Extracellular Polymeric Substances Facilitate the Adsorption and Migration of Cu2+ and Cd2+ in Saturated Porous Media.

Yuhui Wu,Yuesuo Yang,Zhengyu Li,Diane Purchase,Ying Lu,Zhenxue Dai

doi:10.3390/biom11111715

Abstract

Heavy metal contamination in groundwater is a serious environmental problem. Many microorganisms that survive in subsurface porous media also produce extracellular polymeric substances (EPS), but little is known about the effect of these EPS on the fate and transport of heavy metals in aquifers. In this study, EPS extracted from soil with a steam method were used to study the adsorption behaviors of Cu2+ and Cd2+, employing quartz sand as a subsurface porous medium. The results showed that EPS had a good adsorption capacity for Cu2+ (13.5 mg/g) and Cd2+ (14.1 mg/g) that can be viewed using the Temkin and Freundlich models, respectively. At a pH value of 6.5 ± 0.1 and a temperature of 20 °C, EPS showed a greater affinity for Cu2+ than for Cd2+. The binding force between EPS and quartz sand was weak. The prior saturation of the sand media with EPS solution can significantly promote the migration of the Cu2+ and Cd2+ in sand columns by 8.8% and 32.1%, respectively. When treating both metals simultaneously, the migration of Cd2+ was found to be greater than that of Cu2+. This also demonstrated that EPS can promote the co-migration of Cu2+ and Cd2+ in saturated porous media.

Highlights

Published: 17 November 2021Heavy metal pollution is a serious global environmental problem, for developing countries—e.g., China [1]
When extracting extracellular polymeric substances (EPS) from soil using the steam method, a dialysis device should be used for further dialysis and to remove the small molecular substances to reduce the interference in the subsequent experimental results
Due to the fact that a large number of microorganisms exist in soil and aquifers, they must be taken into account in the fate and transport of heavy metals in aquifers

Summary

Introduction

Heavy metal pollution is a serious global environmental problem, for developing countries—e.g., China [1]. Heavy metals (HMs) in soil reduce soil fertility as well as crop yield and quality [5]. They can be leached into aquifers through rainfall and irrigation and cause groundwater pollution. Polluted surface water and sewage can enter groundwater by travelling through porous strata or other hydrogeological connective pathways. Groundwater is the main or even the only source of water supply in arid and semi-arid regions, such as most parts of Africa and North China [6,7,8]. Heavy metals in groundwater pose a real threat to human health

Methods

Results

Conclusion