Phase behaviors of chitosan/lignosulfonate mixed solutions

Abstract

ABSTRACT The positively chitosan, CS, and negatively lignosulfonate, LGS, were statically mixed forming a series of mixed solutions. Experimentally, the light brown LGS solution was slowly flowed into the colorless CS solution to form the as-prepared CS/LGS mixed solutions. These mixing solutions presented regular bi-phases taking the LGS phase at the top and the CS phase at the bottom where the difference is the phase thickness varied with the mixing ratio variety. To keep the static mixing condition up to the 3rd, 12th and 15th days, these CS/LGS mixed solutions presented two-phase change tendencies because the CS percent greater samples kept the bi-phases and the LGS percent greater samples presented a tri-phases with a new darker yellow phase at the bottom and a new light yellow phase at the middle. This indicated that the statical mixing time has caused the electrostatic interaction occurrence between the CS and LGS solutions when the reaction degree was influenced by the mixing ratio. The particle size for the CS/LGS mixed solutions with the mixing ratio at 70/30 and 30/70 vol% both after static mixing of 15 days was analyzed and found it was smaller at about 200–300 nm in the upper phase and greater at about 1100–1300 nm in the bottom phase corresponding to the formed micelles and the precipitated aggregates, respectively. Recorded dynamic conductivity revealed that the electrostatic interaction between the CS and LGS strongly occurred after static mixing of about 300 s and the start time was controlled by the mixing ratio, especially the LGS percent.