Acid drainage is a persistent environmental problem in many mineralized areas, especially where mining has taken place. Not all drainage, however, is.

Slides:

Advertisements

Similar presentations

GEOCHEMICAL CONSEQUENCES OF DIFFERENTIAL SETTLING OF GOLD TAILINGS Barbara L. Sherriff, Nikolay Sidenko University of Manitoba Canada.

Advertisements

Dissociation and pH Dissociation of weak acids/bases controlled by pH Knowing the total amount of S and pH, we can calculate activities of all species.

Dissolution and Precipitation

Topic E – Enviro Chemsitry Part 2 – Acid Deposition

Acid Mine Drainage. Terms Acid Mine Drainage (AMD) –Water that is polluted from contact with mining activity Acid Rock Drainage (ARD) –Natural rock drainage.

Class evaluations.

Acid Mine Drainage Excercise H-ESD : Environmental and Sustainable Development Michael Staudt, GTK.

Remediation of Acid Mine Drainage by Constructed Wetlands.

Surface Water Geochemistry of Deckers Creek Basin Geology 399 Qingyun Sun.

Acid Mine Drainage. Mining & the Environment Mine overburden & waste soils (mine tailings) are waste products generated by the mining industry. When these.

Soil Acidity and Nutrients

E NVIRONMENTAL CHEMISTRY E 12. water and soil. W ATER AND SOIL Solve problems relating to the removal of heavy- metal ions, phosphates and nitrates from.

Figure 4-1. Diagram of a Zn-Cu electrochemical cell. Zn and Cu metal electrodes are immersed in a CuSO 4 solution. Electrons flow from left to right and.

Acid Mine Drainage: From Formation to Remediation CE Aquatic Chemistry Julie Giardina Dominike Merle.

6/12/2015 One Point Quiz  One quiz per table, list everyone’s name  Agree on an answer  You have two minutes.

THE RELATIONSHIP BETWEEN H2CO3* AND HCO3-

6/17/2015 One Point Quiz  One quiz per table, list everyone’s name  Agree on an answer  You have two minutes.

Lecture 263/30/07. E° F 2 (g) + 2e - ↔ 2F Ag + + e - ↔ Ag (s)+0.80 Cu e - ↔ Cu (s)+0.34 Zn e - ↔ Zn (s)-0.76 Quiz 1. Consider these.

Solubility. Solubility “Insoluble” salts are governed by equilibrium reactions, and are really sparingly soluble. There is a dynamic equilibrium between.

Dissolution and Solubility Processes Dissolution-precipitation equilibria affect many soil processes, plant growth, etc Dissolution is the disintegration.

Water quality issues – ‘natural’ controls Acidity – low pH due to infiltration of acidified precipitation; acids from mine drainage; pyrite oxidation.

Solubility and Complexation Equilibria Chapter 18.

The K sp of chromium (III) iodate in water is 5.0 x Estimate the molar solubility of the compound. Cr(IO 3 ) 3 (s)  Cr 3+ (aq) + 3 IO 3 - (aq)

Strong Acid-Weak Base and Weak Acid - Strong Base.

An Introduction to Acid Mine Drainage by George Mitchell and Tim Craddock.

Chemical Weathering Definition: transformation/decomposition of one mineral into another Mineral breakdown carbonate dissolves primary minerals --> secondary.

B. Chemical Weathering Definition

Environmental chemistry

Soil Buffering and Management of Acid Soils. pH pH = - log (H + ) If (H + ) = 1 x mol/L (H + ) = mol/L pH = - log (1 x ) pH = - (-3)

Geology, Mining, and Water Quality by Matthew A. Sares.

Chemical Weathering. I. Introduction Chemical Weathering I. Introduction II. Process of Decomposition A. Overview: Decomposition alters minerals into.

Types of Chemical Weathering. Carbonation Carbonation- the reaction between calcite and weak acids in rain water and acids in groundwater. Rocks that.

H-ESD : Environmental and Sustainable Development

Enter your initial fluid composition on the Basis pane, then go to the Reactants pane to create a reaction path. Choose the type of kinetic reaction.

