Effect of molecular structure on the adsorption behavior of sulfanilamide antibiotics on crumpled graphene balls

A robust self-regenerating graphene-based adsorbent for pharmaceutical removal in various water environments

The presence of active pharmaceutical ingredients (APIs) in wastewater effluents and natural aquatic systems threatens ecological and human health. While activated carbon-based adsorbents, such as GAC and PAC, are widely used for API removal, they exhibit certain deficiencies, including reduced performance due to the presence of natural organic macromolecules (NOMs) and high regeneration costs. There is growing demand for a robust, stable, and self-regenerative adsorbent designed for API removal in various environments. In this study, we synthesized a self-generating metal oxide nano-composite (S-MGC) containing titanium dioxide (TiO2) and silicon dioxide (SiO2) combined with 3D graphene oxide (GO) to adsorb APIs and undergo regeneration via light illumination. We determined optimal TiO2:SiO2:GO compositions for the S-MGCs through experiments using a model contaminant, methylene blue. The physical and chemical properties of S-MGCs were characterized, and their adsorption and photodegradation capabilities were studied using five model APIs, including sulfamethoxazole, carbamazepine, ketoprofen, valsartan, and diclofenac, both in single-component and multi-component mixtures. In the absence of TiO2/SiO2, 3D graphene oxide (CGB) displayed better adsorption performance compared to GAC, and S-MGCs further improve CGB's adsorption capacity. This performance remained consistent in two complex water environments: aqueous solutions at varying NOM levels and artificial urine. TiO2 supported on the GO surface exhibits similar photocatalytic activity to suspended TiO2. In a continuous fixed-bed column test, S-MGCs demonstrated robust API adsorption performance that is maintained in the presence of NOM or urine, and can be regenerated through multiple cycles of adsorption and light illumination.

The Preparation of Crumpled Graphene Oxide Balls and Research in Tribological Properties

In this study, crumpled graphene oxide balls (CGBs) were prepared via capillary compression using a rapidly evaporating aerosol droplet method. The CGBs were observed using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The size distributions of crumpled particles were obtained using a laser nanometer particle size analyzer (DLS). The dispersibility of the water and the ionic liquid (IL) was tested by ultrasonic dispersion. The tribological properties of water or ionic liquids containing crumpled graphene oxide ball additives (W/IL-CGB) were tested by a reciprocating friction tester and compared with water/ionic liquids with graphene oxide. The morphology of the wear scar was observed by a three-dimensional optical microscope and its lubrication mechanism was analyzed. The results show that the CGBs were successfully prepared by rapid evaporation of aerosol droplets, and the obtained CGBs were crumpled paper spheres. The CGBs had good water dispersion and ionic liquid dispersion, and IL-CGB has excellent anti-friction and anti-wear effects on steel-steel friction pairs. During the friction process, the CGB was adsorbed at the interface of the steel-steel friction pair to form a protective layer, which avoids the direct contact of the friction pair, thereby reducing friction and wear.

Surface engineering of multifunctional nanostructured adsorbents for enhanced wastewater treatment: A review

Rapid urbanization and industrialization have significantly contributed to the contamination of the environment through the discharge of wastewater containing various pollutants. The development of high-performance surface functional nanostructured adsorbents is of wide interest for researchers. Therefore, we explore the significant advancements in this field, focusing on the efficiency of nanostructured materials, as well as their nanocomposites, for wastewater treatment applications. The crucial role of surface modification in enhancing the affinity of these nanostructured adsorbents towards targeted pollutants, addressing a key bottleneck in the utilization of nanomaterials for wastewater treatment, was specifically emphasized. In addition to highlighting the advantages of surface engineering in enhancing the efficiency of nanostructured adsorbents, this review also provides a comprehensive overview of the limitations and challenges associated with surface-modified nanostructured adsorbents, including high cost, low stability, poor scalability, and potential nanotoxicity. Addressing these limitations is essential for realizing the commercial viability of these state-of-the-art materials for large-scale wastewater treatment applications. This review also thoroughly discusses the potential scalability and environmental safety aspects of surface-modified nanostructured adsorbents, offering insights into their future prospects for wastewater treatment. It is believed that this review will contribute significantly to the existing body of knowledge in the field and provide valuable information for researchers and practitioners working in the area of environmental remediation and nanomaterials.

