The sol-gel transition of methylcellulose （MC） solution in the presence of NaCl and hexade- cyltrimethylammonium bromide （HTAB）, together with MC/NaCl solution in the presence of HTAB and MC/HATB solution in the p...The sol-gel transition of methylcellulose （MC） solution in the presence of NaCl and hexade- cyltrimethylammonium bromide （HTAB）, together with MC/NaCl solution in the presence of HTAB and MC/HATB solution in the presence of NaCl, was investigated by the rheological measurements. It has been found that the sol-gel transition temperature of MC solution decreases linearly with the concentration of NaCl in solution but increases linearly with the concentration of HTAB in solution, respectively. However, the sol-gel transition temperature of MC/NaCl solution in the presence of HTAB keeps the same value, independent of the concentration of HTAB in solution. On the other hand, the sol-gel transition temperature of MC/HTAB solution decreases linearly with the concentration of NaCl in solution. The experimental results suggest that, for MC/NaCl solution in the presence of HTAB, the salt- induced spherical micelles of HTAB should have formed in bulk solution. For MC solution in the absence of NaC1, no spherical micelles have been formed in bulk solution, though the concentration of HTAB in our experiment is almost one order of magnitude higher than the critical mieelle concentration of HTAB in polymer-free solution. In fact, due to adsorption of HTAB on MC chains, the realconcentration of HTAB in bulk solution, is much less than the apparent concentration of HTAB dissolved in MC solution.展开更多
Surfactant-modified natural zeolites(SMNZ)with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide(HTAB)onto the surface of a natural zeolite.The adsorption behavior of humic acid(HA)...Surfactant-modified natural zeolites(SMNZ)with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide(HTAB)onto the surface of a natural zeolite.The adsorption behavior of humic acid(HA)on SMNZ was investigated.Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite.HA removal efficiency by SMNZ increased with HTAB loading.Coexisting Ca2+in solution favored HA adsorption onto SMNZ.Adsorption capacity decreased with an increasing solution pH.For typical SMNZ with bilayer HTAB coverage,HA adsorption process is well described by a pseudo-second-order kinetic model.The experimental isotherm data fitted well with the Langmuir model.Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^(-1),respectively.E2/E3(absorbance at 250 nm to that at 365 nm)and E4/E6(absorbance at 465 nm to that at 665 nm)ratios of the residual HA in solution were lower than that of the original HA solution.This indicates that the HA fractions with high polar functional groups,low molecular weight(MW),and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage.Results show that HTABmodified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.展开更多
文摘The sol-gel transition of methylcellulose （MC） solution in the presence of NaCl and hexade- cyltrimethylammonium bromide （HTAB）, together with MC/NaCl solution in the presence of HTAB and MC/HATB solution in the presence of NaCl, was investigated by the rheological measurements. It has been found that the sol-gel transition temperature of MC solution decreases linearly with the concentration of NaCl in solution but increases linearly with the concentration of HTAB in solution, respectively. However, the sol-gel transition temperature of MC/NaCl solution in the presence of HTAB keeps the same value, independent of the concentration of HTAB in solution. On the other hand, the sol-gel transition temperature of MC/HTAB solution decreases linearly with the concentration of NaCl in solution. The experimental results suggest that, for MC/NaCl solution in the presence of HTAB, the salt- induced spherical micelles of HTAB should have formed in bulk solution. For MC solution in the absence of NaC1, no spherical micelles have been formed in bulk solution, though the concentration of HTAB in our experiment is almost one order of magnitude higher than the critical mieelle concentration of HTAB in polymer-free solution. In fact, due to adsorption of HTAB on MC chains, the realconcentration of HTAB in bulk solution, is much less than the apparent concentration of HTAB dissolved in MC solution.
基金This work was supported by the National Major Project of Science and Technology Ministry of China(Grant No.2008ZX07421-002)the National Natural Science Foundation of China(Grant No.50908142)the National Science and Technology Infrastructure Program of China(Grant No.2006BAJ08B02).
文摘Surfactant-modified natural zeolites(SMNZ)with different coverage types were prepared by loading hexadecyltrimethyl ammonium bromide(HTAB)onto the surface of a natural zeolite.The adsorption behavior of humic acid(HA)on SMNZ was investigated.Results indicate that the adsorbent SMNZ exhibited a higher affinity toward HA than the natural zeolite.HA removal efficiency by SMNZ increased with HTAB loading.Coexisting Ca2+in solution favored HA adsorption onto SMNZ.Adsorption capacity decreased with an increasing solution pH.For typical SMNZ with bilayer HTAB coverage,HA adsorption process is well described by a pseudo-second-order kinetic model.The experimental isotherm data fitted well with the Langmuir model.Calculated maximum HA adsorption capacities for SMNZ with bilayer HTAB coverage at pH 5.5 and 7.5 were 63 and 41 mg·g^(-1),respectively.E2/E3(absorbance at 250 nm to that at 365 nm)and E4/E6(absorbance at 465 nm to that at 665 nm)ratios of the residual HA in solution were lower than that of the original HA solution.This indicates that the HA fractions with high polar functional groups,low molecular weight(MW),and aromaticity had a stronger tendency for adsorption onto SMNZ with bilayer HTAB coverage.Results show that HTABmodified natural zeolite is a promising adsorbent for removal of HA from aqueous solution.
