Tunable-pore cellulose microsphere adsorbents for column adsorption of dyes

The pore structure of cellulose microspheres is vital for their adsorption performance, however it is still challenge to control pore size and their distribution by a simple and cost-effective method. Here, through adjusting volume ratios of ethylene glycol diacetate to n-octanol in the cellulose solution, we prepare cellulose microspheres with adjustable pore size ranging from the micron- to nanometer scale in a straightforward and scalable method. We show that the average diameter of pores in cellulose microspheres is controlled from 4.58 μm to 108.43 nm with the median of pore diameter being from 1.63 μm to 7.69 nm. Cellulose microspheres exhibited good performance in both static and dynamic adsorption of methylene blue dye with a maximum capacity of 20.6 mg/g. A monolayer adsorption mechanism is revealed through fitting the Langmuir isotherm model. Interestingly, cellulose microspheres exhibit compressive strength comparable to that of adsorption resins, with maximum compressive stress ranging from 5.25 to 52.1 MPa, enabling them to pack in adsorption columns. Notably, a removal efficiency of 94.1 % was achieved by using column adsorption. Cellulose microspheres show adjustable pore size, good mechanical properties, and good adsorption performance, which will accelerate their practical applications in the environmental remediation.