Comparison of aluminum and iron nanoparticles for chromium removal from aqueous solutions and tannery wastewater, empirical modeling and prediction

The tanning industry is considered one of the main sources of pollution. This study aims to investigate the efficiency of nano zero-valent iron (nZVI) and the nano zero-valent aluminum (nZVAl) particles for the removal of chromium (Cr) from aqueous solutions and tannery wastewater. For the aqueous solutions, the maximum removal efficiency of 5 mg/L Cr reached 81.2% using nZVAl and 77.6% using nZVI, under the following conditions: time 20 min, pH 3, stirring rate 200 rpm, and dosage 0.6 g/L. The adsorption data for chromium removal using nZVAl and nZVI fitted well to the Freundlich and Koble-Corrigan models, respectively. For both nanometals, the kinetic data fitted well to pseudo second order (PSO). Response surface methodology (RSM) and artificial neural network (ANN) models with r2-value higher than 0.95 were found to be accurate in predicting chromium removal efficiency using both nanometals. The synthesized nZVI and nZVAl particles were applied to real tannery wastewater samples. The removal efficiencies of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), lead (Pb), nickel (Ni), and arsenic (As) using both nZVAl and nZVI exceeded 98%. For total phosphorus (TP), total nitrogen (TN), and hydrogen sulfide (H2S), nZVI demonstrated a higher removal efficiency compared to nZVAl. A significant increase was also reported for Cr removal, reaching 70% using nZVI and 74% using nZVAl.