Back propagation artificial neural network and central composite design modeling of operational parameter impact for sunset yellow and azur (II) adsorption onto MWCNT and MWCNT-Pd-NPs: Isotherm and kinetic study

Impact operational parameters such as initial dyes concentration, adsorbent mass, pH and sonication time on the efficiency of ultrasound-assisted adsorption of sunset yellow (SY) and azur (II) (AZ) onto MWCNT and MWCNT-Pd-NPs was studied by central composite design (CCD) and back propagation artificial neural network (ANN) models and resulted for tow adsorbent were compared to each other. Optimize conditions from CCD in presence of MWCNT as adsorbent was found to be 6.01 and 9.98 mg L−1 AZ and SY concentration, 0.02 of adsorbent mass, pH 7.0 and 3.8 min sonication time, respectively, while in the presence of MWCNT-Pd-NPs optimize value were obtained at 10.0 and 8.0 mg L−1 AZ and SY concentration, 0.018 of adsorbent mass and pH 5.0 and 3.5 min sonication time, respectively. In these conditions and at desirability value of 0.99, the maximum adsorption efficiency for AZ onto MWCNT and MWCNT-Pd-NPs are 82.97 and 94.95, respectively. Also, the maximum adsorption efficiency for SY onto MWCNT and MWCNT-Pd-NPs are 73.13 and 85.55, respectively. This values show that MWCNT-Pd-NPs in comparison with MWCNT at the lower contact time and adsorbent mass was able to remove greater amounts of under study dyes. Based on the ANN model the absolute average deviations (AADs) of AZ and SY dyes adsorption by MWCNT from experimental data are 0.27% and 0.43%, and the R2 values are 0.911 and 0.954, respectively. Also, the AADs of AZ and SY dyes adsorption by MWCNTs-Pd-NPs are 0.44% and 0.65%, and the R2 values are 0.925% and 0.927%, respectively. This values show that ANN for MWCNT-Pd-NPs in comparison with MWCNT was a more powerful tool for building up to construct an empirical model to predict under study dyes adsorption behavior. In addition, the obtained results have good agreement with experimental data for MWCNT-Pd-NPs in comparison with MWCNT. Finally, the study of equilibrium isotherm and kinetic models of adsorption process are shown that the Langmuir isotherm model and pseudo second order kinetic model were the best models for both adsorbent.