Preparation and application of Mg–Al composite oxide/coconut shell carbon fiber for effective removal of phosphorus from domestic sewage

Long-term nitrogen and phosphorus removal, shifts of functional bacteria and fate of resistance genes in bioretention systems under sulfamethoxazole stress

To understand the long-term performance of bioretention systems under sulfamethoxazole (SMX) stress, an unplanted bioretention system (BRS) and two modified BRSs with coconut-shell activated carbon (CAC) and CAC/zero-valent-iron (Fe⁰) granules (CAC-BRS and Fe/CAC-BRS) were established. Both CAC-BRS and Fe/CAC-BRS significantly outperformed BRS in removing total nitrogen (TN) (CAC-BRS: 82.48%; Fe/CAC-BRS: 78.08%; BRS: 47.51%), total phosphorous (TP) (CAC-BRS: 79.36%; Fe/CAC-BRS: 98.26%; BRS: 41.99%), and SMX (CAC-BRS: 99.74%, Fe/CAC-BRS: 99.80%; BRS: 23.05%) under the long-term SMX exposure (0.8 mg/L, 205 days). High-throughput sequencing revealed that the microbial community structures of the three BRSs shifted greatly in upper zones after SMX exposure. Key functional genera, dominantly Nitrospira, Rhodoplanes, Desulfomicrobium, Geobacter, were identified by combining the functional prediction by the FAPROTAX database with the dominant genera. The higher abundance of nitrogen functional genes (nirK, nirS and nosZ) in CAC-BRS and Fe/CAC-BRS might explain the more efficient TN removal in these two systems. Furthermore, the relative abundance of antibiotic-resistant genes (ARGs) sulI and sulII increased in all BRSs along with SMX exposure, suggesting the selection of bacteria containing sul genes. Substrates tended to become reservoirs of sul genes. Also, co-occurrence network analysis revealed distinct potential host genera of ARGs between upper and lower zones. Notably, Fe/CAC-BRS succeeded to reduce the effluent sul genes by 1-2 orders of magnitude, followed by CAC-BRS after 205-day exposure. This study demonstrated that substrate modification was crucial to maintain highly efficient nutrients and SMX removals, and ultimately extend the service life of BRSs in treating SMX wastewater.

Teamed Boronate Affinity-Functionalized Zn-MOF/PAN-Derived Molecularly Imprinted Hollow Carbon Electrospinning Nanofibers for Selective Adsorption of Shikimic Acid

Electrospun micro-/nanofibers with tailor-made specific binding sites are extremely popular due to their tremendous potential in separation applications. In this work, teamed boronate affinity (TBA)-functionalized molecularly imprinted hollow carbon electrospun nanofibers (MI-HCESNFs) derived from ZIF-8/PAN fibers with selective binding sites toward shikimic acid (SA) are presented. Each ingredient used in this strategy plays its own part: HCESNFs with excellent structural characteristics as the highly porous electrospun substrate, KH560 as the grafting material for the follow-up polyethyleneimine (PEI) modification, PEI as the dendritic platform to approach more boronic acid owing to its long chain with abundant amino groups, and TBA molecular group as the functional monomer to specifically bind with SA under the neutral condition. Benefiting from the porous structure, the high density of boronic acid, and the highly accessible imprinted sites on the surface, MI-HCESNFs show strong affinity and selectivity to the SA molecules. The adsorption capacity of MI-HCESNFs can reach 127.8 mg g-1, which is 3.1 times larger than that of the non-imprinted material. Besides, MI-HCESNFs are stable when treated with continuous ultrasonication and can be recycled eight times with a slight loss of 8.615% on the adsorption quantity. This work presents a new strategy to prepare boronate affinity adsorbents based on the electrospinning technique for the capture of SA and also proposes a path for the integration of molecularly imprinted polymers and electrospinning.

A recognition strategy combining effective boron affinity technology and surface imprinting to prepare highly selective and easily recyclable polymer membrane for separation of drug molecule

Cellulose acetate membrane (CAM) has become one of the most widely used membrane materials by virtue of stability and hydrophilicity. In this work, to achieve the aim of selective recognition and separation of drug molecule shikimic acid (SA), an effective recognition tactics was proposed by combining boron affinity technology with surface imprinting strategy based on cellulose acetate membrane with low price and biocompatibility. The supporting CAM material was prepared through the phase inversion technique by continuous adjustment of different factors including solvent type and kinds of pore-forming agents, and the optimal CAM with multistage structure and highly porosity was applied for the imprinting of SA. Then the imprinted polymer membrane (MIPs-CAM) was developed via boron affinity surface imprinting polymerization. Various methods (FT-IR, UV-vis, SEM, XPS, AFM and TGA) were used to characterize the structure, morphology, elemental composition, surface roughness and thermal property of the obtained membrane. The as-prepared MIPs-CAM showed homogeneous and abundant imprinted layer, good thermal stability. The batch adsorption results showed that the MIPs-CAM had fast adsorption kinetics, specific recognition ability, and the adsorption capacity could obtain 63.598 mg g^-1, which was two times higher than that of non-imprinted membrane (NIPs-CAM). The adsorption isotherms conformed to the Langmuir isotherm and the adsorption processes were spontaneous and endothermic. Additionally, the adsorption capacity of MIPs-CAM still reached 85% of the initial result after five cycles. The experimental results revealed that the molecularly imprinted membrane possessed the advantages of high selectivity and easy recovery compared with the traditional molecular imprinted polymers for SA separation. These results indicate that boron affinity MIPs-CAM with high performance will provide a promising platform for the separation and purification of other cis-diol drug molecules from environmental resources.

