Papers by Keyword: Seed Crystal

Abstract: A seed crystal medium was developed from the powder steel slag and other material in order to carry out a novel method for phosphorus removal and recovery through the crystallization process. Continuous-flow fixed-bed column experiment was conducted to investigate the phosphorus removal capacity with low P concentration (10mg/L), and the influences of HRT, Ca/P ratio and pH on the treatment efficiency were also considered. It was observed that the P concentration of filter effluent was always lower than 0.5mg/L whether under the experimental condition of pH=7 and HRT=60 min or the condition of pH=7, HRT=30min and the Ca/P ratio = 1.5. With the HRT 30min, increasing pH to 7.5 and decreasing Ca/P ratio to 1, the P concentration of filter effluent was still lower than 0.5mg/L. The XRD analysis of the sediment obtained from the filter bed proved that product formed in the phosphorus removal process was Hydroxyapatite (HAP), illustrated that the crystallization occurred in the process of P-removal. The results of this study suggest that the fixed bed - phosphorus crystallization process with seed crystal media is a promising technique for phosphorus removal and recovery.

Abstract: Eco-cement produced from waste concrete was proved to be feasible in early research. The seed crystal of ground granulated blast furnace slag (GGBS) was utilized in this research to lower the sintering temperature of eco-cement clinker. The mineral compositions of clinker with GGBS seed crystal was analyzed by X-ray diffraction (XRD), and the mechanical properties of eco-cement with GGBS seed crystal was also tested. Four main cement minerals were all observed in eco-cement clinker and the compressive strength of the eco-cement pastes can approach to about 66 MPa at 28 curing days. The results showed that GGBS seed crystal was favourable for the formation of cement minerals at a lower temperature. It can help reduce by about 50~100°C for the sintering process of cement clinker. Content of GGBS seed crystal should better be in the rage of 5%~8%, and the suitable sintering temperature should be 1350°C.