About the Eco-Goldex Reagent


Eco-goldex product series represents a group of chemical compounds that are capable of effectively extracting gold from gold ores and E-waste materials. Eco-goldex product series is not a simple chemcial but a chemcial compound that are produced through several common chemicals mixed and fused in high temperature autoclave.

Unlike gold leaching meachanism in sodium cyanide solution that CN- is the only powerful component that attacks (dissolves) gold and forms soluble complex Au(CN) 2 ion, in Eco-goldex solution, several components , though each individual component is not as strong as CN -, involve gold dissolving process and form soluble Au ions. The combined gold dissolving capacity of these individual components released from Eco-goldex is equivalent or even stronger than that of Cyanide. Below are several chemical reactions that may involve in Eco-goldex gold extraction mechanism:

4Au + S2O82- + 4CS(NH2)2 4Au[CS(NH2)2]2+ + 2SO42-

4Au + 4CS(NH2)2 + 2H2O + O2 4Au[CS(NH2)2]2+ + 4OH-

Au + 4NH3 Au(NH3)43+ + 3e

6Au + 4[Fe(CN)6]3- +O2+ 2H2O 6[Au(CN)4]3- + 4Fe3+ + 4OH-+2e

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A common feature of Eco-goldex product series group (O, E,C) is that they are simple system and work in alkaline condition.

Eco-Goldex O Series:
  • pH rang: 9-12, optimum at 11.5, Lime (CaO) or Sodium Hydroxide (NaOH) can be used for pH adjust.
  • Reagent concentration: for most common gold ores (oxide, semi-oxide ores and low sulfide ores), reagent concentration in solution is 0.5-1‰, Complex materials usually consume more reagent. optimum reagent concentrate should be defined through leaching tests.
  • Applicable ores types: Oxidized, Semi-Oxidized Au(Ag, PGM), non-refractory sulfide gold ores or gold concentrates.
  • Applicable method: Heap leach, CIL/CIP, VAT leaching.
  •  

Eco-Goldex E Series:
  • pH rang: Free. Since the reagent itself is alkalinic in solution, and its gold stripping efficiency is so strong and quick, there is no need to control, monitor and adjust pH in E-waste stripping solution.
  • Reagent concentration: for most electronic parts, eco-goldex E concentration in stripping solution is around: 1:15 (reagent : water by weight). If quicker stripping is desired, higher reagent concentrates (i.e. 1:10) can be used.
  • Stripping effect factors: Three factors affect gold stripping speed in E-waste processes: reagent concentrations in solution, solution temperature (idea temperature range: 55- 65 oC), stripping solution dynamic (stirring).
  • Applicable materials: any material contains surface gold (electronic connectors, pins, RAM, CPU, PCB, Jewelry...).
  • Applicable method: Stirring Stripping in Solution.

Eco-Goldex C Series:

    For refractory gold ores, the most effective method to reveal their economic value is to unlock Au from sulfide minerals by either roasting or chemical approaches. Eco-goldex C product series comprises of a leaching supplementary reagent and leaching agent that work together to reach this goal. The supplementary reagent acts to attack the refractory sulfide minerals and then followed by normal leaching.

  • pH rang: 9-12, optimum at 11.5, Lime (CaO) or Sodium Hydroxide (NaOH) can be used for pH adjust.
  • Reagent concentration: for common refractory gold ores (pyrite, arsenopyrite ores and high contents of sulfide ores) 2.5-4 ‰. Optimum reagent concentration should be defined through leaching tests.
  • Applicable ores types: refractory gold ores, high sulfide concent gold concentrates.
  • Applicable method: Heap leach, CIL/CIP, VAT leaching.


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Numerous comparative metallurgical and eco-toxicological tests on Eco-Goldex product series vs Cyanide and Aqua regia on various types of gold ores and gold bearing materials reveal that Eco-goldex has several advantages over cyanide and aqua regia in gold extraction processes. These advantages can be summarized as following:

  • No Permit Needed for Eco-goldex product Purchase and Application
  • One of the biggest barriers for small-medium gold mine operators to develop their gold mine projects is that it is very hard or impossible for them to get government's permit to either purchase or use sodium cyanide in their projects because cyanide is extremely toxic and classified as restricted materials.

    With Eco-goldex product, this barrier will no longer exist because eco-goldex product is classified as ordinary goods and can be transported via marine, air freight and ground. No purchase permit or usage permit are required. Eco-goldex product series has been tested and certified in authorized national institute (CNAS) that eco-goldex product series is classified as ordinary goods.

  • Selective & Extremely Fast gold Stripping Feature
  • Eco-Goldex E product series has a unique feature that it can selectively strip surface gold from plating electronic parts such as pins, connectors, RAM, CPU and PCB, while other metals like copper, aluminium are not or slightly attacked. This selective stripping feature makes gold stripping process much easier and simplifies E-waste recycling processes into separate steps in which specific metals are separated and recovered.

