Surface-Induced Crystallization of Sodium Dodecyl Sulfate (SDS) Micellar Solutions in Confinement

Interface-Templated Crystal Growth in Sodium Dodecyl Sulfate Solutions with NaCl

Many ionic surfactants, such as sodium dodecyl sulfate (SDS) crystallize out of solution if the temperature falls below the crystallization boundary. The crystallization temperature is impacted by solution properties and can be decreased with the addition of salt. We studied SDS crystallization at liquid/vapor interfaces from solutions at high ionic strength (sodium chloride). We show that the surfactant crystals at the surface grow from adsorbed SDS molecules, as evidenced by the preferential orientation of the crystals identified by using grazing incidence X-ray diffraction. We find a unique time scale for the crystal growth from the evolution of structure, surface tension, and visual inspection, which can be controlled through varying the SDS or NaCl concentrations.

Study on SO42−/Cl− Erosion Resistance and Mechanism of Recycled Concrete Containing Municipal Solid Waste Incineration (MSWI) Powder

In this paper, the strength characteristics and erosion resistance of solid waste incineration (MSWI) powder were studied. Firstly, the optimum process for the preparation of regenerated powder from MSWI bottom slag by ball milling was determined as follows: rotational speed 350 r/min, time 45 min. The strength activity index of regenerated powder reached the maximum when the substitute content of powder was 30%. Secondly, the semi-erosion method was used to study the strength variation rule of mortar with different content of MSWI powder in semi-immersion of salt solution. It was found that the higher the content of MSWI powder, the greater the anti-erosion coefficient of mortar specimen. Finally, the capillary rise test, crystallization test and capillary pore water absorption test were used to study the total porosity, coarse capillary-pore porosity and fine-capillary pore porosity of concrete containing MSWI powder. The results showed that, with the increase in MSWI powder content, the above pore structure properties were improved. The results revealed the transport and crystallization process of salt solution in concrete mixed with MSWI powder and the mechanism of corrosion resistance.

A Novel Hydrate Form of Sodium Dodecyl Sulfate and Its Crystallization Process

A novel hydrate form of sodium dodecyl sulfate (SDS) was firstly discovered through a hydrate screening with the use of organic solvents, while SDS is generally prepared solely in aqueous media. Surprisingly, a novel SDS hydrate form with needle-shaped crystals produced by adding acetonitrile to a 20 wt % SDS aqueous solution at a ratio of 3:1 (v/v) and further cooling to around 5 °C could be found with a trace amount in one of the two purchased SDS products that we examined. After comprehensive solid-state characterizations by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), Raman spectroscopy, dynamic vapor sorption (DVS), and elemental analysis (EA), it is also successfully made directly from the synthesis of SDS through esterification and saponification. Four times the equal proportion of acetone was added into the reaction solution at an interval of 5 min to separate the side product, sodium sulfate, from the mother liquor. The desired novel hydrate form of SDS was then obtained by cooling the filtered mother liquor to 5 °C and aged for 8 h for a preferential growth.