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Article | Tropical Aquatic and Soil Pollution | Volume 6 - Issue 1 - 2026 | 1-17 | https://doi.org/10.53623/tasp.v6i1.1002
© 2026 by the author(s), and is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) License Creative Commons Attribution 4.0 International (CC BY 4.0) License

Optimisation of Photocatalytic Degradation for Enhancing Bathroom Greywater Quality Using 2,4,6-Trinitrotoluene/Zeolite Photocatalyst

Author(s): Siti Nor Hidayah Arifin 1 ORCID https://orcid.org/0000-0003-2879-3367 , Paran Gani 1 ORCID https://orcid.org/0000-0002-1650-4241 , Radin Maya Saphira Radin Mohamed 2 ORCID https://orcid.org/0000-0002-2023-9196 , Adel Al-Gheethi 3 , Chin Wei Lai 4 ORCID https://orcid.org/0000-0002-7549-5015 , G. Yasni 5 ORCID https://orcid.org/0000-0001-9184-6092 , Kean Hua Ang 6 ORCID https://orcid.org/0000-0002-2479-4111
Author(s) information:
1 Department of Civil and Construction Engineering, Faculty of Engineering and Science, Curtin University Malaysia, Miri, 98009, Sarawak, Malaysia
2 Micropollutants Research Centre (MPRC), Institute for Integrated Engineering (I2E), Universiti Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat, Johor, Malaysia
3 Global Centre for Environmental Remediation (GCER), University of Newcastle, Newcastle, Australia
4 Nanotechnology and Catalyst Research Centre (NanoCat), Universiti Malaya, 50603 Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia
5 Faculty of Engineering, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia
6 Department of Geography, Faculty of Arts and Social Sciences, University of Malaya, Malaysia

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Tropical Aquatic and Soil Pollution

Volume 6 - Issue 1 - 2026

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This experimental study investigated the solar photocatalytic degradation process for improving bathroom greywater quality using titanium dioxide nanotubes modified 2,4,6-trinitrotoluene with zeolite (TNTs/zeolite) and sought to optimize it. Organic pollutants, suspended solids, and personal care products remained in total household greywater at a proportion of 43–70% from bathroom sources. The optimization method applied was Central Composite Design (CCD) under Response Surface Methodology (RSM), in which three independent variables were considered: pH within a range of 3–10; catalyst loading expressed as the exposed surface area of 1 or 2 cm²; and irradiation time between thirty and one hundred eighty minutes under natural sunlight conditions with average irradiance values between six hundred twenty and seven hundred eighty watts per square meter. Twenty runs were carried out in triplicate. The responses tested were Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), turbidity, pH, and Dissolved Oxygen (DO). The optimum condition predicted by RSM had a pH of 6.25, an irradiation time of 180 minutes, and a catalyst loading of 1 × 1 cm². Experimental validation at this optimum condition confirmed the adequacy of the model, with removals greater than 50% for COD, BOD, TSS, and turbidity. ANOVA showed that the models were statistically significant (p < 0.0001) and highly predictively reliable (R² > 0.90 for most responses). The study demonstrated that TNTs/zeolite under natural sunlight represented a potential low-energy alternative for bathroom greywater treatment with practical possibilities for decentralized reuse applications.

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SUBMITTED: 20 January 2026
ACCEPTED: 02 March 2026
PUBLISHED: 11 March 2026
SUBMITTED to ACCEPTED: 41 days
DOI: https://doi.org/10.53623/tasp.v6i1.1002

Cite this article
Arifin, S. N. H. ., Gani, P., Radin Mohamed, R. M. S. ., Al-Gheethi, A. ., Lai, C. W., Yasni, G., & Ang , K. H. (2026). Optimisation of Photocatalytic Degradation for Enhancing Bathroom Greywater Quality Using 2,4,6-Trinitrotoluene/Zeolite Photocatalyst. Tropical Aquatic and Soil Pollution, 6(1), 1–17. https://doi.org/10.53623/tasp.v6i1.1002
Keywords
Optimisation, Greywater quality, Bathroom greywater, Photocatalysis, TNTs/zeolite
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