Determination of Free Calcium Oxide in Steel Slag by Inductively Coupled Plasma Atomic Emission Spectrometry after Leaching with Strontium Nitrate-Ethylene Glycol

A method for the determination of free calcium oxide in steel slag was established by inductively coupled plasma atomic emission spectrometry after rapid leaching with strontium nitrate-ethylene glycol. Sample was heated and dried after grinding and sieving, 0.200 0 g of sample was mixed with 30 mL of 30 g·L^-1 strontium nitrate-ethylene glycol solution, thus to extract the total calcium oxide in the sample under magnetic stirring at 80-90℃ for 15 min. Sr²⁺ from of strontium nitrate-ethylene glycol solution had the efect of lewis acid, which could speed up the rate of ethylene glycol leaching calcium oxide. The solution obtained was diluted to 50 mL with ethylene glycol and dry filtered. An aliquot of 5.00 mL of the filtrate was diluted to 100 mL with water, the total calcium oxide content in which was determined at 393.366 nm under the optimized ICP-AES conditions. Based on the percentage of mass loss corresponding to 400-550℃ weight loss steps in the TG curve, the content of calcium hydroxide in terms of calcium oxide was calculated, and the content of free calcium oxide could be obtained by the content difference between the total calcium oxide and calcium hydroxide. The results showed that linearity relationship between mass concentrations of calcium oxide and its corresponding spectral intensities was kept within 100.0 mg·L^-1, with detection limit (3s) of 0.02 mg·L^-1. The actual sample was repeatedly analyzed for 11 times and RSDs of the determined values were found in the range of 0.68%-1.4%. Results of the spiked recovery test ranged from 96.5% to 102%. The proposed method was used to analyze 3 actual samples and standard sample of acement clinker, and compared with YB/T 4328-2012, with the determined values obtained by this method basically the same as those obtained by the standard method and the certified value of standard sample.