THE EFFECT OF MESOPOROUS SILICA PORE STRUCTURE ON ADSORPTION OF AMOXICILLIN

• Main Author: Ilmi, Thalabul
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/51980
• Institution: Institut Teknologi Bandung

Nowadays, mesoporous silica is one of the materials that is widely developed and researched because it has good thermal and mechanical stability and has a unique diversity of pore structures. Two of them are KCC-1 and MCM-41 silica. In this study, KCC-1 silica was synthesized using the solvothermal method while MCM- 41 silica using the non-solvothermal method (without heating) with the same silica and surfactant sources, namely TEOS and CTAB. The results obtained from both products are white fine grains. To determine the success of the synthesized product, characterizations such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been carried out. The image obtained shows that KCC-1 silica has bicontinuos concentric lamellar (bcl) morphology and MCM-41 silica has irregular morphology with hexagonal pores. Based on observations on the electron microscopy, this silica has a different pore structure. Silica KCC-1 was observed to have an open pore structure (open channel) while MCM-41 had a closed pore structure (closed channel). The effect of these differences in pore structure was studied through adsorption studies on amoxicillin compounds. After adsorption, the silica KCC-1 and MCM-41 seemed less able to adsorb amoxicillin. Therefore, it is necessary to modify or functionalize the surface of mesoporous silica with organosilanes, namely APTES, to increase its adsorption capability. To determine the success of the modification, tests such as physical tests and IR spectroscopic measurements have been carried out. The physical test was carried out using two types of solvents with different polarity, namely water and toluene. The results showed that the modified silica was dispersed in the organic phase (toluene), which means that the hydrophobicity of the material had increased. This result is also supported by the IR spectrum, namely the emergence of new peaks such as CH stretching vibrations in the wave number range (2900-3000 cm-1), NH2 bending and CH2 bending in the wave number range (1450-1700 cm-1) and there is a decrease in the intensity of Si-OH vibrations at 950 cm-1. From the results of thermogravimetric characterization (TGA), the propyl amine decomposition (APTES) was obtained at 7,66% for KCC-1 while for MCM-41 at 7,14%. This data shows that the amount of propyl amine (APTES) bound to mesoporous silica is almost the same. The adsorption studies carried out in this study consisted of isotherm, kinetics and thermodynamics. Based on the results of the isotherm curve, the qm MCM-41- APTES (184 mg g-1) was better than KCC-1-APTES (119 mg g-1), with the Langmuir model as the adsorption isotherm model that was closest to the experimental data. This result is influenced by differences in the pore structure of silica. With the presence of organic components in the pores of MCM-41 (closed channel), a hydrophobic cavity will be formed which can trap passing adsorbate molecules, so that adsorption will be easier than in open pore structures (KCC-1). However, the kinetics results show that KCC-1-APTES has a faster equilibrium adsorption rate than MCM-41-APTES, with a pseudo-second order kinetics model. This is due to the diffusion of adsorbate in the pore structure that is open (open channel) easier than the one that is closed (closed channel). The adsorption mechanism that occurs can go through several stages, namely film diffusion, intraparticle diffusion and adsorption on the inside of the material surface. The thermodynamic results showed that the adsorption was spontaneous (?Go KCC-1- APTES respectively are -30,68 , -31,93 , -33,18 kJ/mol and ?Go MCM-41-APTES respectively are -31,35 , -33,25 , -35,14 kJ/mol), the degree of irregularity increased (?So KCC-1-APTES is 125 J/mol K and ?So MCM-41-APTES is 189,71 J/mol K) and the adsorption process was endothermic (?Ho KCC-1-APTES is 7,20 kJ/mol and ?Ho MCM-41-APTES is 26,13 kJ/mol). Based on the enthalpy (?Ho) value obtained, the adsorbent-adsorbate interactions that occurs in the MCM-41-APTES is stronger than KCC-1-APTES. The interactions that may occur are the hydrogen bonding on MCM-41-APTES and the dipole-dipole interactions on the KCC-1- APTES. So, the difference in the pore structure of mesoporous silica plays an important role in the effect of the value of the adsorption capacity, the rate f adsorption and the adsorbent-adsorbate interactions that occur.