In this work, α-Fe2O3 nanocrystals are synthesized by co-precipitation method and used as adsorbent to remove Cr6+, Cd2+, and Pb2+ from wastewater at room temperature. The prepared sample is evaluated by XRD, BET surface area, and FESEM for structural and morphological characteristics. XRD patterns confirm the formation of a pure hematite structure of average particle size of ~ 40 nm, which is further supported by the FESEM images of the nanocrystals. The nanocrystals are found to have BET specific surface area of ~ 39.18 m2 g−1. Adsorption experiments are carried out for the different values of pH of the solutions, contact time, and initial concentration of metal ions. High efficiency Cr6+, Cd2+, and Pb2+ removal occur at pH 3, 7, and 5.5, respectively. Equilibrium study reveals that the heavy metal ion adsorption of the α-Fe2O3 nanocrystals followed Langmuir and Freundlich isotherm models. The Cr6+, Cd2+, and Pb2+ adsorption equilibrium data are best fitted to the Langmuir model. The maximum adsorption capacities of α-Fe2O3 nanocrystals related to Cr6+, Cd2+, and Pb2+ are found to be 15.15, 11.63, and 20 mg g−1, respectively. These results clearly suggest that the synthesized α-Fe2O3 nanocrystals can be considered as potential nano-adsorbents for future environmental and health related applications.

Abstract
1. Introduction
2. Experimental
    2.1 Synthesis of adsorbent and characterization
    2.2 Adsorption analysis
3. Results and discussion
    3.1 Properties of prepared α-Fe2O3 nanocrystals
    3.2 Adsorption study
4. Conclusions
References

• Bulgan Tsedenbal(School of Materials Science and Engineering, Changwon National University)
• Ji Eun Lee(School of Materials Science and Engineering, Changwon National University)
• Seok Hwan Huh(School of Mechatronics Convergence Engineerings, Changwon National University)
• Bon Heun Koo(School of Materials Science and Engineering, Changwon National University)
• Chan Gyu Lee(School of Materials Science and Engineering, Changwon National University) Corresponding author