Parametric optimization of hexavalent chromium removal by electrocoagulation technology with vertical rotating cylindrical aluminum electrodes using Taguchi and ANN model

This study aims to evaluate the performance of rotating aluminum electrodes in the electrocoagulation reactor for removing hexavalent chromium (Cr6+) from synthetic tannery wastewater. Taguchi and Artificial Neural Network (ANN) based models were developed to obtain the optimum condition for maximum Cr6+ removal. The optimum working condition obtained by Taguchi approach for the maximum Cr6+ removal (94%) was: Initial Cr6+ concentration (Cr-i(6+)) = 15 mg/L; Current Density (CD) = 14.25 mA/cm(2); Intial pH = 5; Rotational Speed of Electrode (RSE) = 70 rpm. In contrast, the optimal condition for maximum Cr6+ ions removal (98.83%) obtained from the BR-ANN model was: Cr-i(6+) = 15 mg/L; CD = 14.36 mA/cm(2); pHi = 5.2; RSE = 73 rpm. Compared to the Taguchi model, the BR-ANN model outperformed in terms of providing higher Cr6+ removal (+ 4.83%); reduced energy demand (-0.035 KWh/gm Cr6+ remove); lower error function value (chi(2) = -7.9674 and RMSE = -3.5414); and highest R-2 value (0.9991). The data for the conditions 91,007 < Re < 227,517 and Sc = 102.834 were found to fit the equation for the initial Cr6+ concentration of 15 mg/l; Sh = 3.143Re(0.125) Sc-0.33. The Cr6+ removal kinetics was best described by Pseudo 2(nd) Order model, as validated by high R-2 and lower error functions value. The SEM and XRF analysis confirmed that Cr6+ was adsorbed and precipitated along with metal hydroxide sludge. The rotating electrode led to lower SEEC (10.25 kWh/m(3)), as well as maximum Cr6+ removal (98.83%), compared to EC process with stationary electrodes.

Automated summary

This study evaluates the performance of rotating aluminum electrodes in removing hexavalent chromium (Cr6+) from synthetic tannery wastewater using an electrocoagulation reactor. Taguchi and Artificial Neural Network (ANN) models were developed to optimize the conditions for maximum Cr6+ removal. The BR-ANN model provided better results compared to the Taguchi model, achieving higher Cr6+ removal efficiency, reduced energy demand, and improved accuracy. The SEM and XRF analysis confirmed the adsorption and precipitation of Cr6+ with metal hydroxide sludge.