Concept
What Are Hydrotalcites?
- Mg-Al sub-class of layered double hydroxides/hydrotalcites/anionic clays which are both naturally occurring and synthetically produced minerals.
- Hydrotalcite structure is in the form of positively-charged mixed metal hydroxide layers separated by interlayers that contain water + exchangeable anions.
What Does Hydrotalcite Technology Do?
- The technology uses commercially available additives to create synthetic hydrotalcite-minerals which can remediate and neutralise acidic wastewater and capture heavy metals such as uranium, copper, lead, cadmium and anions such as sulphate, chromate and arsenate.
- As hydrotalcites form, metals and anions become trapped and are easily removed from wastewater streams within the hydrotalcite product.
- The technology utilises abundant Fe, Mg and Al which are present in most acid mine wastewaters to create hydrotalcites, alternatively component reagents can be sourced and added.
- Optimal chemistry can be tailored to synthesise hydrotalcite formation – generally achieved by adding Mg and/or Al and then NaOH as a neutralising agent to remediate acidity.
- The synthesised hydrotalcites can be captured and calcined to produce a stable spinel product or silicified to produce synthetic chlorite analogue for permanent storage or reprocessed to extract valuable high-grade metal by-products such as uranium and rare earth metals.
Where Can Hydrotalcite Technology Be Used?
- Applications in mining, minerals processing and building industries, with particular relevance to regions where acidic wastewater requires neutralisation to avoid negative impacts on aquifers and soils.
- Emerging global market as increasingly strict environmental management legislation impacts:
- Existing/abandoned mine sites with acidic drainage/leakage, including mining waste heaps with oxidising sulphide minerals (such as pyrite);
- in-situ uranium leach mine sites (“ISL”), for example leakage from thousands of cold war-era uranium injection/extraction bores in Europe and the US;
- current mine closure policies are becoming increasingly rigid with requirement for long-term solutions for leakage of toxic by-products.
- In areas of high environmental sensitivity where reverse osmosis (“RO”) is required to produce discharge quality water, VCL can pre-condition RO feed by inexpensively and rapidly removing foulants to achieve significantly enhanced efficiencies and cost reductions with reduced plant capacity requirements.

ISL Schematic

ISL Remediation Using “Virtual Curtain” Barrier