Metal Extraction from Mine Wastewater Sludge - Leaching with ammonia and sulfuric acid
(2018) KETM05 20172Chemical Engineering (M.Sc.Eng.)
- Abstract
- Increasing demand for metals might lead to extraction of metals from materials, previously, thought of as waste. A letter by the Swedish Environmental Protection Agency and Geological Survey of Sweden from 2017 encouraged new and innovative waste treatments as well as recycling of waste produced in association with mining. The conventional treatment of acid mine wastewater creates large volumes of metal rich sludge. This thesis has investigated the possibility of extracting zinc and copper from said sludge.
Characterization and leaching of a hydroxide sludge produced in the treatment of acid mine drainage are presented. The sludge is produced when lime is added to the acidic wastewater in order to increase pH and precipitate metals. The... (More) - Increasing demand for metals might lead to extraction of metals from materials, previously, thought of as waste. A letter by the Swedish Environmental Protection Agency and Geological Survey of Sweden from 2017 encouraged new and innovative waste treatments as well as recycling of waste produced in association with mining. The conventional treatment of acid mine wastewater creates large volumes of metal rich sludge. This thesis has investigated the possibility of extracting zinc and copper from said sludge.
Characterization and leaching of a hydroxide sludge produced in the treatment of acid mine drainage are presented. The sludge is produced when lime is added to the acidic wastewater in order to increase pH and precipitate metals. The sludge contained about 0.4 wt.% copper and 1.5 wt.% zinc in addition to high concentrations of calcium, sulfur and iron. Metal concentrations varied in the sludge over time and location for sampling.
Zinc and copper extraction from the sludge was investigated by leaching with ammonia or sulfuric acid. For leaching with ammonia three temperatures (30, 40 and 50 °C) as well as three concentrations (3, 4 and 5 M) were studied. Sulfuric acid leaching was investigated for initial acid concentrations of 0.25, 0.3, 0.4, 0.6 and 0.7 M, corresponding to a pH range of 2.5 to 5.3. All tests were done with a solid to liquid ratio of 1:6 gram per mL.
No correlations between temperature or ammonia concentration on zinc and copper recoveries were found. The highest copper (80 wt.%) and zinc (61 wt.%) recoveries were achieved with 4 M of ammonia at 50 °C. Tests indicated that a leaching time longer than 60 min did not increase recovery.
Leaching with sulfuric acid showed that an increase in acid concentration, and thus a lower pH value, gave larger recovery of all metals. Optimum leaching concentration, for high copper and zinc recoveries and low iron recovery, was found to be 0.6 M sulfuric acid. Recoveries of copper, zinc and iron were 87, 97 and 20 wt.% at 0.6 M, respectively.
Sludge residues produced with ammonia leaching took longer time to dewater and needed more extensively washing compared to residues from sulfuric acid leaching. (Less) - Popular Abstract
- The increasing demand for metals in today’s industrialized society gives materials, previously thought of as wastes, potential to be new raw materials. This work investigates mine wastewater sludge as a potential source of zinc and copper, with promising results!
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8934079
- author
- Kivijärvi, Hanna LU
- supervisor
- organization
- course
- KETM05 20172
- year
- 2018
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- AMD, Leaching, Ammonia, Sulfuric acid, Zinc, Copper, chemical engineering, kemiteknik
- language
- English
- id
- 8934079
- date added to LUP
- 2018-02-19 14:37:17
- date last changed
- 2018-02-19 14:37:17
@misc{8934079,
abstract = {{Increasing demand for metals might lead to extraction of metals from materials, previously, thought of as waste. A letter by the Swedish Environmental Protection Agency and Geological Survey of Sweden from 2017 encouraged new and innovative waste treatments as well as recycling of waste produced in association with mining. The conventional treatment of acid mine wastewater creates large volumes of metal rich sludge. This thesis has investigated the possibility of extracting zinc and copper from said sludge.
Characterization and leaching of a hydroxide sludge produced in the treatment of acid mine drainage are presented. The sludge is produced when lime is added to the acidic wastewater in order to increase pH and precipitate metals. The sludge contained about 0.4 wt.% copper and 1.5 wt.% zinc in addition to high concentrations of calcium, sulfur and iron. Metal concentrations varied in the sludge over time and location for sampling.
Zinc and copper extraction from the sludge was investigated by leaching with ammonia or sulfuric acid. For leaching with ammonia three temperatures (30, 40 and 50 °C) as well as three concentrations (3, 4 and 5 M) were studied. Sulfuric acid leaching was investigated for initial acid concentrations of 0.25, 0.3, 0.4, 0.6 and 0.7 M, corresponding to a pH range of 2.5 to 5.3. All tests were done with a solid to liquid ratio of 1:6 gram per mL.
No correlations between temperature or ammonia concentration on zinc and copper recoveries were found. The highest copper (80 wt.%) and zinc (61 wt.%) recoveries were achieved with 4 M of ammonia at 50 °C. Tests indicated that a leaching time longer than 60 min did not increase recovery.
Leaching with sulfuric acid showed that an increase in acid concentration, and thus a lower pH value, gave larger recovery of all metals. Optimum leaching concentration, for high copper and zinc recoveries and low iron recovery, was found to be 0.6 M sulfuric acid. Recoveries of copper, zinc and iron were 87, 97 and 20 wt.% at 0.6 M, respectively.
Sludge residues produced with ammonia leaching took longer time to dewater and needed more extensively washing compared to residues from sulfuric acid leaching.}},
author = {{Kivijärvi, Hanna}},
language = {{eng}},
note = {{Student Paper}},
title = {{Metal Extraction from Mine Wastewater Sludge - Leaching with ammonia and sulfuric acid}},
year = {{2018}},
}