Determination methods for steady-state concentrations of HO• and SO4•- in electrochemical advanced oxidation processes

Competitive kinetics and scavenging assay are commonly used for radical quantification. However, the accuracy of the two methods has been challenged in electrochemical advanced oxidation processes (EAOPs) since the strong reactivity of electrode against organic indicators may disrupt the quantitative relationship between indicator consumption and radical concentration. The present study focused on screening suitable indicators and developing suitable methods for determining the steady-state concentrations of SO₄^•- and HO^• ([SO₄^•-]_ss and [HO^•]_ss) in several EAOPs for water treatment based on competitive kinetics and scavenging assay. The applicability of the modified methods and available indicators were investigated through experimental and kinetic analysis. In anode alone process, the competitive kinetics was more appropriate than scavenging assay and benzoic acid (BA) met the basic requirement of being a competitor to determine the [HO^•]_ss. In cathode alone process, BA was more resistant to interfering factors than other competitors (ibuprofen, atrazine and nitrobenzene) and its reaction rate involved only the radical oxidation even when the reaction conditions varied over a wide range. Therefore, the [HO^•]_ss could be obtained by the competitive kinetic equation of BA when HO^• existed alone. When HO^• coexisted with SO₄^•-, a two-step method combining scavenging assay and competitive kinetics was proposed to measure [SO₄^•-]_ss and [HO^•]_ss, in which tert-butyl alcohol and BA were added as scavenger and competitor, respectively. Furthermore, the reliability of each approach was verified by the experimental results and kinetic analysis.

Diammonium Porphyrin-Induced CsPbBr3 Nanocrystals to Stabilize Perovskite Films for Efficient and Stable Solar Cells

Employing all-inorganic perovskite quantum dots (QDs) to treat organic-inorganic perovskite films has been well documented as a serviceable tactic to improve the performance of perovskite solar cells (PSCs). However, the inert molecule-coated QDs with zero-dimensional (0D) structure would limit further enhancement of the efficiency and stability of PSCs. Here, we employ a conductive diammonium porphyrin (ZnPy-NH₃Br) to treat CsPbBr₃ QDs coated on a three-dimensional perovskite film, thus constructing a stable 0D-two-dimensional perovskite capping layer. The generation of large-scale nanocube crystals by treating CsPbBr₃ nanocrystallites with ZnPy-NH₃Br in solution demonstrates such an assembly strategy. The formed capping layer can achieve efficient charge transport and separation. As a consequence, the best efficiency of an optimized device is up to 20.0%, which is superior to the control PSCs fabricated without modification (19.1%) and with pure CsPbBr₃ QD modification (19.5%). More importantly, the porphyrin-treated CsPbBr₃ QD-based devices retain over 65 or 85% of their initial efficiency when placed at 85 °C or 45% humidity tracking for 1000 h, respectively. Also, with the incorporation of QD-Por, the device retained 85% of the original efficiency when illuminated at AM 1.5 G for 450 h. Therefore, this work offered a facile avenue to modify perovskite films for fabricating highly efficient and stable PSCs.

Comparison of inert and non-inert cathode in cathode/Fe3+/Peroxymonosulfate processes on iohexol degradation

To investigate the effect of cathode materials on organics degradation in a cathode/Fe³⁺/PMS process, different cathode materials (platinum, copper and iron) were selected and their performances were compared with iohexol as target organics. The optimal conditions were found to be different for different cathode/Fe³⁺/PMS processes. With a relatively high cathodic current input (2.0 mA/cm²), similar results were found for all the three cathode/Fe³⁺/PMS processes. With a small cathodic current input (not higher than 1.0 mA/cm²), the iohexol removal followed the order of Fe-cathode/Fe³⁺/PMS > Cu-cathode/Fe³⁺/PMS > Pt-cathode/Fe³⁺/PMS, due to the corrosion of Cu-cathode and Fe-cathode and the more serious corrosion of Fe-cathode than Cu-cathode. The corrosion of non-inert cathode materials (Cu-cathode and Fe-cathode) meant that these cathodes not only transmitted electrons but also participated in aqueous reactions, which complicated the mechanisms of cathode/Fe³⁺/PMS processes. The radical identification experiments indicated that SO₄^- was more important than OH for iohexol degradation in Cu-cathode/Fe³⁺/PMS process, while OH played a major role in Pt-cathode/Fe³⁺/PMS and Fe-cathode/Fe³⁺/PMS processes. The different reaction mechanisms resulted in different iohexol transformation pathways in cathode/Fe³⁺/PMS processes with different cathode materials.

