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.

Viologen capped by nucleobase—building blocks for functional materials: synthesis and structure–properties relationship

The current study presents a new class of functional derivatives (1–3) consisting of a dicationic viologen (4,4’-bipyridinium unit) (V2+) capped by nucleobases thymine (NB1), adenine (NB2), thymine/adenine (NB1, NB2), and ion-paired with amphiphilic anion 3,4,5-tris(dodecyloxy)benzene sulfonate (DOBS−). The target of our work focuses on the design and synthesis of molecular building blocks in which three different functionalities are combined: chromophore (V2+ unit), molecular recognition (NB unit), and thermotropic liquid crystal (DOBS unit). The resulted materials exhibit liquid crystalline properties at ambient temperature with significant particularities-induced by nucleobases in the mesogen structure. Structure–properties relationship study focuses on providing knowledge about (1) how the thermotropic, redox properties, thermochromism, or ionic conductive properties are influenced by the presence of purinic or pyrimidinic nucleobases, and (2) how effective is their ability to self-assembly by hydrogen bonding in nonpolar solvents. The presence of nucleobases has been proved to have a substantial impact on electron transfer rate during the reduction of viologen moieties by intermolecular aggregation. Ionic conductivity and thermochromic properties of derivatives 1–3 were investigated and compared to a non-containing nucleobase analog methyl viologen with 3,4,5-tris(dodecyloxy)benzene sulfonate anion (MV) as reference. Graphical abstract

Screening of Bacteria in the Biodegradation of Linear Alkyl Benzene Sulfonate (LBAS) From Car Wash Waste Water in Tehran (Iran)

Linear alkyl benzene sulfonate (LABS) is a substance used as a surfactant in anionic detergents. Today, it is the most widely used surfactant in detergent products after soap. The aim of this study was to screen effective isolates for the degradation of LABS from car wash effluents in Tehran (Iran). In this study, 10 effluent samples were randomly collected from car washes in Tehran (Iran). Isolation of mesophilic aerobic bacteria was performed by direct and pre-enrichment culture techniques. Biodegradation of sodium dodecyl sulfonate by isolates and turbidity was investigated by methylene blue active substance (MBAS) method, and the superior strain was identified by molecular method (Polymerase Chain Reaction, PCR), which approximately 86% of the material was degrade by the bacterial isolate, and the isolate was identified as Bacillus licheniformis.The results of MBAS method showed that the rate of LBAS degradation by bacteria was 86%, which indicates the high power of this bacterium to degrade LABS from sewage systems (car wash effluents). It was also shown that the concentration of LABS during 8 days of biodegradation period by this bacterium decreased from 80%, which indicates a significant decrease in LABS by Bacillus licheniformis. According to our results, Bacillus licheniformis can be used to dagrade LABS and its degradation in wastewater treatment systems of car wash effluents whose effluents are based on alkyl benzene sulfonates.