Fibrous chitosan/cellulose composite as an efficient adsorbent for Co(Ⅱ) removal

With the rapid development of industries, the heavy metal-containing wastewater has become one of the most serious environmental problems. Adsorption is a key approach in treating heavy metal-containing wastewater. The performance of adsorbents is determined by the effective exposure of its adsorptive sites, which determines its adsorption capacity. In this study, fibrous chitosan/cellulose composite was prepared using the wet-spinning method to increase its specific surface area, thus enhancing the adsorption capacity. The as-prepared fibrous composite showed a homogeneous fiber structure (diameter: 88 ± 16 μm) and high specific surface area (2.5 m2 g−1). Furthermore, the adsorption capacity towards Co(Ⅱ) was greatly enhanced, more than three times higher than that of the pure chitosan beads (diameter: 2–3 mm). The maximum adsorption capacity was calculated to be 23.6 ± 2.5 mg-Co(Ⅱ) per g-chitosan by the Langmuir isotherm model, an order of magnitude higher than that of pure chitosan beads. In addition, the adsorption kinetic behavior of chitosan/cellulose fibers on Co(Ⅱ) followed the pseudo second-order kinetic model. The optimal pH for Co(Ⅱ) removal was approximately 6.0. Furthermore, FT-IR and XPS analyses indicated the amino groups played a dominant role, with the aid of hydroxyl groups, in the coordination and adsorptive removal of Co(II). Possible interaction configurations were also proposed in this study. In conclusion, the proposed physical modification of chitosan greatly improved its adsorption capacity and mechanical strength, making it a promising biosorbent for Co(II) removal.