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HW Process Technologies, Inc.

Engineered Membrane Separation(EMS) Membrane

Technology Developments for Mining Appl ications

(TT-145)

Metallurgical Processes Committee

Authors

John. A. Lombardi VP Marketing DevelopmentMining (jlombardi@harwest.com)

Oscar A. Osores Process Engineer (oosores@harwest.com)

Company

HW Process Technologies, Inc.

1208 Quail Street Lakewood, CO 80215

United States of America

Phone 303.234.0273 Lima, Peru: 991663137

Fax 303.237.9868

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1.0 Summary

Membrane technology has been available for over 50 years, but has been used

sparingly in the general mining industry. However, recent developments in polymer

chemistry, spiral-wound element construction, pretreatment equipment and techniques,

and an expanded understanding of membrane fouling and cleaning techniques have

dramatically improved the reliability and robustness of membrane-based systems for use

in the mining industry.

Membrane technology for mining applications has gone beyond producing high-quality

water from well- and sea-water by pushing forward with process water treatments to

recover and concentrate metals, reagents and clean, discharge-quality waters.

While process water membrane treatment plants resemble conventional RO

de-salting plants, they are different because of the materials of construction of the

osmosis surfaces, the micro-hydrodynamics of the membrane elements themselves, and

the customized, macro-hydrodynamic plumbing of the vessel arrays that constitute the

treatment plant. These plant differences, plus a wide variation of glues, fabrics and other

materials of construction enable the treatment of pH 1pH 13 solutions, and have opened

up a new world of micro-, ultra-, nano- and hyper-filtration treatment opportunities. The

new paradigm of solution treatments involves the removal of organics and precipitated

and suspended solids, and ion separations, including simple demineralization, multi-valent

ion separation from mono-valent ions and tri-multi-valent species separation from di-multi-

valent ion species.

2.0 Objectives

The main objective of this work is presenting state-of-the-art process alternatives

using membrane technology to face four treatment issues common in the copper, gold

and in general all the mining industry regarding process waters and streams that offer

treatment challenges to the metallurgical and process engineers.

This paper presents flow sheets for: a) acid-mine-drainage treatment circuits with,

and without, copper recovery; b) the treatment of gold mill barren for the production of low

metals content discharge water; c) the treatment of raffinate and/or electrolyte for the

recovery of organic; and d) the treatment of copper-gold cyanide PLS, a special,

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proprietary sub-set of cyanide treatment that is an enabling technology for the treatment

of copper gold ores.

It also contains experimental data and results from the treatment applications in

bench, pilot and industrial-scale membrane plants worldwide.

3. Appl ication and Data Collection

Membrane Technology

Membranes reject species on multiple levels, including the absolute size or shape of

specific non-charged molecules, the charge, charge density and degree of hydration of

charged inorganic salts, and, for organic compounds, on the basis of molecular weight

considerations.

Figure 1: Cut-away of Spiral-wound Membrane Element

Spiral-wound membrane elements (Figure 1) are the preferred membrane type for

mining applications due to the polyamide and fabric characteristics and design that

promotes turbulence flow through the membrane surface, avoiding solids precipitation as

they concentrate.

Both filtration and membrane processes are classified in terms of the pore size of the

barrier to the solid particle or ion respectively in an aqueous media. These processes can

be classified as micro-filtration (removes solid particles up to 0.2 to 0.4 microns),ultra-filtration (removes solid particles up to 30-50 Armstrong), nano-filtration (removes

ions in the range of 5 to 10 Armstrong) and hyper-filtration (removes ions in the range of 1

to 5 Armstrong). This can be observed in Figure 2.

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Particulates

MF 0.2 to 0.4

"In" H2O

DetergentsProtein

BacteriaUF1 0.01 to 0.04

StarchGelatin

UF2 0.003 to 0.00 30 to 50

Metal IonsDyesSO42+ CA2+

NF 5to 10

AcidsNaNO3Cl

-

HF 1to 5

H2O

Figure 2: Filtration and Separation Spectrum

Bench Testing

The first step in the development of the membrane option for the treatment of a mining

process or waste water is bench testing. Typically, 20-liter samples of candidate waters

are recovered (if available) and analyzed. The analysis thats done must recognize the

goal(s) of the water treatment (metals concentration?, clean discharge water

production?, organic recovery?) as well as the membrane treatment variables of

importance like gypsum scale formation potential, dissolved silica contents, chloride

(corrosion), temperature, pH and the like. The bench membrane test enables the selectionof membrane type and quantification of element-by-element separation efficiencies. The

bench test is the first indication of the degree of success attainable using membranes for

each of the goals of any described process or waste water treatment problem. This

relative degree of success can be further defined in regards the development of order-of-

magnitude, budgetary level, capital and operating costs.

Site Pilot Testing

The next step in the membrane process design is the performance of an on-site pilottest (this assumes a reliable flow of candidate water is available). During this period an

entire process is evaluated in real time. Over the years, HWPT has discovered the most

important considerations for new applications always focus upon: pretreatment, proper

membrane selection, proper element construction, rejection of metals by the membranes,

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percentage of overall recovery and, very importantly, development of an effective and

efficient membrane cleaning regime.

Figure 3: HWPTs laboratory bench equipment and 10 GPM pilot system

used for on-site process development.

