This work aims to reduce the influence of Acid Mine Drainage in two mining areas in the Iberian Pyritic Belt, specifically the Caveira Mine System in Portugal, and the Trimpancho Mining Complex in Spain, which both stopped operations in the 1960s. Since then, acid drainage from exposed waste piles has released toxic elements into nearby waterways, causing widespread contamination. Laboratory tests were conducted to find the best materials for neutralization of the acid drainage and subsequently retain Potentially Toxic Elements (PTE). Water samples from both mines showed high levels of toxic metals like As, Fe, Cu, Pb, and Zn, with very low pH levels, so laboratory scale ponds were created where various byproducts and nature-based materials were used to test the ability to neutralize acid drainage from the mines. With these tests it was verified that paper sludge was a great pH neutralizer, increasing mine water pH from 1.64 to 6.23 in 11 days and that industrial activated carbon, biochar, three different sludges and two different clays had great PTE removal ratios for As, Cu, Pb, Mn and Zn. Therefore, column tests with different materials simulated reactive barriers to determine the best combinations for this PTE removal. The tests indicated that sludges and industrial activated carbon are effective for retaining PTE and that multilayered reactive barriers are recommended for large-scale field applications to remediate contaminated water after increasing pH with paper sludge-based ponds.