en Environmental Health, Sciences, and Engineering Environmental Health, Sciences, and Engineering پژوهشي Original Article <div><span style="font-size:14px;"><span style="font-family: times new roman;"><strong>Background:</strong> In the present study, the photocatalytic (TiO₂/UV) batch process has been used for the methyl orange (MO) degradation.<br> <strong>Methods: </strong>In the catalyst range from 0.25 to 1.5 g/L, the optimum concentration of TiO₂ was found to be 0.5 g/L. The kinetic behavior of MO degradation has been evaluated using the non-linear form of pseudo-first order and pseudo-second order models.<br> <strong>Results: </strong>The goodness of the fit was evaluated using the correlation coefficient R2 value and the mean square error (MSE) function.<br> <strong>Conclusion: </strong>The kinetic studies revealed that the pseudo-first order model (k₁= -0.0593 min^-1) is more suitable to fit the experimental data (R₂ = 0.957, MSE = 0.00271) of MO degradation.</span></span><br> &nbsp;</div> Methyl orange, Photocatalytic, AOP, Kinetics 154 160 http://jhehp.zums.ac.ir/browse.php?a_code=A-10-119-1&slc_lang=en&sid=1 Nahid Nabavi nahidnabavi@yahoo.com 10031947532846009432 10031947532846009432 No Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Mazyar Peyda mazyarpeyda@zums.ac.ir 10031947532846009433 10031947532846009433 Yes Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran. Gholamreza Sadeghi sadeghi@zums.ac.ir 10031947532846009434 10031947532846009434 No Department of Environmental Health Engineering, School of Public Health, Zanjan University of Medical Sciences, Zanjan, Iran.