Hydroxyl radical production by abiotic oxidation of pyrite under estuarine conditions:The effects of aging,seawater anions and illumination

Pyrite is widely distributed in estuarine sediments as an inexpensive natural Fenton-like reagent,however,the mechanism on the hydroxyl radical(HO^(·))production by pyrite under estuarine environmental conditions is still poorly understood.The batch experiments were performed to investigate the effects of estuarine conditions including aging(in air,in water),seawater anions(Cl^(-),Br^(-)and HCO_(3)^(-))and light on the HO^(·)production by pyrite oxidation.The one-electron transfer dominated the process from O_(2) to HO^(·)induced by oxidation of pyrite.The Fe(oxyhydr)oxide coatings on the surface of pyrite aged in air and water consumed hydrogen peroxide while mediating the electron transfer,and the combined effect of the two resulted in a suppression of HO^(·)production in the early stage of aging and a promotion of HO^(·)production in the later stage of aging.Corrosion of the surface oxide layers by aggressive anions was the main reason for the inhibition of HO^(·)production by Cl^(-)and Br^(-),and the generation of Cl^(·)and Br^(·)may also play a role in the scavenging of HO^(·).HCO_(3)^(-)increased the average rate of HO^(·)production through surface-CO_(2) complexes formed by adsorption on the surface of pyrite.The significant enhancement of HO^(·)production under light was attributed to the formation of photoelectrons induced by photochemical reactions on pyrite and its surface oxide layers.These findings provide new insights into the environmental chemical behavior of pyrite in the estuary and enrich the understanding of natural remediation of estuarine environments.

Numerical simulation of benzene transport in shoreline groundwater affected by tides under different conditions

The release and transport of benzene in coastal aquifers were investigated in the present study.Numerical simulations were implemented using the SEAM3D,coupled with GMS,to study the behavior of benzene in the subsurface of tidally influenced beaches.The transport and fate of the benzene plume were simulated,considering advection,dispersion,sorption,biodegradation,and dissolution on the beach.Different tide amplitudes,aquifer characteristics,and pollutant release locations were studied.It was found that the tide amplitude,hydraulic conductivity,and longitudinal dispersivity were the primary factors affecting the fate and transport of benzene.The tidal amplitude influenced the transport speed and percentage of biodegradation of benzene plume in the beach.A high tidal range reduced the spreading area and enhanced the rate of benzene biodegradation.Hydraulic conductivity had an impact on plume residence time and the percentage of contaminant biodegradation.Lower hydraulic conductivity induced longer residence time in each beach portion and a higher percentage of biodegradation on the beach.The plume dispersed and the concentration decreased due to high longitudinal dispersivity.The results can be used to support future risk assessment and management for the shorelines impacted by spill and leaking accidents.Modeling the heterogeneous beach aquifer subjected to tides can also be further explored in the future study.

Superwetting polyethersulfone membrane functionalized with ZrO_(2) nanoparticles for polycyclic aromatic hydrocarbon removal

Polycyclic aromatic hydrocarbons(PAHs)are persistent and widespread in the aquatic environment,causing potential hazards for human health.In this study,a superwetting and robust PES-PAA-ZrO_(2)nanofiltration membrane was proposed through surface modification for PAH removal with high efficiency.A ZrO_(2)coating was formed on polyethersulfone(PES)membrane surface through chemical bonding,thus the PES-PAA-ZrO_(2)membrane exhibited super-hydrophilicity,under-water oleophobicity,and excellent stability.In comparison with the original PES membrane,the water contact angle of the modified membrane was significantly decreased from about 50°to less than 10°,and quickly dropped to 0°within 1s.This provided a much lower energy barrier for water permeation due to its super-high water affinity.The wastewater treatment efficiency was increased by about 4 times after modification with more than 90%of PAH rejection rate.The excellent robustness of PES-PAA-ZrO_(2)membrane was verified under various conditions,which gave the membrane practical potential for long-term operation.

Functional flax fiber with UV-induced switchable wettability for multipurpose oil-water separation

The large number of oily wastewater discharges and oil spills are bringing about severe threats to environment and human health.Corresponding to this challenge,a functional PAA-ZnO-HDTMS flax fiber with UV-induced switchable wettability was developed for efficient oil-water separation in this study.The developed flax fiber was obtained through PAA grafted polymerization and then ZnO-HDTMS nanocomposite immobilization.The as-prepared PAA-ZnO-HDTMS flax fiber was hydrophobic initially and could be switched to hydrophilic through UV irradiation.Its hydrophobicity could be easily recovered through being stored in dark environment for several days.To optimize the performance of the PAA-ZnO-HDTMS flax fiber,the effects of ZnO and HDTMS concentrations on its switchable wettability were investigated.The optimized PAA-ZnO-HDTMS flax fiber had a large water contact angle(∼130°)in air and an extremely small oil contact angle(∼0°)underwater initially.After UV treatment,the water contact angle was decreased to 30°,while the underwater oil contact angle was increased to more than 150°.Based on this UV-induced switchable wettability,the developed PAA-ZnO-HDTMS flax fiber was applied to remove oil from immiscible oil-water mixtures and oil-in-water emulsion with great reusability for multiple cycles.Thus,the developed flax fiber could be further fabricated into oil barrier or oil sorbent for oil-water separation,which could be an environmentally-friendly alternative in oil spill response and oily wastewater treatment.