Prediction of Interaction of Citric Acid Modified Cellulose with Water Region Using Molecular Modelling Technique

Abstract

In this paper, chemically modified cellulose was used instead of cellulose as it offers higher adsorption capacities, great chemical strength and good resistance to heat. As part of Phyto-Adsorption Remediation Method, citric acid modified cellulose (CAMC) was used to treat ferric ion. However, there is a large possibility that CAMC molecule might interact with water molecule that contain hydrogen bond and hence pose as a competitor to ferric acid and reduces the efficiency of CAMC in ferric ion removal. Thus, the aim of this work is to identify the most stable hydrogen bond between CAMC and water, by using a computational technique. The interaction between the water molecules and CAMC was observed by varying the volume of water molecule with modified cellulose by an expansion in amorphous region. The simulation result shows that for water loading less than 20 molecules, the interaction between water molecules and CAMC is higher at temperature 311K, whilst for water loading higher than 20 molecules, the interaction weakens at higher temperature. This work proves that water molecules have the tendency to bind to carboxyl group of glucose, to oxygen of ester and to oxygen of anhydride acid of the CAMC molecule, which might pose a competition for ferric acid removal. The calculation of coordination number has shown that the number of atoms present in the first hydration shell (of radius < 2.5Å) is more as the temperature increases from 298K to 311K, which indicates that the adsorption is better at higher temperature. For hydration shell at radius >2.5Å, cell temperature is not significant to the number of atoms present.