Synergetic benefits of microfluidics using artificial cilia and ZnO/SnFe₂O₄ for the degradation of pollutants

Water pollution due to the discharge of organic dye pollutants is a significant environmental concern. To mitigate this environmental threat, microfluidic devices are employed as a promising platform that provides innovative methods and perspectives in achieving effective environmental remediation. Meanwhile, the hydrodynamics of the fluid flow inside such miniaturized systems can also play a crucial role in the pollutant eradication process that can further establish a reliable framework for accomplishing the most promising treatment strategies. Herein, the microfluidic device comprised of ZnO/SnFe2O4 nanoparticles and artificial cilia was proposed to incorporate two essential functions in adequately adsorbing the cationic dye (methylene blue, MB) suspended in the aqueous medium. Amongst these, the employed ZnO/SnFe2O4 nanoparticles acted as an active adsorbent site. Eventually, the cationic MB dye was found to be adsorbed by these nanoparticles due to the presence of a negative surface charge potential. Further, to enhance this adsorption process, the employed artificial cilia were magnetically controlled to exhibit a tilted conical asymmetric motion. Consequently, such dynamic motion of the cilia was observed to enhance the hydrodynamics aspect of the dye-aqueous solution. Essentially, the rate of mass transfer of the dye-aqueous solution toward the absorbent site was improved. Thus, the dye-adsorption efficiency achieved through the proposed synergetic platform was estimated to be 90.2% at the end of 30 min. In comparison with the conventional motions of the artificial cilia, this obtained result with the actuated dynamic motion was found to be enhanced by 12.1%. Further, to aid an efficient adsorption process through the hydrodynamic principles, a flow visualization measurement was performed to identify the optimal design parameters of artificial cilia. Eventually, the spatial representative parameters of artificial cilia were observed to significantly influence the dye-adsorption behavior. The attained expertise from this study will be potentially advantageous for future dye treatment applications in designing several other distinct synergetic components for effective pollutant removal.