Incorporation of contaminant metals into waste derived nanoparticles

Introduction and rationale: The production and refinement of metals ores produces a multitude of heterogeneous wastes (e.g. during steel manufacturing, aluminium extraction and chromium ore processing). These wastes often containing mixtures of potentially toxic elements (e.g. As, Cr, V), which if poorly controlled can be released into discharged effluents. Previous research has mostly focused on the leaching of soluble metals, however, it is increasingly being discovered that the primary flux of contaminants, in most situations, is actually transported as solid particles. Such nanoparticle associated contaminants behave completely differently to dissolved metals and pose uncertain risks to downstream ecosystems. The nanoparticles can be both primary (produced as a by-product of extraction process itself), or secondary (precipitated from solutions after leaching). It is vital to understand the different mechanisms of trace element incorporation to make good predictions of future behaviour and the potential for environmental harm. Understanding the exact mechanism of toxic element uptake and transport has been limited by a lack of suitable analysis methods. These have until now relied on unreliable chemical leaching texts such a sequential extractions which are very difficult to interpret. Recent advances in both high resolution imaging (in transmission election microscopes) and synchrotron based spectroscopy now offer the opportunity to determine both the atom scale structure of host nanoparticles (which can be metal hydroxides, carbonates and/or silicates) and the chemical form of potential harmful elements present in relatively low concentrations. This project seeks to combine traditional chemical analysis methods with cutting edge atomic and molecular scale data from high resolution electron microscopy and synchrotron based spectroscopic analysis to produce new insights into the fate and behaviour of potentially harmful elements associated with nanoparticle phases.

Objectives:
1. Characterisation of micro- and nano-particles occurring within disposed by-products from the iron, aluminium and chromium industries establishing which set of particles pose the greatest risk of spreading contamination beyond controlled processes.
3. Production of specific oxide, carbonate and silicate nanoparticles relevant to industrial waste management and effluents. Experimental program that tracks the fate of metal contaminants during their competitive uptake from mixed source solutions.
2. Development of treatment methods to allow successful removal of contaminant metals associated particles from waste effluents with potential for simultaneous recovery of valuable metals present.