Controlling Heavy Metal Release and pH from Tailing Dam Using Permeable Steel-making Slag Cover System

2 Contents 1. Introduction 2. Materials & Method 3. Result & Discussion 4. Summary & Plans

3 Introduction

4 1. Current Status of Mines in South Korea Category General mine Coal mineTotal MetalNonmetalSubtotal Operating Abandoned2,1102,1982, ,803 Total2,1662,8304, ,396 92% of total Ref. 광해실태조사 (‘09.10~’10.8) (Unit: no.) Ref. Second 5years program for prevention of mine damage(11, Ministry of Trade, Industry and Energy)

5 Introduction 2. Problems of mines  What is Acid Mine Drainage ? FeS 2 + 7/2O 2 + H 2 O → Fe SO H + Fe 2+ +1/4O 2 + H + → Fe /2H 2 O Fe H 2 O ↔ Fe(OH) 3 (S) + 3H +  the outflow of acidic water from metal mines or coal mines  Sources of AMD: tailing piles and ponds, mine waste rock dumps  Low pH (3~5)  Contains various heavy metals  Generate reddish brown precipitate

6 Introduction 2. Problems of mines  What is Tailing ?  Mine dumps  The materials left over after the process of separating the valuable fraction from ore

7 Introduction 2. Problems of by-products disposal  What is Steel-making Slag? -Slag generation amounts is increasing annually -The costs of disposure is increasing -Unlike furnace slag, steel-making slag is being recycled as a relatively low value product -Decrease in new constructions of landfills and roads could lower the recycling rate, and the development of new slag area is needed Slag generation amount(1,0000ton) <Current status and prospect of slag generation amount in South Korea> Steel making slag Furnace slag

8 Introduction 3. Concept & Objectives Me 2+ and H + Releasing H+H+ Me 2+ H+H+ H+H+ H+H+ When it rains… Acid rain (pH around 5) H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Me 2+ Tailing dam

9 Introduction 3. Concept & Objectives When it rains… Acid rain (pH around 5) Slag Cover Free-CaO in Slag F-CaO + H 2 O →Ca(OH) 2 Ca(OH) 2 + a lot of H 2 O → Ca OH - OH - Very high pH effluent (pH 10~11)

10 Introduction 3. Concept & Objectives Soil Pore water (Acid) Rain OH - and Binder release Me 2+ and H + releasing  Without Slag Cover Soil  With Slag Cover H+H+ Me 2+ H+H+ H+H+ H+H+ Binder OH - H + release Neutralization H + +OH - →H 2 O H+H+ H2OH2O H2OH2O Me 2+ release Chemical Stabilization (Me 2+/ Binder) Solid Me 2+ Solid Me 2+ H2OH2O Tailing Slag

11 Introduction 3. Concept & Objectives Tailing Slag In the long term…. Hard pan forms = lowering K value  Without Slag Cover  With Slag Cover My Objectives are…  pH neutralization  Decreasing heavy metal release  (In the long term) Formation of hard pan(a layer of precipitate) at the tailing dam in abandoned mines

12 Materials & Methods

13 Materials & Methods  Steel-making Slag 1. Materials ElementsSiO 2 Al 2 O 3 TiO 2 FeO 3 MgOCaONa 2 OK2OK2OMnOP2O5P2O5 Total Wt.(%)  Tailing -Gwangyang steel company -#. 20(0.85mm)~#.40(0.425mm) -Uljin metal mine -< #.40(0.425mm) PbCuAsHgCdCr 6+ CNPTCEPCE Regulation Level (mg?L) Amount(mg/L) ND0.01ND Component

14 Materials & Methods 2. Methods A. Batch Experiment B. Column Experiment Rainfall simulator Slag only / slag + other material Tailing Sampling bottle Slag or tailing pH5 solution Agitation with rotary shaker pH and chemical concentration analysis pH and Conc. Solid-liquid ratio Slag particle size Shaking time Simulate repeated rainfall pH and Conc. Slag/ tailing thickness ratio Precipitate

15 Materials & Methods 2. Methods A. Batch Experiment Expected Result pH neutralization Heavy metal release reduction 12 slag tailing 12 slag tailing pH Metal conc. Time(hr) 7 5 Slag Slag + Tailing Tailing

16 Results & Discussion

17 Results & Discussion 1.Batch Experiment Slag Slag + tailing Tailing A. Batch Experiment  Solid-liquid ratio 1:43 1g : 4mL  Initial pH 6.68 pH neutralization

18 Results & Discussion 2. Methods Slag Slag + tailing Tailing  Solid-liquid ratio 1:5 4g : 20mL  Initial pH 5 Converged on pH 4 ∴ This tailing cannot be controlled by steel-making slag only => need to add other materials or modify slag

19 Summary & Plans

20 Summary & Further study  Summary - Most of mines in South Korea are abandoned and not under proper management so that they are creating a lot of environmental damage. Especially, the contamination resulting from leakage (AMD) affect the local environment and tailing dam is one of the sources of AMD. - Steel-making slags is a by-product of steel-making process, and decrease in new constructions could lower the recycling rate. Recycling the slags as a tailing dam cover can be a solution. - Slags cannot control AMD solely which means that it needs to be modified or added other materials. 1. Summary

21 Summary & Further study  Further study 2. Further study

22 Thank you!