The properties of Al-rich gelatinous materials precipitated from the filtered solution of tetracalcium sulfoaluminate (CSA) paste and the H3BO3 solution were investigated in this study. Because of amphoteric properties of Al, the stability of Al-rich gelatinous materials depends on the pH of solution. For example, Al-rich gel had a low solubility around 6 of pH, but it had a high solubility in both high alkaline side and high acid side of pH. The change in solubility of Al-rich gel with pH had a major effect on retardation and re-activation of the hydration reaction of CSA with H3BO3 solution. The hydration reaction of CSA with H3BO3 solution can be controlled by changes in pH of solution.
To obtain a fine-grained MgO polycrystals, colloidal processing was conducted. The dispersed aqueous and non-aqueous suspensions of fine MgO particles were prepared. The suspensions were consolidated by slip casting and CIP treatment under 400 MPa and then the compacts were sintered at 1300-1600°C in air. It was difficult to consolidate large compact without cracks via nonaqueous colloidal processing. In case of aqueous colloidal processing, influence of the MgO hydration on the sintering was examined. Undoped MgO bodies were not densified fully even at 1600°C but densification was promoted by adding Fe2O3 or ZrO2. Fine grained ZrO2 dispersed MgO polycrystals were obtained.
We have developed high performance and multi functional inorganic materials for wastewater treatment. We have discovered that a Mg-Al-C1 form hydrotalcite 'TPEX' has high selectivity and large adsorbing capacity for phosphate anions. We have examined granulation of TPEX for a flow method with polystyrene-acrylate, polyacrylate, epoxy resin, polyacrylamido as a binder. From the results, it was cleared that the granular adsorbent granulated with polyacrylamido and epoxy resin as a binder showed high values in adsorbing capacity and physical strength. Adsorbing capacity value of 1.99 mmol·g-1 of the granular adsorbent was equivalent to about 90% of adsorbing capacity of the original TPEX. The granular adsorbent had high break through capacity of about 28 mg asP·g-1 with a flow condition that line velocity was 2.4 m·h-1, and space velocity was 4 h-1. These results suggest that the flow method with the granular adsorbent has the feasibility of effective and simple method that can utilize effectively phosphate adsorption characteristics of TPEX for removing phosphate anions from wastewater or some watersystem.