Abstract: In order to make full use of calcium resources in bovine bone, bovine bone waste was chosen as starting material to prepare calcium citrate by an ultrasonic-assisted direct neutralization method and the process conditions were optimized by the combined use of one-factor-at-a-time method and response surface methodology based on the yield of calcium citrate. The new preparation method was evaluated in comparison to the routine calcium dissolution method. Results showed that the optimum process conditions were determined as follows: solid-to-solvent ratio 1:15 (g/mL), solid-to-citric acid ratio 1:2, ultrasonic power 320 W, temperature 39 ℃, and sonication time 21 min, giving a calcium citrate yield of 71.21%. The purity of the product prepared using the optimized conditions was 94.38%. The amount of dissolved calcium after 21 min reaction in the new method was 85, 5.5 and 4 times as high as that obtained by 60 min standing, stirring or cooking without ultrasonic treatment, respectively. The amount of dissolved calcium was as high as 96.18% after three cycles of ultrasonic treatment. These results confirmed the ultrasonic-assisted method to be an effective method for preparing dissolved organic calcium from bovine bone, which can provide a basis for the industrial production of calcium products from waste bovine bone.

Key words: bovine bone, calcium citrate, ultrasonic, response surface methodology