Objective: Recovery of zinc as zinc metal powder from gypsum sludge

Introduction:Gypsum sludge is generated during 2-stage hydrated lime treatment to the liquid efuent at zinc-lead smelter. The locked-up zinc in the gypsum sludge is the potential source of zinc and the recovery of this metal value from this gypsum sludge at an economical way is a challenge to the metallurgists and chemists.

Experimental Procedure:The process involves a leaching step to obtain neutral zinc sulphate solution and the resultant zinc from the solution is precipitated as zinc hydroxide using a selective and specic precipitant leaving all other impurities in the ltrate.This zinc hydroxide cake is then leached in sodium hydroxide solution to form sodium zincate and electrolysed in an alkaline medium using innovative cathodes and anodes to obtain high pure electrolytic zinc powder.The ow sheet developed is presented

Results:The general composition of gypsum sludge is as follows: Zinc:6-12%, CaCO :20-30%,Ca(OH) :0.5-1.0%,Iron:4-10%,3 2

Cobalt:0.01-0.015%,Magnesium:1- 2%,Chlorides: 0.5 - 1.0 %, Fluorides: 0.004 - 0.01%, Moisture:30 - 40%. By this innovative process of alkaline electrolysis, electrolytic zinc metal powder was produced and the purity (99.3 %) as well as the metallic content (97.1%) is comparable with the other products produced by two other different methods-thermal and atomization processes (98.2%). The product was tried at the purication stage at zinc electrowinning and cadmium plants yielded similar results with that other products generally used.

Conclusion:This process can be adopted to recover zinc from other secondary resources where high chloride levels with low zinc. This is an alternate approach for its recovery which can be adopted to various secondary zinc sources with the following advantages.

1. An innovative technique to produce metallic zinc metal powder with pilot plant proven technology from lean zinc bearing material which can be applied to other zinc bearing secondary sources

2. A novel approach to convert “waste to wealth” in an effective and economical way It is an innovative and used non-conventional electrolyte to produce zinc powder

3. A versatile process to solve he water balance and to eliminate build-up of impurities such as chlorides, uorides and magnesium at zinc hydrometallurgical plants

References:1. R.Raghavan (2000), 'Development of Innovative, Eco-friendly and Economic Technologies Wealth Processing at Hindustan Zinc Limited', MINPREX 2000 International Congress on Mineral Processing and Extraction Metallurgy, Melbourne, Australia, 11-13 September 2000, pp147-167,

2. R.Raghavan (2009), 'NMRF: dedicated to conservation of mineral resources', Minerals & Metals Review, Vol XXXV No.05, May issue, pp 41-45, 2009.

3. R.Raghavan (2010), 'Contributions of Nonferrous Metallurgical Research Foundation on Waste-to-Wealth Technologies', Volume 13, No. 1 February 2010, pp 18-23, IIM Metal News.

4. R.Raghavan (2016), Chapter 23 (pp 447-482) and references therein in Extractive Metallurgy of Non-ferrous Metals, Published by Vijay Nicole Imprints Private Limited, Chennai, ISBN-13:978-81-8209-440-6.

Objective: Recovery of copper from copper bearing materials such as copper cement generated at zinc electrowinning process

Introduction:

Experimental Procedure:

Results:Results are summarized below on various solutions, cakes/residues and nal products

Results obtained on Cu-Cd-Zn cake by Leach-Precipitation-Redissolution-EW process

Cu-Cd Cake(%)

Leached ltrate

Copper residue

(%)

Cu leach solution

Cu-residue

(%)

Cu-cake

(%)

Filtrate after precipitation

Cell Feed

Copper

2.5

200 mg/L

30

55 g/L

3.0

25

2 g/L

52 g/L

Cadmium

5.0

15 g/L

2.0

5 g/L

0.3

0.8

4.5 g/L

0.5 g/L

Zinc

45.0

130 g/

8.0

15 g/L

1.0

1.0

14.5 g/L

2.5 g/L

Cobalt

0.045

120 mg/L

0.15

220 mg/L

0.007

0.005

210 mg/L

10 mg/L

Nickel

0.043

130 mg/L

0.15

300 mg/L

0.003

0.005

285 mg/L

15 mg/L

Iron

0.15

500 mg/l

0.25

750 mg/L

0.75

0.01

5 mg/L

0.5 mg/L

Thallium

0.2

90 mg/L

0.025

80 mg/L

0.005

Trace

1 mg/L

1 mg/L

Conclusion:

Advantages of the process developed:

