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Growing Metals

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Environmental solutions are needed for contaminated sites ... Acid, artisanal, laterite and ultrabasic tailings. Heap-leach pads ... – PowerPoint PPT presentation

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Title: Growing Metals


1
Growing Metals
Using metal-accumulating plants to remediate
contaminated sites
Chris Anderson Soil and Earth Sciences,
Institute of Natural Resources, Massey
University, Palmerston North, New
Zealand Phytomine Environmental Ltd., Wellington,
New Zealand
2
Phytoremediation
  • Environmental solutions are needed for
    contaminated sites
  • Conventional solutions chemical or physical
    methods at high cost
  • Phytoremediation a softer solution that uses
    plants to uptake or degrade contaminants
  • Intelligent synergy of botany, geochemistry and
    microbiology
  • SOLAR DRIVEN BIOPUMPS

3
  • Phytoextraction plant removal of
  • water
  • nitrates, phosphates
  • heavy-metals
  • some organic nasties
  • Phytodegradation and stabilisation enhanced by
  • soil aeration
  • plant exudates
  • soil microbiota stimulated by plant exudates

4
Phytoextraction
  • Natural hyperaccumulation
  • Some plant species have evolved to accumulate
    very high metal concentrations
  • Sb, As, Cd, Co, Cu, Ni, Se, Tl, Mn, Zn
  • Induced hyperaccumulation
  • Forcing plants to accumulate other metals by
    making these soluble in soil solution
  • Au, Pb, Hg, Pd, Pt

5
Natural hyperaccumulation
Data from Reeves, 1992a
6
The phytoextraction operation
Chemicals added
Biopump grown
Plant material harvested and burnt to produce
bio-ore
2
2
Ni
Cu
2

Pd
Au
Bio-ore smelted
Bio-ore landfilled
Phytomining
Phytoremediation
7
(No Transcript)
8
Phytoextraction in action
The location a base-metal smelter, South Africa
The problem Ni contamination over 5ha due to Ni
salt storage and spillage
The solution phytoextraction using a native
nickel-accumulating species
9
Phytoextraction for gold
  • Thio-ligands can induce the solubility and uptake
    of gold from waste, low-grade rock
  • Discovery made in New Zealand
  • Proof of concept achieved and the technology is
    being field tested
  • Aim is a crop of 10 t/ha biomass with 100 mg/kg
    gold concentration dry weight
  • This will yield 1000 g of gold per hectare as
    well as other metals made soluble
  • Current focus is on mercury (Hg) removal at the
    same time as gold

10
An intelligent system
  • Importance of botany and geochemistry is clear,
    but microbiology is also important
  • Bugs for contaminant assessment
  • Bugs as inoculum to increase plant growth and
    metal uptake
  • The choice to use phytoremediation is facilitated
    by a decision support system
  • System developed and used by Phytomine
    Environmental Ltd.

11
Fosterville gold mine, Victoria, Australia
6th May 2002
3rd July 2002
12
17th September 2002
13
17th September 2002
14
29th April
Tui base-metal mine, Coromandel, NZ
22nd May
21st September
15
1st July 2002
16
1st July 2002
17
When to use phyto a DSS
  • Phytoremediation, will only be used for land
    clean-up and management IF the technology will
    deliver the most economically favourable outcome
  • Consider
  • alternatives conventional or inaction
  • revenue from the plants metals and energy
    generation through biomass burning (gasification)
  • proposed end use for the land
  • legislative incentive and public perception
  • The suitability of phytoremediation is thus
    dependant upon economics

18
  • Research tools
  • Greenhouse experiments to study metal uptake
  • Hydroponic and soil systems
  • Geochemical modeling through simple laboratory
    extractions
  • Atomic absorption and ICP analysis for cations
  • IC for anions
  • These tools support field trials

19
Hg volatilisation studies
Air Outlets
Air Tight Plastic Chamber (4.25 L Volume)
B. juncea plantlet grown in hydroponics solution
Air Inlets
KMnO4 H2SO4 Traps
Air Pump
Air Tight Plastic Pot (100 mL Volume)
20
Conclusions
  • Phytoremediation is land-management technology
  • Where suitable, phytoremediation is a low-cost,
    sustainable solution for contaminated land and
    waste-streams
  • Making the technology work relies on the
    intelligent synergy of botany, microbiology and
    geochemistry
  • Revegetation, land stabilisation and
    phytoextraction are all working scenarios of
    phytoremediation

21
Conclusions (contd.)
  • Phytoremediation is suitable for
  • Acid, artisanal, laterite and ultrabasic tailings
  • Heap-leach pads
  • Contaminated water (metals and non-metals)
  • Municipal sewage wastes
  • Soil contamination through industrial/mining
    activity
  • Geogenic sources of metals (e.g. As in
    Bangladesh)
  • A plant-based management system can be designed
    for nearly all contaminating waste-streams and
    for many contaminated sites
  • Implementation depends upon suitable assessment
    and design
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