The adsorption process gives great results for the removal of different types of colored substances or different, mainly organic pollutants from wastewater. In addition to standard adsorbents (such as activated carbon), cheap and natural adsorbents have been increasingly used in recent times (e.g. clay, zeolites), along with waste materials (fly ash from thermal power plants or different agricultural/plant remains), after proper preparation and modification. Research presented in this article was performed with fly ash from thermal power plant Stanari. The aim of this study was to investigate the possibility of removing Bemacid Red (BR) dye from textile industry wastewater by adsorption on fly ash modified with HCl. After a series of experiments, the optimal process parameters were determined. These parameters were then applied to a wastewater sample obtained by simulating polyamide fabric dyeing. The efficiency of adsorption of BR dyes from aqueous solutions depends directly on the process parameters: contact time, pH value, adsorbent dose and initial adsorbate concentration (dye concentration). Under optimal process conditions, a dye removal rate of 97.1 % was achieved. Analyzing the experimentally obtained data using nonlinear adsorption isotherms, a much better agreement of the Freundlich model with the experimental results was determined (the coefficient of determination is R2=0.9787). The obtained data show that the adsorption of Bemacid Red dye on fly ash is multilayered. Optimal parameters of the adsorption process were applied to wastewater obtained by simulating the process of dyeing polyamide fabric with BR dye. The efficiency of adsorption under defined conditions was confirmed through the 100 % removal of dye from a real wastewater sample.
