Atmospheric-pressure Liquid Discharge For Determination Of Metal Elements In Salt Lakes Potassium Ore With Optical Emission Spectrometry

The guarantee of sylvine resources matters to the national food security and sustainable development. Even through that sylvine resources are relatively abundant all around the world, it’s relatively poor in our country. In the respect of demands of sylvine, the foreign-trade dependence of sylvine in our country keeps above 50% all the time, which lead to the low security of sylvine resources. Thus, our country move forward to make more efforts on potassium ore prospecting these years. Many researches including prediction, selection, mineralization model and material composition of potassium ores had been developed. Relative chemical analysis, new refining and mining technology had been strengthened, in order to change the passive situation of the insufficient guarantee of sylvine resources of our country.The content of element potassium(K) in samples obtained from the research area is the direct sign to prospecting potassium and the measurement of other major elements (such as Ca, Na, Mg and so on) is the vital basis to estimate the ore formation. The estimate of water chemistry characteristics of research area can help us to find potassium from the angle of mineralization. All these works are rely on the relevant chemical analytical work. With the deepening of the potassium mineral exploration and research work, there’re higher requirements of chemical analysis and test from the perspective of accuracy, fast and convenient. To develop some portable instruments that can analyze samples in the field is the issue people have pay close attention to In recent years.The liquid discharge plasma has the advantages as follows:It’s easy to form liquid electrode construction which made the miniaturization to come true; It also effectively reduce the sample size, analyze time and operation cost which has better selectivity and stability compared with electrochemical analysis method. This method has characteristics of small volume, low power, low or no gas consumption, and portability and can be developed for on-line measurement in the fields.This project aimed to devise a small-sized source which based on the liquid discharge plasma. We priority used ac and dc power, the spectrum of each elements in the solution was got by the spectrograph when the solution was inspired by this small-sized source. We optimized the work parameters, consist of the kind and pH of the electrolyte、the flow rate、the discharge power etc., then we studied the analysis performance of each element. Finally we applied this method to the determination of metal elements of seven lakes in Qinghai Province. The concrete research content is as follows:1. A method to determine the main elements of the potassium ore was established which based on the alternating current driven atmospheric-pressure liquid discharge with optical emission spectrometry. K, Ca, Na, Mg, Cu, Sr, Li and Rb in the liquid sample were produced their own emission spectrums respectively under the power of ac-EALD, and then these emission spectrums can be detected by the spectrometer. We optimized parameters which could influence the determination of these elements during the experiment process, such as the negative high voltage of the detector, the slit width, the kind of acidic electrolyte solution, pH of acidic electrolyte solution, discharge power, electrode distance, flow rate etc.. The detection limits of eight elements of this method was from 0.07 to 1.06 mg/L and the corresponding standard deviation(n=20) is near 5%. We also conducted the recovery experiment of this sample, and the recovery was between 93.1% to 102.4%. Compared with traditional measurement, the device of this method was simple, low energy consumption, had no gas consumptionand made the instrument more protable and miniaturized. Thus, it provieded a good application foreground in determination of potassium ore in the fields.2. We studied a method determine the main elements of the potassium ore was established which based on the direct current driven atmospheric-pressure liquid discharge with optical emission spectrometry. On the basis of the former study, we used direct current discharge power as the driving power. We also optimized a series of parameters such as spectrometer parameters, electrolyte, pH, electrode distance, flow rate, discharge current and others. What’s more, we discussed the mutual interference between elements in this method. The experiment proofed that the mutual interference between elements can be eliminated by proper dilution of samples. On this basis, the detection limit of eight elements were between 0.009 and 0.15 mg/L, the corresponding standard deviation(n=20) was within 1%. We tested the simulated brine sample and the result showsed a high accuracy of each element. The RSD of all elements which in this method were all within 2%. We also conducted the recovery experiment of this sample, and the recoveries were between 92.2%-102%.3. The devices of ac-EALD and dc-EALD were compared, including their operation conditions, apparent features of plasma, analytical character and stability. The detection limit of each elements of dc-EALD was just 10% of ac-EALD while the former RSD of detecting results of each element was just 20% of the later, and the flow rate of dc-EALD was faster than ac-EALD. These all made it clear that the analytical performance of dc-EALD was lightly above ac-EALD, but they all can be used for sample detection.4. This paper analyzed 20 samples in seven lakes including Qinghai Lake, Erhai Lake, Small Chaidan Lake and other four lakes. We used ICP-AES, ICP-MS and the method in this study to analyze and determine K, Ca, Na, Mg, Cu, Sr, Li and Rb of these 20 samples. The results showed that the result of each element determined by the method are in accordance with the existing methods. The relative deviation were all below 10% and the method RSD of each element were below 5%, these all proved the feasibility of this method. Meanwhile, the data indicated that areas in Chaka Lake and Small Chaidan Lake are the relatively favorable areas to prospect potassium ore, while from the analyze of some individual factors, areas in Gahai Lake, Tuosu Lake and other lakes are also show concentrated brine and can be considered to be promising prospecting areas for potassium ore.