Qiu Xueqing

Surface Behavior of Aminosulfonate Formaldehyde Condensates and Its Dispersion Effect on Cement Paste

The surface physicochemical properties of aminosulfonate formaldehyde condensates (ASP) and naphthalene sulfonate formaldehyde condensates (FDN) and the dispersion effect on cement paste were investigated. The results showed that these two superplastcizers could hardly reduce the surface tension of aqueous solution, and the surface activity and foam production was rather weak. The adsorption of ASP and FDN on the cement particles followed the Langmuir adsorption equation, characterized as monolayer adsorption. The maximum adsorptive amount of ASP on the cement particles was 3.83 mg/g at 20°C, and the adsorption rate constant was 1.00 s−1, which were less than those of FDN, respectively. The ζ potential of cement particles containing ASP was larger than that containing FDN, and the loss of ζ potential was much less. Study on the XPS spectrograms presented that, the thickness of adsorption layer of ASP on the cement particles was 7.26 nm, while that of FDN was 1.50 nm. It could be concluded that the electrostatic repulsion effect and steric repulsion effect of ASP were stronger than those of FDN, hence ASP had better dispersion effect and fluidity‐retaining ability on the cement paste. When the dosage of superplasticizer was 0.5 wt% of the cement, the fluidity of cement paste with adding ASP was 270 mm, while that with adding FDN was only 150 mm at a mass ratio of water to cement of 0.28. The residual fluidity of cement paste with adding ASP was 167 mm with 2.5 h elapsed at an initial fluidity of 200 mm, while that with adding FDN was only 101 mm.

Determination of Lignin in Tobacco by Mid-infrared Spectroscopy

An in situ method for rapidly determining the lignin content in tobacco was developed with mid-infrared (MIR) spectrometry, and the lignin contents in ground tobacco stem and leaf were separately determined by this method. The calibration curve of the lignin content in tobacco was obtained on the basis of absorption peak area of lignin at 1508 cm-1 with determination coefficient of 0.9914. The results showed that the lignin contents in the ground stem and leaf of B1F burley tobacco in“Shuangxi”brand were 2.45% and 1.21% with the relative standard deviations of 3.88% and 4.17%, respectively. The average recoveries of this method ranged from 96.96% to 106.01%. With good reproducibility, this method is simple in operation and rapid for determining the lignin content in tobacco.