Industrial & Engineering Chemistry Research, Vol.58, No.27, 12207-12215, 2019
Simultaneous Optimization of Adsorption Capacity and Stability of Hydrothermally Synthesized Spinel Ion Sieve Composite Adsorbents for Selective Removal of Lithium from Aqueous Solutions
The main aim of this paper was synthesis of spinel type lithium manganese oxide adsorbent with high adsorption capacity and stability for selective removal of lithium ion. In contrast with the previous works reported by other researchers, simultaneous improvements of adsorbent stability and adsorption capacity were investigated by insertion of cobalt into the spinel structure of lithium manganese oxide and optimization of the adsorbent preparation conditions. To this aim, the effects of calcination temperature and molar ratios of Li/Mn and Co/Mn on adsorbent capacity and stability were investigated via hydrothermal method for adsorbent preparation. Experiments were designed by using Design Expert Software and response surface methodology considering three independent variables each at three levels. It was found that the adsorbent synthesized at optimum conditions has high adsorption capacity of 53.52 mg/g and with only 2.52% adsorption capacity loss for two consecutive adsorption cycles. This achievement was also confirmed by XRD analysis. The structural morphology of the optimized adsorbent was characterized by SEM analysis. The result of BET analysis showed that the specific surface area of the optimized adsorbent was 2.564 m(2)/g. Finally, the results of selectivity adsorption experiment revealed that the optimized adsorbent can be considered as a promising tool for selective separation of lithium ions from sodium ions with molar selectivity of 90.32.