FIRST INVESTIGATION OF MONTMORILONITE-CARRAGEENAN BASED NANOCOMPOSITES WITH ELECTRONIC STRUCTURE COMPUTATIONS

• Main Author: Nauval Farras R, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/57463
• Institution: Institut Teknologi Bandung

Liquid waste which mostly contains dyes is a big environmental problem in Indonesia. One of the proposed solutions is to absorb liquid waste to purify water using a carrageenan-based gel as an absorbent. That material is chosen because it is cheap and abundant. However, carrageenan breaks down easily after being in the water for some time. Therefore, it is proposed to prepare an MMT-carrageenan nanocomposite. In the manufacture of a nanocomposite, it is necessary to know the suitability of properties between the composite materials. For this final project, this is done by examining the mechanism of interaction, changes in structure, and changes in properties due to interaction with water. Furthermore, these results can also be used to estimate the interaction mechanism between the material and the dye-material. This research was conducted by simulation on a computer. There are many methods to choose from, which are classified as HF, post-HF (PHF), and DFT methods. All three have their own advantages and disadvantages in terms of accuracy and usage of computing power. In this final project, the numerical method is determined which is then used to simulate the MMT, carrageenan, MMT-water system, and MMT-water system. The purpose of the simulation is to determine the interaction mechanism, changes in molecular and electronic structures, changes in electronic (bandwidth) and optical (absorbance) properties, and estimates of the interaction mechanism between the two materials and the dye-material. The results obtained are as follows. Of the methods tested, the HF method is fast and less accurate, the PHF method is slow and accurate, and the DFT method is fast and accurate. Finally, the PBE method, which is a variation of DFT, was chosen. Simulations on montmorillonite, carrageenan, montmorillonite-water system, and carrageenan-water system gave the following results. First, water is adsorbed byboth materials by forming hydrogen bonds. As a result, MMT undergoes compaction whereas carrageenan stretches. This causes MMT to be durable and strong while carrageenan is easily destroyed. Then, the MMT underwent a drastic change in its electronic structure, so that its electrical conductivity changed (insulator to conductor). Carrageenan does not experience it so that the electrical conductivity is the same (semiconductor). Changes in optical properties followed changes in electrical conductivity, with the MMT absorbance before adsorption in the range 46 to 257 nm and afterward at 96 to 353 nm, with one peak at 1604 nm. Carrageenan absorbance was in the range of 68 nm to 411 nm before water adsorption and 79 to 416 nm after. These results were used to estimate the interaction of both material and material-dye.