A high activity adsorbent of ZnO-Al2O3 nanocomposite particles: Synthesis, characterization and dye removal efficiency

- Seed particles were used to stabilize the ZnO on surfaces of Al2O3 particles.
- ZnO-Al2O3 nanocomposite particles showed great methyl orange adsorption efficiency.
- Morphology in nanoscale is a measure of potential surface charges of the ZnO.
- Surface area is a measure of how much of this potential can be realized.
- There is an optimum between the amount of ZnO and Al2O3 in dye adsorption.

In order to stabilize the ZnO species on surfaces of Al2O3 particles, the ZnO-Al2O3 nanocomposite particles with different ZnO contents were prepared by heterogeneous precipitation method using bayerite seed particles. The as-prepared nanocomposites were characterized in terms of crystal structure, morphology and surface area. The results indicated the formation of wurtzite-type ZnO nanoflakes (thickness of 40-80 nm) on surfaces of γ-Al2O3 particles, which led to nanocomposite particles with high surface areas depending on Al2O3 content. The obtained nanocomposites were used as promising adsorbents in adsorption of methyl orange (MO) from aqueous solution as an anionic dye and were compared with pure ZnO and Al2O3 adsorbents. The nanocomposite adsorbents showed a superior MO removal efficiency than pure adsorbents, which was attributed to unique morphology of ZnO active sites with activated surface charge and also high surface area obtained in nanocomposite adsorbents. Moreover, it was found that there is an optimum between the amount of ZnO active sites and Al2O3 for the maximum of percentage removal of MO, which was obtained for 40%ZnO-Al2O3 adsorbent with 98% efficiency and low equilibrium time of 20 min with a fixed adsorbent concentration of 500 ppm and a fixed dye concentration of 50 ppm.