Waste-to-Resource Strategy to Fabricate Functionalized MOFs Composite Material Based on Durian Shell Biomass Carbon Fiber and Fe3O4 for Highly Efficient and Recyclable Dye Adsorption

Recently, metal–organic frameworks (MOFs), which are porous inorganic–organic hybrid materials consisting of metal ions (clusters or secondary building units) and organic ligands through coordination bonds, have attracted wide attention because of their high surface area, huge ordered porosity, uniform structural cavities, and excellent thermal/chemical stability. In this work, durian shell biomass carbon fiber and Fe₃O₄ functionalized metal–organic framework composite material (durian shell fiber-Fe₃O₄-MOF, DFM) was synthesized and employed for the adsorption removal of methylene blue (MB) from wastewater. The morphology, structure, and chemical elements of the DFM material were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscope (XPS) techniques. Adsorption conditions such as pH, adsorption time, and temperature were optimized. The adsorption isotherm and kinetics results show that the adsorption process of DFM material to MB is more in line with the Freundlich model and pseudo-second-order kinetic model. Using these models, the maximum adsorption capacity of 53.31 mg/g was obtained by calculation. In addition, DFM material could be easily reused through an external magnet and the removal rate of MB was still 80% after five adsorption cycles. The obtained results show that DFM composite material, as an economical, environmentally friendly, recyclable new adsorbent, can simply and effectively remove MB from wastewater.

High Selectivity and Reusability of Biomass-Based Adsorbent for Chloramphenicol Removal

Recently, biomass-based materials have attracted increasing attention because of their advantages of low cost, environment-friendly and nonpollution. Herein, the feasibility of using corn stalk biomass fiber (CF) and Fe₃O₄ embedded chitosan (CS) as a novel biomass-based adsorbent (CFS) to remove chloramphenicol (CAPC) from aqueous solution. Structure of CFS was characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM) and zeta potential techniques. The effects of solution pH, adsorption time and ion strength on the adsorption capacity were examined. Adsorption isotherms obtained from batch experiments were better fitted by Langmuir model compared with Freundlich model, Dubinin–Radushkevich model and Temkin model. Adsorption kinetic data matched well to the pseudo-second order kinetic model. CAPC adsorption was endothermic, spontaneous, and entropy-increasing nature on CFS. In addition, the CFS could be separated by an external magnetic field, recycled, and reused without any significant loss in the adsorption capacity of CAPC. Based on these excellent performances, there is potential that CFS can be considered as a proficient and economically suitable material for the CAPC removal from the water environment.

Feasibility of using Mg/Al-based layered double hydroxides as an inactivating agent to interrupt phosphorus release from contaminated agricultural drainage ditch sediments

This study aimed to evaluate the feasibility of using Mg/Al-based layered double hydroxides (Mg/Al-LDHs) treatment to prevent phosphorus release from sediments of agricultural drainage ditches. A high-resolution diffusive gradient film technique and a high-resolution peeper technique were used to measure the phosphorus and iron concentrations in the overlying water and sediment profiles at sub-millimeter vertical resolution. Results demonstrated that Mg/Al-LDHs effectively reduced the concentrations of soluble reactive P (SRP) (about 69%) in the overlying water and the concentrations of SRP (about 37.42%) and labile P (about 36.72%) in the pore water. The highly positive correlation (p < 0.01) between SRP and soluble Fe, labile P and labile Fe in the sediment profiles provided high-resolution evidence for the simultaneous release of iron and phosphorus in sediments. Furthermore, Mg/Al-LDHs inactivated mobile P (NH₄Cl-P and BD-P) in the uppermost sediment (0-50 mm) and then transformed the mobile P to more stable P (NaOH-rP, HCl-P, and Res-P) (about 81% of total extractable P). An inactivation layer with low phosphorus concentrations was observed in the upper sediment. In brief, the addition of Mg/Al-LDHs to the sediment surface of agricultural drainage ditches was effective in reducing SRP concentrations in the overlying water while effectively hindering the release of sediment internal phosphorus from the pore water to the overlying water.

Advanced treatment of phosphorus-containing tail water by Fe-Mg-Zr layered double hydroxide beads: Performance and mechanism

The adsorption process for low concentration phosphorus wastewater treatment has advantages of simple convenience, stable performance and less sludge, while most of current adsorbents fail to be separated for reuse. Meanwhile, few people pay attention to the removal of low concentration phosphorus from tail water by adsorbents. In this study, a newly efficient Fe-Mg-Zr layered double hydroxide beads were prepared by simple in-situ crosslinking method and applied for low concentration phosphorus adsorption from real tail water. The maximum adsorption capacity of Fe-Mg-Zr beads was 21.61 mg/g, showing more practical application value for phosphorus removal. Fixed bed experiments showed that 5.0 g adsorbent could removed 2.12 mg phosphorus from tail wastewater containing 1.03 mg/L phosphorus. The beads adsorbent can be reused with excellent adsorption performance even after five cycles of adsorption-desorption operation. After detailed analyses, it was found that ligand exchange and ion exchange were the dominant mechanisms for phosphorus adsorption by this beads. Overall, the material has the advantages of simple preparation, good adsorption performance, easy separation and recycle, indicating a great potential for low concentration phosphorus wastewater treatment.