Hydroxyl-enhanced magnetic chitosan microbeads for boron adsorption: Parameter optimization and selectivity in saline water

Hydroxyl-enhanced materials are considered promising for boron adsorption. But, the use of these materials is hindered by issues of selectivity and separation notably in the presence of co-existing ions. Therefore, magnetic chitosan-based microbeads (MC) were synthesized and functionalized with a glycidol to produce boron-selective adsorbent (MCG). The resulting multi-hydroxyl microbeads were found to be a better substitute to the existing boron adsorbents. The adsorbents were characterized by scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The BET surface area and vibrating sample magnetometry analyzes confirmed that the functionalized beads had a saturation magnetization, surface area, pore size, and diameter of 46.53 Am2/kg, 598 m2/g, 2.9 nm and ∼ 150-400 μm respectively. Under optimized condition, the MCG showed high adsorption affinity and remarkable selectivity towards boron in the presence of co-existing metal ions (Cu2 +, Fe3 +, and Ni2 +) and salts of Mg2 +, Ca2 +, Na+ and K+ ions. MCG has 128.5 mg/g of boron loading capacity within the first 100 min, which is relatively higher than reported values. The spent beads were separated easily from the suspensions by an external magnet and reuse repeatedly.