3D-printed catalytic ceramic membranes for advanced oxidation of emerging contaminants

Abstract

Contaminants of emerging concerns (CECs) have been detected in surface water ranging from several nanograms to micrograms per liter, and the high exposure to these chemicals may cause toxicity to human’s cerebral, cardiovascular or respiratory system. For example, amitriptyline (ATT) is a tricyclic antidepressant mainly used for the treatment of depression and various pains from neuropathic pain to migraine. However, conventional water and wastewater treatment system cannot remove ATT efficiently, and the catalytic ozonation process, producing powerful hydroxyl radicals (∙OH), are also limited to treating ATT due to recovery issues of powder catalysts and fast decay of ∙OH before reacting with ATT. To overcome these limitations, copper-nickel oxide (CuNiO) catalysts were synthesized and incorporated on the surface and pore walls of 3D-printed ceramic membranes to enhance the advanced oxidation process with ozone. CuNiO nanoparticles were successfully fabricated via hydrothermal methods and exhibited the elevated first-order kinetic constant (k) from 0.020 $s^{-1}$ to 0.028 $s^{-1}$ when 10 mg/L CuNiO catalyst was applied during removal of 2 mg/L ATT with 0.5 mg $O_3$/L in batch mode. Moreover, the ATT removal was increased as pH increased, while the presence of natural organic matter (NOM) scavenged the reaction of hydroxyl radicals with ATT. In order to overcome the recovery issue of powdered catalysts, and to increase the contact between hydroxyl radicals and ATT, CuNiO catalyst was incorporated by a precursor filling-calcination method on the surface and pore walls of the ceramic membrane. The hybrid system of catalytic ozonation with CuNiO incorporated ceramic membrane enhanced ATT removal by about 10% compared to the system without catalyst. Also, ATT removal increased about 20% in the hybrid system than the batch system, leading ATT removal to more than 70% only in ten seconds of contact time. 3D-printed ceramic membrane (3DP CM) was developed due to its simple printing with complex design applicability, which is expected to increase oxidation efficiency with lower applied pressures. The 3DP CM showed 27,500 $L/m^2/h/bar$ of water permeability. Although catalytic ozonation with CuNiO incorporated 3DP CM did not achieve a better ATT removal efficiency than $O_3$-CuNiO/CM due to some issues such as the low resolution of 3D ceramic printing, crack formation during the sintering process, and difficulties in sintering temperature scheme, it required much less pressure compared to conventional CM system, thus, 3DP CM could be regarded as one of the potentially applicable technologies in catalytic ceramic membrane fabrications. In conclusion, CuNiO catalyst incorporated ceramic membrane enhanced ATT removal by the elevated generation of ∙OH and the reaction in confound pores. CuNiO catalyst incorporated 3D-printed ceramic membrane is expected to increase ATT removal in case the resolution and crack issues are overcome.