Selective Laser Sintering of a Chitosan/MOF Composite: 3D-Printed Adsorbent for Arsenic.

Metal-organic framework/biopolymer composites have shown significant potential for removing pollutants such as arsenic from aquatic environments. However, due to the poor mechanical properties and challenges in incorporating these materials into existing water treatment systems, their use in real-world applications is limited. In this study, we developed mechanically strong porous filters for adsorbing arsenic (As-(III) and As-(V)) by utilizing the selective laser sintering (SLS) 3D printing technique. In the printed filter disks, polystyrene is used as the polymeric supporting matrix, and a bimetallic Mn-doped MIL-100-(Fe)-based MOF/chitosan composite CS-MIL-100-(Fe, Mn) (hereafter: CS/MOF) as the adsorptive filler, with 5, 10, and 15 wt % filler concentrations. With powder X-ray diffraction (PXRD), it was confirmed that the crystal phase of the CS/MOF is preserved in the printed filters. Scanning electron microscopy (SEM) revealed the hierarchical porous structure of the composite consisting of the meso- and macroporous channel networks formed by the partially sintered polystyrene particles, along with the micro- and mesopores of the CS/MOF adhered to the polymer surface. The filters efficiently removed As-(III) and As-(V), and the highest adsorption rate of 99% was achieved at the filler concentration of 15 wt %. The developed filter maintained its optimal adsorption efficiency toward arsenic species, even in the presence of multiple competitive anions such as sulfate, phosphate, nitrate, and carbonate. The filter also exhibited the potential for reducing the As-(III) and As-(V) concentrations from 2.5 mg/L to lower than 10 μg/L from tap water, which was modified to simulate a typical inorganic composition of arsenic-polluted groundwater.