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The release of metal elements from stainless-steel products in contact with food may endanger human health. To protect human health, different countries or international organisations have formulated corresponding regulations or technical guidelines. Limits for only five metal elements are stipulated in the China National Food Safety Standard (GB 4806.9) and food simulants and test conditions are fixed regardless of the actual use condition. In this study, inductively coupled plasma mass spectroscopy and inductively coupled plasma optical emission spectroscopy were used to measure the concentrations of six metal contaminants and impurities and 11 metals and alloy component released from stainless-steel sheets on Chinese market. The effects were also investigated on metal release of six grades (201, 202, 304, 430, 443, and 30Cr13) and 6 exposure conditions (food simulant 5 g L−1 citric acid or 4 vol% acetic acid, contact temperature 70 °C or 100 °C, and contact time 2 h, 0.5 h, or 0.5 h followed by ambient temperature for 24 h). For reusable stainless-steel sheets, especially for grade 30Cr13, it was essential to perform three consecutive release tests to check compliance. However, there was no need to conduct three consecutive release tests for the other five grades if the results of the first test met the regulations. It was recommended that 5 g L−1 citric acid should be used as food simulant and contact temperature and time should be based on the actual using conditions. No relationships were found between metal release amounts and contact test temperature or time. The specific release limits for Pb, Cr, As, Cd, and Ni should be lowered and Al, Mn, and Fe be added in GB 4806.9. The results of this study can be a reference for further analysis of the release behaviour of metal elements in actual stainless-steel products. [ABSTRACT FROM AUTHOR]

In this study, the effect of pulp temperature on coal flotation was investigated. Waste vegetable oil was used as collector. Experiments were carried out at different temperatures (5, 25, 50, and 75°C) and the pros and cons of each temperature for flotation performance were revealed. While flotation performance was lower in higher pulp temperatures (50 and 75°C), flotation performance was found higher in lower pulp temperatures (5 and 25°C). Highest combustible recovery values were obtained at 25°C pulp temperature, and the lowest ash product was obtained at 75°C. However, the lowest combustible recovery value was obtained in flotation at 75°C. [ABSTRACT FROM AUTHOR]