Influence of Different Types of Emulsifiers on Properties of Emulsified Asphalt Binder and Its Evaporation Residue by Molecular Dynamics Simulation

There is an important role in the properties of emulsified asphalt binder and its evaporation residue about emulsifier, which has been confirmed by experiment and chemical tests. However, there is little research about the emulsifier at microperspective. Therefore, the influence of two kinds of emulsifiers, a typical cationic emulsifier (dodecyl benzene sulfonate) and a typical anionic emulsifier (dodecyl primary amine), on technical properties of emulsified asphalt binder and its evaporation residues such as store stability, workability, breaking behavior, and mechanical properties are investigated using a microapproach. Results show that there is an effective role in the storage stability, workability, and demulsification of emulsified asphalt binder about cationic emulsifier compared with anionic emulsifier. The anionic emulsifier makes the density of evaporation residue larger. However, the mechanical properties of anionic emulsified asphalt evaporation residue are conversely smaller compared with the cationic emulsified asphalt evaporation residue. The adhesion behavior results have confirmed that the anionic emulsified asphalt evaporation residue has a negative adhesion with aggregate due to its anion. The mechanism of the different emulsifiers on asphalt binders and their evaporation residue is explored at a microscale to help us to understand emulsified asphalt binder and its evaporation residue more in depth.

Efficient Adsorption of Pb(II) by Sodium Dodecyl Benzene Sulfonate Intercalated Calcium Aluminum Hydrotalcites: Kinetic, Isotherm and Mechanisms

CaAl-LDHs and sodium dodecyl benzene sulfonate (SDBS) intercalated CaAl-LDHs (SDBS-CaAl-LDHs) was acquired by co-precipitation. The two samples were characterized by XRD, XPS, FT-IR, TG and SEM. The factors affecting adsorption (pH, adsorption time，initial concentration) of Pb2+ by two adsorbents were studied. The results showed that SDBS-CaAl-LDHs has higher adsorption ability for lead ions removal than that of CaAl-LDHs. Kinetic data for lead ions were in keeping with pseudo-2nd-order model, the adsorption isotherms followed Langmuir and Freundlich isotherm model for CaAl-LDHs. The adsorption by SDBS-CaAl-LDHs were in keeping with the pseudo-second-order kinetic and Langmuir model, suggesting lead ions were chemical adsorption. Adsorption was thought to form through Pb species in the precipitates, such as formation of hydroxides and carbonates for lead ions by XRD analysis. Therefore, based on the structural and morphological features, as well as XRD, XPS and SEM, the lead ion adsorption mechanism on SDBS-CaAl-LDHs involved the electrostatic attraction, precipitation, complexation and ion exchange. The Langmuir adsorption capacities for SDBS-CaAl-LDHs were found as 797.63, 828.76, 854.29 mg×g−1 at 293k, 303k, 313k, respectively, when the pH is about 5.2, and thus, making it a highly economical adsorbent for the treatment of contaminated water.

Remediation of Cr(VI)/Cd(ІІ)-Contaminated Groundwater with Simulated Permeable Reaction Barriers Filled with Composite of Sodium Dodecyl Benzene Sulfonate-Modified Maifanite and Anhydride-Modified Fe@SiO2@Polyethyleneimine: Environmental Factors and Effectiveness

A composite material of sodium dodecyl benzene sulfonate- (SDBS-) modified maifanite and anhydride-modified Fe@SiO2@PEI (PEI) was used as an adsorbent for the removal of hexavalent chromium (Cr(VI)) and bivalent cadmium (Cd(II)) from groundwater by using column experiments and simulated PRB test. In this study, the optimum proportion of SDBS-modified maifanite and anhydride-modified Fe@SiO2@PEI was 5 : 1. In the column experiments, it was found that the penetration time increased with the increase of the initial concentrations (30, 60, and 90 mg/L) and the decrease of the flow rates (5.45, 10.9, and 16.35 mL/min) at an influent pH of 6.5 ± 0.3 . It was also obtained that the removal rates of Cr(VI) and Cd(ІІ) reached 99.93% and 99.79% at an initial Cr(VI) and Cd(ІІ) concentration of 30 mg/L with the flow rate of 10.9 mL/min, respectively, at 6 h. Furthermore, excellent removal effectiveness of Cr(VI) and Cd(ІІ) (85.94% and 83.45%, respectively) was still achieved in simulated PRB test at a flow rate of 5.45 mL/min with the heavy metal solution concentration of 5.0 ± 0.5 mg/L (Cr(VI) and Cd(II) concentration were, respectively, 5.0 ± 0 . 5 mg/L); and the adsorbent had not completely failed by the end of the trial. Yoon-Nelson model was successfully applied to predict the breakthrough curves for the assessment of composite material heavy metal removal performance and was in good agreement with the experimental data of the heavy metal removal efficiency. The strong removal ability of the adsorbent could be attributed to the fact that maifanite with a large diameter can provide support and increase the permeability coefficient and porosity and that zero-valent iron (ZVI) can convert Cr(VI) to Cr(III) and improve the adsorption capacity of maifanite. The obtained results suggested that the novel PRB fillers have great significance for preventing and controlling Cr(VI)/Cd(ІІ)-contaminated groundwater.

Synthesis of Organo-Quartz from Lumajang Sea Sand Using Sodium Dodecyl Benzene Sulfonate (SDBS) Modificator for Adsorption of Fe3+

This study aims to determine the effect of sea sand modification with SDBS for adsorption of Fe3+. Sea sand was treated with 0.1 M HCl solution at 25oC. Organo-quartz was prepared at SDBS concentration of below, equal, and above the CMC value by shaking the mixture for 4 hours at 100 rpm. Characterization by FTIR spectrophotometry showed a change in the spectra pattern. The activation caused increasing of -OH silanol while modifications make them decrease. Characterization with SEM showed that the morphology of the sea sand was not uniform with irregular white chunks. The EDX results showed that the dominant elements were C (13.89% ± 10.86), O (40.48% ± 6.58), Si (16.51% ± 8.13), and Fe (11.68% ± 14.38). Adsorption was carried out using Fe3+ at 50 ppm. The Fe3+ analysis was conducted by AAS. The adsorption value by activated sea sand was 58.22% ± 7.23% whereas without treatment sea sand was 70.46% ± 5.54, and the modified sea sand was 53.24% ± 4.86. The lower adsorption is probably caused by the dissolved iron oxides in sea sand during activation.