3D-printed heterogeneous Cu2O monoliths: Reusable supports for Antibiotic Treatmentantibiotic treatment of wastewater

3D printed monoliths: From powder to an efficient catalyst for antibiotic degradation

To improve the effectiveness and durability of wastewater treatment technologies, researchers are showing a growing interest in 3D printing technology. This technology has attracted significant interest owing to its ability to fabricate challenging complex geometries using different material compositions. This manuscript is focused on the development of 3D monoliths from noncommercial filaments, i.e., a powder blend of iron oxide and polylactic acid (PLA) at 15 wt% of the former. Different monolith designs have been prepared to improve the fluid dynamics of the process, so a simple cylinder (15-Fe3O4@PLA) and a cylinder with double the length and an internal mesh (15-Fe3O4@PLA-DM) were used. These monoliths were characterized by Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Mössbauer spectroscopy, then used for water-based ofloxacin degradation in a continuous down-up flow configuration. Additionally, computational fluid dynamics simulations were performed to estimate the degradation rate constants and analyze the distribution of fluid velocity and pollutant concentration along the 15-Fe3O4@PLA-reactor. The oxidant dose was also optimized to develop the highest degradation rate. The degradation of the target pollutant for those monoliths was 55 and 82 % under optimized conditions. In addition, the 15-Fe3O4@PLA-DM monolith was operated for long term experiments, keeping the degradation performance at a good 67 % for up to 120 h. Finally a fixed-bed reactor was mounted with printed pellets of the mixture (15:85), Fe3O4:PLA, after being ground in a range of 125-200 μm. Under this setup configuration, we observed the total degradation of ofloxacin. 3D printing technology is cheap, reproducible and time saving in the development of supported catalysts in comparison with conventional deposition techniques. Moreover, the leaching of active sites on streams was largely diminished. In fact under continuous operation the leached Fe concentration is below 0.1 ppm, corroborating the good adhesion of the catalyst in the PLA support.

Activation of Peracetic Acid by CoFe2O4 for Efficient Degradation of Ofloxacin: Reactive Species and Mechanism

Peroxyacetic acid (PAA)-based advanced oxidation processes (AOPs) have attracted much attention in wastewater treatment by reason of high selectivity, long half-life reactive oxygen species (ROS), and wider applicability. In this study, cobalt ferrite (CoFe2O4) was applied to activate PAA for the removal of ofloxacin (OFX). The degradation of OFX could reach 83.0% via the CoFe2O4/PAA system under neutral conditions. The low concentration of co-existing anions and organic matter displayed negligible influence on OFX removal. The contributions of hydroxyl radicals (·OH), organic radicals (R-O·), and other reactive species to OFX degradation in CoFe2O4/PAA were systematically evaluated. Organic radicals (especially CH3C(O)OO·) and singlet oxygen (1O2) were verified to be the main reactive species leading to OFX destruction. The Co(II)/Co(III) redox cycle occurring on the surface of CoFe2O4 played a significant role in PAA activation. The catalytic performance of CoFe2O4 remained above 80% after five cycles. Furthermore, the ecotoxicity of OFX was reduced after treatment with the CoFe2O4/PAA system. This study will facilitate further research and development of the CoFe2O4/PAA system as a new strategy for wastewater treatment.

Ag2S Nanoparticles Supported on 3D Flower-Shaped Bi2WO6 Enhanced Visible Light Catalytic Degradation of Tetracycline

A three-dimensional flower-shaped Bi2WO6 has been prepared by a hydrothermal procedure without the addition of an auxiliary agent and under neutral conditions with ultrapure water serving as solvent, and the Ag2S-Bi2WO6 composite with weight ratios of 5, 10, and 15% was prepared by a hydrothermal method. The crystallinity, morphology, mode of binding, and optical properties of the Ag2S-Bi2WO6 composite were characterized, the results of which showed that the composite had excellent dispersion, crystallinity, and purity. The composite with a weight ratio of 10% had the best photocatalytic performance, and the degradation rate of tetracycline reached 95.51% within 120 min, an increase of 27.35% over Bi2WO6. In experiments, some focus was given to the effect of the initial solution pH and the concentrations of humic acid and inorganic anions on the degradation efficiency. Based on free radical capture experiments and the semiconductor theory, the main active substances and mechanisms in the optical catalytic reaction process were studied, and speculation was given concerning the degradation pathway for the target pollutants. This study has conceived novel methods for the development of dual semiconductor systems consisting of a Ag NP composite and in doing so has provided new approaches for the development and photocatalysis for water pollution control.

Application of three dimensional-printed devices in extraction technologies

Sample pretreatment is an important and necessary process in chemical analysis. Traditional sample preparation methods normally consume moderate to large quantities of solvents and reagents, are time- and labor-intensive and can be prone to error (since they usually involve multiple steps). In the past quarter century or so, modern sample preparation techniques have evolved, from the advent of solid-phase microextraction and liquid-phase microextraction to the present day where they are now widely applied to extract analytes from simple as well as complex matrices leveraging on their extremely low solvent consumption, high extraction efficiency, generally straightforward and simple operation and integration of most, if not all, of the following aspects: Sampling, cleanup, extraction, preconcentration and ready-to-inject status of the final extract. One of the most interesting features of the progress of microextraction techniques over the years lies in the development of devices, apparatus and tools to facilitate and improve their operations. This review explores the application of a recent material fabrication technology that has been receiving a lot of interest, that of three-dimensional (3D) printing, to the manipulation of microextraction. The review highlights the use of 3D-printed devices in the extraction of various analytes and in different methods to address, and improves upon some current extraction (and microextraction) problems, issues and concerns.