Solvent-assisted cavitation for enhanced removal of organic pollutants - Degradation of 4-aminophenol

Nano Zr/Cu oxide modified poly-β-cyclodextrin peroxidase mimic for potable discrimination of aminophenol isomers and catalytic degradation of methyl red

To high-performance recognize or degrade o/p-aminophenol and methyl red, nano Zr/Cu oxide decorated poly-β-cyclodextrin (CuO/ZrO2@p-β-CD) was developed under microwave-assisted conditions. Fibrous CuO/ZrO2@p-β-CD expressed synergistic peroxidase-like activity to degrade >90.4 % methyl red in the air. When applied to accelerate the oxidization of 2,2'-azinobis (3-ethyl benzothiazoline-6-sulfonic acid) ammonium salt (ABTS), Km/Vmax could be 0.053 mM/2.92 × 10-8 M/s. Trace aminophenol isomers (o-AP and m-AP) could exclusively alter CuO/ZrO2@p-β-CD-ABTS from green to colorless or to purple-red with remarkable time-resolved effect. Under the optimized conditions, CuO/ZrO2@p-β-CD was successfully applied for intelligent monitoring or degradation o-AP, m-AP or methyl red in practice with the help of a smartphone. The recoveries for UV-vis spectral/RGB detection of o-AP and m-AP could reach 100.0 % ~ 102.9 %/98.0 % ~ 102.5 % and 97.8 % ~ 101.1 %/96.8 % ~ 103.33 %. The catalytic detection or quantitative degradation mechanisms were investigated in detail. This work will provide a potential for quantitative monitoring or degradation of organic pollutions.

Efficient removal of succinic acid by continuous hydrodynamic cavitation combined with ozone and side influent injection

Micropollutants (MPs) encompass a range of human-made pollutants present in trace amounts in environmental systems. MPs include pharmaceuticals, personal care products, pesticides, persistent organic pollutants, micro- and nano-plastics, and artificial sweeteners, all posing ecological risks. Conventional municipal wastewater treatment methods often face challenges in completely removing MPs due to their chemical characteristics, stability, and resistance to biodegradation. In this research, an Advanced Oxidation Process, combining hydrodynamic cavitation (HC) with dissolved ozone (O3) and side injection, was employed to efficiently degrade succinic acid (SA), an ozone-resistant compound and common byproduct. The HC/O3 process was run to treat different synthetic effluents, focusing on evaluating the influence of O3-to-total organic carbon (TOC) ratio, cavitation number (Cv) and O3 dosage. Notably, the results from a series of 14 experiments highlighted the critical significance of a low O3-to-TOC ratio value of 0.08 mg/mg and Cv value of 0.056 in HC for achieving efficient SA removal of 41.2% from an initial SA solution (106.3 mg/L). Regarding a series of four proof-of-concept experiments and their replications, the average TOC removal reached 62% when treating wastewater treatment plant effluent spiked with SA. This significant removal rate was achieved under initial conditions: Cv of 0.02, O3-to-TOC ratio set at 0.77 mg/mg, TOC concentration of 47.7 mg/L, 106 mg/L of SA, and a temperature of 25 °C. Notably, the electrical energy per order required for the 62% reduction in TOC was a modest 12.5 kWh/m3/order, indicating the potential of the continuous HC/O3 process as a promising approach for degrading a wide range of MPs.

Spindle-shaped Cu-Ru mesoporous nanospheres with enhanced enzyme-like activity for visual differentiation of toxic o-/m-aminophenol and recognition mechanisms

To effectively differentiate toxic aminophenol isomers, a kind of spindle-shaped Cu-Ru bimetal mesoporous nanozyme (Cu-Ru MPNZ) with high specific surface was developed by one-pot homogeneous reduction method, directed by hexadecyl trimethyl ammonium bromide (CTAB) in this work. By virtue of the distinctive microstructure, Cu-Ru MPNZ expressed superior bi-functional oxidase- and peroxidase-mimic activity to catalyze the oxidation of 3,3',5,5,'-tetramethylbenzidine (TMB) and 2,2'-azinobis (3-ethylbenzothiazoline-6- sulfonic acid) ammonium salt (ABTS) with low Michaelis-Menten constants and quick reaction rates. Especially, toxic aminophenol isomers could exclusively react with the oxydates of TMB or ABTS to express differentiable signals in color. Under the optimal conditions, Cu-Ru MPNZ was successfully applied for visual differentiation of toxic aminophenol isomers in real aqueous, juices and medicinal samples with low detection limits (1.60 × 10-8 mol/L for o-aminophenol and 3.25 × 10-8 mol/L for m-aminophenol) and satisfactory recoveries (96.6-103.5%). The different recognition mechanisms of Cu-Ru MPNZ to toxic o- and m-aminophenol isomers were proposed for the first time as far as we known. This work will provide a potential way to monitor different organic isomer pollution in future.

Nanobiohybrids: Synthesis strategies and environmental applications from micropollutants sensing and removal to global warming mitigation

Micropollutants contamination and global warming are critical environmental issues that require urgent attention due to natural and anthropogenic activities posing serious threats to human health and ecosystems. However, traditional technologies (such as adsorption, precipitation, biodegradation, and membrane separation et al.) are facing challenges of low utilization efficiency of oxidants, poor selectivity, and complex in-situ monitoring operations. To address these technical bottlenecks, nanobiohybrids, synthesized by interfacing the nanomaterials and biosystems, have recently emerged as eco-friendly technologies. In this review, we summarize the synthesis approaches of nanobiohybrids and their utilization as emerging environmental technologies for addressing environmental problems. Studies demonstrate that enzymes, cells, and living plants can be integrated with a wide range of nanomaterials including reticular frameworks, semiconductor nanoparticles and single-walled carbon nanotubes. Moreover, nanobiohybrids demonstrate excellent performance for micropollutant removal, carbon dioxide conversion, and sensing of toxic metal ions and organic micropollutants. Therefore, nanobiohybrids are expected to be environmental friendly, efficient, and cost-effective techniques for addressing environmental micropollutants issues and mitigating global warming, benefiting both humans and ecosystems alike.

Comparative Study of 4-Aminophenol Removal from Aqueous Solutions by Emulsion Liquid Membranes Using Acid and Basic Type 1 Facilitations: Optimisation and Kinetics

The molecule 4-aminophenol (4AP) is recognised as a serious environmental pollutant that enters the environment during the manufacture and processing of a variety of industrial processes and through the degradation of some pharmaceutical products. This paper describes a comparative study of 4AP removal from aqueous solutions by emulsion liquid membranes using acid and basic type 1-facilitated transports. The results are explained by analysing the stripping process through both the different relative acid/basic strength of the hydroxyl and amine groups of the 4AP molecule and the hydrogen-bonding capacity with water of the ionisation products generated by the reaction of 4AP with HCl or NaOH. To optimize the 4AP removal process, the influence of different experimental conditions (stripping agent concentration in the product phase, surfactant concentration in the membrane phase, stirring rate, feed phase/emulsion phase volume ratio, product phase/membrane phase volume ratio and emulsification rate and time) were studied. The kinetics of the removal process has been analysed by fitting the experimental results to first order, second order and the Behnajady and Avrami models. The Behnajady model presents an excellent fit, allowing to calculate both the initial removal rate and the maximal removal conversion. Optimal conditions of the removal process obtained through these parameters are in full agreement with those obtained from the experimental study.