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Foam fractionation is an effective separation technique in recovery of metal ions and surfactant from wastewater. In this paper, recovery of Cd(II) and surfactant in permeate from MEUF by foam fractionation with mixed anionic-nonionic surfactant were studied. Effects of the molar ratio of anionic-nonionic surfactant, Cd(II) concentration, pH on the foam properties and separation efficiency of the three matters were investigated. When the Cd(II) concentration of the feed solution was 10 mg/L, the molar ratio of Triton X-100/SDS was 0.1, the best Cd(II) removal percentage 99.1% was achieved. In addition, the removal percentages of the two surfactants were also relatively high at this condition. The mechanism of the effect of Triton X-100 on removal of Cd(II) by foam fractionation was also investigated by measurement of zeta potential and analysis of FTIR spectra. Results showed that a small amount of nonionic surfactant can significant enhance the removal percentage of Cd(II) by improvement of foam properties of anionic surfactant, while excessive nonionic surfactant may lower the removal percentage due to its negative effect on adsorption of Cd(II) at gas-liquid interface. [ABSTRACT FROM AUTHOR]

The SDS is investigated as a surfactant for heavy metal ion removal via micellar enhanced ultrafiltration (MEUF). It is important to recover and reuse surfactant from the retentate stream due to the high cost of surfactant. Repeated acidification is a new way to recover and reuse surfactant. The effects of pH, the initial surfactant concentration of simulated retentate solution, the volume of concentrated solution, and acidification times on SDS recovery and reuse were studied. At pH 1.0, the Cd 2+ was effectively separated from the surfactant micelles, and the SDS had the highest recovery rate. Additionally, the rate of the removal by reused SDS of metal ions was higher than 85% at pH 1.0. When the initial SDS concentration of the simulated retentate solution was 2.0 CMC, the efficiency of SDS recovery and reuse was better than of that at 1.0 CMC. The smaller the concentrated solution volume was, the higher the rates of separation and removal by reused SDS of metal ions were. SDS can be repeatedly used when the concentration achieves its CMC. [ABSTRACT FROM AUTHOR]

A bi-solvent system (ethanol and water) with the presence of l -glutamic acid (L-glu) was developed to achieve the controlled synthesis of whisker-like or urchin-like Sr-substituted HA (SrHA) through hydrothermal treatment. The effects of initial temperature of aqueous solution (ASIT), the presence of Sr, and ethanol proportion on HA morphology were investigated and the underlying mechanisms were illustrated. The results indicate that Sr and ethanol have antagonistic effects on the size of HA whisker, the introduction of Sr tends to reduce the whisker size, while the addition of ethanol tends to increase the nucleation efficiency. Finally, the whisker size and uniformity of SrHA can be regulated via ethanol proportion in the bi-solvent system. ASIT mainly affects the uniformity of solution by affecting Brownian motion in solution, which couples with the different solubility of l -glu and reactant ions in water and ethanol, ultimately determines whether the morphology of HA is whisker-like or urchin-like. Our bi-solvent system simplifies the complex process of template agent screening compared with the ways that introducing several templates agents to achieve the morphology regulation, and enriches the methods of controlled synthesis of different morphological Sr-HA. This feasible method may provide new strategy for simplifying the synthesis of other ions-doping HA with a certain morphology. [ABSTRACT FROM AUTHOR]

Surfactants widely exist in oil-in-water (O/W) emulsions, and they may exert significant influence on membrane performance during ultrafiltration (UF) of O/W emulsions using ceramic membrane. In this paper, we investigated UF of O/W emulsions stabilized by three surfactants (SDBS, CTAB and Tween-80 as anionic, cationic and nonionic surfactant) at different concentrations (0.25–2 CMC) using silicon carbide (SiC) ceramic membranes. SiC ceramic membrane showed satisfactory separation ability for O/W emulsions with oil rejection higher than 90%. Influence of surfactant on properties of O/W emulsions, oil rejection and permeate flux were studied. The main fouling types for all O/W emulsions were cake filtration and standard pore blocking based on analysis of flux data using Hermia's blocking model, and highest fouling degree occurred in CTAB prepared emulsions which has a opposite charge to ceramic membrane. Generation of fouling is not only related to blocking and adsorption of oil droplets on membrane, but also referred to surfactant adsorption on membrane. Surfactant adsorption on ceramic membrane during UF of O/W emulsions was further investigated based on Zhu and Gu's model. Surfactant was found to deposited in hemimicelle form on membrane surface and in membrane pores which have an important influence on membrane fouling. [ABSTRACT FROM AUTHOR]