Hydrated Nano-Blast Furnace Slag: A Green and Efficient Adsorbent for Industrial Wastewater Treatment

Abstract This study investigated the efficiency of hydrated nanoscale blast furnace slag (NBFS) as a cost-effective and sustainable adsorbent for removing iron, copper, and zinc ions from wastewater. The NBFS was modified through a dual process involving nanoscale transformation and hydration with water (20 wt.%) for 7 days, enhancing its surface area and reactivity. The hydrated NBFS was characterized using XRF, SEM, EDS, FTIR, and XRD techniques, revealing its amorphous to crystalline transformation and the presence of OH − as a functional group. Batch adsorption experiments were conducted to optimize the parameters of adsorbent dosage, pH, contact time, initial ion concentration, and temperature. The results demonstrated remarkable removal efficiencies of 99.4% for Fe, 96.2% for Cu, and 93.7% for Zn at an optimal pH of 6, a contact time of 90 min, and a temperature of 70 °C. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model, indicating a chemisorption mechanism with monolayer coverage. Thermodynamic studies confirmed that the adsorption process was spontaneous. Additionally, the hydrated NBFS exhibited excellent reusability, maintaining a high removal efficiency over five consecutive adsorption-desorption cycles.