CHEMOSPHERE
·
2023
·
IF 8.8
Zejun Wang,Zhibing Yang,Yi-Feng Chen
Surfactant-enhanced aquifer remediation has been proved successful to remove dense non-aqueous phase liquids (DNAPLs) from contaminated sites. However, the underlying mechanisms of the DNAPL mobilization and solubilization at the pore scale remains to be addressed for efficient application to the field remediation system. In this work, the emerging microfluidic and imaging technologies are applied to investigate the dynamics of DNAPL remediation. Visualized experiments of the evolution of DNAPL remediation are performed to study the role of surfactant type, concentration and injection rate. The DNAPL remediation is dominated by mobilization followed by solubilization for most surfactants. Mobilization occurs as soon as surfactants and DNAPL are in contact until forming a new stable phase structure, and the solubilization continues until the end of injection. We observe the breakup behavior of long droplets and ganglia during the mobilization, which is attributed to the surfactant-reduced interfacial tension and thus expedites DNAPL mobilization and redistribution. During the solubilization, the formation of micelles incorporating DNAPL fractions increases the DNAPL concentration gradient and thus enhances the mass transfer, but the rate-limited diffusion of micelles reduces the mass transfer rate coefficient. Increasing the surfactant content and decreasing the injection rate can promote mobilization and solubilization. The DNAPL mobilization ability of the surfactants SDS and SDBS is stronger than SAOS and Tween 80 regardless of the injection rates. Tween 80 may be considered an ideal surfactant of only solubilization but not mobilization is desired. This work elucidates the pore-scale mechanisms during surfactant-enhanced DNAPL remediation, which are beneficial for upscaling studies, predictive modeling, and operation optimization of DNAPL remediation in the field.
研究领域:
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF CONTAMINANT HYDROLOGY
·
2026
·
IF 5.5
Yongqiang Chen,Zhi Dou,Meng Chen,Zejun Wang,Jinguo Wang
Migration direction determines DNAPL fate across the sand-clay interface. • DNAPL accumulates above the interface when migrating from clay to sand. • Clay lenses are more effective than sand lenses in hindering vertical transport. • Capillary barrier effects dictate DNAPL redistribution at contrasting interfaces. Heterogeneous porous media, characterized by contrasting interfaces such as those between sand and clay, are ubiquitous in vadose zones. However, the transport mechanisms of Dense Non-Aqueous Phase Liquids (DNAPLs) across these interfaces remain poorly understood. This study uses an innovative stratified nuclear magnetic resonance (NMR) methodology which enables spatially-resolved T 2 spectral analysis via a spin-echo single-point imaging (SE-SPI) sequence to investigate the spontaneous infiltration behavior and underlying mechanisms of DNAPL across variably configured sand-clay interfaces. Through experiments simulating distinct interfacial scenarios, real-time, non-destructive monitoring of DNAPL spatial distribution was achieved. The results show that DNAPL transport depth and vertical distribution are critically governed by both the direction of interfacial crossing and the lens type within stratified media. Specifically, when migrating from clay to sand, DNAPL accumulates above the interface, while the reverse direction leads to predominant retention below. Notably, clay lenses exert a more pronounced capillary barrier effect than sand lenses, significantly reducing vertical migration. The study quantitatively establishes that interfacial capillary barrier effects, represented by newly proposed metrics such as retention rate and capillary retention efficiency, critically determine the redistribution patterns of DNAPL. This study clarifies the governing role of interfacial capillary barriers and provides quantitative metrics necessary to predict DNAPL fate and optimize mitigation efforts in heterogeneous subsurface environments. Download: Download high-res image (153KB) Download: Download full-size image
✓ 已验证
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2021
·
IF 10.588
Zhuning Geng,Bo Liu,Guanghe Li,Fang Zhang
Electrical resistance heating (ERH) has been widely applied for contaminant remediation in heterogeneous sites especially when low permeability zones exist, yet requires high energy input. To address the low energy-efficiency of ERH using conventional alternating current (AC), pulsed direct current (PDC) obtained by current rectification was introduced for heating to enhance dense nonaqueous phase liquid (DNAPL) migration in low permeability zones. Here we showed the proof-of-concept in a lab-scale two-dimensional heterogeneous sand system (40 cm × 30 cm) with trichloroethylene (TCE) DNAPL in the central low permeability zone. Applying PDC achieved faster temperature increase compared to that with the conventional AC of the same voltage gradient. The overall TCE removal efficiency from the cell increased from 79.0% to 89.6% with increasing PDC voltage gradient from 3 to 3.75 V cm –1 , compared to that of 9.4–91.1% with conventional AC. The lowest energy consumption of PDC was 390 kWh kg –1 at a medium voltage gradient of 3.5 V cm –1 , which was 27.8% lower compared to that with AC at the same voltage gradient. These results suggest that remediation using pulsed direct current is a promising approach to improve the energy-efficiency and effectiveness of ERH.
研究领域:
环境工程
·
污染修复
·
岩土工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ADVANCES IN WATER RESOURCES
·
2026
·
IF 4.1
Kun Xing,Xiaoqing Shi,Amalia Kokkinaki,Zhibing Yang,Xueyuan Kang,Liangchao Zou
Microfluidic rough-fracture experiments track residual DNAPL morphology, interfacial area, and dissolution. • Interfacial-area scaling depends on residual architecture and dissolution stage. • Interface renewal and hydraulic accessibility jointly control DNAPL dissolution in rough fractures. Residual dense non-aqueous phase liquids (DNAPLs) trapped in fractured rock can sustain groundwater contamination through long-term dissolution. In rough fractures, aperture-field anisotropy controls preferential flow and residual source-zone architecture, causing interfaces of similar geometric area to differ in hydraulic accessibility. However, direct pore-scale evidence remains limited on how residual architecture and hydraulic accessibility jointly control dissolution pathways and interfacial-area-based mass-transfer scaling. Here, microfluidic experiments were used to quantify the co-evolution of residual DNAPL saturation, specific water–DNAPL interfacial area ( a s ), and the image-derived apparent dissolution coefficient ( K app ). Aperture-field anisotropy and displacement history generated pool-dominated (PP), ganglia-dominated (GP), and mixed (MP) residual architectures with distinct dissolution pathways. Across Re = 0.395–6.583, flow rate altered dissolution kinetics and stage duration, but the dominant architecture-dependent response remained identifiable. PP systems underwent fragmentation-driven interface generation followed by contraction-dominated depletion, GP systems were dominated by ganglia contraction, and MP systems exhibited spatially sequential dissolution. GP trajectories generally occupied higher K app ranges, whereas MP trajectories occupied lower ranges. Aperture-field anisotropy modified residual morphology, pool elongation, interfacial-area evolution, and fragmentation persistence, indicating a pathway-level control on dissolution behavior. The proportional K app − a s relationship did not hold universally: fragmentation-dominated stages produced scattered relationships, whereas contraction-dominated stages yielded more coherent but architecture-dependent responses. During GP Stage III, K app decreased more rapidly than total a s , indicating reduced apparent transfer efficiency per unit geometric interface. These findings show that predictive models of DNAPL dissolution in fractured media should account for residual source-zone architecture, aperture-field anisotropy, dissolution stage, and the evolving hydraulic effectiveness of the water–DNAPL interface.
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）