Ni, Co-Embedded MOF-Derived N-Doped Bimetallic Porous Carbon for Adsorption-Photocatalytic Degradation of Organic Dyes and Antibiotics.

An efficient protocol for photocatalytic degradation of organic dyes and antibiotics has been successfully established via MOF-derived (MOF = metal-organic framework) Ni, Co-embedded N-doped bimetallic porous carbon nanocomposites (NiCo/NC). Such a NiCo/NC nanocomposite features well-distributed structures, suitable specific surface areas, and more active sites determined by various characterization analyses. The catalyst exhibits higher photocatalytic performance and stability toward the liquid-phase degradation of methylene blue (MB) under visible light irradiation for 60 min, after the adsorption-desorption equilibrium and the thorough degradation into H2O and CO2. Radical quenching experiments further confirmed the dominant effect of electron holes h+ and superoxide radical anions ·O2- for the MB photodegradation process. NiCo/NC was also appropriate for the degradation of Rhodamine B, methyl orange, tetracycline hydrochloride, and norfloxacin. Moreover, NiCo/NC is robust, and its photocatalytic activity is basically maintained after 8 cycles. This work is expected to provide additional information for the design of MOF-derived carbon material with more excellent properties and lay the foundation for further industrial applications.

A review of chloride ions removal from high chloride industrial wastewater: Sources, hazards, and mechanisms.

To reduce metal pipe corrosion, improve product quality, and meet zero liquid discharge (ZLD) criteria, managing chloride ion concentrations in industrial wastewaters from metallurgical and chemical sectors has become increasingly important. This review provides detailed information on the sources, concentration levels, and deleterious effects of chloride ions in representative industrial wastewaters, and also summarizes and discusses various chloride ion removal techniques, including precipitation, ion exchange, physical separation, and advanced oxidation (AOPs). Among these, AOPs are particularly promising due to their ability to couple with other technologies and the diversity of their auxiliary technologies. The development of dechlorination electrode materials by electro-adsorption (CDI) can be inspired by the electrode materials used in chloride ion battery (CIB). This review also provides insights into exploring the effective combination of multiple chloride removal mechanisms, as well as the development of environmentally friendly composite materials. This review provides a theoretical basis and development direction for the effective treatment and secondary utilization of chlorine-containing industrial wastewater in the future.

Recyclable Magnetic Iron Immobilized onto Chitosan with Bridging Cu Ion for the Enhanced Adsorption of Methyl Orange.

Chitosan (CS) is a natural and low-cost adsorbent for capturing metal ions and organic compounds. However, the high solubility of CS in acidic solution would make it difficult to recycle the adsorbent from the liquid phase. In this study, the CS/Fe3O4 was prepared via Fe3O4 nanoparticles immobilized onto a CS surface, and the DCS/Fe3O4-Cu was further fabricated after surface modification and the adsorption of Cu ions. The meticulously tailored material displayed the sub-micron size of an agglomerated structure with numerous magnetic Fe3O4 nanoparticles. During the adsorption of methyl orange (MO), the DCS/Fe3O4-Cu delivered a superior removal efficiency of 96.4% at 40 min, which is more than twice the removal efficiency of 38.7% for pristine CS/Fe3O4. At an initial MO concentration of 100 mg L-1, the DCS/Fe3O4-Cu exhibited the maximum adsorption capacity of 144.60 mg g-1. The experimental data were well explained by the pseudo-second-order model and Langmuir isotherm, suggesting the dominant monolayer adsorption. The composite adsorbent still maintained a large removal rate of 93.5% after five regeneration cycles. This work develops an effective strategy to simultaneously achieve high adsorption performance and convenient recyclability for wastewater treatment.

Calcination-Induced Oxygen Vacancies Enhancing the Photocatalytic Performance of a Recycled Bi2O3/BiOCl Heterojunction Nanosheet.

