Abstract
Using the mixed fatty acids (MFA) produced by waste cooking oil as flotation collectors directly, the flotation effect is usually not satisfactory, especially at lower temperature, which may be due to the presence of large amounts of saturated fatty acids. In this study, waste cooking oil was separated into saturated fatty acids (SFA) and unsaturated fatty acids (UFA). The separation mechanism was studied by molecular simulation based on quantum and molecular mechanics. SFA and UFA were analyzed by iodine value, melting point measurement and Fourier transform infrared (FT-IR) spectroscopy to check the result of the separation. The micro-flotation and bench-scale flotation tests were performed to investigate the flotation differences between SFA and UFA. The results showed that the poor flotation performance of waste cooking oil was due to the large amount of SFA in presence. If the SFA was separated out, the TFe grade and recovery of the flotation concentrates would be increased by 4.09 and 2.70 percentage points, respectively and the SiO2 grade would be 4.03 percentage points lower at the same time. This study would provide technical supports and theoretical guidance for the waste cooking oil application in the field of mineral processing.
Highlights
Waste cooking oil refers to vegetable oil and animal fat losing food value and the wastes of oil deep processing [1]
Dissolution characteristics, the degree of unsaturation and the molecular properties of saturated fatty acids (SFA) and unsaturated fatty acids (UFA) were analyzed by iodine value, melting point and infrared spectroscopy to check the separation effect of different types fatty acids from waste cooking oil
The results showed that the UFA had an iodine value of 162.9, indicating a high degree of unsaturation and its melting point was −17.3 ◦ C, which meant that UFA would possess better dispersibility and solubility at room temperature
Summary
Waste cooking oil refers to vegetable oil and animal fat losing food value and the wastes of oil deep processing [1]. As a large edible oil consumption country, it’s estimated that China has produced considerable amount of waste cooking oil annually (about 8–15 million tons) and half of them could be collected for recycling [3,4]. Waste cooking oil is not satisfactorily recycled for industry use in the past years, as 40–60% is back flow to dining tables through various illegal channels [5] and the rest is mostly disposed as rubbish. The main chemical composition of waste cooking oil is the higher fatty acid glyceride [6], which can be used to produce anionic fatty acids for mineral flotation. The traditional process of preparing fatty acids mainly through chemical synthesis [7]. With the increase in industrial costs, the new material choices such as waste cooking oil to prepare fatty acids will increasingly receive attention
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