Quantum Adsorption’s Mechanism of Gelatin-Cellulose Hydrogel for Effective Removal of Copper and Cobalt ions from Wastewater using Artificial Neural Network

Abstract

Heavy metal ions are one of the most toxic materials in the environment. Adsorption is the most used process for the removal of heavy metals from wastewater because is recognized as economical, effective and versatile method. Much research has been conducted into processes to remove heavy metals using different adsorbents. Various adsorbents have been used to remove harmful heavy metal ions from wastewater. Zeolite, clay, activated carbon and biopolymers are the most common adsorbents used. Due to complex nature on adsorption process, ANN (Artificial Neural Network) have been found to be one the most promising numerical simulation techniques to make reliable predictions. In order to obtain extensive information on the adsorption process of metal ions on the functional groups of adsorbents, quantum adsorption mechanism was investigated using DFT (Density Functional Theory).

In this study, n-GCHM and GCHM@Fe3O4 were used to remove Cu(II) and Co(II) metal ions from laboratory-prepared synthetic wastewater. Batch experiments were conducted to obtain the optimum conditions for the Cu(II) and Co(II) metal ions. The effect of parameters such as pH, contact time, and initial concentration were also determined.

The optimal conditions found were 120 minutes of contact time and a pH of 5. The maximum adsorption capacity of Cu(II) and Co(II) was 5.8343 mg/g and 4.7148 mg/g, respectively using n-GCHM while that using GCHM@Fe3O4 the monolayer capacity was 4.7148 mg/g for Cu(II) and 8.1499 mg/g for Co(II). The high percentage removal of Cu(II) was 70.5% with n-GCHM and 89.4% for Co(II) with GCHM@Fe3O4, all to the pH 5. The experimental data fit well to Pseudo-first-order kinetic and Freundlich isotherm models for both metal ions.

The experimental data conformed adequately to the film diffusion model for both metal ions at pH 5 with n-GCHM, but the Co(II) results fit well to the particle diffusion model with GCHM@Fe3O4.

The molecular orbital approach (MOs) has shown that the HOMO and LUMO was located on the arginine (-NCN-) and LUMO on glutamine (-NCO-). The quantum adsorption mechanism has shown that the binding energy of Cu(II) and Co(II) on imine functional group (arginine) was of -60604.399 eV and -53649.06 eV, respectively. On -NCO- functional group (glutamine), the binding energy was of -58587.608 eV and -51632.618 eV, respectively for Cu(II) and Co(II).