Application of Response Surface Methodology (RSM) in optimisation of fluoride removal by magnetic chitosan/graphene oxide composite: kinetics and isotherm study Seyed Yaser Hashemi, Ali Azari, Mohammad Raeesi, Kamyar Yaghmaeian International Journal of Environmental Analytical Chemistry, 2023 The presence of fluoride ions is considered a threat to public health and the environment due to health challenges. Graphene, as an adsorbent with a porous structure and high surface area, has been used on a large scale to effectively remove organic and inorganic contaminants from aqueous media. Therefore, the present study aimed to use magnetic chitosan/graphene oxide (MCGO) composite in fluoride adsorption and study adsorption isotherms and kinetics. At first, a magnetic chitosan/graphene oxide compound was synthesised and its characteristics were determined by SEM, XRD and FTIR. Then, fluoride adsorption process experiments were performed by studying the effect of pH, contact time, adsorbent mass, and fluoride initial concentration. TheLangmuir, Freundlich, Temkin, and Dubinin and Radushkevich isotherm models were also studied to describe the equilibrium of the adsorbate between the solid and fluid phases, and the pseudo-first-order, pseudo-second-order, Intraparticle diffusion, and Elovich kinetic models were analyzed to investigate the adsorption behaviour. To evaluate the effect of each parameter, R software based on Response Surface Methodology (RSM) was used. All experiments were repeated three times and the average was considered as presented as the final results. The results showed that the maximum fluoride adsorption was at pH5. The equilibrium time was reported at 136 minutes and the maximum removal percentage obtained 91% in optimal conditions. Investigation of the isotherm and kinetics showed that the results of fluoride adsorption process were correlated with Langmuir isotherm model (R2 > 0.99) and Elovich kinetic model (R2 > 0.989), respectively. It can be concluded that theMCGOcomposite is an effective adsorbent for fluoride removal from water resources.
Spatial modelling of PM2.5 concentrations in Tehran using Kriging and inverse distance weighting (IDW) methods Kazhal Masroor, Farzad Fanaei, Somayeh Yousefi, Mohammad Raeesi, Hossein Abbaslou, Abbas Shahsavani, Mostafa Hadei Journal of Air Pollution and Health, 2020 Introduction: Estimating air pollution levels in areas with no measurements is a major concern in health-related studies. Therefore, the aim of this study was to investigate the amount of exposure to particulate matter below 2.5 ยต (PM2.5) in the metropolis of Tehran.Materials and methods: The hourly concentrations of PM2.5 during 2017-2018 period were acquired from the Department of Environment (DOE) and Air Quality Control Company of Tehran (AQCC). The hourly concentrations were validated and 24-h concentrations were calculated. Inverse distance weighting (IDW), Universal Kriging, and Ordinary Kriging were used to spa- tially model the PM2.5 over Tehran metropolis area. Root Mean Square Error (RMSE) and Mean Error (ME) were used to measure and control for the ac- curacy of the methods.Results: The results of this study showed that RMSE and MENA values in Kriging method was less than the IDW, which indicates that the Kriging was the best method to estimate PM2.5 concentrations. According to the final map, the highest annual concentrations of PM2.5 were observed in the southern and southwestern areas of Tehran (districts 10, 15, 16, 17, and 18). The lowest exposure to PM2.5 was found to be in districts 1, 2, 3, 6, and 8.Conclusion: It can be concluded that Kriging method can predict spatial vari- ations of PM2.5 more accurately than IDW method.
