83 ng/mL, which is of the same order of magnitude as the determination conducted with AAS although the conditions used with the exfoliated biochar-based plastic electrode is very mild compared to those required in AAS analysis.