Abstract
Sorption of Sr2+, Co2+ and Pb2+ from aqueous waste solution on six hydroxyapatite (HAP) samples was studied. Formation of in situ apatite barriers in soil using water soluble reagents for sequestering Sr (2+), Co (2+) and Pb (2+) ions from their aqueous waste solutions as an application for HAP uses is of high interest. This technique is based on injecting a solution of calcium citrate and sodium phosphate into the soil to form insoluble calcium phosphates that transform into apatite. Both batch and column techniques were used. A synthetic mixed waste solution of Sr2+, Co2+ and Pb2+ ions is percolated from up to down into the sorbent column at constant flow rate. The obtained data show that the HAP barrier formed in the soil has a high efficiency for sequestering the studied metal ions from the aqueous solutions. The maximum capacity of HAP to Sr (2+), Co (2+) and Pb (2+) is about 530 mg g(-1), 375 mg g(-1) and 590 mg g(-1), respectively. Therefore, it is recommended to inject HAP into the soil under any tanks of liquid waste in order to work as a barrier to protect the environment from the hazardous radionuclides or heavy metals present in the tank, in case of any leakage from the tank.