Crude glycerol,by-product in biodiesel production process,contains high amount of fatty acids which cannot be used directly without removing its strong dark color.We aimed to remove the coloring impurities in crude fatty acids using acid-activated clay as adsorbent.Crude fatty acid solution was obtained by acid-precipitation and hexane extraction and then,decolorization was performed.The effects of bleaching temperature,contact time,the amount of acid-activated clay and concentration of coloring impurities were investigated.No significant effect of bleaching temperature and contact time was observed.In optimization study using central composite design,complete decolorization was achieved at optimized condition,in which 3.5 g of clay was added into 10 mL of crude fatty acid solution with 20 of OD373.Notably,peroxides more than 80% were also concurrently removed.However,37% loss in fatty acids was observed during decolorization.Clay was repeatedly used without loss of adsorption capability if calcinating clay at 600oC after use.