A) Ac id-mine-drainage treatment c ircu its wi th , and w ithout , copper recovery

Acid mine drainage can be successfully processed and made adequate for discharge

using membrane technology.

Figure 4: AMD treatment circuits without and with copper recovery

The pre-treatment stage consists of a solid liquid separation using a combination of

traditional filtering systems such as sand, bag or cartridge filters followed by an ultra-

filtration stage.

The ultra-filtration stage uses membranes with bigger pore sizes than hyper- or nano-

filtration membranes (0.04 microns) and works on high recovery and low operating

pressure.

This pre-treatment phase generates clear water with very low suspended solids

content (TSS), able to be processed through the ion separation membranes.

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The membrane process will generate two process streams: the larger process stream

that will contain very little dissolved solids (TDS), which is called permeate, and a smaller

volumetric flow which contains all the feed chemical species concentrated, hence a high

TDS content, called concentrateThis membrane process will be characterized by its recovery. The recovery is

expressed as a percentage, and is defined as the amount of produced permeate water

divided by the feed volumetric flow multiplied by 100.

The recovery will depend on the feed water chemistry, dissolved solids (TDS) content

and temperature.

A typical process would be on the 65-70% recovery range. Recovery in this range

results in a 3X concentration of the dissolved solids component of the feed water. For

example, a 250 ppm CuSO4 feed water would be recovered to a 1/3rd

volume, 750 ppmCu, membrane concentrate stream. The mentioned bench and pilot tests allow defining

the achievable recovery to be expected on an industrial-scale operation.

The produced permeate flow is very low in dissolved solids content and, relative to its

metals content, is typically compliant with all requirements for discharge into the

environment. Depending on the membrane used for the treatment, the pH characteristic

of the permeate may or may not be different from that of the feed water. In the case of

Acid Rock Drainage treatments, the pH of permeate is typically unchanged from that of

the feed water, and a small addition of caustic or lime is required to make the permeatecircum-neutral. The permeate is also an ideal candidate for alternative uses like make-up

water for flotation circuits, cooling towers and boilers.

A cost-benefit evaluation is required to determine the advisability of recovery of

valuable metals from a membrane concentrate.

Alternatives for concentrate post treatment, as shown in Figure 4, include simple lime

neutralization (FeCl3is referenced only as a typical flocculant additive) and SX recovery, a

metals recovery method most specific to copper. Alternatively, for a copper AMD, the

metals could be removed and the raffinate could be lime treated. In the end, under the

best circumstance, the membrane treatment process for AMD can produce metal

(copper), sludge filter-cake, and a 100% compliant volume of discharge water. In this

case, except for waste solids, the treatment is a Zero-Liquid (waste)-Discharge (Z-L-D)

process.

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ElementEMSFeed

(ppm)EMSConcentrate

(ppm)EMSPermeate

(ppm)

SO4 7,300 23,000 126pH 2.84 2.62 3.14

Al 563 1850 8Cu 1218 4175 28

Fe 84 269 1.3

Mg 324 1120 7.3

Mo 0.03 0.02 0.01

Na 30 128 3.0

SiO2 REACTIVE 28 70

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their high pH, various metals traces including gold, cyanide content, high calcium and high

carbonates or sulfates depending on the ore and processing characteristics.

In order to maintain water balances during the mining operation, it is required to treat

this barren stream, generating water that can be discharged in strict accordance to thedischarge regulations and standards.

HWPT has designed, supplied and installed 1750 M3/Hr Engineered Membrane

Separation System (EMS) at Yanacocha. Each individual skid produces 250 M3/Hr

EMSPermeate and is pre-engineered to minimize field installation.

This process has been on line for five years, assisting the mine with water balance

and resource recovery. Operation has been simple and straightforward with a minimum

amount of operator interface.

Figure 5: Yanacocha 1000 m3/h EMSplant, the worlds largest

membrane technology application in mining

Resource recovery in the form of gold, cyanide and strict environmental compliance

has made this investment by Newmont a huge success with the added value these plants

provide.

Yanacocha will add two more treatment plants (500 m3/h of produced permeate) to be

installed during 2010.

Merrill-CroweBarren

Solution

ConcentrateReturned

to Process

Discharge toEnvironment

EMS

System

Figure 6: Yanacocha treatment flow sheet

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C) Treatment of raffinate and/or electrolyte for the recovery of organic

The membrane treatment of raffinate and electrolyte provide a low-pressure, high-

efficiency copper SX-organic recovery method.

EMS

Return Organicto SX

Raffinate 95% by-volumeto Heap

EMS

Return to SX

Rich ElectrolyteTo EW Cells

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Heap

Gold Recovery

EMS

SystemCu CN Cu Rec'

CN

Au CNCuCN

CuAuCN

Figure 8: Treatment of copper-gold streams

Conclusions

EMSmembrane technology has been successfully and cost-effectively applied to

mining and refinery process and wastewater streams. It enhances separation processes

in a robust, reliable, and cost-effective manner.

Bench and pilot testing allows setting the design basis for a large industrial-scale

efficient process uniquely designed to fit the application requirements.

Both permeate and concentrate provide added value to the projects. Low operator

input, low maintenance, high availability, and smaller footprint than traditional water

treatment systems are also benefits from using the membrane technology on mining.

Mining applications and required separations provide a large variety of solutions the

industry requires to improve the performance, availability and results from the extraction

processes.

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