Application of Nanoscale Zero‐Valent Iron‐Loaded Natural Zeolite for Tetracycline Removal Process

The enhancement of tetracycline degradation through zero-valent iron combined with microorganisms during wastewater treatment: Mechanism and contribution

Ttetracycline (TC) posed potential threats to human health and ecological environment due to its mutagenicity, deformity and strong toxicity. However, few researches focused on the mechanism and their contribution of TC removal through microorganisms combined with zero-valent iron (ZVI) in wastewater treatment field. In this study, three groups of anaerobic reactors, added with ZVI, activated sludge (AS), ZVI coupled with activated sludge (ZVI + AS), respectively, were performed to explore the mechanism and the contribution of ZVI combined with microorganisms on TC removal. The results showed that the additive effects of ZVI and microorganisms improved TC removal. In ZVI + AS reactor, TC was mainly removed by the ZVI adsorption, chemical reduction and microbial adsorption. At the initial period of the reaction, microorganisms played a major role in the ZVI + AS reactors, contributing 80%. The fraction of ZVI adsorption and chemical reduction were 15.5% and 4.5%, respectively. Afterwards, the microbial adsorption gradually reached saturation and the chemical reduction as well as the adsorption of ZVI did their stuff. However, iron-encrustation covered on the adsorption sites of microorganisms and the inhibitory effect of TC on biological activity led to the decreasing TC removal in the ZVI + AS reactor after 23 h 10 min. The optimum reaction time for TC removal in ZVI coupling microbial system was about 70 min. In 1 h 10 min, the TC removal efficiencies were 15%, 63% and 75% in ZVI, AS and ZVI + AS reactors, respectively. Finally, in order to relieve the influence of TC on activated sludge and the iron cladding, a two-stage process was proposed to be explored later in the future.

Adsorption of Methylene Blue and Tetracycline by Zeolites Immobilized on a PBAT Electrospun Membrane

The detection of emerging contaminants in bodies of water has steadily increased in recent years, becoming a severe problem threatening human and ecosystem health. Developing new materials with adsorption properties to remove these pollutants represents an important step toward a potential solution. In this paper, a polybutylene adipate terephthalate (PBAT) nanofibrous membrane incorporating clinoptilolite zeolite was developed and its excellent performance in removing tetracycline (TC) and methylene blue (MB) from water was demonstrated. The composite membrane was prepared in two steps: firstly, a homogeneous dispersion of clinoptilolite (1 wt% respect to polymer) in a PBAT solution (12.6 wt%) was electrospun; secondly, the electrospun membrane was subjected to an acid treatment that improved its wettability through the protonation of the surface silanol groups of clinoptilolite. The resulting membrane was hydrophilic and showed higher adsorption for TC (800 mg/g) and MB (100 mg/g), using a low dose (90 mg/L) powdered zeolite. The maximum removal capacity was obtained at neutral pH, being the cation exchange reaction the main adsorption mechanism. Pseudo-second-order kinetics and Henry's law agree well with the proposed chemisorption and the high affinity of TC and MB for the adsorbent. The material can be reused after the removal process without generating additional contamination, although losing some effectivity.

Removal of tetracycline by biochar-supported biogenetic sulfidated zero valent iron: Kinetics, pathways and mechanism

The application of zero-valent iron (ZVI) is limited due to passivation and agglomeration. Therefore, biochar loading (MB) and biogenetic sulfidation via sulfate-reducing bacteria (SRB) were used to improve the reactivity of ZVI (BS-ZVI@MB) towards tetracycline (TC) degradation. Biochar provided more attachment sites for ZVI and SRB, thus alleviating the agglomeration. Additionally, quinone groups on biochar enhanced the electrons transfer through the measurement of electron donating/accepting capacities, and biogenetic sulfidation could inhibit the surface passivation of ZVI. Fe(Ⅱ/Ⅲ) produced after the addition of BS-ZVI@MB could complex with the A ring in TC to form Fe(Ⅱ/Ⅲ)-TC, which brought the oxidation of TC by complexed Fe(Ⅲ). Reactive oxygen species (ROS)(primarily •OH) were generated during the oxidation of Fe(Ⅱ), so as to promote the TC degradation. Extracellular polymeric substances (EPS) secreted from SRB had a slight quenching effect on ROS. Meanwhile, EPS formed a protective layer with Fe(Ⅱ/Ⅲ) on BS-ZVI@MB, reducing its reactivity with TC. Overall, this study showed an efficient modification technology of ZVI by biogenetic sulfidation and biochar loading for TC degradation.

A mild and one-pot method to activate lignin-derived biomass by using boric acid for aqueous tetracycline antibiotics removal in water

A mild and one-pot activation approach of activated carbon was found. The feasibility of boric acid as the activated reagent which was used for the adsorption of four tetracyclines antibiotics (TCs) in water. Boric acid activated carbon (BAC) from bioresource has a much higher removal efficiency than currently reported biochar. The maximum adsorption capacity of BAC is 173.9 mg/g for TCs. BAC is an ecofriendly, nontoxic, and low-cost absorbent from sawdust waste. BAC and TCs could keep coalescing at least 55 days on the surface without stable release. BAC was fully characterized by using scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman, zeta potential, and Brunauer-Emmett-Teller analysis; the large surface area and rich pore structure were proved. The interaction between BAC and TCs are hydrogen bond interaction, π-π interaction, and electrostatic interaction. These interactions are also related to the surface charge of BAC and the TCs' species of ions in different pH. Furthermore, the adsorption kinetics and adsorption isotherm of BAC were studied thoroughly. The pseudo-first-order, pseudo-second-order, intra-particle diffusion, Elovich Langmuir, Freundlich, and Dubinin-Radushkevich models were fitted and the physical adsorption process was proved. After the study on adsorption thermodynamics, adsorption exhibits a spontaneous and favorable process.

Orderly Porous Covalent Organic Frameworks-based Materials: Superior Adsorbents for Pollutants Removal from Aqueous Solutions

Covalent organic frameworks (COFs) are a new type of crystalline porous polymers known for chemical stability, excellent structural regularity, robust framework, and inherent porosity, making them promising materials for capturing various types of pollutants from aqueous solutions. This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants. Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints, including batch experiments, theoretical calculations, and advanced spectroscopy analysis. The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents. Several commonly used strategies to enhance COF-based materials’ adsorption performance and the relationship between structural property and sorption ability are also discussed. Finally, a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.

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Covalent organic frameworks (COFs) are a new type of crystalline porous materials known for chemical stability, high specific surface area, and orderly porous channels.With the rapid growth of industrialization, water pollutants remain a serious issue of public health and environmental protection

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COFs as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants in water is becoming a hot topic

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Information about the interaction mechanisms between various pollutants and COFs materials are summarized.The perspectives and challenges are proposed to provide some useful inspiration for the application of COFs in environmental pollution management