Optimization and modelling using the response surface methodology for methylene blue removal by electrocoagulation/hazelnut shell adsorption coupling in a batch system

Abstract

The present work examined the removal of methylene blue (MB) from aqueous solutions through an electrocoagulation/hazelnut shell (EC/HNS) adsorption coupling process. The process was evaluated using a Box–Behnken design (BBD) under the response surface methodology (RSM). According to the obtained results from BBD–RSM regression analysis, we found that the experimental data are best fitted to the second-order polynomial model with coefficient of determination (R2) value of 0.9534, adjust coefficient (Radj2) value of 0.9926 and predicted correlation coefficient (RPred2) value of 0.9973. The maximum MB removal efficiency was obtained under optimized conditions (HNS dosage, 6 g/L; reaction time, 17.75 min; and current density, 2.6 mA/cm2). Under the optimum conditions, the MB removal rate reached 99.45%, and the RSM predictive value was 98.71% with a small deviation. These results confirmed that the RSM model accurately and reliably analysed the process of removing MB from wastewater.