Abstract
Rhodamine B (Rh B) is a toxic dye that is harmful to the environment, humans, and animals, and thus the discharge of Rh B wastewater has become a critical concern. In the present study, reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO) was used to treat Rh B aqueous solutions. The nZVI/rGO composites were synthesized with the chemical deposition method and were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2-sorption, and X-ray photoelectron spectroscopy (XPS) analysis. The effects of several important parameters (initial pH, initial concentration, temperature, and contact time) on the removal of Rh B by nZVI/rGO were optimized by response surface methodology (RSM) and artificial neural network hybridized with genetic algorithm (ANN-GA). The results suggest that the ANN-GA model was more accurate than the RSM model. The predicted optimum value of Rh B removal efficiency (90.0%) was determined using the ANN-GA model, which was compatible with the experimental value (86.4%). Moreover, the Langmuir, Freundlich, and Temkin isotherm equations were applied to fit the adsorption equilibrium data, and the Freundlich isotherm was the most suitable model for describing the process for sorption of Rh B onto the nZVI/rGO composites. The maximum adsorption capacity based on the Langmuir isotherm was 87.72 mg/g. The removal process of Rh B could be completed within 20 min, which was well described by the pseudo-second order kinetic model.
Highlights
Dyes and pigments constitute a very important class of water pollutants due to their large scale usage in various industries, such as textile, printing, plastics, and leather, which can lead to water coloration [1,2]
Rhodamine B (Rh B) is a synthetic basic dye imparting red color in aqueous solutions that is widely used as a colorant in the textile and food industries, and for cell fluorescence staining in the laboratory [2,5,6]
The major objective of the present study is to investigate the feasibility of using nanoscale zero-valent iron (nZVI)/rGO for the removal of Rh B from aqueous solutions
Summary
Dyes and pigments constitute a very important class of water pollutants due to their large scale usage in various industries, such as textile, printing, plastics, and leather, which can lead to water coloration [1,2]. A growing number of studies have reported the application of nanoscale zero-valent iron (nZVI) for environmental remediation due to its high effectiveness, versatility, and unique properties, such as large specific surface area, small particle size, excellent reactivity, and high injectability into an aqueous solution [14,15,16]. The unavoidable simplifications and assumptions for some highly complex processes can lead to inaccurate predictions during the development of mechanistic models [28,29]. Both the empirical and statistical models can be utilized for the known data to extract knowledge about operating conditions without knowing the sophisticated underlying mechanism of the process [28]. Batch experiments were carried out to study the adsorption isotherm models and kinetics models
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