Abstract
The ongoing boom of industrialization is conflicted by concerns regarding increased levels of environmental contamination, in particular the uncontrolled release of heavy metal ions and radionuclides into soils and groundwater systems. The extent of contamination can be substantial, hence ways to remediate and reduce the volume of waste for further treatment and ultimate disposal are highly desired. In the current study, flotation has been considered as an engineering solution to rapidly separate cesium contaminated clays from low-level contaminated and pristine clays. Cesium (Cs+) sorption by montmorillonite clay particles was considered over a range of ionic concentrations (0.01–500 mM), showing a multistage sorption isotherm that can be interpreted using a two-site model, which considers both interlayer ion-exchange and specific ion sorption on the clay basal planes at higher cesium concentrations. Assessment by X-ray photoelectron spectroscopy (XPS) and zeta potential confirmed the increased surface contamination with increasing Cs+ concentration, with the surface enrichment sufficiently altering the surface chemistry of the contaminated clays for them to favourably interact with the flotation collector, ethylhexadecyldimethyl-ammonium-bromide (EDAB). Within a critical concentration range of EDAB, the cesium contaminated clays were separated from pristine clays using flotation, with recovery efficiencies of ∼75% for the contaminated clays, compared to <25% for the pristine clays. When contaminated and pristine clays were blended, separation by flotation once again demonstrated excellent selectivity for the contaminated clays. The current study highlights the potential for flotation to rapidly treat contaminated clay rich soils and significantly reduce the volume of contaminated solids for further treatment or ultimate disposal.
Highlights
Rapid industrial growth and the historical impact of mining, coal and the petrochemical industries, along with fertilizer, pesticide, gasoline, paint production and their use, have inadvertently contaminated the environment [1]
Uncontrolled release of heavy metal ions and radionuclides and their gradual accumulation in soils and groundwater systems can lead to an environmental hazard
While the particle size and size distribution were unaffected by the Cs levels, the apparent surface charge of MMT decreased with increasing Cs
Summary
Rapid industrial growth and the historical impact of mining, coal and the petrochemical industries, along with fertilizer, pesticide, gasoline, paint production and their use, have inadvertently contaminated the environment [1]. Several methods to treat contaminated soils have been considered including i) thermal cesium removal technology [12], ii) soil washing and separation [13], and iii) decontamination of cesium contaminated soil using superconducting magnets [14], to name just a few of the piloted methods While these studies have shown promise to decontaminate soils, it would be desirable to first reduce the volume of waste to be decontaminated by separating waste that can be classified as non-active. Sodium tetraphenylborate (NaTPB) is added to form cesium tetraphenyl-borate(CsTPB) which is floated to decontaminate the aqueous phase [29] Based on those previous demonstrations, flotation is being considered in the current study to selectively separate Cs-loaded (contaminated) clays (Cs-MMT) from uncontaminated clays (MMT). Flotation in the presence of a collector (ethylhexadecyldimethyl-ammoniumbromide [EDAB]) has been demonstrated with the mechanism for selective separation understood from the physicochemical characterization of MMT and Cs-MMTs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
