Hydrothermal process has been applied for effective production of Hydrogen from biowastes. In this study hydrothermal process for production of valuable Hydroxylapatitefrom chicken manure containing phosphorus was focused on. Conditions of 400?C and 26 - 27 MPa with addition of 1 mmol Ca(OH)2 were determined as the optimal by using O-phospho-DL-serine as a model compound. Afterwards, the real biowaste containing phosphorous, chicken manure was processed under the same conditions. Formation of a Hydroxylapatite; in the solid residue was confirmed from X-ray diffraction (XRD) patterns, after purification. It was found that 27.9% of P in the chicken manure was converted to Hydroxylapatite. With the use of acetic acid as a chemical purification medium, Hydroxylapatite was obtained.
Production of poultry is rapidly expanding worldwide to meet the needs of the increasing human population. This cause an increased poultry biowaste, i.e. chicken manure [
Valuable material, Hydroxylapatite is a calcium orthophosphate with chemical composition of Ca10(PO4)6(OH)2. There are chemical similarities between Hydroxyapatite and the mineral part of human bone. Therefore it is highly used for biomedical applications [3-5].
Catalysts were used to enhance the reaction rate of the hydrothermal process in sub or supercritical water at low reaction temperature [
In earlier study, various catalysts and additives used for hydrothermal process were studied and Ca(OH)2 was found to be a suitable additive because it could suppress the production of heteroatom pollutants in the gas phase and enhance the Hydrogen yield. Ca(OH)2 is also reasonable than other additives and catalysts currently available. The additive cost is an important factor for treatment of a large amount of biowaste [
First, selecting and using pure test samples of O-phospho-DL-serine with P, as a model compound, the optimum conditions were determined for the hydrothermal process. Then, these conditions were applied to a real biowaste, chicken manure.
The objective of this study was providing production of Hydroxylapatite as a valuable material through the hydrothermal process by using biowaste, chicken manure with Ca(OH)2.
The experimental setup is basically same as that reported the earlier study [
O-phospho-DL-serine, Ca(OH)2 which was used as the additive is of analytical grade, acetic acid which was used in purification process, pure Hydroxylapatite, and CaCO3 were purchased from Wako Chemical Co. Ltd (Japan).
Commercially available chicken manure was purchased from G. I. Ltd. (Japan). The chicken manure’s elemental compositions were 30.3% C, 4.7% H, 2.6% N, 0.8% S, 4.4% K [
About 400 mg sample was put into the reactortogether with 1 mmol Ca(OH)2 and 5 ml water. Then, N2 gas was introduced to purge the residual O2 gas in the reactor. The reactor was put in the ovenand heated to 400˚C at 1.5˚C min−1. The reactor was maintained at 400˚C for 40 minutes to complete the hydrothermal process under the pressure of 26 - 27 MPa. Then, the oven was cooled down to 30˚C. And the generated components were analyzed.
Ionic chemical species dissolved in the liquid phase were analyzed with an ion chromatograph (HIC-SP Suppressor Ion Chromatograph, Shimadzu). The parameters and conditions; Shimadzu IC-SC-1 Column for Cation (+), Shodex ICSI-50 Column for Anion (−), Oxalic acid 3.0 mM Mobile phase for Cation (+), Na2CO3 3.2 mM and NaHCO3 1.0 mM Mobile phase for Anion (−), 1.5 mLmin−1 flow for (+) Cation and Anion (−), 40˚C column temperature for Cation (+), 25˚C column temperature for Anion (−) were used for the IC [
An XRD system (RINT 2500/PC by Rigaku Co., Japan) was used for identification of residual solid samples. The diffraction data were collected from 20˚ to 60˚ in 2θ values with a step of 0.02˚. An elemental analyzer (Perkin Elmer 2400 Series II CHNS/O System) was used for determination of C, H, and N.
The resulting gaseous components were analyzed using a gas chromatograph (GC Shimadzu 5A) equipped with a thermal conductivity detector (TCD).
Porapak Q (length: 2 m, diameter: 3 mm) Column, Argon carrier gas, 98 kPa inlet pressure, 80˚C inlet temperature and 50˚C column temperature were used for H2 analysis as the parameters and conditions [
Porapak Q (length: 2 m, diameter: 3 mm) Column, Helium carrier gas, 170 kPa inlet pressure, 80˚C inlet temperature and 50˚C column temperature were used for CH4, CO, etc. analysis as the parameters and conditions [
Acetic acid solution was usedas weak acidfor purification of Hydroxylapatite.
In the earlier paper, the effect of added Ca(OH)2 amount on the concentration of phosphate ion dissolved in the liquid phase for O-phospho-DL-serine was reported [
The temperature for the hydrothermal process was held at 400˚C, without the additive, 93.3% of sample phosphorus was converted to phosphate ion. As the amount of Ca(OH)2 was increased, the phosphate ion yield was suppressed [