Abstract The removal of selenium ions from aqueous media using nickel–aluminum complex hydroxide series (NA) and nickel–aluminum–zirconium series (NAZ) at different molar ratios was assessed. The synthesized NA and NAZ were characterized to elucidate their morphological and structural properties, and batch adsorption experiments were conducted to understand the effect of various parameters (e.g., pH, temperature, concentration, contact time, and coexisting species) on their selenium-ion adsorption performance. In particular, the adsorbent with a 1:1 Ni 2+ /Al 3+ molar ratio (NA11) and that with a 0.9:1.0:0.09 Ni 2+ /Al 3+ /Zr 4+ ratio (NAZ1) were selected for adsorption experiments. NA11 and NAZ1 demonstrated the efficient adsorption of selenium ions over a wide pH range. The selenium-ion adsorption capacity increased with increasing initial concentration and contact time. To elucidate the mechanism of selenium-ion adsorption, the ion-exchange capability, elemental distribution, and binding energy were analyzed in detail. Our obtained results revealed that adsorption mechanism of selenium-ions was related to the surface properties of adsorbents and ion exchange between selenium-ions and sulfate ions in the interlayer region of adsorbents. In addition, anions such as phosphate ions were found to affect the selenium-ion adsorption ability in a binary solution system. Selenium ions adsorbed onto NA11 and NAZ1 were easily desorbed using sodium hydroxide and hydrochloric acid solutions at high concentrations. Thus, NA11 and NAZ1 were found to be promising adsorbents for recovering selenium ions in industrial wastewater through adsorption/desorption using desorption solutions.
Ogata et al. (Fri,) studied this question.