Residual aqueous ozone determination by gas diffusion reverse flow injection analysis

Abstract

A novel system based on reverse flow injection analysis with a gaseous diffusion step (GD-r-FIA) has been developed for the analysis of ozone. It includes an automatic microburet injection system. The ozone diffuses through a microporous membrane of polyvinylidene difluoride (PVDF) from the donor stream to the acceptor stream containing nitrite ions. The nitrite concentration in the acceptor solution decreases due to the ozone reduction reaction. In this way, a simple indirect measurement of the ozone concentration can be performed using the Griess-Ilosvay reaction for the nitrite ion. This correlates with the decrease in absorbance of the azoic dye formed with the ozone concentration in the donor stream. The system has been optimised by investigating the effect of the nitrite concentration in the acceptor stream on the diffusion flow. The optimum nitrite concentration was set at 0.250 ppm with a flow rate of 1.5 ml/min. The efficiency of the ozone diffusion through the membrane was only 4.4%. This affects the average sensitivity, which is low (0.0092+/-0.0012 AU/ppm), although the detection limit is similar to that obtained with other reported methods (0.03 ppm). The main advantage of the system reported here is that it has a linear range that is an order of magnitude broader than those observed for other GD-FIA systems. This is especially useful for continuous monitoring systems, since the residual ozone concentration is normally between 0.05 and 5.0 ppm. Additionally, using the reverse flow injection analysis (FIA) technique minimises chemical consumption and residue generation. Finally, the stability of the ozone solution and the repeatability and reproducibility of the method have been studied.

The Effects of Negative Ions and Ozone on Various Bacteria and The Evaluation of Their Use in Hospital Wastewater Disinfection

“…Ortamın bağıl nem oranıyla doğru orantılı olarak ozonun inhibitör etkinliğinin de arttığı gözlenmiş ve bu durumun ozonun reaksiyona gireceği su oranının artışı sonucu oluşacak radikal oranının artmasına bağlı olduğu belirtilmiştir [17] . Ozonun sudaki etkinliğinin havadaki etkinliğinden çok daha yüksek olduğu ve suda hızla ayrıştığından çok daha güvenli olduğu bildirilmiştir [9,19] . Bizim çalışmamızda da agar plak yüzeyine uygulanan ozon işlemine kıyasla bakteri süspansiyonlarının direkt ozonlanmasının daha etkili olduğu görülmüştür.…”

The Permeation of High Concentration Hydrogen Sulfide (H2S) Gas Using PTFE (Polytetrafluoroethylene) and PVDF (Polyvinylidene Fluoride) membranes

“…The common membrane for the H2S gas permeation process is hydrophobic [4], including PVDF (Poly-Vinylidene Difluoride), PTFE (Poly-Tetrafluoroethylene), PP (Polypropylene), and PE (Polyethylene) membranes [5]. Among these membranes (PTFE, PVDF, PP, and PE), PTFE and PVDF membranes have more advantages [6]. Besides these membranes are hydrophobic membranes which are very stable in the gas permeation process; the PTFE membrane is also inert.…”

Gas diffusion as a new fluidic unit operation for centrifugal microfluidic platforms

“…33 Some of the published applications comprise the use and integration of membranes 34 as micro-valves using different robust elastomeric membrane materials such as polytetrafluorethylene (PTFE), fluorinated ethylene propylene (FEP) or Viton. Other applications integrate such membranes in microfluidic systems as preconcentration 35,36 and gas diffusion steps, 37,38 and as phase separation techniques such as pervaporation, 39 bubble elimination, gas removal, 40 distillation 41 and liquid-liquid extraction. 42 However, a robust and reproducible method to integrate such membrane functionalities within microfluidic devices is still an important challenge.…”

“…The membrane is clamped between microfluidic channels, which are mechanized on the top and bottom of the microfluidic device blocks. 37,38,52,53 The research group has a wide experience on continuous flow injection systems involving gas diffusion. Different analytes, such as sulfur dioxide (SO 2 ), 52 ammonium ion (NH 4 + ) 37 and ozone (O 3 ), 38 have been satisfactorily determined.…”

“…37,38,52,53 The research group has a wide experience on continuous flow injection systems involving gas diffusion. Different analytes, such as sulfur dioxide (SO 2 ), 52 ammonium ion (NH 4 + ) 37 and ozone (O 3 ), 38 have been satisfactorily determined. According to this, the integration of PVDF membranes inside a microfluidic disc is proposed in this work.…”