Simultaneous recovery of zinc, cadmium and copper from copper bearing material The process is very simple, easy to operate, cost effective and eco-friendly with various copper products can be achieved with exibility of the end product needed Zinc, if present high in the copper bearing material can be recovered as zinc sulphate crystals as bye-product This process utilises the most common, easily available and cheap chemicals for purifying the copper sulphate solutions Technologically superior and economic in comparison with other processes in practice and recovery efciency is high The chemicals used are non-toxic and the process does not generate any gaseous or liquid efuent, making the process more environment friendly

References:1. R.Raghavan and P.K.Mohanan, Innovative Processing of Copper-Cadmium-Zinc Cementation Residue Generated at the Zinc Hydrometallurgical Plant Through Selective Leaching and Selective Precipitation and Recovery of Copper Cathode Sheet, Accepted for Presentation at the International Symposium onFrontiers in Materials Processing held at Bangalore during November 14-17, 1998 organised by Indian Institute of Metals, Paper No.A 29.2. R.Raghavan (2000), 'Development of Innovative, Eco-friendly and Economic Technologies Wealth Processing at Hindustan Zinc Limited', MINPREX 2000 International Congress on Mineral Processing and Extraction Metallurgy, Melbourne, Australia, 11-13 September2000, pp147-167,3. R.Raghavan (2009), 'NMRF: dedicated to conservation of mineral resources', Minerals & Metals Review, Vol XXXV No.05, May issue, pp 41-45, 2009.4. R.Raghavan (2010), 'Contributions of Nonferrous Metallurgical Research Foundation on Waste-to-Wealth Technologies', Volume 13, No. 1 February 2010, pp 18-23, IIM Metal News.

In order to develop a simple hydrometallurgical process for the recovery of copper from copper bearing material generated at the zinc purication stage as well to apply other copper bearing material such as copper dross from lead smelter and other secondary resources investigations have been carried out to produce different copper products such as copper cathode, copper metal powder and or copper sulphate solution.

The process involved the following stages for treating the copper-cadmium-zinc cement generated at the zinc purication stage are: (1) selective leaching of zinc and cadmium using a selective leachant to obtain an enriched high quality copper cement (2) leaching of copper rich residue to solubilize copper and residual zinc (3) selective precipitation of copper from leached solution (4) releaching of the copper residue (5) electrolysis to produce copper either copper metal powder or copper cathode sheet. In the absence of cadmium and zinc the process involved only the stages of 2 to 5 leaving the stage 1. Copper sulphate solution can be used for the production of copper sulphate crystals.

Constituents Copper cathode

Copper metal powder

Copper sulphate crystals

Zinc sulphate crystals

Copper (%) 99.900

99.90

24.1

0.0005

Impurities (%) 0.0414

0.0378

Lead (%) 0.014

0.02

0.0005

0.0005

Zinc (%) 0.025

0.015

0.2

21.80

Cadmium (%) 0.0004

0.0005

0.06

0.06

Cobalt (%) 0.0003

0.0003

0.001

0.002

Nickel (%) 0.0006

0.0006

0.001

0.001

Iron (%) 0.0009

0.001

0.025

0.001

Manganese (%) 0.0002

0.0004

0.014

0.0005

Results of the products obtained during the process

The results shown for the copper bearing material generated at zinc purication stage. However, the solution and residue analysis would be different depending upon the input with the products analysis would be more or less same quality.

Flow Sheet On the Recovery of Copper From Copper Bearing Materials

Production of Zinc As Zinc Metal Powder From Gypsum Sludge Through Alkaline Electrolytic Process (250 Kg/Day)

PRODUCTION OF ELECTROLYTIC ZINC METAL POWDER FROM

GYPSUM SLUDGE THROUGH ALKALINE ELECTROLYSIS

GENERATION OF GYPSUM SLUDGE AT ETP(2-STAGE HL-HL TREATMENT)

WASTE TO WEALTH INNOVATIVE TECHNOLOGIES FOR NON - FERROUS METALLURGICAL WASTESDr.R.Raghavan, Chief Advisor, Non-ferrous Metallurgical Research Foundation, Chennai

Email Id: dr.r.raghavan@gmail.com Webpage: https//raghavanr.weebly.com

Indian Institute Of Metals, NMD-ATM

72nd Annual Technical MeetingNovember 11-14, 2017

Poster number:

WASTE TO WEALTH INNOVATIVE TECHNOLOGIES FOR NON - FERROUS METALLURGICAL WASTESDr.R.Raghavan, Chief Advisor, Non-ferrous Metallurgical Research Foundation, Chennai

Email Id: dr.r.raghavan@gmail.com Webpage: https//raghavanr.weebly.com

Objective: : Recovery of lead from lead bearing materials such used lead acid batteries (ULAB)

Introduction:Lead paste from the Used Lead Acid Batteries (ULAB) mostly contain lead in the form of PbO, PbSO , PbO and 4 2

Pb(met) which is similar to that of the lead sulphate residues that are produced at zinc-lead smelter with varying composition of lead and impurities. Four different hyrometallurgical processes were tried and provided satisfactory results.

