en Water quality and wastewater treatment and reuse Original articles <div style="text-align: justify;"><strong><em>Introduction:</em></strong> Microcystin-leucine arginine (MC-LR) is a toxin with harmful effects on the liver, kidney, heart, and gastrointestinal tract. So, effective removal of MC-LR from water resources is of great importance. The aim of this study was to remove microcystin-LR (MC-LR) from aqueous solution by Titanium Dioxide (TiO₂).<br> <strong><em>Materials and Methods:</em></strong> In the present study, TiO₂, as a semiconductor, was used for photodegradation of MC-LR under ultraviolet light (UV). The Response Surface Methodology was applied to investigate the effects of operating variables such as pH (A), contact time (B), and catalyst dose (B) on the removal of MC-LR. The MC-LR concentration was measured by high-performance liquid chromatography (HPLC).<br> <strong><em>Results: </em></strong>The results showed that single variables such as A, B, and C had significant effects on MC-LR removal (p_value< 0.05). In other words, increase of the contact time and catalyst dose had a positive effect on enhancing the removal efficiency of MC-LR, but the effect of pH was negative. The analysis of variance showed that BC, A², and C² variables had a significant effect on the MC-LR removal (p_value< 0.05). Finally, the maximum removal efficiency of MC-LR was 95.1%, which occurred at pH = 5, contact time = 30 minutes, and catalyst dose = 1 g/l.<br> <strong><em>Conclusion: </em></strong>According to the findings, TiO₂, as a photocatalyst, had an appropriate effect on degradation of the MC-LR.</div> Microcystin-LR, TiO2, Photocatalytic Degradation, Response Surface Methodology. 1063 1076 http://jehsd.ssu.ac.ir/browse.php?a_code=A-10-170-1&slc_lang=en&sid=1 Negar Jafari 0000-0003-4584-981X No Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran and Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. Afshin Ebrahimi a_ebrahimi@hlth.mui.ac.ir 0000-0002-3640-087X No Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran and Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. Karim Ebrahimpour 0000-0002-6230-0119 No Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran and Department of Environmental Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran. Ali Abdolahnejad abdolahnejad.a@gmail.com 0000-0003-0193-7690 Yes Department of Public Health, Maragheh University of Medical Sciences, Maragheh, Iran.