Acid Pollution of Natural Waters. Outline of Topics Background –Acids and bases –pH ranges in the hydrosphere –Biological effects of acid pollution Sources.

If Fe is left outside it will eventually rust. What causes this redox reaction? Fe changes into Fe 2+ and O 2 changes into OH 1-. Write 2 balanced half.

Magnetite, Fe3O4 crystallizes with the spinel structure. The large oxygen ions are close packed in a cubic arrangement and the smaller Fe.

Seasonal Changes in Biogeochemistry of a Natural Wetland Receiving Drainage from an Abandoned Mine Diane McKnight and Eric August – University of Colorado.

 The primary acid-generating process at these sites is the dissolution of pyrite: 2FeS 2 + 7O 2 + 2H 2 O > 2Fe S O 4 + 2H 2 SO 4  Iron and/or sulfur.

Refers to the leaching of acidic waters from previously mined metal or coal sources. Sulfuric acid (acid rock drainage) comes from natural oxidation of.

Acid Mine Drainage. Yellow boy in a stream receiving acid drainage from surface coal mining. An Enviromental problem in coal- Mining region Degrades water.

General Chemistry II Chemical Equilibrium for Gases and for Sparingly-Soluble Ionic Solids Lecture 2

Weathering, Erosion & Soils Weathering is the the breakdown of solid rock at or near the Earth's surface.

DISSOLUTION. The simplest weathering reaction is dissolution of soluble salts, e.g. CaSO 4 (anhydrite)  Ca 2+ + SO 4 2- Solubility - The total amount.

Karst Chemistry II. Conductivity – Specific Conductance Conductance – the electrical conductivity of aqueous solution, and is directly related to the.

Acid Mine Drainage H-ESD : Environmental and Sustainable Development Michael Staudt, GTK.

Class average for Exam I 70. Fe(OH) 3 Fe 3+ (aq) + 3 OH - (aq) [Fe 3+ ][OH - ] 3 = 1.1 x [y][3y] 3 = 1.1 x If there is another source of.

Reactions of Carbonate Minerals with Acid Mine Drainage: Is Dolostone or Limestone Better?

Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002 General Chemistry Principles and Modern Applications Petrucci Harwood Herring.

Lecture 21. Water-Related Complexes Ferric iron, will form a Fe(H 2 O) 6 3+ aquo-complex. The positive charge of the central ion tends to repel hydrogens.

Solubility (cont.); Mineral Surfaces & Reactions Lecture 22.

Weathering, Erosion & Deposition ESS Weathering The breaking up of rock into smaller pieces.

E 12 Water and Soil Solve problems relating to removal of heavy –metal ions and phosphates by chemical precipitation

Acidity Ability of a fluid to neutralize strong base. Measured by titration to pH ~8.3. Expressed as meq base kg –1.

Petroleum engineers use a variety of flooding agents (seawater, hot water, acids, CO 2, and alkali solutions) to displace fluids and increase production.

Act2 and Tact Calculate stability diagrams on activity, fugacity, and temperature axes. Calculate solubility diagrams. Project traces of React runs onto.

Q H+H+ H+H+ ADP ATP H+H+ H+H+ NAD NADH e – acceptor End product H+H+ H+H+ H+H+ H+H+ e – donor e – donor End product H+H+ H+H+ H+H+ H+H+ Cytoplasm Environment.

Substrate combines with enzyme to form activated complex, which can decay to give catalytic product Michaelis-Menten equation gives rate of forward reaction.

React Conceptual Model Equilibrium in Multicomponent Systems The “basis” Secondary species Mass action Mass balance.

Hot groundwaters that circulate within the Earth’s crust. Involved in formation of ore deposits, chemical alteration of rocks and sediments, and the origin.

Kinetic reactions React, X1t, and X2t can trace several types of reactions according to kinetic rate laws: Mineral precipitation and dissolution. Redox.