Experimental Procedure:The washed ULAB cake was used for all practical purposes. Washed cake was subjected to sodium sulphide treatment to produce quality lead concentrate; secondly, the washed cake was leached in alkaline solution and the resultant solution was electrolyzed and high pure lead metal was obtained with value-added red lead was obtained; in the third approach brine leaching followed by cementation to obtain lead sponge and the nal approach the washed cake was subjected to brine leaching followed by sodium sulphide treatment to obtain high quality lead concentrate which can be used at lead processing pyrometallurgical or electrolytic process.

Results: obtained on the recovery of lead by different processing techniques from washed ULAB Paste are presented below:

Conclusion:

References:1. R.Raghavan, P.K.Mohanan, S.C.Patnaik (1998), 'Innovative processing technique to produce zinc concentrate from zinc leach residue with simultaneous recovery of lead and silver', Hydrometallurgy, 48 (1998) 225-237 and the references quoted therein 2. R.Raghavan, P.K.Mohanan, S.R.Swarnkar (2000), 'Hydrometallurgical processing lead-bearing materials for the recovery of lead and silver as lead concentrate and lead metal', Hydrometallurgy 58 (2000) 103-116 and the references quoted therein 3. R.Raghavan (2009), 'Emerging Hydrometallurgical Process Options for Used Lead Acid Batteries', paper presented at the National Seminar on Lead Acid Batteries-Technology, Applications & recycling during 16-19 February 2009 at Bangalore. and the references quoted therein 4. R.Raghavan (2000), 'Development of Innovative, Eco-friendly and Economic Technologies Wealth Processing at Hindustan Zinc Limited', MINPREX 2000 International Congress on Mineral Processing and Extraction Metallurgy, Melbourne, Australia, 11-13 September2000, pp147-167,5. R.Raghavan (2009), 'NMRF: dedicated to conservation of mineral resources', Minerals & Metals Review, Vol XXXV No.05, May issue, pp 41-45, 2009.6. R.Raghavan (2010), 'Contributions of Nonferrous Metallurgical Research Foundation on Waste-to-Wealth Technologies', Volume 13, No. 1 February 2010, pp 18-23, IIM Metal News.

Objective: : Recovery of antimony from lead-antimony bearing materials

Introduction:

Experimental Procedure:

Results:

Conclusion: Indigenous route to extract antimony from lead-antimony bearing secondary resources. Produced minimum levels of impurities in the nal product Cost effective hydrometallurgical process Used very simple equipment, cheap and easily available chemicals Avoiding building up of antimony levels in the lead rening process Can effectively adopted from other antimony bearing materials The solution after cementation can be used for the manufacture of iron oxide suitable for paint industry after appropriate treatment to maintain zero liquid discharge.

References:1. R.Raghavan, P.K.Mohanan, S.C.Patnaik (1998), 'Innovative processing technique to produce zinc concentrate from zinc leach residue with simultaneous recovery of lead and silver', Hydrometallurgy, 48 (1998) 225-237 and the references cited therein.

2. R.Raghavan, P.K.Mohanan, S.R.Swarnkar (2000), 'Hydrometallurgical processing lead-bearing materials for the recovery of lead and silver as lead concentrate and lead metal', Hydrometallurgy 58 (2000) 103-116 and references cited therein.

3. R.Raghavan (2009), 'Emerging Hydrometallurgical Process Options for Used Lead Acid Batteries', paper presented at the National Seminar on Lead Acid Batteries-Technology, Applications & recycling during 16-19 February 2009 at Bangalore and the references cited therein.

4. R.Raghavan (2000), 'Development of Innovative, Eco-friendly and Economic Technologies Wealth Processing at Hindustan Zinc Limited', MINPREX 2000 International Congress on Mineral Processing and Extraction Metallurgy, Melbourne, Australia, 11-13 September2000, pp147-167,

5. R.Raghavan (2009), 'NMRF: dedicated to conservation of mineral resources', Minerals & Metals Review, Vol XXXV No.05, May issue, pp 41-45, 2009.

