Combining Experimental Data with Statistical Methods to Evaluate Hydrolyzed Reactive Dye Removal by α-Fe2O3 in a Cellulose-Based Membrane

Abstract

Water contaminated with toxic dyes poses serious problems for human health and environmental ecosystems. Unfixed reactive dyes and their hydrolyzed form are soluble in water, thus, their removal is particularly challenging. Among the different methodologies, adsorption is probably the most common since it is easy to handle and has a low cost. Here, the removal by adsorption of hydrolyzed Reactive Black 5 (hydRB5) from a model wastewater through cellulose acetate/hematite membranes (CA/α-Fe2O3), designated as M1, M2 and M3, was performed. The pristine cellulose acetate membrane (CA) was designated as M0. Toward understanding the adsorption mechanism of hydRB5 on membranes, the rate of adsorption and maximum value of the adsorption capacity were evaluated using kinetic and isothermal studies, respectively. The results showed that the adsorption mechanism follows pseudo-first-order kinetics, and data are best fitted by the Langmuir isotherm method with a maximum adsorption capacity of 105.26 mg g−1 in pH~7. Furthermore, these membranes can be also regenerated by washing with NaOH and NaCl solutions, and the regeneration efficiency remains effective over five cycles. To complete the work, two statistical models were applied, an Analysis of Variance (ANOVA) and a Response Surface Methodology (RSM). The optimum value found is located in the usable region, and the experimental validation shows good agreement between the predicted optimum values and the experimental data. These composite membranes are also good candidates for the adsorption of other pollutants, even at industrial scale, due to their effective regeneration process and low production costs.

Design of Experiments for Increasing of Methylene Blue Adsorption onto Cellulose Derivative-Based Composites

“…The maximum adsorption was achieved at pH = 9.0 with removal efficiencies of 44.5% for M0, 55% for M1, 71.4% for M2 and 50.4% for M3, after 300 minutes at 25 ℃. A common situation was observed before 18 due to an increase in the electrostatic interactions between cationic dye molecules and negative surface charge on adsorbents. It is known that at pH < pH PZC , the adsorbent surface was positively charged, and the interactions between MB and composite membranes were smaller due to the protonation of carboxyl groups belonging to the cellulose backbone.…”

“…A similar behaviour was discussed by us previously. 18 Figure 1(a) represents the effect of pH on the adsorption capacity of each membrane. The maximum adsorption was achieved at pH = 9.0 with removal efficiencies of 44.5% for M0, 55% for M1, 71.4% for M2 and 50.4% for M3, after 300 minutes at 25 ℃.…”

“…At first, the adsorption rate increased rapidly and gradually slowed down until reaching equilibrium. 18 This is explained by the fact that adsorption in the first place occurred on the external surfaces of the composite, resulting in a fast adsorption rate, and with surface saturation MB gradually diffused into the interior of pores, which produced a decrease in the adsorption rate. 18,26,28 As shown in Figure 1(b), the maximum removal efficiency was achieved within 240 to 300 minutes, without further change in the equilibrium adsorption capacity (q e ) after 300 minutes.…”

“…Firstly, we used carbon nanoparticles 12,16 and then we adopted the iron oxide nanoparticles. [17][18] Both nanoparticles showed good physicochemical properties such as optical, semiconducting, ferromagnetic and antimicrobial activity against common strains. However, the iron oxide nanoparticles proved to be more effective for the functionalization of cellulose acetate due to its lower cost of production, simplicity of manipulation and greater physicochemical properties.…”

“…Therefore, this work focused on the use of previously synthesized hematite-cellulose acetate composites as adsorbents, in the form of films formed by phase inversion methodology, for the removal of MB from a model wastewater. From our previous work, 12,18 we know the dual advantages of these membranes: adsorbents and filters. Here, the cellulose-based materials are being used as adsorbents and, subsequently, will be tested as filters (permeability, fouling and selectivity will be analysed).…”