Varala, S.Kumari, A.Buruga, K.Bhargava, S.K.Parthasarathy, R.2026-02-032025Environmental Progress and Sustainable Energy, 2025, 44, 1, pp. -19447442https://doi.org/10.1002/ep.14523https://idr.nitk.ac.in/handle/123456789/20517Natural coagulants are a biodegradable and potential alternative to chemical coagulants. Cassia fistula seeds and Cactus opuntia f-indica are employed herein to reduce the concentration of methylene blue dye in aqueous solutions. Maximum removal efficiency was obtained by optimizing the process parameters by the Taguchi method in the design of experiments (DOE). At optimum conditions, the removal efficiencies of C. fistula seeds and Cactus opuntia f-indica were 98.27% and 92.75%, respectively. The adsorption kinetics data were fitted to pseudo-first-order, pseudo-second-order, Elovich, intra-particle diffusion, and Boyd kinetic models. Accordingly, intra-particle diffusion and pseudo-second-order kinetics suggested the coagulation process to be an adsorption process controlled by the solid-phase sorption with intra-particle diffusion as the rate-limiting step. A comparative study was also conducted using alum to determine its effectiveness in reducing dye concentration. Results suggested biocoagulants are appropriate alternatives for reducing dye concentrations in wastewater and treating textile and dye industrial effluents. © 2024 American Institute of Chemical Engineers.Biological water treatmentCoagulationEffluent treatmentIndustrial water treatmentTextile chemical treatmentVat dyesBiocoagulantCactus opuntia f-indicaCassia fistulaCationic dyesChemical coagulantsDye concentrationIntra-particle diffusionMethylene BlueRemoval efficienciesTaguchi's methodsWastewater treatment