Development of porous calcite structure from industrial waste for efficient adsorbent for protein

Abstract

Porous adsorbent (PA) with high specific surface area and calcite surface was prepared from an industrial waste, electric arc furnace oxidizing slag (EOS). As the EOS is composed of silica and metal oxide nanoparticle like CaO, MgO, and so on, the metal oxide parts were selectively dissolved by acid treatment. The remained silica part exhibited porous structure due to the assembly of nanoparticles. Then, calcite was developed on the silica surface by simply titrating the silica framework with carbonate under basic condition. According to the x-ray diffraction pattern and scanning electron microscopy, we could hypothesize that the EOS had dense texture of amorphous nanoparticles. On the other hand, the PA had well-crystallized calcite particles with sufficient interparticle pores. The zeta potential of EOS shifted to positive region upon transformation to PA, possibly due to the change in surface-exposed moiety from silica to calcite. The albumin adsorption profiled exhibited that the PA had very high protein adsorption capacity up to 3.33 mg-protein/mg-adsorbent at 5 mg/L of protein concentration, while the EOS itself did not show meaningful adsorption.