Application of Nano-Al2O3 Powder for Removal of Hexavalent Chromium from Aqueous Solutions

Pollution due to heavy metals is one of the most serious environmental problems nowadays. Extensive application of Cr (VI) leads to discharge a large amount of chromium containing wastewater into the environment. The aim of this research was evaluation of alumina nanoparticles efficiency to remove chromium (VI) from aqueous solutions through adsorption. This fundamental and practical study was performed in batch conditions and room-temperature. The structure of the sorbent was characterized by TEM technique. Residual concentrations of Cr (VI) were measured by a spectrophotometer at 540nm. Effects of the process parameters such as Al2O3 loading (0.5–2 g/L), contact time (5-90 min), and pH (5-9) were investigated. The results showed that removal efficiency of Cr (VI) increase with increasing of contact time and pH. The optimum pH was found to be 5 with decreasing of removal efficiency afterward. The value of qm (mg/L) in this work was 30.3 for each gram of nano-alumina adsorbent. Furthermore, chromium sorption kinetics was well fitted by pseudo-second-order kinetic model, and well explained by Freundlich isotherm (R2>0.992). In general, alumina nanoparticle powder is recognized as an effective sorbent to remove chromium (VI) from aqueous solutions.