Improved Solid-Phase Synthesis of Phosphorylated Cellulose Microsphere Adsorbents for Highly Effective Pb2+ Removal from Water: Batch and Fixed-Bed Column Performance and Adsorption Mechanism

A highly effective adsorbent with phosphate groups bound to cellulose microspheres was designed by an improved solid-phase modification method to adsorb lead ions from water by a batch and fixed-bed column method. The phosphorylated cellulose microsphere adsorbents were prepared through esterification by which phosphate groups were introduced to the interface of regenerated cellulose microspheres which were previously prepared through a sol–gel transition process from a simple cellulose solution. Their morphological, structural, and physicochemical properties were characterized by SEM, FTIR, XRD, and DSC, etc. Furthermore, EDX and XPS were used to confirm the chemical modification process and to investigate their phosphate adsorption mechanism. In the batch adsorption experiments, the equilibrium time and adsorption capacity were determined by both equilibrium and kinetic adsorption experiments, which were also conducted to investigate the adsorption mechanism. In the dynamic adsorption experiments, multiple operation conditions such as flow rate, initial concentration, bed height, and pH were evaluated, and the experiment data were fitted to several dynamic adsorption models, such as Adams–Bohart, Thomas, Yoon–Nelson, Bed Depth Service Time (BDST), and Dose Response, to study the performance of adsorption of Pb2+ onto the adsorbents. The results suggested that chemical adsorption was the main controlled process during the adsorption process and that the adsorbents could highly effectively capture Pb2+ from water via chelation.