The process of biodiesel purification is an important step in getting biodiesel products that meet specifications as a substitute for fossil-based fuels. Dry washing method has been developed to achieve an effective purification strategy in order to produce high-quality biodiesel. Bentonite can be used as dry washing agent because it has a good adsorbing properties as well as a large pore and surface area therefore can attract polar substances such as glycerol and methanol. The purpose of this research is to know the capability of activated bentonite as dry washing agent for purification of biodiesel produced from waste cooking oil. The activation process of bentonite was carried out using sulfuric acid with concentration 1.5 M. Characterization of the bentonite was conducted using X-Ray Diffraction (XRD) for minerals content and Brunauer–Emmett–Teller (BET) method for surface area. Bentonite was used as dry washing agent for biodiesel purification by varying washing time (10, 20, 30, 40 and 50 minutes) and adsorbent amount (1, 2, 3, 4 and 5%). The experimental results showed that purification of biodiesel by dry washing using activated bentonite resulted in a better yield and quality than wet washing and dry washing using non-activated bentonite, except the acid number. The best operation condition resulted from this research is at 10 minutes washing time and 1% adsorbent with yield of 94.1%; acid number of 0.4208 mg KOH/gram; density of 0.8838 gram/cm3, viscosity of 3.0617 mm2/s and water content of 1.17%.

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Glycerolysis is the simplest, least expensive, and most prevalent technique for producing mono-diacylglycerol (MDAG). MDAG, a product derived from palm oil, is crucial to the fat-based food sector. Chemical glycerolysis generally leaves crude MDAG with glycerol residues that exceed the European Union’s maximum (up to 7.5%); thus, it must be purified. Cream demulsification is one of the conventional ways of purification for separating glycerol residues from MDAG. This study investigates the impacts of adding electrolytes (calcium chloride, ammonium bicarbonate, magnesium sulfate, and sodium sulfite) and the effects of electrolyte concentration (2.5%, 5%, 7.5%, and 10% w/v) on the concentration of glycerol, monoglycerol, diglycerol, and triglyceride. Electrolytes have a role in transforming the MDAG emulsion system from a water-in-oil (w/o) system to an oil-in-water (o/w) system, causing the emulsion to break down and form cream. Glycerol and water create a polar phase (skim), whereas MDAG form a non-polar phase (cream). The analysis showed that the highest yield was obtained by adding 5% sodium sulfite (SS) electrolyte, which was 44.51±0.60%. Increasing the electrolyte concentration from 2.5% to 5% resulted in a larger yield, but a further increase of up to 10% did not improve the yield. The glycerol content also de creased from 13.36±0.82% to 1.8±0.32% with the addition of 5% SS electrolyte. This result is in line with the fact that the amount of MAG and DAG increased after the creaming demulsification with 5% SS electrolyte (41.68±1.23% and 25.75±0.26%, respectively).

The glycerolysis of crude palm oil (CPO) using potassium hydroxide was studied. This work aimed to evaluate free fatty acid (FFA) conversion in CPO through glycerolysis using crude glycerol. The effect of molar ratios of FFA to crude glycerol, reaction temperature, stirring speed, and catalyst loading was investigated. The best conditions for the highest FFA conversion of 95.45% were found: 1:4 of FFA to crude glycerol molar ratio, 75°C of reaction temperature, 250 rpm stirring speed, and 0.75% (w/w of oil) of catalyst loading. These conditions have decreased the FFA of CPO from 6.15% to 0.28% in 90 minutes. A kinetic model of the second-order reaction rate was used to quantify the influence of process parameters. It can be concluded that the crude glycerol as a side product of transesterification can be utilized in glycerolysis to lower the cost of biodiesel production.

The results showed that the highest yield was obtained, namely 10.97% in the treatment of the raw material to solvent ratio of 1:30 and the extraction time of 120 minutes, while the lowest yield was 2.66% in the treatment of the raw material to solvent ratio of 1:20 and the extraction time of 30 minutes. Based on the phytochemical analysis, the highest concentrations of phenolic compounds and flavonoids, namely 66.12 mg GAE/g and 95.70 mg QE/g, were obtained from the treatment of the ratio of raw materials to solvents of 1:25 and extraction time of 120 minutes. Meanwhile, the lowest concentrations of phenol and flavonoids, namely 24.87 mg GAE/g and 39 mg QE/g, were achieved in the treatment of the raw material to solvent ratio of 1:20 and the extraction time of 30 minutes. The FTIR  of amla seed oil with different aw material to solvent ratio and extraction times indicated the presence of the same functional group content. In the form of O-H indicating the presence of polyphenolic compounds, C=O indicating the presence of ascorbic acid compounds, C-O indicating the presence of pectin compounds, and C-O-C indicating flavonoid compounds in amla seed oil. The fatty acid components contained in amla seed oil analyzed using GCMS showed that the content of unsaturated fatty acids was higher than saturated fatty acids with linoleic acid as the main component. Physical-chemical analysis of pH, density, acid number, FFA, and peroxide number showed that the extracted oil quality was better than in previous studies.

Esterification followed by transesterification process is widely applied for biodiesel production from oil with high free fatty acids (FFA) content to remove the FFA and increase the yield of biodiesel. The aim of this research was to study the esterification of waste cooking oil using the hydrodynamic cavitation apparatus. Waste cooking oil with initial FFA content 4.33% was esterified with methanol using sulfuric acid 1%-w/w as the catalyst. The reaction condition was kept constant for 120 minutes of total reaction time. At the best operating condition i.e. molar ratio of waste cooking oil to methanol 1:10 and reaction temperature 50 °C, the initial FFA of waste cooking oil 4.33% reduced to 0.76%. The experimental results also showed that the hydrodynamic cavitation had better performance than the conventional process using mechanical stirring.

Kinetics describing chemical glycerolysis reaction of free fatty acid (FFA) in crude palm oil (CPO) with crude glycerol has been investigated. In this study, the kinetics was explored under the conventional procedure using KOH as a homogenous catalyst. The FFA value was measured by the acid-base titration technique. The effect of FFA to glycerol molar ratio and reaction temperature are examined to determine the best condition for FFA reduction. The glycerolysis achieved a maximum FFA reduction from 6.15% to 0.28% under the following conditions: FFA to glycerol molar ratio of 1:4 and 75°C temperature. Under these conditions, the total reaction orders and the reaction rate constant of glycerolysis were determined by establishing six kinetic models. It was found that the highest R2 was 0.89, which was presented from model 5 (α=2, β=0): ^j = kCAOt. The calculated rate constant, activation energy, and pre-exponential factor were’ 6^5608 L mol-1 min−1, 9,432 cal mol-1, and 5.4x106 L mol-1 min−1, respectively.