Abstract
Spent bleaching earth (SBE) which is generated from bleaching process is a valuable industrial waste of edible vegetable oil production because of residual edible vegetable oil absorbed. The residual oil in spent bleaching earth can be recovered and reused for application in the industries such as the production of biodiesel and lubricant. Currently, microwave-assisted extraction (MAE) technique is widely used because this method has a shorter extraction time and less solvent consumption when compared with traditional methods. In this study, MAE combined with solvent reflux was optimized using solvent screening experiments and response surface methodology (RSM) to obtain the highest yield of MAE extraction of residual soybean oil from spent bleaching earth. The extraction yield of residual soybean oil obtained from selected solvent were hexane-ethanol mixture (2:1 v/v, 10.19%) > hexane-ethanol mixture (1:1 v/v, 10.00%) >hexane-ethanol mixture (1:2 v/v, 9.98%) > hexane-ethanol mixture (1:3 v/v, 9.83%) > hexane-ethanol mixture (3:1 v/v, 8.59%) > hexane (8.17%) > acetone (7.73%). The regression coefficient (R-squared = 0.9852) expresses the accuracy of the regression and indicates the relationship between experimental data and predicted result, with high regression coefficient close to 1, which is remarkably desired. The experiment conditions for optimal MAE extraction of residual soybean oil from SBE were hexane-ethanol mixture (2:1 v/v), liquid to solid ratio 15.56:1 mL/g, extraction time 12.22 min, and microwave power 350 W. Under such conditions, the highest predicted value of the extraction yield of residual soybean oil was 10.43%.
Highlights
To remove impurities, raw vegetable oils are purified
This is due to the fact that the type of solvent employed in microwave-assisted extraction (MAE) is important
The microwave absorption capacity of a solvent is determined by type, and the solubility of the target molecule should be considered when selecting a solvent for MAE
Summary
The bleaching process is one of the purification processes in which soap materials and other impurities in the oil are removed by absorbents. SBE is a flammable waste material that can cause a fire if not properly stored or treated [1]. The waste contains 20 to 40% oils, fats, and pigments by weight, depending on various factors such as the processing technology and the type of oil [2]. The presence of oil in the clay, the potential leakage of fats into the water path, and the possibility of spontaneous combustion contribute to problems, hazards, and safety concerns, when SBE is disposed of in landfills. Due to the rapid growth of industries and the concomitant increase in the rate of waste material production, the disposal of SBE has become a potential problem in
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