Two gram of SPI powder was suspended in 14.6ml deionized water and stirred for 1h to make uniform slurries. The solid con-tent of these slurries was around 11%. The pH of SPI slurry was adjusted to 10±0.1 with 2mol/L sodium hydroxide using a dig-ital pH analyzer. Varying amounts of UA (3%, 5%, 7%, and 10% of the SPI dry base) were then added to the SPI slurry. The pH of the slurry was maintained at 10.0 by adding sodium hydroxide. EDC (30wt%of UA)was thenadded to the slurry to activate the carboxyl group ( COOH). The mixture was stirred for 5h at room temper-ature (23◦C). The same pH, solid content and stirring conditions were used for SPI slurry control preparation.