Co-contaminant effects on ofloxacin adsorption onto activated carbon, graphite, and humic acid

Assessing sorption of fluoroquinolone antibiotics in soils from a Kd compilation based on pure organic and mineral components

The presence of fluoroquinolone (FQ) antibiotics in soils may cause a threat to human health due to overexposure and the generation of antibiotic resistance genes. Understanding their sorption behavior in soils is important to predict subsequent FQ (bio) availability. Here, FQ sorption in pure soil organic (i.e., humic substances) and mineral (i.e., metal oxides; phyllosilicates) components is evaluated through a solid-liquid distribution coefficient (Kd (FQ)) dataset consisting of 243 entries originated from 80 different studies, to elucidate their respective contribution to the overall Kd (FQ) in bulk soils. First, different factors affecting FQ sorption and desorption in each of these soil phases are critically discussed. The strong role of pH in Kd (FQ), due to the simultaneous effect on both FQ speciation and surface charge changes, encouraged the derivation of normalized sorption coefficients for the cationic, zwitterionic and anionic FQ species in humic substances and in different phyllosilicates. Kd (FQ) in metal oxides revealed a key role of metal nature and material specific surface area due to complexation sorption mechanisms at neutral pH. Cumulative distribution functions (CDF) were applied to each dataset to establish a sorption affinity range for each phase and to derive best estimate Kd (FQ) values for those materials where normalized sorption coefficients to FQ species were unavailable. The data analysis conducted in the different soil phases set the basis for a Kd (FQ) prediction model, which combined the respective sorption affinity of each phase for FQ and phase abundance in soil to estimate Kd (FQ) in bulk soils. The model was subsequently validated with sorption data in well characterized soils compiled from the literature.

Interaction of Antibiotics and Humic Substances: Environmental Consequences and Remediation Prospects

The occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystems. Humic substances (HS) influence the mobility, reactivity, and bioavailability of antibiotics in the environment significantly due to their interaction. As a result, HS can affect the dissemination of antibiotic-resistance genes, which is one of the main problems arising from contamination with antibiotics. The review provides quantitative data on the binding of HS with fluoroquinolones, macrolides, sulfonamides, and tetracyclines and reports the proposed mechanisms of their interaction. The main issues of the quantification of antibiotic-HS interaction are discussed, which are a development of standard approaches and the accumulation of a dataset using a standard methodology. This would allow the implementation of a meta-analysis of data to reveal the patterns of the binding of antibiotics to HS. Examples of successful development of humic-based sorbents for fluoroquinolone and tetracycline removal from environmental water systems or polluted wastewaters were given. Data on the various effects of HS on the dissemination of antibiotic-resistance genes (ARGs) were summarized. The detailed characterization of HS properties as a key point of assessing the environmental consequences of the formation of antibiotic-HS complexes, such as the dissemination of antibiotic resistance, was proposed.

Highly Effective Removal of Ofloxacin from Water with Copper-Doped ZIF-8

Residual antibiotics in wastewater have gained widespread attention because of their toxicity to humans and the environment. In this work, Cu-doped ZIF-8s (Cu-ZIF-8s) were successfully synthesized by the impregnation of Cu²⁺ in ZIF-8 and applied in the removal of ofloxacin (OFX) from water. Remarkably, excellent adsorption performance was obtained in Cu-ZIF-8s, especially for Cu-ZIF-8-1, in which the adsorption capacity (599.96 mg·g⁻¹) was 4.2 times higher than that of ZIF-8 and superior to various adsorbents reported previously. The adsorption kinetics and adsorption isotherm follow the pseudo-second-order model and the Langmuir model, respectively. Furthermore, the removal efficiencies of OFX in Cu-ZIF-8-1 reached over 90% at low concentrations. It was revealed that electrostatic interaction and complexation play important roles in the adsorption process. In addition, the material can be regenerated by simple methods. Therefore, the obtained Cu-doped MOFs may have a promising application in the treatment of antibiotic-containing wastewater.

Impact of Zr6 Node in a Metal-Organic Framework for Adsorptive Removal of Antibiotics from Water

Quinolone-based antibiotics commonly detected in surface, ground, and drinking water are difficult to remove and therefore pose a threat as organic contaminants of aqueous environment. We performed adsorptive removal of quinolone antibiotics, nalidixic acid and ofloxacin, using a zirconium-porphyrin-based metal-organic framework (MOF), PCN-224. PCN-224 exhibits the highest adsorption capacities for both nalidixic acid and ofloxacin among those reported for MOFs to date. The accessible metal sites of Zr metal nodes are responsible for efficient adsorptive removal. This study offers a pragmatic approach to design MOFs optimized for adsorptive removal of antibiotics.

