Environmental valorization of iron-laden waste: dual application in wastewater treatment and evaluation of the physico-mechanical and microstructural performance of cementitious composites.

Increased global population, industrialization, and urbanization have significantly increased the total wastewater discharge and solid waste production, causing substantial environmental pollution through contamination of soil and water resources, and greenhouse gas emissions. To solve these issues, remediation of this waste into added-value materials is a sustainable way for waste management. This study examines the circular economy principles of utilizing iron-laden waste (ILW) as an adsorbent for treatment of metal plating industrial wastewater; then the spent waste was subjected to partially substitute OPC in cement composite at weight percentages varying from 5 to 50%. The cement hydration kinetics of the produced composites was examined by assessing the physico-mechanical and microstructural characteristics at various processing ages. Water absorption, bulk density, setting times, leachability, and compressive strength in moist/dry conditions were evaluated at specific curing times (i.e., 7, 28, and 90 days). XRD and SEM methods were used to examine the preparations' phase composition and microstructure. The results revealed that ILW exhibited high treatment efficiency for the removal of metal ions from industrial wastewater. The removal efficiency was 99% for Cr (VI), and complete removal of Ni (II), Cu (II) and Pb (II) was achieved. Then, incorporating contaminated ILW in the cement composite showed that the 10% ILW-doped composite had superior mechanical properties in wet/dry conditions compared to its higher volume blended counterparts. With the addition of ILW up to 50%, the microstructure further deteriorated because of the reduced bonding phases and the existence of large voids scattered throughout the cement matrix. Compressive strength consequently declined in both wet and dry conditions. Additionally, all leaching test results indicated that risks of metal ions release from all ILW-doped composites are minor and their reuse in construction application may constitute a sustainable alternative method for efficient solid waste management.