Abstract
BackgroundAnnually, large quantities of dyes are produced and consumed in different industries. The discharge of highly colored textile effluents to the aquatic environments causes serious health problems in living organisms. This paper investigates the performance of each of the electro-oxidation and electro-reduction pathways in the removal of reactive red 120 (RR120) from synthetic textile effluents using a novel electrochemical reactor.MethodsIn the current study, a two-compartment reactor divided by cellulosic separator was applied in batch mode using graphite anodes and stainless steel cathodes. Central Composite Design was used to design the experiments and find the optimal conditions. The operational parameters were initial dye concentration (100–500 mg L−1), sodium chloride concentration (2500–12,500 mg L−1), electrolysis time (7.5–37.5 min), and current intensity (0.06–0.3 A).ResultsThe results showed that electro-oxidation was much more efficient than electro-reduction in the removal of RR120. According to the developed models, current intensity was the most effective factor on the electro-oxidation of RR120 as well as in power consumption (Coefficients of 12.06 and 0.73, respectively). With regard to the dye removal through electro-reduction, electrolysis time (coefficient of 8.05) was the most influential factor. Under optimal conditions (RR120 = 200 mg.L−1, NaCl = 7914.29 mg.L−1, current intensity = 0.12 A, and reaction time = 30 min), the dye was removed as 99.44 and 32.38% via electro-oxidation and electro-reduction mechanisms, respectively, with consuming only 1.21 kwhm−3 of electrical energy.ConclusionsAccording to the results, electro-oxidation using graphite anodes in a cell divided by cellulosic separator is very efficient, compared to electro-reduction, in the removal of RR120 from aqueous solutions.
Highlights
Large quantities of dyes are produced and consumed in different industries
The current study aimed to evaluate the performance of EO and ER using graphite anodes and stainless steel cathodes in the removal of reactive red 120 (RR120) dye from synthetic textile wastewater
In each experiment, sampling was done from both parts of the reactor at the time determined by Central composite design (CCD), and the pH of the samples was neutralized by dilute solutions of Sulfuric acid (H2SO4) and NaOH
Summary
Chemicals Double Distilled Water (DDW) was used to prepare stock solutions and required dilutions. Experimental design Experiments were designed based on CCD, a wellknown design of Response Surface Methodology (RSM) in the Design Expert 7.0 (trial version). This number was obtained by defining the actual values of independent variables in the initial (−α) and end (+α) points by user while the three other levels of each parameter were suggested by CCD. In each experiment, sampling was done from both parts of the reactor at the time determined by CCD, and the pH of the samples was neutralized by dilute solutions of H2SO4 and NaOH. To measure the remained concentration of dye, the Milton Roy Company Spectronic 20 Spectrophotometer (UV–VIS) was applied at 530 nm
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