A comparison of the acid mine drainage (AMD) neutralization potential of low grade nickel laterite and other alkaline-generating materials

Abstract

Acid mine drainage (AMD) is a serious environmental problem caused by the weathering of sulfur-rich minerals found in mine sites, typically pyrite. Passive treatment methods have been extensively studied exploring various materials and treatment systems. Limestone is typically used as neutralizing media through open channels or anoxic limestone drains. However, the armouring that occurs when heavy metals precipitate on the surface restricts the lifespan of limestone treatment systems to 15-20 years. Goethite has been characterized to be a good adsorbent of heavy metals found in wastewater. It is abundant in a layer of nickel laterite deposit which are considered mine wastes due to the low amount of nickel present. This study investigates the performance of locally available nickel laterite ore rock, limestone, fly ash, and cement waste as media for AMD neutralization. The treatment efficiency are evaluated based on the physiochemical properties of the AMD, namely: pH, redox potential (ORP), conductivity, total dissolved solids (TDS), and dissolved oxygen (DO).

Evaluation of Efficiencies of Locally Available Neutralizing Agents for Passive Treatment of Acid Mine Drainage

“…Goethite was identified as a major component. Moreover, LGO was able to remove >99% Fe and Al, 94% Ni, and 93% of sulfate despite only raising pH from 2.21 to 5.36 [33]. This shows the potential of LGO to complement an alkaline-generating material in treating AMD to make up permeable reactive barriers.…”

“…Meanwhile, TDS and conductivity results from the solution treated by limestone had a significant increase when ratio of 1.0 and 1.5 were used, then had a decrease when the ratio of 2.0 was employed. Heavy metal ions were removed through adsorption onto goethite present in LGO while precipitation is the main suspect in the removal of heavy metal ions in the other three materials which resulted to a more alkaline effluent [33,40,48]. In relation to its pH results, ratio 1.5 for limestone also had the lowest pH attained which could suggest that heavy metals in AMD were not able to precipitate as much at that pH level as compared to the other ratios.…”

Formation mechanism of carbide slag composite sustained-alkalinity-release particles for the source control of acid mine drainage

“…Petrik 27 suggested that fly ash alone is a cost-effective alkaline treatment material, but fly ash increases the effluent turbidity and is not conducive to the separation of metals and raw materials. Turigan 28 replaced limestone with low-grade nickel soil, but the nickel soil could buffer the pH to only 4.7 at the highest, allowing very few types of heavy metals to be removed. The main component of carbide slag is Ca(OH) 2 , which is highly soluble, releases a large amount of alkalinity and has a high removal efficiency for heavy metal ions 29 .…”