TRACE METAL TRANSFER FROM ROCKS TO THE PEDO- AND HYDRO- SPHERES.

Configure your animation in Xtplot, then check “Save animation to image files” and click Run. Save images here Choose PNG, JPEG, TIFF, or Bitmap.

Set the simulation’s duration

Set the initial fluid composition on the Basis pane.

X position (m) I s o t p i c m n C , d a y Bulk fluid CO (aq)

Chemical Weathering SAPROLITE.

Solubility and Complexation Equilibria

What is acid rock drainage?

Set the chemical composition of initial system on the Basis pane.

Presentation transcript:

Acid drainage is a persistent environmental problem in many mineralized areas, especially where mining has taken place. Not all drainage, however, is acidic or rich in metals. Primary controls on drainage pH and metal content seem to be Exposure of sulfide minerals to weathering Availability of atmospheric oxygen Ability of nonsulfide minerals to buffer acidity Acid drainage and buffering

Task 1 — Role of atmospheric oxygen Simulate pyrite dissolution into a hypothetical groundwater Consider systems isolated from and open to exchange with the atmosphere

Pyrite reacted (cm 3 ) pH Open to atmospheric fO 2 Isolated Role of atmospheric oxygen

Water in the absence of O 2 supply becomes saturated with respect to a sulfide mineral after only a small amount of dissolution. As a result, pH and fluid composition change little. O 2 additionally promotes metabolism of bacteria that catalyze sulfide mineral dissolution and oxidation of dissolved iron. Role of atmospheric oxygen

Pyrite reacted (mmoles) Reaction products (mmoles) FeSO 4 + H+H+ SO 4 2− HSO 4 − Fe(SO 4 ) 2 − Open to atmospheric O 2

FeS /4 O 2 (aq) + 1/2 H 2 O  FeSO SO 4 2− + H + Pyrite Equilibrium with atmospheric oxygen FeS /4 O 2 (aq) + 1/2 H 2 O  FeSO HSO 4 − Pyrite Initial reaction As pH decreases

Task 2 — Buffering by wall rocks Build upon the previous example React pyrite into a fluid in equilibrium with calcite

Pyrite reacted (cm 3 ) pH No calcite Calcite Open to atmospheric O 2

0.51 –4 – Pyrite reacted (cm 3 ) Volume Change (cm 3 ) Gypsum Fe(OH) 3 Calcite

No calciteCalcite pH * Fe (mg kg −1 ) SO Ca HCO *CO 2 degassing, not accounted for here, would further increase pH Reaction of 1 cm 3 Pyrite in system open to atmospheric O 2 Resulting fluid chemistry

Effect of pH on ferric iron solubility Oxidation of ferrous iron Fe H 2 O  Fe(OH) 3 + H + Ferric hydroxide Fe O 2 (aq) H 2 O  Fe(OH) H + Ferric hydroxide HFO precipitation

Initial stage of calcite dosing As pH increases CaCO H +  Ca 2+ + CO 2 (aq) + H 2 O Calcite CaCO 3 + H +  Ca 2+ + HCO 3 − Calcite pH adjustment

Task 3 — Co-Precipitation React calcite into acidic, metal-rich fluid Assume iron is already oxidized HFO precipitates as pH increases What metals sorb to HFO?

Calcite reacted (mmoles) Jarosite-Na Minerals (mmoles) Calcite Fe(OH) 3 HFO precipitation

pH Fraction sorbed AsO 4 3− As(OH) 4 − Pb 2+ Cu 2+ Zn 2+ HFO complexation

ComponentMaximum sorbed (mg kg −1 ) In solution (mg kg −1 ) As(OH) 4 − AsO 4 3− Cu Pb Zn Sorption capacity Capacity for each metal to sorb if it occupied every surface site. Account for amount of precipitate, number of sites, and site types accepting each metal.

Craig M. Bethke and Brian Farrell © Copyright 2016 Aqueous Solutions LLC. This document may be reproduced and modified freely to support any licensed use of The Geochemist’s Workbench® software, provided that any derived materials acknowledge original authorship.