Abstract
Over the years, the Industrial Revolution has led affluent consumer societies to be extensively dependent on material products for improved quality of life. Many vital needs such as food, water, medication, shelter, clothing and fuel are essential materials. Thus, there has been a global increase in production and manufacturing industries to accommodate the increasing demand for products by the growing population. This has led to an undeniable need for the production and use of these chemicals. However, their increasing presence in the ecosystem has become a significant concern to human health and the environment. The continuous release of chemicals seen in recent decades can induce acute toxicity, and the bioaccumulation and biomagnification of contaminants can give rise to undesirable long-term effects. As a result, much attention has been paid to these emerging contaminants (ECs) due to their considerably increasing detection in various environments, especially in aqueous environments.
Moreover, these ECs are present in the environment at trace levels, and their fate and impact of these contaminants in the environment are not well documented and understood. Thus, more advanced technologies are needed to study and remediate the environments of these compounds. As such, the current study aimed to develop improved methods of extraction and removal technologies of ECs in water systems. Thus, magnetic mesoporous carbons nanocomposites derived from PET waste plastic bottles and acid mine drainage (AMD-mag@PET-MPC, AMD-mag@PET-MPAC-25%, and AMD-mag@PET-MPAC-50%) synthesised for the analysis and the adsorptive removal of ECs. The adsorbent materials were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (SEM/EDS), Transmission electron microscope (TEM), Zeta potential and Brunauer–Emmett–Teller (BET). The adsorbent materials displayed attractive characteristics, including porous nature, high surface area, high loading capacity, thermal stability and reusability.
The adsorbent materials were applied for adsorptive removal of perfluorooctanoic acid (PFOA), perfluoroundecanoic acid (PFUnDA) and fluoroquinolone antibiotics, acetaminophen (ACT), caffeine (CAF), and carbamazepine (CBZ). The analytes were analyzed using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) and high-performance liquid chromatography-diode array
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detector (HPLC-DAD). All materials were evaluated in terms of adsorption capacity and their suitability for removing the targeted analytes. The obtained results revealed that the AMD-mag@PET-MPAC-50% was better suited for the removal of ACT, CAF and CBZ, achieving around 99.5% removal efficiency (%RE) and 106 mg/g maximum adsorption capacity. The AMD-mag@PET-MPC adsorbent material was suitable for PFAS removal and obtained 97.6% removal and up to 356 mg/g adsorption capacity.
Similarly, AMD-mag@PET-MPAC-25% best fitted the removal of the fluoroquinolone (FQ) antibiotics and attained >95% removal efficiency and 337 mg/g adsorption capacity. The adsorption mechanisms were driven by pore filling, hydrogen bonding and electrostatic interactions between the targeted analytes and respective adsorbents. The applicability of these materials was assessed by employing them in real water matrices.
In addition to adsorptive removal, the prepared sorbent materials were further applied for the development of a sample preparation method that is magnetic solid phase extraction (MSPE) for the extraction and preconcentration of fluoroquinolone antibiotics and perfluoroalkyl substances before UHPLC-MS/MS detection and quantification. A multivariate approach was applied to optimize the method and investigate the influential parameters. Under optimal conditions, the MSPE/UHPLC-MS/MS method was validated in terms of limit of detection (LOD), limit of quantification (LOQ), accuracy, linearity and precision. When applied to PFAS analysis, the LOD and LOQ were 0.5-1.90 and 1.7-0.6 ng/L, respectively, with a linearity range of 0.001-5 μg/L with a correlation coefficient (R2) of 0.9974 and the relative standard deviation (%RSD) of 1.6-1.8. Similarly, the FQ analysis attained 0.6-2.1 LODs and 2.0-7.0 LOQs, a linearity range of 0.0003-100 μg/L with 0.9979 R2 value and the %RSD of 1.2-2.6. The methods were applied for the determination of fluoroquinolone antibiotics and perfluoroalkyl substances in wastewater and river water samples and achieved recoveries of up to 104 and 101%, respectively.
The bioremediation of these targeted analytes was also investigated using Histosol OP-BIO10. The physicochemical properties such as pH, conductivity, chemical oxygen demand (COD), phosphates, total dissolved solids (TDS) and turbidity were determined before and after the bioremediation process. The results obtained revealed that the histosol effectively reduced the phosphates, turbidity, and COD levels of the samples while the TDS and conductivity levels remained relatively the same. Furthermore, the bioremediation results revealed that the Histosol OP-BIO10 could remove fluoroquinolone antibiotics more and achieved above 70% removal efficiency compared to the other pollutants, attaining around 20% removal efficiency.