Performance of Cu-cathode/Fe3+/peroxymonosulfate process on iohexol degradation

Copper was used as a non-inert cathode material in a Cathode/Fe³⁺/peroxymonosulfate(PMS) system, and the performance of this novel Cu-cathode/Fe³⁺/PMS system was tested with a typical iodinated X-ray contrast media (iohexol) as target organics. The reaction mechanisms and the iohexol degradation pathways were investigated. The operational conditions of Cu-cathode/Fe³⁺/PMS process on iohexol degradation were optimized to be 1.0 mM Fe³⁺ dosage, 3.0 mM PMS dosage and 0.50 mA/cm² of current input. The much lower current applied in the present study than previous reports would help to save energy and be more economical. Compared with typical inert cathode (Pt-cathode), the Cu-cathode/Fe³⁺/PMS process has better performance on both iohexol removal and deiodination, due to that Cu-cathode participated in Fe²⁺ regeneration and PMS activation via surface Cu°-Cu⁺(s)-Cu²⁺-Cu° redox cycle. Fe²⁺ could be produced via reactions between Fe³⁺ and Cu/Cu⁺(s) as well as cathodic reduction of Fe³⁺. SO₄^- was generated from PMS activation by Fe²⁺, Cu/Cu⁺(s) and cathodic reduction. OH was also generated in this process but SO₄^- played a dominant role in iohexol degradation. The intermediate products of iohexol and its transformation pathways were complex due to the varied reaction mechanisms involving both oxidation and reduction in Cu-cathode/Fe³⁺/PMS process.

Solvent-based separation and recycling of waste plastics: A review

Since the creation of first man-made plastic, the global production and consumption of plastics have been continuously increasing. However, because plastic materials are durable and very slow to degrade, they become waste with high staying power. The over-consumption, disposal, and littering of plastics result in pollution, thus causing serious environmental consequences. To date, only a fraction of waste plastics is reused and recycled. In fact, recycling plastics remains a great challenge because of technical challenges and relatively insufficient profits, especially in mixed plastics. This review focuses on an environmentally friendly and potentially profitable method for plastics separation and recovery and solvents extraction. It includes the dissolution/reprecipitation method and supercritical fluid extraction, which produce high-quality recovered plastics comparable to virgin materials. These methods are summarized and discussed taking mass-produced plastics (PS, PC, Polyolefins, PET, ABS, and PVC) as examples. To exploit the method, the quality and efficiency of solvent extraction are elaborated. By eliminating these technical challenges, the solvent extraction method is becoming more promising and sustainable for plastic issues and polymer markets.

Laboratory simulations of the mixed solvent extraction recovery of dominate polymers in electronic waste

The recovery of four dominant plastics from electronic waste (e-waste) using mixed solvent extraction was studied. The target plastics included polycarbonate (PC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), and styrene acrylonitrile (SAN). The extraction procedure for multi-polymers at room temperature yielded PC, PS, ABS, and SAN in acceptable recovery rates (64%, 86%, 127%, and 143%, respectively, where recovery rate is defined as the mass ratio of the recovered plastic to the added standard polymer). Fourier transform infrared spectroscopy (FTIR) was used to verify the recovered plastics' purity using a similarity analysis. The similarities ranged from 0.98 to 0.99. Another similar process, which was denoted as an alternative method for plastic recovery, was examined as well. Nonetheless, the FTIR results showed degradation may occur over time. Additionally, the recovery cost estimation model of our method was established. The recovery cost estimation indicated that a certain range of proportion of plastics in e-waste, especially with a higher proportion of PC and PS, can achieve a lower cost than virgin polymer product. It also reduced 99.6%, 30.7% and 75.8% of energy consumptions and CO₂ emissions during the recovery of PC, PS and ABS, and reduced the amount of plastic waste disposal via landfill or incineration and associated environmental impacts.

Inhibitory effect of miR-145 on RPE cell proliferation

OBJECTIVE

This study aims to explore the impact of micro RNA miR-145 on retinal pigment epithelial cell proliferation and apoptosis.

METHODS

A stable culture and passage system of hPNE cells was first established, and its migration ability was determined. Then, miR-145 lentiviral vectors were constructed to transfect hPRE cells. Thereafter, hRPE cell proliferation was detected by MTT assay after they were transfected by lentivirus, cell cycle was analyzed by flow cytometry, and apoptosis was detected by Annexin V/PI double staining immunofluorescence.

RESULTS

Cultured hPRE cells had good migrating and metastatic ability, in which subsequent lentivirus infection experiments can be carried out. After transfection by miR-145 lentiviral vectors, hPRE cell proliferation slowed down and RPE cells in the G₁ phase was inhibited; thus, apoptosis rate increased.

CONCLUSION

MiR-145 can slow down retinal pigment epithelial cell proliferation and increase their apoptosis rate. This has a certain therapeutic potential for diseases caused by RPE cell proliferation such as PVR.