چكيده به لاتين
Environmental pollution with microplastics has become an important environmental challenge in recent years due to its persistence and affinity with pollutants. Therefore, effective methods to remove microplastics are needed. In this study, the efficiency of removing polyethylene terephthalate microplastics from mineral water bottle residues (weathered for 30 days in front of sunlight) was investigated using magnetic magnesium-aluminum layered double hydroxide (Fe3O4@Mg/Al LDH). Layered double hydroxides (LDH) are classified as clay compounds that have a positive charge and layers in which there are interlayer anions with a negative charge. LDH can be considered the most suitable adsorbent for anionic pollutants without any change because it has a high anion exchange capacity. Due to its magnetic properties, iron oxide (Fe3O4) can play an effective role in removing microplastics and facilitating the separation of the adsorbent, which was used as the core of the adsorbent. In this research, Fe3O4@Mg/Al LDH composite was synthesized by solvothermal and coprecipitation methods. Magneticabsorption experiments were performed in discontinuous conditions in a 100 ml beaker with a sample volume of 50 mm and by the classical method (OFAT) by changing one parameter and keeping other parameters constant. The effect of parameters (3-5-7-9-11) pH, adsorbent dose (200-1200) mg per liter, contact time (0-300) minutes, and microplastic concentration (200-1400) mg per liter were investigated. The results showed that with the adsorbent dose of 600 mg per liter, the microplastic concentration of 1000 mg per liter, and the contact time of 300 minutes, with an increase in pH from 3 to 9 due to the electrostatic attraction between the microplastic and the adsorbent, the removal efficiency increased from 31.7% to 45.6%. It also decreased to 34.6% at pH 11 due to electrostatic repulsion. At pH=7, the microplastic concentration was 1000 mg/L and the contact time was 300 minutes, with the increase of the adsorbent dose from 200 mg/L to 1000 mg/L, the removal efficiency reached 10.6% to 100%. Also, by increasing the contact time, under the conditions of pH=7 and the dose of 1000 mg/liter of absorbent and microplastics, the removal efficiency increased and reached 100% in 150 minutes, and also with the increase of the concentration of microplastics from 200 mg/liter to 1000 mg/liter under the conditions of pH=7 and the dose Adsorbent 1000 mg per liter and contact time of 150 minutes, the removal efficiency was still 100% and decreased to 75.84% at the concentration of 1400 mg per liter. Kinetic models were used for adsorption analysis. The pseudo-first-order model had a better match with the laboratory data. The adsorption mechanism was probably physical adsorption (electrostatic interaction and van der Waals forces). The results of FTIR, XRD, SEM, VSM, and TEM tests showed the successful synthesis of Fe3O4@Mg/Al LDH, and SEM, and EDX analysis showed the successful adsorption of the adsorbent on microplastic. This research provides a new insight for purifying water environments from microplastics.
