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BIOSORPTION OF COBALT AND COPPER FROM HYDROMETALLURGICAL SOLUTIONS

MEDIATED BY Pseudomonas spp

PRESENTATION BY:

NONJABULO PRUDENCE DLAMINI

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PRESENTATION LAYOUT

Introduction

Scope of the work

Experimental design

Results & discussions

Conclusions

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INTRODUCTION

The use of micro-organisms in the dissolution of metals bearing minerals and the removal of some anions e.g. phosphates and ammonia is well known e.g. sulphur oxidisers Acidithiobacillus spp, Leptospirillum spp and Sulpholobus spp. (Acharya,1990) (Momba, 2005).

However, not much has been done on the use of microorganisms in the removal of leached metals from their aqueous solutions. E.g. Fixation of Ni and Fe by Pseudonomonas species through biosorption (Danalkova et al,2005).

In this study copper and cobalt are being removed from hydrometallurgical solutions using microorganisms

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The use of biological methods for heavy metal recovery have gained considerable momentum due to their high efficiency, low operating costs and simplicity.

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SCOPE OF THE WORK

This project was aimed at testing the viability of using bacteria as;

Alternatives to costly metal removal

techniques (water purification). Biosorbents to recover precious metals

from hydrometallurgical process solutions.

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EXPERIMENTAL DESIGN

Sampling

•Soil & water samples were collected from water bodies around the small scale mines.

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Sampled sites

•Acidic•Turbidity high•Conductivity high

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CULTURING AND IDENTIFICATION

Soil samples were suspended in distilled water, vortexed (thoroughly mixed).

oBoth the water and soil samples supernatant were diluted in a sterile phosphate buffer and there after inoculated in Pseudomonas agar base.

oThe isolation of bacteria using Pseudomonas agar base yielded positive results meaning that there blue-green colonies of Pseudomonas spp were observed.

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Synthetic solutions

Solutions of different concentrations (0.07M, 0.33M and 0.66M) were prepared using copper and cobalt sulphate.

Batch scale experiments to test the effects of

Contact time, concentration, pH, temperature, co-ions, biomass concentration were conducted.

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Metal recovery

Bacteria : water (3:1) ratio Bacteria were inoculated into synthetic

solutions water samples and recovery was allowed to take place over a period of 24 h in a shaking incubator (150 rpm) at 36.5°C.

Metal concentrations were analysed using AAS and ICP.

Control experiments were conducted to monitor parameters like precipitation.

The same procedure was repeated for hydrometallurgical solutions which had lower metal concentrations.

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Results & discussions

Contact time and temperature had an almost similar effect on the rate of biosorption. Increased up to a certain level then decreased.

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pH

Maximum uptake of Cu and Co by Pseudomonas spp was attained at pH 6.5.

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Biomass (bacterial concentration)

3 : 1

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Co-ions

Mixing copper & cobalt enhanced removal of copper.

Ionic radii

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Kinetic models

y = -1219.9x + 9.1768

R2 = 0.8615

0.55

0.75

0.95

1.15

1.35

1.55

1.75

1.95

2.15

2.35

2.55

0.0057 0.0059 0.0061 0.0063 0.0065 0.0067 0.0069 0.00711/C

1/(

x/m

)

Langmuir equation model

R2= 0.8615

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y = -6.3649x + 13.903R2 = 0.9622

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

2.14 2.16 2.18 2.2 2.22 2.24 2.26

Log C

Log

x/m

Freundlich equation model

The Freundlich equation gave a plot with higher correlation as compared to the Langmuir equation. The Freundlich gave an R2 value of 0.9622 whereas the Langmuir had an R2 value of 0.8615. Therefore the Fruendlich plot is favoured over the Langmuir.

R2=0.9622

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Recovery from hydrometallurgical solutions

Sampled site

Copper Cobalt

% recovery % recovery

Nigel river 50 45Big dam 42 35HVH mine site A 37 65HVH mine site B 73 46HVH mine site C 61 11Shaft No 2 A 29 22Shaft No 2 B 24 40Shaft No 2 C 36 20

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INTERACTION OF MICROBES WITH METALS (SEM)

SEM micrograph of the dried metal solution before interaction with Pseudomonas spp rods.

SEM micrograph showing the dried mixture of metal solution with Pseudomonas spp

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TEM

metal bioaccumulation on the periplasmic wall of the Pseudomonas spp rods.

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Conclusions

Pseudomonas spp reclaim both copper and cobalt from their sulphate synthetic solutions .

It tends to remove or extract more metal ions at low concentrations and the ratio of bacteria population to solution volume being 3:1 works best.

The maximum uptake of both copper and cobalt occurred at a pH of 6.5 beyond which the adsorption rates decreased.

The bacteria have successfully removed up to 45 % of copper from 0.07M and up 40 % from 0.07M cobalt from cobalt sulphate solutions and 73 % and 65 % of copper and cobalt respectively from mine water samples.

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ACKNOWLEDGEMENTS

Nigel town municipality and small scale miners.

National research foundation and the University of Johannesburg for financial assistance.

Mr E. Fosso-Kankeu

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….THANK YOU…

…….THANK YOU……

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