Synthesis of molecularly imprinted polymers for extraction of fluoroquinolones in environmental, food and biological samples

In recent years, fluoroquinolones have been found present in important water resources and food sources which compromises the food quality and availability, thereby, causing risks to the consumer. Despite the recent advancement in the development of analytical instrumentation for routine monitoring of fluoroquinolones in water, food, and biological samples, sample pre-treatment is still a major bottleneck of the analytical methods. Therefore, fast, selective, sensitive, and cost-effective sample preparation methods prior to instrumental analysis for fluoroquinolones residues in environmental, food and biological samples are increasingly important. Solid-phase extraction using different adsorbents is one of the most widely used pre-concentration/clean-up techniques for analysis of fluoroquinolones. Molecularly imprinted polymers (MIPs) serve as excellent effective adsorbent materials for selective extraction, separation, clean-up and preconcentration of various pollutants in different complex matrices. Therefore, synthesis of MIPs remains crucial for their applications in sample preparation as this offers much-needed selectivity in the extraction of compounds in complex samples. In this study, the progress made in the synthesis of MIPs for fluoroquinolones and their applications in water, food and biological samples were reviewed. The present review discusses the selection of all the elements of molecular imprinting for fluoroquinolones, polymerization processes and molecular recognition mechanisms. In conclusion, the related challenges and gaps are given to offer ideas for future research focussing on MIPs for fluoroquinolones.

Sorption of pharmaceuticals and personal care products on soil and soil components: Influencing factors and mechanisms

The sorption of pharmaceuticals and personal care products (PPCPs) on soil and soil components makes an important contribution to the fate, migration and bioavailability of PPCPs. Previous reviews have mostly focused on the sorption of PPCPs on single soil components (e.g., minerals and soil organic matter). However, the sorption of PPCPs within the whole soil system has not been systematically analyzed. This paper reviews the recent progress on PPCP sorption on soil and soil components. We have evaluated the sorption of a wide range of PPCPs in research fields that are usually considered in isolation (e.g., humic acids (HAs), montmorillonite, kaolinite, and goethite), and established a bridge between PPCPs and sorbent. The sorption mechanisms of PPCPs, e.g., cation exchange, surface complexation, electrostatic interaction and hydrogen bonding, are discussed and critically evaluated. We also assessed the influence of environmental factors (pH, ionic strength, organic matter and temperature) on sorption. This review summarizes the knowledge of PPCPs sorption on soil gained in recent years, which can provide new strategies for solving the problem of antibiotic pollution.

Enhanced adsorption of hydrophobic organic contaminants by high surface area porous graphene

The relatively low surface area and micropore volume of graphene nanosheets (GNS) limit their potential application as effective adsorbents for hydrophobic organic contaminants (HOCs). In this study, KOH etching was used to develop activated GNS (K-GNS) for adsorption of model HOCs such as naphthalene, phenol, nitrobenzene, and bisphenol A. After activation, the specific surface area (SSA) of K-GNS increased to 885 m²/g, which was three times larger than that of GNS. The micropore volume of K-GNS substantially increased and the C/O ratio was doubled. Accordingly, the adsorption capacity of these HOCs on K-GNS was larger than that of pristine GNS (P-GNS) by 2-8 times. The kinetic data was fitted by the pseudo-second-order model, and the adsorption isotherms of HOCs on P-GNS and K-GNS were fitted by the Freundlich model. The desorption studies showed the K-GNS had a lower rate of release than P-GNS. The high adsorption of naphthalene, phenol, nitrobenzene, and bisphenol A on P-GNS and K-GNS is dominated by hydrophobic and π-π interactions. Additionally, the π-π EDA interaction and hydrogen bond between K-GNS and substituents cannot be ignored.

Comparison of Sorption to Carbon-Based Materials and Nanomaterials Using Inverse Liquid Chromatography

Sorption studies of carbon-based materials and nanomaterials are typically conducted using batch experiments, but the analysis of weakly sorbing compounds may be challenging. Column chromatography represents a promising complement as higher sorbent to solution ratios can be applied. The sorbent is packed in a column, and sorption data are calculated by relating sorbate retention times to that of a nonretarded tracer. In this study, sorption of heterocyclic organic compounds (pyrazole, pyrrole, furan, and thiophene) by carbon-based materials (activated carbon, biochar, and graphite) and nanomaterials (functionalized carbon nanotubes and graphene platelets) was compared for the first time using column chromatography. D₂O was used as nonretarded tracer. Sorption isotherms were nonlinear and described well by the Freundlich model. Sorption differed between the materials regarding determined Freundlich coefficients ( K_f) by more than two orders of magnitude for isotherms in a similar concentration range. Normalization of K_f with the surface area of the sorbent significantly reduced but did not remove the differences between the sorbents. Overall, column chromatography represents the opportunity to study sorption of weakly sorbing compounds to diverse carbon-based sorbent materials with a single experimental approach, which is challenging in batch experiments because of the very different sorption properties of some sorbent materials.