The Iron Modification Effect on Performance of Natural Adsorbent Scoria for Malachite Green Dye Removal from Aquatic Environments: Modeling, Optimization, Isotherms, and Kinetic Evaluation

Malachite green (MG) is a synthetic dye which is widely used as biocide in aquaculture and dyeing agent in textile industries. This dye could be difficult to remove from aquatic environments due to its features and low degradability. According to the effect of ferrous on the physical and chemical characteristics of scoria, this study was to evaluate iron-coated scoria performance in removing MG from aqueous solutions. Adsorption process is carried out in vitro at different pH, adsorbent dosage, contact time, and constant concentration of the dye. Results indicated that all parameters of the model were inaccurate ranges, which confirm the validity of the obtained model to predict the amount of MG removal. Moreover, MG removal rate increased with increasing the pH, the adsorbent dosage, and the contact time. The highest efficiency was 94.2% obtained at pH = 11, adsorbent dose = 1.4 g/L, and contact time = 75 min. Adsorption of MG on iron-coated scoria was found to follow both the Langmuir and Freundlich isotherms and pseudo-second-order kinetic model. The separation factor and adsorption intensity in the iron-modified scoria were obtained lower than the bare scoria. According to the results, it can be concluded that iron via chemical changes of adsorbent structure causes increase in the efficiency of scoria for removal of MG.