Sulfate Reduction
Reduction of Sulfate Levels without the Use of an HDS Process, Lime and Membranes.
The Sulfates Reduction Technology that was developed especially for the AMD (Acid Mining Drainage) crisis in South Africa is based on and is a modification of the P2W Electrolytic Process that was implemented successfully for the last 7 years in Latin America, Europe, the Far East and Africa. The electrolytic processes are the core technology of the company and have been successfully used in the industry, especially in the Gold Mining sector.
One of the processes that are causing high concentrations of Sulfates in water affected by mining is commonly referred to as Acid Mine Drainage (AMD) or Acid Rock Drainage (ARD), and is associated with the formation of acid water from Metal and Coal mines where pyrites are predominantly present. The chemistry of oxidation of pyrites and the production of ferrous ions and (subsequently) ferric ions are very complex. This complexity has considerably inhibited the design and application of effective mine water treatment options.
Although a host of chemical processes contribute to acid mine drainage, pyrite oxidation is by far the greatest contributor. A general equation for this process is:
2FeS2(s) + 7O2(g) + 2H2O(l) = 2Fe2+(aq) + 4SO42−(aq) + 4H+(aq)
The oxidation of the sulfide to sulfate solubilizes the ferrous iron (iron II) which is subsequently oxidized to ferric iron (iron III):
4Fe2+(aq) + O2(g) + 4H+(aq) = 4Fe³Save+(aq) + 2H2O(l)
Two years of intensive experiences with different types of South Africa AMD water samples for Heavy Metals, Sulfate and Uranium removal, lead to a proven electrolytic process that meets all SA SANS drinking water regulations.
The suggested mechanism of the electrolytic process is the creation and the formation of Metallic Nanoparticles Crystalline of M1M2SO4 and M1M2M3SO4 type.
Advanced EDS measurements find that we have two types of elemental compositions:
Fe-Al-S-O; according to different standards analysis we assume that it belongs to the family of (Fe)a(Al)b(SO4)c(OH)d X (H2O) e
Fe-Al-Ca-S-O; we assume that it belongs to the family of (Fe)a(Al)b(SO4)c(OH)d X (H2O) e and a mixture of other metal/nonmetal salt complexes.
SEM analysis gave us a good view regarding the crystals size that distribute from tens to hundreds of nm and form aggregates in size of µm. Some analysis showed amorphous structures (probably because of the Al contribution).
XRD analysis gave us spectra of different Metal – Oxide of Iron (Fe), Aluminum (Al), Manganese (Mn) in different oxidation states.
| Units Regulation | SANS 241- (2011) | Raw Feed (before HDS) | After P2W Treatment | |
| TDS | mg/L | Less then 1200 | 4890 | 1060 |
| Conductivity | S2/cm | Less then 1700 | 4150 | 1430 |
| pH | mg/L | 5-9.7 | 3.9 | 8 |
| Calcium | mg/L | Less then 150 | 584 | 69 |
| Magnesium | mg/L | Less then 70 | 345 | 0.5 |
| Sodium | mg/L | Less then 200 | 150 | 148 |
| Sulphate | mg/L | Less then 250 | 3600 | 200 |
| Chloride | mg/L | Less then 300 | 130 | 127 |
| Iron | mg/L | 0.3 | 772 | 0.05 |
| Aluminum | mg/L | Less then 0.3 | 48 | Less then 0.1 |
| Manganese | mg/L | Less then 0.1 | 275 | 0.05 |
Although a host of chemical processes contribute to acid mine drainage, pyrite oxidation is by far the greatest contributor. A general equation for this process is:
2FeS2(s) + 7O2(g) + 2H2O(l) = 2Fe2+(aq) + 4SO42−(aq) + 4H+(aq)
The oxidation of the sulfide to sulfate solubilizes the ferrous iron (iron II) which is subsequently oxidized to ferric iron (iron III):
4Fe2+(aq) + O2(g) + 4H+(aq) = 4Fe³+(aq) + 2H2O(l)
Two years of intensive experiences with different types of South Africa AMD water samples for heavy metals, sulfate and Uranium removal, lead to a proven electrolytic process that meets all SA SANS drinking water regulations.
The suggested mechanism of the electrolytic process is the creation and the formation of Metallic Nanoparticles Crystalline of M1M2SO4 and M1M2M3SO4 type.
Advanced EDS measurements find that we have two types of elemental compositions:
Fe-Al-S-O; according to different standards analysis we assume that it belongs to the family of (Fe)a(Al)b(SO4)c(OH)d X (H2O) e
Fe-Al-Ca-S-O; we assume that it belongs to the family of (Fe)a(Al)b(SO4)c(OH)d X (H2O) e and a mixture of other metal/nonmetal salt complexes.
SEM analysis gave us a good picture regarding the crystals size that distribute from tens to hundreds of nm and form aggregates in size of µm. Some analysis showed amorphous structures (probably because of the Al contribution).
XRD analysis gave us a spectra of different Metal – Oxide of Iron (Fe), Aluminum (Al), Manganese (Mn) in different oxidation states.
More tests are done to investigate the effect of initial pH, heavy metals concentrations and the sulfate levels on the complex type and the ability to capture more trace elements.
Technology Highlights:
- Totally Eliminates the Need to Use the HDS Process.
- No Lime/Limestone are Used in the Process
- Creates a Dramatically Less Amount of Sludge Compared to all other Technologies in The Market. (0.5% Dry Sludge is Remained that Can be Used by The Industry for the Purposes of Metal Recovery).
- Does not involve any Membranes in the Process, hence does not have any Brine as a Byproduct and a 100% Recovery is Achieved.
- Successfully Removes Uranium from the Water to levels that are Below 5 Ppb.
