Remediation of acid mine drainage and immobilization of rare earth elements: Comparison between natural and residual alkaline materials

• Published in: Applied geochemistry 2023-11, Vol.158, p.105800, Article 105800
• Main Authors: Kotte-Hewa, Dileesha Jayahansani, Durce, Delphine, Salah, Sonia, Ruiz Cánovas, Carlos, Smolders, Erik
• Format: Article
• Language: English
• Subjects: acid mine drainage; Acid mine water remediation; alkalinity; alkalinization; biomass; Biomass ash; Blast furnace slag; circular economy; combustion; furnaces; geochemistry; gypsum; limestone; neutralization; Passive treatment systems; pyrite; Rare earth elements; remediation; slags; sulfates; toxicity; Waste products
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2023.105800

Acid mine drainage (AMD) is a well-known source of toxic trace metals in freshwaters. Traditional passive treatment systems rely on AMD neutralization with limestone and removal of most common toxic transition metals such as Cu and Zn with little attention to rare earth elements (REE). Alkaline waste materials now receive increasing attention as low cost AMD treatment alternatives in the circular economy. This study was set up to identify the efficiency of alkaline waste materials remediating AMD and scavenging REE in addition to other toxic trace elements. An AMD sample was collected from a lixiviate coming from pyrite heaps in the Iberian Pyrite Belt (pH = 1.8, 30 μM ∑REY). The sample was treated with either blast furnace slag (BFS) generated during smelting of iron ore in a blast furnace or biomass ashes (BA) derived from combustion of biomass, thereby using analytical grade CaCO3, and NaOH as reference products. The batch alkalinization experiments were conducted by adding each alkaline material at an amount to obtain an equal pH to ≈6.5. The required amounts of the products were NaOH