During pryo-rening operation of lead bullion obtained from sintering-blast furnace route, antimony is removed by the addition of sodium hydroxide in presence of sodium nitrate by Harris Process (Softening) converting antimony as sodium antimonate along with other impurities present such as arsenic and tin. Lead oxide formed due to the surface oxidation of molten lead along with sodium antimonate which forms a scum over the molten metal and forms dross. This dross is removed manually which contains mostly metallic lead, lead oxide and sodium antimonate. It is usually treated in a rotary furnace and obtain lead-antimony alloy. Attempts made to treat this antimony bearing dross obtained from lead rening through hydrometallurgical metal route to obtain pure antimony and succeeded in obtaining high quality antimony sponge. The process was simple and easy to implement with high purity antimony sponge. This method was adopted at low antimony levels and high content of antimony and succeeded to produce antimony sponge. This method can be sued for the production of lead-antimony alloy by suitable addition of lead while melting the sponge. The ow sheet developed is presented in Figure and results obtained in Table.

Process involves crushing and grinding, leaching, solid-liquid separation cementation, and melting of sponge

Option 1: Production of lead concentrate

Cons�tuent

Lead Paste

Washed

lead paste

Lead conc. (PbS)

Lead Metal

powder

Lead Ingot

Litharge Red Lead

Pb3O4

Lead

68.0

78.0

55.8

99.9

99.98

91.1

85.3

Zinc

0.005

0.006

0.003

0.001

0.0005

0.020

0.380

Copper

0.02

0.021

0.015

0.002

0.001

0.0167

0.0058

Cadmium

0.005

0.005

0.004

0.001

0.0001

0.0087

0.035

Cobalt

Nil

Nil

Nil

Trace

Trace

Trace

Trace

Nickel

Nil

Nil

Nil

Trace

Trace

Trace

Trace

Total Sulphur

6.0

5.0

12.0

---

----

----

----

An�mony

0.5

0.5

0.4

0.005

0.005

0.001

0.002

Silver

0.005

0.005

0.004

---

----

----

----

Iron

0.05

0.04

0.04

---

----

----

----

Bismuth

0.005

0.005

0.004

0.002

0.003

0.006

0.01

From these studies it can be seen that the hydrometallurgical treatments with different options can be viable alternate method to recover lead from the lead paste. The option can be se lec ted depend ing upon the inpu t and ou tpu t requirements with the available facilities. The process is very simple and effective to treat any kind of lead bearing materials. The efuent generated during the process was subjected to suitable treatment to obtain a value-added product and the efuent can be recycled at the processing unit.

Washed lead paste PbS Precipita�on Na2S solu�on

Solid

Liquid

Lead Concentrate

Lead Recovery thro’

Pyro route

Lead Recovery

thro” Fluobor

Process Discard

route

Washed lead paste

Brine leaching

NaCl solu�on

S

L

Precipita�on

Lead Recovery thro’

Pyro route

Repulping and

S/L separa�on

Na2S solu�on

L

S

L

S

Discard

Lead Recovery thro”

Fluobor process

Option 2: Recovery of lead through brine leach-lead concentrate

Washed Lead Paste

DESULPHURISATION

LIQ

SOLPRECIPITATION

Ba(OH)2

S

LCAUSTIC LEACHING&

SOLID/LIQUID

SEPARTION

LEAD PLUMBATE

SOLUTION

METALLIC LEAD AND OTHERS

SOURCE FOR ALLOY MAKING

ELECTROLYSIS

LEAD SPONGE Pb3O4

POWDER

MELTING

LEAD METAL

+

ROASTING

LITHARGE

BaSO4

Option 3: Recovery of lead through electrolytic route

Washed Lead Paste

DESULPHURISATION

L

SPRECIPITATION

Ba(OH)2

S

LBRINE LEACHING&

LIQUID/SOLID SEPARTION

FILTRATE/LIQUID RESIDUE TO DISCARD

AFTER REPULBING

AND FILTRATION

CEMENTATION

LEAD SPONGE

NaCl + AlCl3

SOLUTION

MELTING

LEAD METAL

ALUMINUM

REMOVAL

Al(OH)3

BaSO4

NaCl

NaCl

Op�on 4: Recovery of lead through combina�on of brine leach and cementa�on

Constituent

Antimony dross-Input

Leach Solution

Leached residue

Antimony sponge

Results obtained on low antimony dross

Antimony 5.5 % 3.7 g/L 2.1 % 89.2 %

Lead 73.2 % 1.6 g/L 81.9 % 3.9 %

Silver

0.002 %

1.0 mg/L

0.001 %

0.021 %

Results obtained on high antimony dross

Antimony

47.2 %

40.5 g/L

13.4 %

98.4 %

Lead

24.6 %

3.0 g/L

43.0 %

0.75 %

Silver

0.010 %

4.9 mg/L

0.01 %

0.012 %

The major advantages of the process are summarized below:

-

SOLUTIONAFTER

RECYCLE TOETP

Flow Sheet For The Recovery of Antimony From Lead-antimony Dross

Indian Institute Of Metals, NMD-ATM

72nd Annual Technical MeetingNovember 11-14, 2017

Poster number: