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Two-way Valorization of Blast Furnace Slag: Synthesis of Precipitated Calcium Carbonate and Zeolitic Heavy Metal Adsorbent
Published on: February 21, 2017
Integrated acid mine drainage management using fly ash
Viswanath R K Vadapalli1, Mugera W Gitari, Leslie F Petrik
1Natural Resources and Environment, CSIR, Pretoria, South Africa. rvadapalli@csir.co.za
Summary
This study demonstrates how Fly Ash (FA) effectively neutralizes Acid Mine Drainage (AMD) and its residue can be used for mine backfill and zeolite synthesis, achieving zero waste in AMD management.
Area of Science:
- Environmental Science
- Materials Science
- Chemical Engineering
Background:
- Acid Mine Drainage (AMD) poses significant environmental challenges due to its acidity and high contaminant load.
- Fly Ash (FA), a byproduct of coal combustion, presents a disposal challenge and is explored as a potential solution for AMD treatment.
- Developing integrated waste management strategies is crucial for sustainable mining operations.
Purpose of the Study:
- To investigate the efficacy of South African Fly Ash (FA) in neutralizing and removing contaminants from Acid Mine Drainage (AMD).
- To evaluate the potential of FA residue (solid residue, SR) as a mine backfill material and for synthesizing zeolite-P.
- To assess the performance of synthesized zeolite-P in polishing process water from the primary FA-AMD treatment, aiming for a zero-waste solution.
Main Methods:
- FA was mixed with AMD at various ratios to achieve circumneutral pH; supernatants were analyzed using ICP-MS and IC.
- Solid residue (SR) was tested for strength after mixing with Ordinary Portland Cement (OPC) and curing for 410 days.
- Zeolite-P was synthesized from SR via a two-step process (ageing and hydrothermal synthesis); its polishing capability was tested using process water.
Main Results:
- FA successfully ameliorated AMD, removing major contaminants (Fe, Al, Mg, Mn, SO4) and trace elements (Zn, Ni, Cu, Pb).
- SR demonstrated increasing strength over 410 days, reaching approximately 0.3 MPa unconfined compressive strength and 150 MPa elastic modulus.
- Synthesized zeolite-P effectively removed Ca, Sr, Ba, and V from process water, with partial Mo removal and Na exchange.
Conclusions:
- Fly Ash is a viable material for treating Acid Mine Drainage, offering a dual benefit of contaminant removal and waste valorization.
- The solid residue from FA-AMD treatment can be utilized as a strength-gaining mine backfill material.
- Synthesized zeolite-P effectively polishes treated AMD water, contributing to an integrated, zero-waste AMD management strategy using Fly Ash.
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