MAGNETITE (Fe3O4)-CHITOSAN HYBRID NANO PARTICLES USED FOR HUMIC ACID REMOVAL FROM PEAT WATER

• Main Author: AFRITA PURBA SIBORO (NIM : 20513027), SONITA
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/24350
• Institution: Institut Teknologi Bandung

Peat water contains many organic compounds derived from plants decomposition, with the main substance is humic acid. The existence of humic acid in peat water cause it less favorable to be used as drinking water. Humic acid increases the acidity of peat water causing teeth damaging, bonded with heavy metal, and the decomposition process of humic acid produce smelly odor on water. Many purification methods have been carried out to purify peat water, like oxidation, flocculation-coagulation, extracoagulation, however the most optimum and efective way is adsorption method. The most frequently used adsorbent in adsorption method is magnetite, however magnetite is tend to form agregate and is unstable in acid. Thus, to overcome the weaknesses of magnetite, chitosan is used to modify the magnetite surface. Chitosan increase the stability of magnetite in acid and protect magnetite surface to prevent the particles aggregation. Magnetite was sinthesized by mixing FeSO4.7H2O and FeCl3.H2O in aquades at 600 rpm centrifugation. In another vessel, chitosan was dissolved in 0.1% acetic acid. Magnetite chitosan hybrid adsorbent was synthesized by mixing magnetite solution to chitosan solution, added ammonia dropwise, and the solutions was stirred at 1000 rpm for 4 hours. The result was dried to obtain adsorbent powder for characterization. The adsorbent is characterized by FTIR, SEM-EDX, TEM, XRD, and TGA-DTG. The result of FTIR characterization indicate the presence of the interaction between chitosan and magnetit, showed a strong absorption band at 3415.93 cm-1 due to N-H stretching vibrations in magnetit-chitosan molecule that was supposed derived from chitosan (3421.72 cm-1). Chitosan C=O streching vibration (1647.21 cm-1) also can be found at shiftted peak at 1625.99 cm-1 indicated the presence of an interaction between magnetite and chitosan. Others chitosan peaks also can be found at wave number of 1566.20 cm-1 (N-H bending vibration), 1485 cm-1 (C-H bending vibration), 1323.17 cm-1 (C-N streching vibration), and 1068.56 cm-1 (C-O streching vibration). Magnetite Fe-O vibration (578.64 cm-1) also can be found in magnetite-chitosan hybrid at shifted peak 574.79 cm-1. The result of SEM characterization show the differences between magnetite adsorbent before and after hybridized with chitosan. Before hybridized with chitosan, magnetite formed as an aggregate particles with unidentical surface and not in spherical formed. After hybridized with chitosan, magnetite particles became in sperical form, indicated that there are no aggregation between the particles. EDS characterization also showed Fe mass percentage of Fe was decreased from 77.9% in magnetite to 56.31% in magnetite-chitosan hybrid. The decreasing of Fe mass percentage proved the existence of chitosan molecule in magnetite due to the presence of 12.43% mass of C atom. The result of TEM characterization also prove the same result, magnetite-chitosan hybrid was shown as different bright granula with chitosan layer in approximately 5-7 nm and magnetite-chitosan hybrid diameter in approximately 18-23 nm. TGA characterization showed that the remaining of magnetite before hybridized with chitosan was 80,3% at temperature of 996.6oC, whereas the remaining of magnetite-chitosan hybrid was 4.70%. The remaining product after TGA was caused by the decomposition of chitosan at 300oC, therefore the presence of magnetite-chitosan adsorbent became less. The results of DTG showed the presence of decomposition at temperatures of 300 °C which is not present in the magnetite before chitosan hybridized. Batch adsorption experiments were carried out and the optimum humic acid adsorption onto magnetite-chitosan hybrid occured with adsorption capacity of 26.08 mg/g, initial concentration of 20 mg / L, at pH 4 using 0.05 gram dosage of adsorbent and contact time of 60 minutes. Adsorption isotherms studied through the use of graphical methods revealed that the adsorption of humic acid onto magnetite-chitosan follows the Langmuir model, with the maximum adsorption capacity of 42.92 mg/g and correlation coefficient of 0.9972 respectively. Humic acid adsorption from peat water using magnetite-chitosan hybrid yields of 82.62% uptake. This result is better when compared with the absorption capacity of magnetite adsorbent that only 32.87% and chitosan adsorbent that only around 62.96%. The ability of the adsorbent to adsorp humic acid from peat water is lower when compared to standard humic acid of 85.01%, due to the influence of the matrix in peat water. The adsorption of humic acid on magnetite-chitosan was best described with the pseudo-second-order kinetic model with rate constant of 0.71-0.89 g mg-1 min-1.