Biomimetic System for the Application of Nanomaterials in Fluid Purification: Removal of Arsenic with Ferrihydrite

The role of soils in the disposition, sequestration and decontamination of environmental contaminants

Soil serves as both a 'source' and 'sink' for contaminants. As a source, contaminants are derived from both 'geogenic' and 'anthropogenic' origins. Typically, while some of the inorganic contaminants including potentially toxic elements are derived from geogenic origin (e.g. arsenic and selenium) through weathering of parent materials, the majority of organic (e.g. pesticides and microplastics) as well as inorganic (e.g. lead, cadmium) contaminants are derived from anthropogenic origin. As a sink, soil plays a critical role in the transformation of these contaminants and their subsequent transfer to environmental compartments, including groundwater (e.g. pesticides), surface water (phosphate and nitrate), ocean (e.g. microplastics) and atmosphere (e.g. nitrous oxide emission). A complex transformation process of contaminants in soil involving adsorption, precipitation, redox reactions and biodegradation control the mobility, bioavailability and environmental toxicity of these contaminants. Soil also plays a major role in the decontamination of contaminants, and the 'cleaning' action of soil is controlled primarily by the physico-chemical interactions of contaminants with various soil components, and the biochemical transformations facilitated by soil microorganisms. In this article, we examine the geogenic and anthropogenic sources of contaminants reaching the soil, and discuss the role of soil in the sequestration and decontamination of contaminants in relation to various physico-chemical and microbial transformation reactions of contaminants with various soil components. Finally, we propose future actions that would help to maintain the role of soils in protecting the environment from contaminants and delivering sustainable development goals. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Nano-enhanced Dialytic Fluid Purification: CFD Modeling of Pb(II) Removal by Manganese Oxide

Nano-enhanced dialytic fluid purification is an evolution of biomedical dialysis that has been proposed as a novel method for applying nanomaterials in water treatment. Using nanosized hexagonal birnessite (δ-MnO2) in a simplified dialytic system, we demonstrate herein an almost complete removal (98%) of Pb(II) within 3 h of treatment while monitoring environmental variables pH and Eh (redox potential). A mathematical model of the purification process is constructed in COMSOL Multiphysics to demonstrate how nanoadsorption using free-flowing nanoparticles in a dialytic system can be studied theoretically using computational fluid dynamics (CFD). The CFD model closely agrees with experimental results, estimating a 95% removal over 3 h of treatment and suggesting an 18% consumption of available adsorbent capacity. Additional insights into the progress and mechanisms of the adsorption process are also revealed. Finally, the nanoenhanced model is compared against standard dialysis absent of nanomaterials using COMSOL, and key differences in removal efficiency are highlighted. Results indicate that nanoenhanced dialysis can attain almost complete removal in 3 h of treatment or reach the same removal goal as standard dialysis in less than two-third of the treatment time.