Grantee Research Project Results

Nanobubble-Enhanced Soil Remediation: A Green And Efficient Strategy For Oil Contamination Cleanup

EPA Grant Number: SU841130
Title: Nanobubble-Enhanced Soil Remediation: A Green And Efficient Strategy For Oil Contamination Cleanup
Investigators: Zhang, Wen , Marhaba, Taha
Institution: New Jersey Institute of Technology
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: March 1, 2025 through February 28, 2027
Project Amount: $75,000
RFA: 21st Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity, and the Planet Phase I (2024) RFA Text
Research Category: P3 Awards , Heavy Metal Contamination of Soil/Water , Clean Water , Waste Reduction and Pollution Prevention , Groundwater, Organic Contaminants, Treatment, Modeling , Groundwater, Contaminant Fate and Transport , Groundwater, Metals, Treatment, Biotransformation , Groundwater, Contaminants, Treatment , Health Effects , Pollution Prevention/Sustainable Development , Water Quality , Human Health , Land and Waste Management , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety , Sustainable and Healthy Communities , Environment , Water Treatment

Description:

This project embarks on a green soil rinsing or cleaning process using fine bubbles-enriched water to enhance the oil desorption, mobilization and removal from contaminated soil matrix. Nanobubbles in water have repeatedly been reported to exhibit unique physicochemical and fluid dynamic properties that macrobubbles or microbubbles do not have. For example, nanobubbles have a long residence time in water due to their low buoyancy and high stability against coalesces, collapse or burst, and the formation of bulk bubbles. Nanobubbles have a higher efficiency of mass transfer compared to bulk scale bubbles due to the high specific surface areas. The high specific surface also facilitates physical adsorption and chemical reactions in the gas liquid interface. The collapse of nanobubbles creates shock waves, which in turn, promotes the formation of hydroxyl radicals (•OH), which may even promote degradation of organic matters or disinfection under proper conditions (e.g., sonication agitation or UV irradiation). With respect to soil remediation, the high surface areas and hydrophobicity of nanobubbles could effectively adsorb, immobilize and detach soil contaminants such as heavy metals and hydrophobic organic pollutants. Non-toxic gases such as oxygen (O₂), carbon dioxide (CO₂) or hydrogen (H₂) could be used to produce nanobubbles in water for rinsing the contaminated soil. We hypothesize that due to their different redox potentials and chemical impacts, different gaseous nanobubbles may result in different oil-bubble and soil-bubble interactions, which ultimately affect oil removal from contaminated soil. Our prior study discovered that CO₂ nanobubbles achieved the highest leaching rate of Pb from soil, followed by CH₄ and H₂ nanobubbles. Moreover, the CO₂ nanobubble water rinse resulted in different leaching kinetics of different metals (Pb, Cu, Zn, and Cr) from the contaminated soil column. Thus, this project will reveal new insights into the oil removal and leaching mechanisms under different conditions and potentially result in a transformative solution to address soil remediation. The research findings will potentially enable a greener soil rinsing process that could reduce or even eliminate the use of synthetic chemicals such as surfactants or solvents that could harm our environment or human health. Besides research efforts, new course modules and research seminars will be developed to integrate the research activities into student engagement and education to showcase our sustainable soil treatment approaches. Undergraduates and graduates in different STEM disciplines (e.g., civil, chemical and environmental engineering) will be invited to participate in these research seminars or the research project tasks under PI’s team’s mentorship.

Objective:

Extensive industrial and agricultural activities as well as wastewater discharge or surface runoff bring tons of pollutants such as heavy metals, organic solvents, chemical fertilizers and pesticides and cause soil pollution. New Jersey, for instance, has many brown sites and superfund sites in the US that are characterized by persistent legacy soil or water contaminants that must be treated to prevent human exposure. Soil remediation is critical to prevent surface water or groundwater pollution, protect human health and improve agricultural product quality. Conventional soil remediation includes soil washing/flushing, thermal desorption, vitrification, photocatalyst and bioremediation, which, however, are relatively expensive, time consuming and chemically intensive. This project aims to develop a green and powerful washing process using nanobubbles water for soil contaminant removal. The project will examine (1) the removal of oil (e.g., diesel and gasoline) from simulated contaminated soil through nanobubble water mixing and washing under various conditions (e.g., sonication and surfactant addition); (2) the mechanisms of interaction between different types of nanobubbles (e.g., CO₂ and O₃), soil and contaminants. The project findings will provide an insight for novel chemical-free and sustainable soil cleaning technologies for remediation of contaminated soil.

Expected Results:

The anticipated research outputs include peer-reviewed journal articles, conference presentations, soil washing protocols, patent applications and project reports. Moreover, educational activities will be run collaboratively with industrial partners in soil remediation companies. The potential project outcome includes transformative knowledge to alleviate soil contamination in different affected small, rural, tribal and/or underserved communities via devising this novel soil washing technique or process using nanobubbles. Consequently, the soil decontamination can improve human health and well-being and also boost environmental quality, aesthetic values, economic competitiveness. The measure of success is the numbers of peer-reviewed journal publications or presentations, workshop attendance/feedback, industrial collaborations for future pilot studies or commercialization.

Supplemental Keywords:

nanobubbles, oil, soil remediation, soil washing