Determination Of Total Phosphorus Based On The Photocatalytic Digestion And Micro-spectrometer

Phosphorus is one of the essential elements for biological growth. The contents of phosphorus increased gradually in natural waters due to human influences. It wouldn cause mass multiplication of water plant if phosphorus composition is too large in rivers or lakes. as the result of large scale propagation, a large number of plants and animals would die in waters, which would cause great damage to the environment. So, to control the total phosphorus in waters effectively becomes more and more important. Total phosphorus in the environment exists in various forms, it is divided into inorganic phosphate and organic phosphorus compounds. The organic phosphorus compounds can not be detected directly, it can only be deteminated after transformed into inorganic phosphate by a kind of digestion method. Now, the standard method of TP digestion is the Persulfate Digestion or nitric acid - perchloric acid oxidation digestion. But this method requires high temperature, and pressure-resistant containers,the detection process is cumbersome, consuming time and energy, it can not achieve real-time online monitoring of TP in waters.Photocatalytic oxidation is a new technology recently thrived, which is widely used in the aspect of degradation of organic compounds. This method is high degradation rate, simple,no secondary pollution, etc. In this paper, a new method of TP determination was introduced, using photocatalytic oxidation digestion method replace the traditional high-temperature digestion. By taking nano-titania as photocatalyst and Fe3+ as auxiliary catalyst, Organic phosphorus compounds are degraded to phosphate In the irradiation of low-power ultraviolet lamp.Afterwards, the inorganic phosphate concentration is determinated by malachite green-malachite green spectrophotometry. Thus, total phosphorus in waters is obtained.In this paper, we have prepared coloured solution and digestion solution which can be stored stably and made a simple photocatalytic reactor. This method adopts micro biochemical analyze to proceed spectrum testing and uses dual wavelength method to eliminate background interference, which simplifies the process to TP determination greatly. Besides, the method can determinate TP in waters rapidly which has low energy consumption and is easy to realize the TP on-line monitoring.This paper, we take ATP, ADP and AMP that is prodcuted by aquatic animals and plants as Organic phosphorus standard sample to proceed digestion and it can be degraded in 30 minute. The digestion rate of the three organic phosphorus can reach seperately up to 90.2%, 96.7%, 98.1%. For the determination of the actual water samples, the detection limit reached 2.91*10^-3mg/L. Compared with national standard method(potassium persulfate digestion-ammonium molybdate spectrophotometric method), the detection results are satisfactory. This method can be used to determination of total phosphorus in waters.