University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 56 9 2025 11 22 Experimental Study and evaluation of kinetic models of cadmium desorption from bed sediment load in a circular Flume Experimental Study and evaluation of kinetic models of cadmium desorption from bed sediment load in a circular Flume 2393 2410 105175 10.22059/ijswr.2025.398307.669973 FA Mohsen Nasrabadi Department of Water Science and Engineering, Faculty of Agriculture and Environment,, Arak University, Arak, Iran. Mohammad Hosein Omid Department of Irrigation and Reclamation Engineering,, Faculties of Agricultural and Natural Resources, University of Tehran, Karaj, Iran. Journal Article 2025 07 10 Most surface water sources and rivers are exposed to various pollutants in all around the world. One of the industrial pollutants is the entry of heavy metals into rivers and their absorption by sediments. On the other hand, heavy metals may be released from sediments under various environmental conditions. In this study, in order to investigate the cadmium desorption from sediments, the sediments with an average diameter of 0.54 mm were first artificially contaminated with cadmium at different concentrations. Then, the effect of cadmium concentration and flow velocity on the desorption rate from contaminated sediments was investigated experimentally in a circular flume with a diameter of 1.6 m and a width of 0.2 m at velocities of 0.18 and 0.35 m/s. Desorption experiments revealed that nearly all of the desorbable cadmium was extracted from the sediments in about 30 min. With increasing cadmium concentration, the desorption rate also increased, so that with increasing concentration from 7 mg/kg to 49.5 mg/kg, the desorption rate increased from 10.7 to 30%. Also, increasing the flow rate had a negligible effect on the desorption rate; so that at the maximum concentration, the desorption rate was observed to be 25 and 30% for velocities of 0.18 and 0.35 m/s, respectively. After examining the desorption kinetic models, it was found that the double parabolic diffusion equations with R2 = 0.99, SSE = 5.77, KGE = 0.85, and mean relative error of 7.02% are more accurate than the other equations. The results of the experiments in this study showed that most sediment particles and cadmium have formed strong chemical bonds and that the processes of adsorption and desorption of heavy metals by sediments are irreversible.  Most surface water sources and rivers are exposed to various pollutants in all around the world. One of the industrial pollutants is the entry of heavy metals into rivers and their absorption by sediments. On the other hand, heavy metals may be released from sediments under various environmental conditions. In this study, in order to investigate the cadmium desorption from sediments, the sediments with an average diameter of 0.54 mm were first artificially contaminated with cadmium at different concentrations. Then, the effect of cadmium concentration and flow velocity on the desorption rate from contaminated sediments was investigated experimentally in a circular flume with a diameter of 1.6 m and a width of 0.2 m at velocities of 0.18 and 0.35 m/s. Desorption experiments revealed that nearly all of the desorbable cadmium was extracted from the sediments in about 30 min. With increasing cadmium concentration, the desorption rate also increased, so that with increasing concentration from 7 mg/kg to 49.5 mg/kg, the desorption rate increased from 10.7 to 30%. Also, increasing the flow rate had a negligible effect on the desorption rate; so that at the maximum concentration, the desorption rate was observed to be 25 and 30% for velocities of 0.18 and 0.35 m/s, respectively. After examining the desorption kinetic models, it was found that the double parabolic diffusion equations with R2 = 0.99, SSE = 5.77, KGE = 0.85, and mean relative error of 7.02% are more accurate than the other equations. The results of the experiments in this study showed that most sediment particles and cadmium have formed strong chemical bonds and that the processes of adsorption and desorption of heavy metals by sediments are irreversible.  https://ijswr.ut.ac.ir/article_105175_7966f0f8ced822b3dc8ec6313faedec4.pdf