This study aims to investigate the possibility of biodiesel production from used frying oil and purify the produced biodiesel using dry (activated charcoal - magnesium silicate) and wet (acid water) washing methods. A biodiesel production pilot unit was constructed and installed at the energy laboratory, Agric. Eng. Dept., Faculty of Agric, Mansoura Univ., Egypt. Methanol and potassium hydroxide were used as catalysts. Glycerol was the bottom layer that was deposited by gravity, and the upper layer was biodiesel. Biodiesel was purified using dry washing (5% activated charcoal and 1% magnesium silicate) (w/w) at 65 °C and stirring for10,20, and 30 minutes, and then microfiltratied to separate biodiesel from dry purifiers. The biodiesel produced was also purified using acid water. Impure biodiesel was washed with 10% acid water at 55 °C. A decrease in free fatty acids was obscured during the 30-minute stirring period, from 2.26% before purification to levels of 0.23,0.14 and 0.23% for the activated charcoal, magnesium silicate, and acid water, respectively. The physical properties of the produced biodiesel were estimated. Purification with the activated charcoal gave the best results compared to purification with magnesium silicate and acid water, as it was lower in viscosity (7.88–5.70%), higher in flash point (5.72–8.58%), and the least in biodiesel losses. During purification, it was less than magnesium silicate and acid water by (5% and 25%) respectively. The rest of the properties are among those listed according to ASTM D6751. It was also the cheapest material used for the purification process.