ADSORPTION KINETICS OF LOW MOLECULAR WEIGHT POLYCYCLIC AROMATIC HYDROCARBONS ONTO PHENYL ACETIC ACID MODIFIED BIOSILICA FROM CYCLOTELLA STRIATA TBI DIATOM

• Main Author: Yusuf Fakhrizal, Zaki
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/81568
• Institution: Institut Teknologi Bandung

Low molecular weight (LMW) polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene, anthracene, and fluorene, are volatile, carcinogenic, and highly toxic. One of the methods to concentrate and purify LMW PAHs as a pre-concentration stage of samples from polluted environments is the adsorption method. Biosilica is a biosorbent from diatomaceous microalgae that has the potential to be used as a PAH adsorbent because it has a large surface area and can be modified with hydrophobic groups that can interact with LMW PAH. In this study, biosilica was extracted from the diatom Cyclotella striata from Teluk Bidadari Indonesia (TBI), and then activated to add silanol groups on its surface, and subsequently modified with phenyl acetic acid as a hydrophobic compound that can interact with LMW PAH. Furthermore, phenyl acetic acid-modified biosilica was characterized and evaluated in terms of adsorption performance as anthracene, phenanthrene, and fluorene adsorbent. Extraction of biosilica from biomass by nitric acid oxidation followed by calcination at 550 °C resulted in pure biosilica. Biosilica extraction was successfully carried out with a productivity of 2 grams of biosilica for every 100 grams of Cyclotella striata biomass. The FTIR spectrum of activated biosilica showed an increase in the intensity of the Si-OH peak at wavenumber 960 cm-1 . Meanwhile, the FTIR spectrum of phenyl acetic acidmodified biosilica indicates the presence of new groups in the sample, compared to pure biosilica, namely the C=O group absorbing at 1700 cm-1 and C-H at 1400 cm-1 . This indicates that the modification of biosilica with phenyl acetic acid has been successfully carried out. The adsorption kinetics study of anthracene, phenanthrene, and fluorene on pure biosilica and phenyl acetic acid modified biosilica followed a pseudo second-order kinetics model. Based on the kinetic model, the modified biosilica had higher adsorption capacity compared to pure biosilica towards anthracene (73.7 vs. 60.6 mg/g), phenanthrene (66.7 vs. 51.6 mg/g), and fluorene (57.7 vs. 40.2 mg/g). Phenyl acetic acid modification slowed down the adsorption process of anthracene and fluorene on biosilica, indicated by a smaller initial adsorption rate compared to pure biosilica. Despite the decrease in adsorption rate, the adsorption half-time of modified biosilica is still quite low, indicating that adsorption still occurs rapidly (3.5–6.5 minutes). Adsorption kinetics modeling with the Weber-Morris intraparticle diffusion model shows that the LMW PAH adsorption process on pure biosilica is limited by three rate-limiting steps, in contrast to modified biosilica which is only limited by two rate-limiting steps.