Description
Soil contamination by refined petroleum hydrocarbons remains a significant environmental problem due to these compounds' toxicity, persistence, and mobility. Bioremediation has emerged as an environmentally friendly and cost-effective approach that uses microorganisms to degrade hydrocarbons into less harmful substances. However, its overall performance is often limited by nonuniform distribution of biological amendments, preferential flow in highly permeable zones, and insufficient contact between reactive agents and contaminants. In addition, limited oxygen availability in conventional liquid-based systems constrains aerobic biotreatment and reduces microbial degradation efficiency.
Foam-assisted (bio)remediation technologies have shown promise in overcoming these limitations by acting as transport and flow-control media, enabling remediation amendment delivery, contaminant displacement, preferential-pathway blocking, and enhanced oxygen vectorization for aerobic biodegradation through interfacial and multiphase flow processes in porous media. The effectiveness of this approach is governed by the foaming properties, interfacial behavior, and sorption/desorption characteristics of the surfactant formulations injected into porous media.
This work aims to evaluate environmentally friendly and cost-effective surfactant formulations to produce stable foams suitable for biological amendment transport. Surfactant selection is critical: biosurfactants such as rhamnolipid and saponin offer low toxicity and high biodegradability but are more expensive, while synthetic surfactants (Sodium dodecyl sulfate (SDS), Tween 80, Triton X-100, and Cocamidopropyl Betaine (CAPB)) are cheaper but potentially less sustainable. In this study, single (control), binary, and ternary surfactant formulations were investigated through bulk characterization and batch experiments.
Surface activity of surfactants was investigated using dynamic surface tension measurements performed with a Drop Shape Analyzer (DSA 100, Krüss) over a broad concentration range to establish surface tension-concentration relationships and determine critical micelle concentrations (CMC). These measurements were used to assess synergistic effects in mixed surfactant systems, which directly influence foam generation and foam stability under environmental conditions.
Foam behavior was evaluated using bulk foam analysis using the Dynamic Foam Analyzer (DFA 100, Krüss) to characterize foamability, foam stability, and foam structure, which is critical for foam transport in porous media. Foamability was quantified based on initial foam height and generation efficiency, while foam stability was assessed through foam half-life measurements. The foam structure was further analyzed by monitoring the bubble size distribution and its temporal evolution, providing insight into bubble coalescence, coarsening, and liquid drainage mechanisms.
To evaluate contaminant bioavailability, the desorption characteristics of surfactant formulations were planned to be investigated through batch experiments. These experiments aim to quantify surfactant-enhanced desorption of contaminants from soil.
Overall, this study demonstrates how surfactant formulation controls foam properties, interfacial behavior, and contaminant desorption mechanisms. By investigating surface activity, foam generation, foam stability, and desorption processes, the results provide a mechanistic foundation for understanding foam-assisted bioremediation processes.
| Speaker information | PhD 2nd year |
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