In the current study, the effects pertaining to the addition of bulking agent on the density and the surface free energy of the paper-sheets were evaluated. Bulking agent addition resulted in the reduction of the density of wheat straw pulp paper (WBKP). The tensile strength of the handsheets varied in proportion to the reduction of sheet density. Basically, the decrease in tensile strength of the handsheets was dependent on the decrease in inter-fiber bonding strength, which follows the Page equation theory. The bulking promoter S enhanced the sheet sizing performance by its addition, and it improved the sizing performance further when used in combination with AKD sizing agent. Wetting characteristics of the handsheets were determined by contact angle measurements. The addition of bulking agent S reduced the ϒ_s ^d, which reduced the hydrophilicity of the paper. In addition, the use of the bulking agent in combination with AKD sizing agent resulted in the reduction of the paper ϒ_s ^d.

Commercially available oxidized black colored polyacrylonitrile (PAN) fiber was heat treated above 900 ̊C under helium or ammonia gas flow. Ammonia gas treatment made specific surface area of the oxidized PAN increase from 7 m²/g to 1000 m²/g or more, becoming activated carbon fiber (ACF), whereas helium treatment resulted in the maximum surface area of only 60 m²/g. Adsorption of phosphate improved from 0.022 mmol/g for oxidized PAN to 0.057 mmol/g for the helium treatments at pH range of 5-6. In case of ammonia treatment, the adsorption amount of phosphate attained 0.056 to 0.17 mmol/g in maximum, depending on the treating temperature ranging from 925 to 975 ̊C. The adsorption sites for negatively charged phosphate could be estimated to be positively charged quaternary nitrogen species generated on PAN fiber surface by the heat treatment. Langmuir adsorption affinity of PAN-ACF was derived from isotherms to be 0.6 L/mmol or more; moderate adsorption affinity was exhibited.