Date of Award

Summer 2024

Document Type

Open Access Dissertation

Department

Environmental Health Sciences

First Advisor

Jamie Lead

Abstract

To protect humans and the environment, human actions that may expose living organisms to toxic metals are heavily regulated in developed countries. The use and production of toxicants in commercial applications is tightly controlled in the United States of America by federal and state laws. Due to this fact, United States manufacturing companies are required to control the amount of regulated toxicants that leave their facilities. Toxic metals in wastewater are heavily regulated by federal and state law, with manufacturing facilities permitted individually for the concentrations of metals they are allowed to discharge via their wastewater. From previous research conducted in our laboratory, we know that our in-house synthesized polyvinylpyrrolidone-coated magnetite (iron oxide) nanoparticles are capable of removing dissolved cadmium, chromium, nickel, and lead from both synthetic soft water and synthetic sea water. We decided to assess the real-world utility of nanoparticle-mediated metal water treatment.

A customer discovery process was conducted to determine whether there was a real-world need for nanoparticle-mediated metal water treatment. During this customer discovery process, 98 individuals from 24 different potential customer sectors were interviewed using a semi-structured questionnaire. A customer discovery process was conducted to determine who had a real-world need for nanoparticle-mediated metal water treatment. The surface finishing sector, particularly the electroplating industryindustry, was identified as the best fit for our nanotechnology following these interviews. To better interpret and apply our customer discovery data, a universal, mix-method quantitative/qualitative approach was developed to determine optimal customer segment and value propositions for a new technology, along with the minimum performance requirements the technology must meet before it can move onto the next commercialization stage. Applying this method to our metal treatment nanotechnology supported our initial qualitative conclusion from the customer discovery process, that our polyvinylpyrrolidone-coated magnetite nanoparticles are highly suited for the treatment of metals in electroplating wastewater. Proof-of-concept metal treatment experiments with real electroplating wastewater provided by a Lexington, SC company further supported this conclusion.

Polyvinylpyrrolidone-coated magnetite nanoparticles were synthesized using a hydrothermal batch method previously developed in our laboratory. Synthesized nanoparticles were characterized using dynamic light scattering, laser Doppler microelectrophoresis, transmission electron microscopy, and inductively coupled plasma mass spectrometry. Metal treatment experiments were conducted by adding our nanoparticles to the metal containing water and then magnetically separating for one hour. Electroplating wastewater samples were tested under a range of conditions to determine the optimal nanoparticle treatment conditions. Inductively coupled plasma mass spectrometry was used to measure the concentrations of silver, lead, chromium, nickel, copper, and zinc in both treated and untreated electroplating wastewater. Treatment conditions varied by wastewater sample based on the volume of bleach necessary for completing the necessary cyanide destruction procedure, which is a commonly required pre-treatment process for plating companies using metal-cyanide salts in their plating baths. The best metal treatment results occurred at pH ≥ 11.5 with excess bleach added following the complete destruction of cyanide. Under these conditions, aqueous metals formed a precipitate that aggregated easily with the nanoparticles and was subsequently magnetically separated from solution. The remaining metal/nanoparticle solid phase was then bath ultrasonicated in water or acidified water to recover the metals and nanoparticles. Nanoparticles were washed and reused for a total of five wastewater treatment cycles. Our results indicate that these nanoparticles are capable of ≥90% removal efficiency, meeting our partnering company’s legal metal treatment requirements (i.e. discharge limits), and that subsequent removal of metals and reuse of nanoparticles is feasible. This work strongly supports our hypothesis that these nanoparticles are suitable candidates for electroplating wastewater treatment as they can remove metals to below the legal discharge limits after which the metals can be easily recovered.

Rights

© 2024, Madeleine Mary Meyer

Download

Share

COinS