Kinetics, thermodynamics, isotherm modeling for removal of reactive Red 35 and disperse yellow 56 dyes using batch bi-polar aluminum electrocoagulation

Aluminum Electrocoagulation technique was employed for the efficiency of the removal of two anionic dyes; Reactive Red 35 and Disperse Yellow 56 in a batch bi-polar system. Optimization of different operational factors such as pH (2-11), current density (43.4 and 104.2 A/m(2)), initial dye concentration (10-150 mg/L), number of electrodes (3-9), and magnetic stirring speed (250-1000 rpm) were conducted experimentally. It was found that the optimum conditions which gave higher percent removal for both dyes were pHi 8, magnetic stirring speed 750 rpm, 9 Al electrodes, current density 43.4 A/m2, C-(sic) 70, and 50 mg/L for RR35 and DY56, respectively. Pseudo-first-order kinetic model best fitted the data. Different isotherm models were applied and it was found that the Langmuir and Flory-Huggins adsorption isotherms are the most fitting. The studied thermodynamic parameters clarified that the process is spontaneous and endothermic. Energy dispersive X-ray spectroscopy, and Fourier transform infrared were the way to assure that the removal of dyes was according to the adsorption onto the insoluble aluminum hydroxide flocs. The energy consumption was found to be 15.82 and 20.02 kWh/kg for RR35 and DY56, respectively. The operating cost was 0.95 and 0.6 US$/m(3) for RR35 and DY56, respectively. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.

Automated summary

Aluminum Electrocoagulation technique was utilized to efficiently remove two anionic dyes in a batch bi-polar system. The optimal conditions for higher removal percentage were identified, and pseudo-first-order kinetic model best fitted the data. Different isotherm models showed that Langmuir and Flory-Huggins adsorption isotherms were the most fitting. The studied thermodynamic parameters clarified that the process is spontaneous and endothermic.