Usage of the sol–gel process on the fabrication of macroporous adsorbent activated-gamma alumina spheres

In this work, we have developed a chemical process to agglomerate activated-gamma alumina microparticles. It is based on the sol–gel process. The process which was developed preserves the characteristics of porosity of the alumina microparticles. It allows us to obtain dried spheres with or without the introduction of a biomass type MDF (medium density fiberboard) with the following characteristics: medium diameter between 2.5 and 3.3 mm; narrow diameter range; high sphericity (0.90); high mechanical resistance (0.04 kg f/sphere); high specific surface area (257 m²/g); a network of micropores, mesopores and macropores which connects the surface and the core of the adsorbent sphere. It also allows us to obtain adsorbent alumina spheres with displaced core from the shallowest layers or even completely hollow. The possibility to add increasingly higher adsorbents biomass contents makes this process cheaper to fabricate adsorbent spheres. Besides that preliminary tests of adsorption show that dried spheres with and without MDF reach, respectively, an efficiency of removing Cd/Cu/Zn/As of 30.9%/13.5%/59.9%/43.9% and 71.3%/24.9%/48.4%/43.7%. All of these described characteristics suggest that the present method produces a good adsorbent for heavy metals and arsenic.