Improving the co-removal efficiency of dyes from water by a novel four-component chitosan flexible film containing graphene oxide

One of the major environmental and public problems in the world is water pollution, which has always received significant attention [1]. Industries such as painting, leather, clothing, pulp, paper, textiles, and others use a variety of dyes [2]. In the textile industry, two types of dyes are used to dye fabrics: natural dyes and synthetic dyes. In the present study, a novel four-component flexible film based on α-ketoglutaric acid, chitosan, polyaniline, and graphene oxide (α-CTS-PANI-GO) was synthesized and characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Raman spectroscopy. The simultaneous removal properties of α-CTS-PANI-GO were evaluated in the removal of cationic and anionic dyes, Methylene Blue (MB) and Acid Orange 7 (AO7). Using the Central Composite Decomposition (CCD), the effect of different variables such as pH, temperature, adsorbent dose, and time on AO7 and MB removal was studied. pH 8, temperature 75 °C, adsorbent dose 0.04 g and time 75 minutes were calculated by the experimental design method for maximum absorption. Furthermore, the analysis of variance (ANOVA) was used to determine the adequacy of the model. The complete diversity of the results obtained by ANOVA is divided into two variations: One is related to the model and the other is related to experimental errors and thus determines whether the change is significant from the model or not. It is calculated by the factor F-value which is expressed as the square-to-residual error ratio of the mean model. The F-value obtained in the present study was 19.55 and 22.50, which suggested the fitness of the response surface model for MB and AO7, respectively. Also, using the experimental design, the optimal values for maximum removal were obtained. Various isotherm models, such as Langmuir and Freundlich, were investigated, and the processing of experimental equilibrium data confirmed the suitability and application of the Langmuir model. Analysis of experimental adsorption data using various kinetic models, such as quasi-first and second-order models, shows the applicability of the first-order equation. The results showed that in the optimal conditions, the removal percentage was about 95% for AO7 and 80% for MB, which indicates the successful performance of the synthetic film compared to the method.