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Integrated adsorption-solar photocatalytic membrane reactor for degradation of hazardous Congo red using Fe-doped ZnO and Fe-doped ZnO/rGO nanocomposites


In this work, synergistic effect of solar photocatalysis integrated with adsorption process towards the degradation of Congo red (CR) was investigated via two different approaches using a photocatalytic membrane reactor. In the first approach, sequential treatments were conducted through the adsorption by graphene oxide (GO) and then followed by photocatalytic oxidation using Fe-doped ZnO nanocomposites (NCs). In the second approach, however, CR solution was treated by photocatalytic oxidation using Fe-doped ZnO/rGO NCs. These nanocomposites were synthesized by a sol-gel method. The NCs were characterized by X-ray diffraction (XRD), photoluminescence (PL), Fourier transmission infrared (FTIR), ultraviolet–visible (UV-vis) spectroscopy, and field emission scanning electron microscopy (FESEM). It was observed that Fe-doped ZnO could enhance the photoactivity of ZnO under solar light. When Fe-doped ZnO were decorated on GO sheets, however, this provided a surface enhancement for adsorption of organic pollutants. The photocatalytic performances using both approaches were evaluated based on the degradation of CR molecules in aqueous solution under solar irradiation. Nanofiltration (NF) performance in terms of CR residual removal from water and their fouling behavior during post-separation of photocatalysts was studied. Serious flux declined and thicker fouling layer on membrane were found in photocatalytic membrane reactor using Fe-doped ZnO/rGO NCs which could be attributed to the stronger π–π interaction between rGO and CR solution.

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The authors also wish to thank Mohd Noorsyakir Bin Saipol Yazan and Muhammad Nazrul Bin Zaharifrom CRIM for FESEM and AFM analysis, Mohd. Razif Maafol, Salehuddin Arifen, and Wan Mohd Nazir Bin Wan Taha from the Department of Chemical and Process Engineering, UKM for their technical assistance.


The authors wish to thank the financial support for this research from Grant number DIP-2016-031. One of the authors C.B. Ong, wishes to acknowledge the Ministry of Education Malaysia for supporting her post-graduate study in terms of financial via MyBrain.

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Correspondence to Abdul Wahab Mohammad.

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Responsible editor: Suresh Pillai

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Ong, C.B., Mohammad, A.W. & Ng, L.Y. Integrated adsorption-solar photocatalytic membrane reactor for degradation of hazardous Congo red using Fe-doped ZnO and Fe-doped ZnO/rGO nanocomposites. Environ Sci Pollut Res 26, 33856–33869 (2019).

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  • Integrated process
  • Photocatalytic membrane reactor
  • Adsorption
  • Fe-doped ZnO/rGO
  • Nanocomposites
  • Congo red