An integrated photocatalytic microfluidic platform enabling total phosphorus digestion

Abstract

This paper presents an integrated thermally assisted photocatalytic microfluidic chip and its application to the digestion of total phosphorus (TP) in freshwater. A micro heater, a micro temperature sensor, thermal-isolation channels and a polymethylsiloxane (PDMS) reaction chamber were fabricated on the microfluidic chip. Nano-TiO 2 film sputtered on the surface of silicon in the reaction area was used as the photocatalyst, and a micro ultraviolet A-ray-lightemitting diode (UVA-LED) array fabricated by MEMS technology were attached to the top of reaction chamber for TP degradation. In this study, sodium tripolyphosphate (Na 5 P 3 O 10 ) and sodium glycerophosphate (C 3 H 7 Na 2 O 6 P) were chosen as the typical components of TP, and these water samples were digested under UVA light irradiation and heating at the same time. Compared with the conventional high-temperature TP digestion which works at 120 °C for 30 min, the thermally assisted UVA digestion method could work at relatively low temperature, and the power consumption is decreased to less than 2 W. Since this digestion method could work without an oxidizing reagent, it is compatible with the electrochemical detection process, which makes it possible to achieve a fully functional detection chip by integrating the digestion unit and electrochemical microelectrode, to realize the on-chip detection of TP, and other water quality parameters such as total nitrogen and chemical oxygen demand.

An Integrated Optofluidic Platform Enabling Total Phosphorus On-Chip Digestion and Online Real-Time Detection

“…Ascorbic acid (C6H8O6) was used to prepare the chromogenic agent A. Meanwhile, ammonium molybdate [(NH4)6Mo7O24·4H2O)], potassium antimony tartrate (KSbC4H4O7·1/2H2O) and H2SO4 were used to prepare the chromogenic agent B. Potassium persulfate (K2S2O8) was utilized as digesting oxidant [12,17,18]. Various parameters affecting the performance of the optofluidic platform were investigated, such as digestion temperature (controlled by the heater), pH values (adjusted by adding H2SO4/NaOH solutions) and the initial concentration of the K2S2O8 solution.…”

“…In the experiment of phosphate online digestion and online real-time monitoring, sodium glycerophosphate (C 3 H 7 Na 2 O 6 P), sodium tripolyphosphate (Na 5 P 3 O 10 ), tetrasodium pyrophosphate (Na 4 P 2 O 7 ) and disodium guanosine 5 -monophosphate (C 10 H 12 N 5 Na 2 O 8 P) were employed as the typical phosphate solution samples, and their initial concentration was set as 0.3 mg/L (by weight of P [12,17,18]. Various parameters affecting the performance of the optofluidic platform were investigated, such as digestion temperature (controlled by the heater), pH values (adjusted by adding H 2 SO 4 /NaOH solutions) and the initial concentration of the K 2 S 2 O 8 solution.…”

“…In recent years, online detection of phosphorus has attracted attention, and researchers have tried to make a breakthrough using optofluidic technology. For example, Tong et al designed a photocatalytic microreactor for phosphorus digestion in 2015 [12]. The TiO 2 film was immobilized in a microreactor irradiated by UV light for photocatalytic digestion of the phosphorus samples.…”

Microfluidic chip with interdigitated ultra‐microelectrode array for total phosphorus detection

“…The performance of this chip is compared with microdisk gold electrodes. This chip was utilised in the detection of TP in standard water samples to validate its use for in-situ monitoring of an automated, distributed sensor system combined with microdigestion chips [13] Fig. 1.…”

Real-time spectroscopic monitoring of photocatalytic activity promoted by graphene in a microfluidic reactor

“…In addition, it has attracted extensive attention for the harvesting of solar energy, caused by its potential capacity for converting photon energy into chemical energy 3 4 . Various photocatalytic microreactors have been developed for the purpose of obtaining a large surface-to-volume ratio, short diffusion distance, and uniform irradiation 5 6 7 . Particularly, they are useful tools for the rapid screening of photocatalysts, with significantly reduced consumption of catalysts and reagents 8 9 .…”