A review on carbon-based biowaste and organic polymer materials for sustainable treatment of sulfonamides from pharmaceutical wastewater

Frequent detection of sulfonamides (SAs) pharmaceuticals in wastewater has necessitated the discovery of suitable technology for their sustainable remediation. Adsorption has been widely investigated due to its effectiveness, simplicity, and availability of various adsorbent materials from natural and artificial sources. This review highlighted the potentials of carbon-based adsorbents derived from agricultural wastes such as lignocellulose, biochar, activated carbon, carbon nanotubes graphene materials as well as organic polymers such as chitosan, molecularly imprinted polymers, metal, and covalent frameworks for SAs removal from wastewater. The promising features of these materials including higher porosity, rich carbon-content, robustness, good stability as well as ease of modification have been emphasized. Thus, the materials have demonstrated excellent performance towards the SAs removal, attributed to their porous nature that provided sufficient active sites for the adsorption of SAs molecules. The modification of physico-chemical features of the materials have been discussed as efficient means for enhancing their adsorption and reusable performance. The article also proposed various interactive mechanisms for the SAs adsorption. Lastly, the prospects and challenges have been highlighted to expand the knowledge gap on the application of the materials for the sustainable removal of the SAs.

Influences of dissolved organic matters on the adsorption and bioavailability of sulfadiazine: Molecular weight- and type-dependent heterogeneities

The bioavailability of contaminants in aquatic environments was highly related with the existing forms (soluble or adsorbed) and properties of dissolved organic matters (DOMs). In this study, the molecular weight (MWs)-dependent effects of DOMs on the adsorption and bioavailability of sulfadiazine were explored. Colloid ZnO and Al2O3 were employed as the representative colloidal particles, and algae-derived organic matter (AOM) and humic acid (HA) were selected as typical autochthonous and allochthonous DOMs. The ultrafiltration procedure was applied to divide the bulk DOMs into high MW (HMW-, 1 kDã0.45 μm) and low MW (LMW-, <1 kDa) fractions. Results showed that HMW-DOM contained more aromatic and protein-like substances as compared to the LMW counterparts. In addition, presence of AOM promoted sulfadiazine adsorption capabilities by 1.19-4.54 folds and mitigated the inhibition ratio by 0.56-0.78 folds, whereas those of HA inhibited sulfadiazine adsorption by 0.27-0.84 folds and enhanced the biotoxicity by 1.21-1.45 folds. Regardless of different DOM types, HMW-fraction exhibited highest effects on sulfadiazine adsorption and bioavailability, followed by the bulk- and LMW-fractions. Two-dimensional correlation spectroscopy showed that sulfadiazine was adsorbed on colloidal surfaces prior to AOM, and the subsequent adsorption of AOM can provide additional sites for sulfadiazine adsorption, which decreased the concentrations of aqueous sulfadiazine as well as the biotoxicity to Microcystis aeruginosa (M. aeruginosa). The HA, however, was preferentially adsorbed on colloidal surfaces, which hindered the subsequent sulfadiazine adsorption and resulted in a high sulfadiazine abundance in aqueous solution as well as the enhanced biotoxicity to M. aeruginosa. This study highlighted the importance of the types and MWs of DOMs in influencing the behaviors and ecological effects of aquatic contaminants.

Efficient adsorptive removal of used drugs during the COVID-19 pandemic from contaminated water by magnetic graphene oxide/MIL-88 metal-organic framework/alginate hydrogel beads

Currently, the presence of drugs used in the COVID-19 pandemic in water bodies is worrisome due to their high toxicity, which necessitates their critical removal by developing highly efficient adsorbents. Hence, in this study, alginate hydrogel beads of magnetic graphene oxide@MIL-88 metal-organic framework (GO@Fe3O4@MIL-88@Alg) were prepared for the first time and then utilized as a new absorption system for the removal of COVID-19 drugs such as doxycycline (DOX), hydroxychloroquine (HCQ), naproxen (NAP), and dipyrone (DIP) from aqueous solutions by batch adsorption manner. The effects of different experimental factors, such as adsorbent dosage, contact time, pH, drug concentration, temperature, ionic strength, presence of an external magnetic field (EMF), and magnet distance from the adsorption flask were optimized for the removal of COVID-19 drugs. The adsorption equilibrium isotherm proved that the adsorption process of DOX, HCQ, NAP, and DIP drugs on GO@Fe3O4@MIL-88@Alg hydrogel beads conformed to the Langmuir model and followed the pseudo-second-order adsorption kinetics. The maximum adsorption capacities of DOX, HCQ, NAP, and DIP drugs obtained for GO@Fe3O4@MIL-88@Alg hydrogel beads with the Langmuir model were 131.57, 79.92, 55.55, and 49.26 mg/g at 298 K, respectively. The thermodynamic study suggested a spontaneous endothermic adsorption process. Also, the conclusion from this study confirmed the validity of GO@Fe3O4@MIL-88@Alg hydrogel beads for excellent removal of COVID-19 drugs from water samples. It was also found that the GO@Fe3O4@MIL-88@Alg hydrogel beads could be reused with satisfactory removal efficiency in six cycles. Based on the study, the GO@Fe3O4@MIL-88@Alg hydrogel beads could be considered a sustainable, simple, economical, environmentally friendly absorption system for the removal of pharmaceutical contaminants from water.