Applications of functional nanoparticle-stabilized surfactant foam in petroleum-contaminated soil remediation.

Surfactant foam (SF) can be used to remediate petroleum-contaminated soil because of its easy transfer to inhomogeneous and low-permeability formations. Nanoparticles (NPs) not only stabilize SF under extreme conditions but also impart various functions, aiding the removal of petroleum contaminants. This review discusses the stabilization mechanisms of nanoparticle-stabilized SF (NP-SF) as well as the effects of NP size, chargeability, wettability, and NP-to-surfactant ratio on foam stability. SF stabilized by inert SiO2 NPs is most commonly used to remediate soil contaminated with crude oil and diesel. Low dose of SF stabilized by nano zero-valent iron is cost-effective for treating soil contaminated with chlorinated organics and heavy metal ions. The efficiency and recyclability of Al2O3/Fe3O4 NPs in the remediation of diesel and crude oil contamination could be enhanced by applying a magnetic field. This review provides a theoretical basis and practical guidelines for developing functional NP-SF to improve the remediation of petroleum-contaminated soils. Future research should focus on the structural design of photocatalytic NPs and the application of catalytic NP-SF in soil remediation.

Coupling surfactants with ISCO for remediating of NAPLs: Recent progress and application challenges.

Non-aqueous phase liquids (NAPLs) pose a serious risk to the soil-groundwater environment. Coupling surfactants with in situ chemical oxidation (ISCO) technology is a promising strategy, which is attributed to the enhanced desorption and solubilization efficiency of NAPL contaminants. However, the complex interactions among surfactants, oxidation systems, and NAPL contaminants have not been fully revealed. This review provides a comprehensive overview on the development of surfactant-coupled ISCO technology focusing on the effects of surfactants on oxidation systems and NAPLs degradation behavior. Specifically, we discussed the compatibility between surfactants and oxidation systems, including the non-productive consumption of oxidants by surfactants, the role of surfactants in catalytic oxidation systems, and the loss of surfactants solubilization capacity during oxidation process. The effect of surfactants on the degradation behavior of NAPL contaminants is then thoroughly summarized in terms of degradation kinetics, byproducts and degradation mechanisms. This review demonstrates that it is crucial to minimize the negative effects of surfactants on NAPL contaminants oxidation process by fully understanding the interaction between surfactants and oxidation systems, which would promote the successful implementation of surfactant-coupled ISCO technology in remediation of NAPLs-contaminated sites.

The combined effect of Diversispora versiformis and sodium bentonite contributes on the colonization of Phragmites in cadmium-contaminated soil.

To promote the colonization of Phragmites in Cd polluted, nutrient deprived and structural damaged soil, the combined remediation using chemical and microbial modifiers were carried out in potting experiments. The co-application of Diversispora versiformis and sodium bentonite significantly improved the soil structure and phosphorus utilization of the plant, while decreasing the content of cadmium bound by diethylenetriaminepentaacetic acid by 77.72%. As a result, the Phragmites height, tillers, and photosynthetic capacity were increased by 71.60%, 38.37%, and 17.54%, respectively. Further analysis suggested the co-application increased the abundance of phosphorus-releasing microbial communities like Pseudomonassp. and Gemmatimonadetes. Results of rhizosphere metabolites also proved that the signal molecule of lysophosphatidylcholine regulated the phosphorus fixation and utilization by the plant. This work finds composite modifiers are effective in the colonization of Phragmites in Cd contaminated soil by decreasing the bioavailable Cd, increasing the abundance of functional microbial communities and regulating the phosphorus fixation.

The effects of biochar and dredged sediments on soil structure and fertility promote the growth, photosynthetic and rhizosphere microbial diversity of Phragmites communis (Cav.) Trin. ex Steud.

The improvement of urban river revetment soil is conducive to promote the growth of pioneer plants which can accelerate the restoration of ecosystems. How to effectively amend soil structure and composition to provide a suitable soil rhizosphere for rapid plant expansion is essential to be solved in the study. Biochar and lake dredged sediments were used to amend an urban river bank soil, where compaction and lack of mineral nutrition hindered the growth of Phragmites. The study found that the addition of 50% mass of dredged sediments combined with 5% mass of straw biochar increased the plant height maximum growth rate, tiller number per unit area, and root biomass by 32.93%, 29.62%, and 41.39%, respectively. The reason for these positive effects on plant growth mainly involved the improvement of rhizosphere soil properties. Addition of biochar increased porosity and available phosphorus content while dredged sediments increased soil organic carbon, thereby increasing the underground unit total phosphorus content of Phragmites by 18.18%. An increase of the Alpha diversity index of rhizosphere microorganisms (8.18%) and the decrease in infection rate of arbuscular mycorrhizal fungi (23.61%) also proved that the rapid expansion of Phragmites was improved owing to changes of the soil physicochemical properties. The combination of biochar and dredged sediments realized synergistic improvement of soil physical structure and increase of nutrient content, which helped promote the growth and expansion of the underground part of Phragmites. This cost-effective method can be feasible used for improvement of urban river revetment ecosystem.