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. 2022 Oct 12;12(20):3568.
doi: 10.3390/nano12203568.

Psyllium-Husk-Assisted Synthesis of ZnO Microstructures with Improved Photocatalytic Properties for the Degradation of Methylene Blue (MB)

Syed Nizam Uddin Shah Bukhari  1   2 , Aqeel Ahmed Shah  3 , Muhammad Ali Bhatti  4 , Aneela Tahira  5 , Iftikhar Ahmed Channa  3 , Abdul Karim Shah  6 , Ali Dad Chandio  3 , Wael A Mahdi  7 , Sultan Alshehri  7 , Zaffar Hussain Ibhupoto  5 , Wen Liu  8
Affiliations

Psyllium-Husk-Assisted Synthesis of ZnO Microstructures with Improved Photocatalytic Properties for the Degradation of Methylene Blue (MB)

Syed Nizam Uddin Shah Bukhari et al. Nanomaterials (Basel). .

Abstract

Wastewater from the textile industry is chronic and hazardous for the human body due to the presence of a variety of organic dyes; therefore, its complete treatment requires efficient, simple, and low cost technology. For this purpose, we grew ZnO microstructures in the presence of psyllium husk, and the role of psyllium husk was to modify the surface of the ZnO microstructures, create defects in the semiconducting crystal structures, and to alter the morphology of the nanostructured material. The growth process involved a hydrothermal method followed by calcination in air. Additionally, the psyllium husk, after thermal combustion, added a certain value of carbon into the ZnO nanomaterial, consequently enhancing the photocatalytic activity towards the degradation of methylene blue. We also investigated the effect of varying doses of photocatalyst on the photocatalytic properties towards the photodegradation of methylene blue in aqueous solution under the illumination of ultraviolet light. The structure and morphology of the prepared ZnO microstructures were explored by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The degradation of methylene blue was monitored under the irradiation of ultraviolet light and in the dark. Also, the degradation of methylene blue was measured with and without photocatalyst. The photodegradation of methylene blue is highly increased using the ZnO sample prepared with psyllium husk. The photodegradation efficiency is found to be approximately 99.35% for this sample. The outperforming functionality of psyllium-husk-assisted ZnO sample is attributed to large surface area of carbon material from the psyllium husk and the synergetic effect between the incorporated carbon and ZnO itself. Based on the performance of the hybrid material, it is safe to say that psyllium husk has high potential for use where surface roughness, morphology alteration, and defects in the crystal structure are vital for the enhancing the functionality of a nanostructured material. The observed performance of ZnO in the presence of psyllium husk provides evidence for the fabrication of a low cost and efficient photocatalyst for the wastewater treatment problems.

Keywords: ZnO; hydrothermal method; methylene blue; photodegradation; psyllium husk.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) XRD diffraction patterns of pure zinc oxide and psyllium-husk-assisted ZnO. (b) XRD pattern showing peak shift.
Scheme 1
Scheme 1
Shows main chemical constituents of psyllium husk.
Figure 2
Figure 2
SEM images (a) pure ZnO and (b) psyllium–ZnO microstructures.
Figure 3
Figure 3
FTIR spectra showing curves for bare MB and ZnO–psyllium husk before and after color removal.
Figure 4
Figure 4
Absorption spectra inset with Tauc plots for pure ZnO and its hybrid with psyllium husk.
Figure 5
Figure 5
Graphs for MB dye without any catalyst. (a) Absorption spectra, (b) Ct/Co curve, (c) kinetics of degradation, and (d) efficiency of dye removal.
Figure 6
Figure 6
(a) Absorption spectra for pristine ZnO, (b) Ct/Co vs time curve for, (c) kinetics of photodegradation for ZnO towards MB, and (d) dye degradation efficiency graph.
Figure 7
Figure 7
Low concentration absorption spectra under UV irradiation for psyllium-added ZnO with various concentrations of 5 mg (a), 10 mg (b), 15 mg (c), and 20 mg (d).
Figure 8
Figure 8
Graphs for various concentrations of 5, 10, 15, and 20 mg of ZnO that contains psyllium: (a) Ct/Co curve, (b) kinetics of degradation, and (c) efficiency of degradation at low concentration.
Figure 9
Figure 9
High concentration absorption spectra under UV irradiation for psyllium-added ZnO with various concentrations of 5 mg (a), 10 mg (b), 15 mg (c), and 20 mg (d).
Figure 10
Figure 10
Degradation kinetics for psyllium–ZnO towards removal of MB: (a) Ct/Co vs. time, (b) ln (Co/Ct) vs. time, and (c) dye removal % age vs. time at high concentration.
Figure 11
Figure 11
Scavenger study of ascorbic acid (C6H6O8), sodium borohydride (NaBH4), and ethylenediamine tetraacetate (EDTA) for the illustration of reactive species involved in the photodegradation of MB. (a) Ct/Co mechanism for scavengers; (b) Reaction kinetics for scavengers; (c) Removal of dye with respect to time.
Scheme 2
Scheme 2
Photodegradation mechanism on ZnO hybrid material produced from psyllium husk.
See this image and copyright information in PMC

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