Emeraldine Salt-Nanocarbon Composites as a Material for Copper Recovery from Industrial Wastewaters
Authors: Stando Paweł , Stando Grzegorz , Sahlman Mika , Lundström Mari , Janas Dawid 
Published: September 2023

Nanocarbon films are characterized by high surface area[1], appreciable electrical conductivity[2], and good mechanical properties[3]. These properties make them suitable for application as electrode materials in various electrochemical processes. For instance, nanocarbon electrodes can be used for selective deposition of metals onto their surface[4]. In particular, it is beneficial to accumulate Cu atoms on the surface of carbon nanomaterials as such composite exhibits much improved electrical conductivity and strength. To make this process as efficient as possible, functional groups containing oxygen or nitrogen are attached to the nanocarbon surface, prior to electrodeposition, but their presence may deteriorate the capabilities of material for charge propagation.
Alternatively, conductive polymers such as polyaniline (PANI) can be physically attached to carbon to improve their electrochemical properties[5], without introducing defects in the structure that negatively affect the electrical properties of the material. Different forms of PANI have substantial effects on the properties of composites, emeraldine salts (ES) have been chosen based upon their higher electrical properties. ES are characterized by the highest increase in electrical and mechanical properties of composites.
Our research focused on the selective deposition of metals onto
ES-nanocarbon composites from industrial wastewaters, which contained such metals as magnesium, iron, nickel, and copper. Aniline was electropolymerized onto the nanocarbon surface by cyclic voltammetry to make the material more suitable for recovery of metals from such source. The process of copper recovery was highly selective, which was confirmed by characterization of the surface by EDX mapping. Despite the trace amounts of copper (428 ppm) in the used industrial wastewater, Cu nanoparticles were highly visible on the PANI-nanocarbon surface after just one hour of the process. Analogously, nickel has also been recovered by this method, which demonstrates that the presented approach may be tuned for deposition of various metals onto nanocarbon to make previously unreported nanocarbon-metal composites.

P.S. would like to thank the Ministry of Education and Science (MEiN/2022/DIR/3086) of Poland for financial support, which enabled the attendance to the conference. G.S. and P.S. would like to thank the Ministry of Education and Science of Poland for financial support of scientific work from budget funds for science in the years 2019–2023 as a research project under the “Diamond Grant” program (grant agreement 0036/DIA/201948). G.S., P.S. and D.J. would like to thank the National Centre for Research and Development, Poland (under the Leader program, grant agreement LIDER/0001/L-8/16/NCBR/2017). P.S. acknowledges the National Agency for Academic Exchange of Poland (NAWA, (under the Academic International Partnerships program, grant agreement PPI/APM/2018/1/00004) for supporting training in the Aalto University, which enabled the execution of the study. GS would like to thank also NAWA (under the Iwanowska program, grant agreement PPN/IWA/2019/1/00017/UO/00001) for financial support during the stay at the University of Pittsburgh in the USA.

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