    In addition, eco-goldex E series has outstanding quick gold tripping efficiency that can strip surface gold within tens of second.

    best e-waste stripping chemical



  • Low Toxicology
  • Both Eco-goldex E and O product series are low-toxic. eco-toxicology test results indicate that the O series is about 100 times less toxic than sodium cyanide, while the E series is 200 times less toxic than cyanide. Also the low-toxic components in eco-goldex solution can be naturally decomposed quickly, no toxic composition can be analysed in barren solution after 3-4 days.

    eco-friendly gold leaching, sustainable gold mining


  • Better Leaching Performance Than Cyanide
  • Eco-goldex product has proven better leaching performance than cyanide. For most common gold ores, eco-goldex (O) can reach 90% leaching rate in 48 hours (CIL/CIP) while eco-goldex reagent consumption rate is lower than cyanide.

    The the charts below show original industrial CIP test results on sulfide (pyrite, arsenopyrite) gold ores at a gold mine in Myanmar with eco-goldex O product series. Test results indicate that Eco-goldex O product series has better leaching performance in gold ore leaching kinetics (short leaching time), less reagent consumption rate. (Click the images to view their large size charts).

   
   


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As an alternative of sodium cyanide in gold leaching/stripping, Eco-goldex reagents do share many similarities with cyanidation such as in leaching conditions and flowsheet, but gold recovery (precipitation) methods of the three reagents derived pregnant solution are not the same. For example, the conventional Activated Carbon adsorption method works well for the O series pregnant solution but may not work well for the E series pregnant solution. Proper gold precipitation methods should be carefully selected to achiev satisfying gold recovery rate.

The table below lists available methods that can be effectively used for gold recovery from Eco-goldex reagent derived pregnant solutions.

Method Code Method Name O(C) Series Preg-solution E Series Preg-solution Notes
A CIL/CIP X    
B RIL/RIP X X(1)  
C Zinc Powder/strips X    
D Zinc strips + ammonia solution   X(2)  
E Electrowinning X X  
F Thiox+PAC precipitation   X(3)  


(1). Resin used in Eco-goldex E series pregnant solution can only be processed with Incineration method, elute does not work well.
(2). The zinc strips/powder + ammonia solution method is dedicated for gold precipitation from Eco-goldex E reagent derived pregnant solution. Due to the harsh smell of ammonia solution and extensive sulfuric acid applied in this method, we officially discontinued technical support of this method.
(3). The Thiox+PAC precipitation method is specially formulated for gold precipitation from E series pregnant solution process.

Among the four methods developed for gold recovery in E series preg-solution, each one of them is effective but to achieve the best gold recovery rate(>95%), we recommend the following combinations:
  1. D + B
  2. E + B
  3. F + B

Among the three combinations, we recommend the combination of ii and iii for the reason of simplicity and friendly working condition.

The reason why not use the method D (resin adsorption column) alone since it is used in all combination is that gold recovery from Resin adsorption in E series preg-solution can ONLY be achieved through resin incineration that is not the best practice for large quantity process.
Eco-goldex O product series has been successfully used in gold mines with various scales from artisanal to large scale gold mine operators including countries in China, Vietnam, Myanmar, the Philippines, Canada, Mexico, USA, Brazil, Tanzania, and Burkina Faso.

Eco-goldex E product series, so far, is the only type of this kind fast gold stripping reagent globally accepted and welcomed by its users in E-waste material recycling business.

Eco-goldex E product series users are from more than 45 countries with most of them from Europe, USA, Canada, Mexico, SE Asia.

Eco-goldex provides both E product series and (semi-) automatic gold stripping system to E-waste recycling business. With a state of the  art new design of gold precipitation from the E series preg-solution, eco-goldex proudly announces its finalization of its gold stripping and precipitation circuit and related system configurations. With the new systems, gold stripping in E-waste materials is accomplished  in such an effective approach that no other method can compete it in the market. Gold precipitation will be through a two-stage process with the first stage being either Thiox chemical precipitation or electrowinning , and followed by the second stage Resin adsorption method.

After this two-stage recovery processes, 98% gold (and other precious metals if any) will be recovered from the preg-solution and the waste solution can either be recycled in the stripping solution or disposed without further treatment.
The two different gold stripping and recovery flowsheet and equipment layouts are shown as follow:

Precipitation method Stripping / Precipitation Flowsheet Stripping / Precipitation System Layout
Thiox +Pac + Resin Adsorption gold precipitation Au precipitation
Electrowinning + Resin Adsorption Au precipitation method Precious metal precipitation method

 

As a responsible gold stripping reagent developer and supplier, Eco-goldex has developed a comprehensive sets of technology from gold stripping to gold precipitation and final waste solution treatment before disposal.

With the two new methods of gold precipitation systems, not only the precious metals will be precipitated , some base metals (if there is any) will be removed from the stripping solution and the solution pH will be neatralized to normal and can be safely disposed as regular industrial waste water or can be recyced into the stripping system. the clean and pH neautralized preg-solution look like as shown the photos below.

e-waste solution treatment


Due to the feature of metal ions in E series preg-solution, precious metals recovery from loaded Resin beads are through incineration, resin elute method won't apply to this process. For this reason, Resin adsorption circuit is restricted to a small portion(about 5-15% in gold precipitation) in the whole precious metal precipitation process.

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