With the rapid development of industry, bismuth-based semiconductors have been widely used for the photocatalytic degradation of organic contaminants discharged into wastewater. Herein, a Bi2O3/BiOCl (BBOC) heterojunction was constructed with high photocatalytic activity toward Rhodamine B (RhB) in the first cycle of the photocatalysis test, while the photocatalytic performance was drastically reduced after repeated testing. The adsorbed RhB molecules occupying the facial active sites of BBOC contributed to the decline of photocatalytic activity. The spent BBOC can be reactivated by the decomposition of the adsorbed RhB and the introduction of oxygen vacancies during calcination under an air atmosphere. The BBOC thus recovered exhibited a superior apparent rate constant of 0.08087 min-1 compared with 0.05228 min-1 of pristine BBOC. This study provided an effective strategy to investigate the deactivation/activation mechanism of bismuth-based heterojunction photocatalysts.

Enhanced Adsorption-Photocatalytic Degradation of Organic Pollutants via a ZIF-67-Derived Co-N Codoped Carbon Matrix Catalyst.

Stable and efficient photocatalytic degradation of organic pollutants has been achieved via a ZIF-67-derived Co-embedded N-doped nanoporous carbon material catalyst (Co-N/C). The catalyst features a well-distributed structure, suitable specific surface area, and more active sites according to the various characterization analyses. The photocatalytic activity of Co-N/C was evaluated by the degradation of the target pollutant Rhodamine B (RhB). As a result, RhB could establish an adsorption-desorption equilibrium in the dark within 30 min and was thoroughly degraded into H2O and CO2 by Co-N/C under 500 W visible light irradiation in 40 min. Moreover, radical-quenching experiments and reactive oxygen species monitoring were performed to further probe the plausible photodegradation mechanism of RhB. Co-N/C is also appropriate for other alternative dyes and antibiotics affording ideal removal efficiencies. After the reaction, Co-N/C could be facilely separated by an external magnetic field and reused for eight reaction cycles without obvious deactivation of its photocatalytic properties. This study is expected to provide an instructive guideline for the design of efficient and recyclable composite photocatalysts derived from metal-organic frameworks for a broad range of environmental remediation processes.

Heterostructured α-Bi2O3/BiOCl Nanosheet for Photocatalytic Applications.

Photocatalytic degradation of organic pollutants in wastewater is recognized as a promising technology. However, photocatalyst Bi2O3 responds to visible light and suffers from low quantum yield. In this study, the α-Bi2O3 was synthetized and used for removing Cl- in acidic solutions to transform BiOCl. A heterostructured α-Bi2O3/BiOCl nanosheet can be fabricated by coupling Bi2O3 (narrow band gap) with layered BiOCl (rapid photoelectron transmission). During the degradation of Rhodamine B (RhB), the Bi2O3/BiOCl composite material presented excellent photocatalytic activity. Under visible light irradiation for 60 min, the Bi2O3/BiOCl photocatalyst delivered a superior removal rate of 99.9%, which was much higher than pristine Bi2O3 (36.0%) and BiOCl (74.4%). Radical quenching experiments and electron spin resonance spectra further confirmed the dominant effect of electron holes h+ and superoxide radical anions ·O2- for the photodegradation process. This work develops a green strategy to synthesize a high-performance photocatalyst for organic dye degradation.

The Performance and Mechanism of a Mg-Al Double-Layer Oxide in Chloride ion Removal from an Aqueous Solution.

The increasing threat of chloride ions (Cl-) has led researchers to explore efficient removal technologies. Sewage treatment with a double-layer hydroxide/oxide (LDH/LDO) is receiving increasing attention. In this work, Mg-Al LDO adsorbents were produced by the calcination of the Mg-Al LDH precursor, which was constituted by improved coprecipitation. The influence of calcination temperature, calcination time, adsorbent dosage, Cl- initial concentration, contact time, and adsorption temperature on Cl- elimination was investigated systematically. The experimental results showed that a better porous structure endowed the Mg-Al LDO with outstanding adsorption properties for Cl-. The adsorption process was well matched to the pseudo-second-order kinetics model and the Freundlich model. Under optimal conditions, more than 97% of the Cl- could be eliminated. Moreover, the removal efficiency was greater than 90% even after 11 adsorption-desorption cycles. It was found that the electrostatic interaction between Cl- and the positively charged Mg-Al LDO laminate, coupled with the reconstruction of the layer structure, was what dominated the Cl- removal process.