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Humic Acid with Vertical Adsorption Conformation Enhanced the Transport of Petroleum Hydrocarbon-Contaminated Colloids

Environmental Science & Technology 2025 9 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count. Score: 53 ? 0–100 AI score estimating relevance to the microplastics field. Papers below 30 are filtered from public browse.

Yong Liu, Jie Ma, Yong Liu, Jie Ma, Jie Ma, Jie Ma, Ping Zhou, Jie Ma, Bingcong Feng, Bingcong Feng, Bingcong Feng, Bingcong Feng, Bingcong Feng, Bingcong Feng, Bingcong Feng, Bingcong Feng, Yong Liu, Bingcong Feng, Bingcong Feng, Yujie Zhao Liping Weng, Liping Weng, Wanli Lian, Yujie Zhao Bingcong Feng, Li Li, Bingcong Feng, Jie Ma, Yujie Zhao Liping Weng, Jie Ma, Li Li, Yujie Zhao Liping Weng, Liping Weng, Liping Weng, Yujie Zhao Yujie Zhao Yujie Zhao Liping Weng, Liping Weng, Liping Weng, Yujie Zhao Liping Weng, Lei Gan, Yujie Zhao Liping Weng, Li Li, Liping Weng, Liping Weng, Haiming Li, Yujie Zhao

Summary

Researchers investigated how humic acid, a natural organic substance in soil, affects the movement of petroleum-contaminated soil particles through sand. They found that when oil residues occupy the surface of soil colloids, humic acid adopts a vertical orientation that actually enhances particle transport through porous media. The study suggests this mechanism could accelerate the spread of hydrocarbon-contaminated particles in groundwater systems.

Humic acid (HA) enhances colloidal transport in porous media, yet the mechanisms by which the HA adsorption conformation affects colloid transport remain unclear. This study investigated the influence of HA on the transport of petroleum-hydrocarbon-contaminated soil colloids (TPHs-SC) in saturated sand columns. The presence of TPHs on the colloidal surface occupied adsorption sites, hindering HA from forming a horizontal adsorption conformation, as observed on uncontaminated soil colloids (SC). Instead, a vertical adsorption conformation was formed, reducing the overall adsorption of HA. Vertically adsorbed HA increased the colloidal diffuse double-layer potential and extended the Derjaguin-Landau-Verwey-Overbeek energies between colloids and water-bearing media. This was evidenced by higher ζ potentials (-28.5 to -34.0 mV) and enhanced TPHs-SC transport compared to SC (ζ potentials ranging from -25.2 to -29.5 mV) in the presence of HA, particularly under alkaline conditions. Additionally, weak van der Waals and electrostatic interactions between TPHs near colloidal surfaces and free HA/TPHs formed a zonal distribution, facilitating the cotransport of colloids with TPHs. These findings underscore the significance of the HA adsorption conformation in TPHs-SC transport and provide insights into the critical mechanisms from an environmental structural chemistry perspective.

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