barrel tests
barrel tests
barrel tests
Raffinate Neutralization
Raffinate Neutralization Setup
Raffinate Neutralization Setup
Calcium Polysulfide Experiments
Calcium Polysulfide Experiments
Calcium Polysulfide Experiments
Humidity Cell Testing
Humidity Cell Testing
Humidity Cell Testing
Uranium Mine
Uranium Mine
Uranium Mine
Copper and Gold Mine South America
Copper and Gold Mine South America
Copper and Gold Mine South America

NATURE OF SERVICES

Examples of services typically provided by MGC include:


Geochemical modeling to predict the behavior (fate and mobility) of contaminants in groundwater, including:
  • Source term definitions
  • Pit lake models 
  • Block Cave discharge predictive models
  • Solute transport models to evaluate liner requirements for tailings and waste rock disposal
  • Third party evaluations of models prepared by others
  • Kinetic based dissolution/precipitation models including transport

Geochemical Fingerprint analysis to define sources or distinct waters or other forensic applications using:
  • Major ion characteristics
  • Trace metals
  • Stable isotope ratio analysis

Mine permitting issues involving:
  • Acid Base Accounting
  • Evaluation of leach testing results
  • Humidity cell tests
  • Closure issues

Design and implementation of client specific testing plans:
  • Sequential Batch Tests
  • Barrel and larger scale tests
  • Field programs
  • Specialized laboratory testing
  • To estimate sorption parameters
  • To evaluate reactions paths
  • To evaluate specialized treatment options

Geochemical training through short courses and client requested seminars

Statistical and geostatistical analysis of chemical data sets

Expertise in the behavior of specific metals and contaminants in groundwater including:
  • Arsenic
  • Uranium
  • Barium
  • Copper
  • Sulfate
  • Cyanide
  • Chromium
  • Nickel
  • Lead
  • Fuels and fuel fingerprinting
  • Fate and mobility of organic compounds

Geochemical Modeling using PHREEQC, PHreePlot, MINTEQA2, Geochemist’s Workbench, EQ3NR/EQ6, PHAST for Windows, HYDRA/MEDUSA, and EnviroInsite.
  • Third Party Review of Geochemical Models
  • Estimation of thermodynamic parameters (speciation reactions, solubility products, surface complexation reactions, solid solutions) 

SOLID SOLUTION DIAGRAMS
The significance of solid solution reactions has been well known for many years, although it is still not being utilized to its full potential.   PHREEQC and PhreePlot can model these reactions and I have prepared USER_PUNCH and USER_GRAPH scripts to prepare Lippmann diagrams. 
  
Here is a USER_GRAPH figure generated in PHREEQC. 


Radium solid solution with Barite or Barium sulfate has long been an important process used to control radium in Uranium Mill tailings.
Until recently, the RaSO4 BaSO4 system was considered to behave as an ideal solid solution; and the following figure generated in PhreePlot shows that behavior. 

Lippmann Diagram for (Ba,Ra)SO4 ideal solid solution, prepared using PhreePlot



However, recent information indicates that the system is not an ideal solution solution,  but  rather it appears to be a regular solution with an a0 of 1.0.  


Lippmann Diagram for (Ba,Ra)SO4 regular solid solution, prepared using PhreePlot 



We can also us PhreePlot to estimate the Guggenheim non dimensional parameters. 
This will be discussed in a later update to this web site.


USING PHREEPLOT TO UNDERSTAND Eh-pH DIAGRAMS

While evaluating some remediation options for uranium, I prepared the following diagram for the system U-V-Ca-CO3.



The field for Tyuyamunite Ca(UO2)2(VO4)2 had an unusual shape with a "bite" taken out of the bottom.  the abrupt change in slopes suggest some process was active in the pH region around 7.   The same effect is also seen in the stability field for  the  UO2(am,hyd,NEA) solid.   It is apparent that it is related to changes in the proportion of the Ca2UO2(CO3)3 complex.   A concentration contour diagram was prepared and it showed the greater uranium concentrations in the middle of the field for tyuyamunite.   This is contrary to the behavior that would be seen if an old style calculation was prepared.  But the predominance method used to prepare these diagrams provides more details.  A ridge of approximately 1 mg/L U is present in the middle of the tyuyamunite field.  

The calculations used to set up this diagram allowed for the precipitation of calcite, and the formation of calcite causes a decrease in the amount of the Ca2UO2(CO3)3 complex.  So more tyuyamunite forms and the dissolved uranium concentration decreases with increasing pH.