ADSORPTION OF METHYL ORANGE USING ADSORBENT ? CARRAGEENAN MODIFIED WITH POLYETHYLENIMINE AND EPICHLOROHYDRIN

• Main Author: Pricilla Hilmawan, Felice
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/83331
• Institution: Institut Teknologi Bandung

The pollution of dyes in aquatic environments is one of the serious environmental issues, with the potential to harm aquatic ecosystems and the life that depends on them. Methyl orange, one of the azo dyes widely used in industry, is often detected in wastewater. Its presence at high concentrations can have significant negative impacts on aquatic organisms. Therefore, developing effective methods to remove methyl orange from water has become a top priority in environmental research. Adsorption has been recognized as one of the most efficient methods to address this problem, and the selection of an appropriate adsorbent material is key to the method’s success. In this study, ?-carrageenan, a natural polysaccharide derived from seaweed, was chosen as the base material for the adsorbent due to its environmentally friendly nature, low cost, and abundant availability. To enhance its adsorption capacity for methyl orange, ?-carrageenan was modified with polyethyleneimine (PEI) and epichlorohydrin (EPC). PEI was used to improve electrostatic interactions between the adsorbent and dye through positively charged amino groups, while EPC acted as a cross-linking agent to ensure the adsorbent's structure remained stable and did not dissolve in water during the adsorption process. The experimental design used in this study was Central Composite Design (CCD), which is part of Response Surface Methodology (RSM). CCD was chosen for its ability to efficiently optimize the variables influencing the adsorption process. In this study, the variables optimized were the concentrations of PEI and EPC, aiming to achieve optimal conditions that yield maximum adsorption capacity and minimum swelling degree. The results of the experimental design indicated that the optimal composition was 1.6% w/w PEI and 3.2% w/w EPC. The use of CCD not only allowed for the determination of the optimum point but also provided a deeper understanding of the interactions between the variables tested. The characterization of the modified adsorbent was carried out using Fourier Transform Infrared (FTIR) Spectrophotometer and Scanning Electron Microscope (SEM). FTIR was used to identify the functional groups involved in the modification process, while SEM was employed to analyze the surface morphology of the adsorbent. The characterization results showed significant changes in the chemical structure and morphology of the adsorbent, indicating the successful modification with PEI and EPC. The adsorption parameters tested included the solution pH, contact time, initial methyl orange concentration, and adsorbent mass. The experimental results showed that methyl orange adsorption by ?-car/PEI/EPC reached optimal conditions at pH 4, with a contact time of 90 minutes and an adsorbent mass of 0.05 grams. Under these conditions, the obtained swelling degree was 312.18%, indicating that the adsorbent has a high capacity to absorb methyl orange. Additionally, adsorption kinetics and thermodynamics studies were conducted to understand the mechanisms behind the adsorption process. The kinetic study revealed that methyl orange adsorption followed a pseudo-first-order kinetic model, suggesting that the adsorption rate is influenced by the concentration of dye remaining in the solution. Meanwhile, the isotherm study indicated that the adsorption followed the Sips isotherm model, which combines aspects of the Langmuir and Freundlich models, suggesting surface heterogeneity of the adsorbent. Further thermodynamic studies demonstrated that the adsorption process is spontaneous and endothermic. This was evidenced by the negative Gibbs free energy (?G) values at various temperatures, namely ?17.63 kJ/mol at 30, 40, and 50 °C, respectively. The enthalpy (?H) value of 17.58 kJ/mol and entropy (?S) value of 160.19 J/K/mol.