Recyclable 3D-Printed Composite Hydrogel Containing Rice Husk Biochar for Organic Contaminants Adsorption in Tap Water

Water and wastewater treatment face significant challenges in removing organic contaminants, and the search for efficient processes and materials is crucial to reducing this issue. Herein, the design and manufacturing of 3D-printed composite hydrogels using a combination of alginate and rice husk biochar was proposed. These composite hydrogels were evaluated as adsorbents for removing ibuprofen (IBU) and methylene blue (MB) from tap water. Various characterization techniques, including FTIR, XRD, SEM, and BET analyses, confirmed the successful formation of the composite hydrogels. Also, the properties of the composite hydrogels, such as total porosity, cross-linking density, and swelling, were found to vary with the biochar content in the composite. Batch experiments demonstrated that the hydrogel containing 10% w/w biochar (Alg/Biochar10) has significant adsorption capacities for IBU (111.4 mg/g) and MB (214.6 mg/g). These values represented substantial increases of 48% (IBU) and 58% (MB) compared to the conventional hydrogel without biochar, highlighting the enhanced performance achieved by incorporating biochar into the composite. The adsorption kinetics of both IBU and MB followed the pseudo-first-order model, while the Freundlich isotherm model provided insights into the adsorption mechanism. Notably, the adsorption of MB on the composite hydrogel was particularly favorable due to electrostatic interactions between the adsorbent and the adsorbate. Furthermore, the composite hydrogel exhibited recyclability and reusability, as demonstrated through 20 reuse cycles, indicating its stability and practical applicability. In summary, the original 3D-printed composite hydrogels manufactured with the alginate/rice husk biochar ink showed great potential as adsorbent materials for organic removal from water and wastewater.