廃石こうボードを再利用した晶析型脱リン材へのPVB(Polyvinyl Butyral)被膜による耐久性の向上

抄録

From a viewpoint of creation of a recycling society, it is essential to establish a method for recycling waste gypsum boards because large amount of gypsum board are scrapped with rehabilitation of architectural structure. For this purpose, we tried to reuse gypsum boards as phosphorus adsorbents and reported that carbonation of gypsum boards was effective method for the preparation of phosphorus adsorbents with high performance. However, the surface layers of carbonated gypsum boards were easy to peel out after immersion in a phosphorus solution due to the dissolution of gypsum. In this study, aiming at improving the durability of the phosphorus adsorbent we attempted to coat the surface of gypsum boards with PVB(Polyvinyl Butyral) before carbonation. Test pieces cut out from commercial gypsum board were coated PVB by immersing in PVB acetone solution and drying in air. The amount of adhering PVB to the gypsum board increased with increasing PVB concentration. The surfaces of the PVB coated gypsum boards were covered with uniform shaped CaCO₃ crystals. Although the PVB coated specimens showed slightly low phosphorus removal ratio in the early stage of phosphorus removal, all samples showed high phosphorus removal ratio more than 90% regardless of PVB coating after 5days immersion. Moreover, although the surface of the samples without PVB coating suffered damage on immersing in the phosphorus solutions, the PVB coated samples kept initial appearance even after long-term immersion in the phosphorus solution.