Efficient, rapid and simple adsorption method by polydopamine polystyrene nanofibers mat for removal of multi-class antibiotic residues in environmental water

Macro-manufacturing robust and stable metal-organic framework beads for antibiotics removal from wastewater

Metal-organic frameworks (MOFs) have shown great prospects in wastewater remediation. However, the easy aggregation, difficult separation and inferior reusability greatly limit their large-scale application. Herein, we proposed a facile, green and low-cost strategy to construct robust and stable MOF-based hydrogel beads (Fe-BTC-HBs) in a gram scale, and employed them to remove antibiotics from wastewater. As a result, the Fe-BTC-HBs demonstrated outstanding adsorption capacity for both ofloxacin (OFL) and tetracycline (TC) (281.17 mg/g for OFL and 223.60 mg/g for TC) under a near-neutral environment. The main adsorption mechanisms of OFL and TC were hydrogen bonding and π-π stacking interaction. Owing to its macroscopic granule and stable structure, Fe-BTC-HBs can be separated rapidly from wastewater after capturing antibiotics, and more than 85% adsorption capacity still remained after six cycles, while the powdered Fe-BTC only showed less than 6% recovery efficiency with massive weight loss (around 92%). In real industrial effluent, the adsorption performance of Fe-BTC-HBs toward two antibiotics exhibited negligible decreases (2.9% for OFL and 2.2% for TC) compared with that in corresponding solutions. Furthermore, Fe-BTC-HBs also had appealing economic and environmental benefit. Overall, the macro-manufactured MOF beads have the promising potential for the large-scale wastewater treatment.

Mixed-Solvent-Mediated Strategy for Enhancing Light Absorption of Polydopamine and Adhesion Persistence of Dopamine Solutions

Mussel-inspired polydopamine (PDA) and its derivative materials have exhibited a huge potential as a facile and versatile route to fabricate multifunctional coatings on virtually any substrate surface. However, their performance and applicability are frequently obstructed by limited optical absorption in visible regions of PDA and poor surface adhesion persistence of dopamine solutions. Herein, we report a facile strategy to improve these problems by rationally regulating the dopamine polymerization pathway through mixed-solvent-mediated periodate oxidation of dopamine. The spectral analysis, ultrahigh-performance liquid chromatography coupled with high-resolution mass spectrometry, and density functional theory simulations systematically demonstrate that the mixed-solvent reaction systems can effectively accelerate the periodate-induced formation of cyclized moieties in the PDA microstructure and inhibit their further oxidative cleavage, thus contributing to narrowing the inherent energy band gap of PDA and improving the long-lasting surface deposition performance of aged dopamine solutions. Moreover, the newly constructed cyclized species-rich PDA coatings have excellent surface uniformity and significantly enhanced chemical stability. Benefiting from these fascinating properties, they have been further used for permanent dyeing of natural gray hair with remarkably improved blackening effect and excellent practicability, which exhibited their promising prospect in real-world applications.

A study on the adsorption behaviors of three hydrophobic quinolones by ordered mesoporous CMK-3

In this work, a series of ordered mesoporous carbon nanomaterials (CMK-3) have been synthesized by a hard-template method at temperatures of 80 °C, 100 °C and 130 °C, which can serve as adsorbents for efficient adsorption of quinolones in aqueous solutions. The physicochemical properties and the morphologies of these CMK-3 have been well characterized, showing mesoporous channels with the specific surface area reaching up to 1290 m²/g. Adsorption studies have been performed on three hydrophobic quinolones: norfloxacin (NOR), ciprofloxacin (CIP) and enrofloxacin (ENR), with the adsorption capacities of 403 mg/g, 479 mg/g and 510 mg/g, respectively, at room temperature. The adsorption kinetics of the three quinolones are in accordance with the pseudo-second kinetic model, and the adsorption isotherm curves conform to Langmuir isotherm model. Significantly, the adsorption thermodynamics confirms that the adsorption processes are spontaneous endothermic. Finally, the adsorption mechanism has been discussed, which can be attributed to the synergistic effect of pore diffusion, hydrophobic bond, and electron donor-acceptor interaction.

Enhanced carriers separation in novel in-plane amorphous carbon/g-C3N4 nanosheets for photocatalytic environment remediation

Although carbon-based materials/g-C₃N₄ heterostructure with an up-down structure in space can inhibit the recombination of charge carriers, the electron transfer is still suppressed by the interlayer van der Waals force. Herein, amorphous carbon is successfully introduced into the g-C₃N₄ nanosheet (CNS) by a self-conversion process to form an in-plane heterostructure of amorphous carbon/g-C₃N₄ (CNSC₁). Kelvin probe atomic force microscopy (KPFM) and density functional theory (DFT) confirm that g-C₃N₄ and amorphous carbon are in the same plane, which can generate the surface electric field of CNSC₁, providing a driving force for the transfer of electrons from g-C₃N₄ to amorphous carbon. Meanwhile, the sp²-hybridized π conjugation bond of amorphous carbon can rapidly capture and store photogenerated electrons, inhibiting charge carrier recombination and thus generating more electrons to facilitate the yield of hydroxyl radicals. The photocatalytic activity of CNSC₁ for the degradation of tetracycline and rhodamine B is 2.7 times and 4.8 times higher than that of CNS, respectively, due to the efficient interface charge separation. This work is expected to provide a new idea for the combination of carbon materials and g-C₃N₄.

New Polymeric Adsorbents Functionalized with Aminobenzoic Groups for the Removal of Residual Antibiotics

In this paper, we present the synthesis of new polymeric adsorbents derived from macroporous chloromethylated styrene–divinylbenzene (DVB) copolymers with different cross-linking degrees functionalized with the following aminobenzoic groups: styrene—6.7% DVB (PAB1), styrene—10% DVB (PAB2), and styrene—15% DVB (PAB3). The new polymeric products, PAB1, PAB2, and PAB3, were characterized by FTIR spectroscopy, thermogravimetric analysis, and EDX, SEM, and BET analysis, respectively. The evolution of the functionalization reaction was followed by FTIR spectroscopy, which revealed a decrease in the intensity of the γCH₂Cl band at 1260 cm⁻¹, and, simultaneously, the appearance of C=O carboxylic bands from 1685–1695 cm⁻¹ and at 1748 cm⁻¹. The thermal stability increased with the increase in the cross-linking degree. The data obtained from the EDX analysis of the novel cross-linked copolymers confirmed the functionalization with aminobenzoic groups through the presence and content of nitrogen, as follows: PAB1: N% = 0.47; PAB2: N% = 0.85; and PAB3: N% = 1.30. The adsorption performances of the novel polymeric adsorbents, PAB1, PAB2, and PAB3, were tested in the adsorption of three antibiotics, tetracycline, sulfamethoxazole, and amoxicillin, from aqueous solutions, by using extensive kinetic, equilibrium, and thermodynamic studies. The best adsorption capacity was demonstrated by the tetracycline. Amoxicillin adsorption was also attempted, but it did not show positive results.