Technological applications of organo-montmorillonites in the removal of pyrimethanil from water: adsorption/desorption and flocculation studies

Interaction behavior, mechanisms and hazardous changes of microplastics on single and binary component pesticide in the environment and food: Diethofencarb and pyrimethanil

In order to investigate the adsorption behavior and mechanism of microplastics (MPs) on multiple coexisting pesticides in practical systems, as well as their hazardous changes upon binding, diethofencarb and pyrimethanil were selected to be studied with four MPs. The adsorption rate of both pesticides would be faster in the binary-component case, conforming to pseudo-second-order kinetics, with adsorption sites and chemical adsorption dominating. And the more hydrophobic the pesticide, the faster the adsorption rate and the higher the adsorption capacity. Diethofencarb belonged to monolayer adsorption, whereas pyrimethanil belonged to monomolecular combined with multilayer adsorption, depending on the size of pesticides. And the adsorption process was both competitive and synergistic when pesticides coexist. In addition, the adsorption process was a spontaneous heat absorption process. Electrostatic forces have little effect on adsorption, while the adsorption capacity can be altered by the adsorption sites and hydrophobicity of MPs. The salting-out effect also facilitated the adsorption process. As for changes in hazard, the bioluminescence of A. fischeri wasn't significantly inhibited, lacking of acute environmental toxicity. However, in vitro digestion experiments demonstrated a significant increase in bioavailability of diethofencarb and pyrimethanil in combination with MPs. These findings suggest the stronger adsorption behaviors and higher loading capacities between pesticides and MPs could lead more serious hazards to the human body, which deserves further attention.

Reviving the Potential of Vermiculite-Based Adsorbents: Exceptional Ibuprofen Removal on Novel Amide-Containing Gemini Surfactants

In this study, we introduce a novel series of gemini surfactants with amide groups (HDAB, HDAHD, and HDAPX) and use these surfactants to decorate sodium vermiculite (Na-Vt) for the adsorption of Ibuprofen (IBP) from wastewater. Exceptional IBP uptake on organo-vermiculites (organo-Vts) is obtained, with maximum adsorption capacities reaching 249.87, 342.21, and 460.15 mg/g for HDAB-Vt, HDAHD-Vt, and HDAPX-Vt (C0 = 500 mg/L, modifier dosage = 0.2 CEC), respectively. The adsorption of IBP is well fitted by pseudo-second-order, intraparticle diffusion, and Freundlich isotherm models, verifying chemical adsorption processes with multilayer arrangement of IBP in organo-Vts. Thermodynamically, the removal of IBP on HDAHD-Vt is exothermic, while the endothermic nature aptly describes the adsorption process of HDAB-Vt and HDAPX-Vt. Moreover, organo-Vts can be stably regenerated in three cycles. Outstanding adsorption performance of organo-Vts is attributed to synergistic effects of the partition process and functional interaction, which are influenced by the steric hindrance and chain configuration of the modifier. A combined evaluation of adsorption tests and fitting calculations is employed to reveal the adsorption mechanism: (i) the incorporation of amides into the alkyl chain significantly enhances the utilization of the interlayer space in organo-Vts. (ii) Smaller steric hindrance and higher rigidity of the modifier spacer contribute to improved adsorption performance. The findings in this study rekindle interest in Vt-based adsorbents, which demonstrate comparable potential to other emerging adsorbents that are yet to be fully explored.

"Functional connector" strategy on tunable organo-vermiculites: The superb adsorption towards Congo Red

With the increasingly worldwide concentration of environmental pollution, exploiting cost-effective adsorbents has been a research hotspot. Here we introduce novel "functional connector" amide-containing gemini surfactants (LDAB, LDAPP, LDAMP and LDABP) and apply to modify Na-vermiculite (Na-Vt) for Congo red (CR) removal. Chain amide as the functional connector in the modifier, increases 6.9 times of CR uptake than traditional organo-Vts, which is further enhanced by tunning the functional group of modifier spacers. Superb uptake of CR on organo-Vts reaches 1214.05, 1375.47 and 1449.80 mg/g, and the removal efficiencies achieve 80.94%, 91.70% and 96.65% on LDAB-Vt, LDAPP-Vt and LDAMP-Vt, respectively. Notably, the maximum experimental adsorption capacity of LDAPP-Vt is 1759.64 mg/g. These experimental values are among the highest reported CR adsorbents. A combination experimental and theoretical analysis is conducted to unveil the structure-adsorptivity relationship: (i) Adsorptivity enhancement of organo-Vts is more effectively by regulating functional chains than the functional spacer. (ii) para-substituted aromatic spacers own the best adsorptive configuration and strongest stability for π-π interaction. (iii) π-π interaction provided by isolated aromatic ring is stronger than biphenyl, whose steric hindrance depresses the adsorptivity. Results in this study not only explain a new "functional connector" strategy to Vt-based adsorbents, but also provide a practical designing strategy for organic adsorbents characterized with high uptake capacity.

Organo-Montmorillonite Modified by Gemini Quaternary Ammonium Surfactants with Different Counterions for Adsorption toward Phenol

The discharge of industrial phenol pollutants causes great harm to the natural environment and human health. In this study, phenol removal from water was studied via the adsorption of Na-montmorillonite (Na-Mt) modified by a series of Gemini quaternary ammonium surfactants with different counterions [(C₁₁H₂₃CONH(CH₂)₂N⁺ (CH₃)₂(CH₂)₂ N⁺(CH₃)₂ (CH₂)₂NHCOC₁₁H₂₃·2Y^-, Y = CH₃CO₃^-, C₆H₅COO^- and Br^-, 12-2-12·2Y^-]. The results of the phenol adsorption indicated that MMt-12-2-12·2Br^-, MMt-12-2-12·2CH₃CO₃^- and MMt-12-2-12·2C₆H₅COO^- reached the optimum adsorption capacity, which was 115.110 mg/g, 100.834 mg/g and 99.985 mg/g, respectively, under the conditions of the saturated intercalation concentration at 2.0 times that of the cation exchange capacity (CEC) of the original Na-Mt, 0.04 g of adsorbent and a pH = 10. The adsorption kinetics of all adsorption processes were in good agreement with the pseudo-second-order kinetics model, and the adsorption isotherm was better modeled by Freundlich isotherm. Thermodynamic parameters revealed that the adsorption of phenol was a physical, spontaneous and exothermic process. The results also showed that the counterions of the surfactant had a certain influence on the adsorption performance of MMt for phenol, especially the rigid structure, hydrophobicity, and hydration of the counterions.

Influence of sodium dodecyl sulfate coating on adsorption of methylene blue by biochar from aqueous solution

Biochar is regarded as a promising new class of materials due to its multifunctional character and the possibility of effectively coupling different properties. With increasing introduction into the environment, environmental chemicals such as surfactants will load onto the released biochar and change its physicochemical characteristics and adsorption behavior toward pollutants. In this study, sodium dodecyl sulfate (SDS), as one type of anionic surfactant, was coated onto biochar with different loading amounts. The influence of SDS loading onto biochar's physicochemical properties were investigated by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, zeta potential and Brunauer-Emmett-Teller (BET) surface area and pore size distribution analysis. Results showed that the pore size of the biochar decreased gradually with the increase of SDS loading because of the surface-adsorption and pore-blocking processes; the pH of the point of zero charge (pH_PZC) decreased with increasing SDS loading. Although surface-coating with SDS decreased the pore size of the biochar, its adsorption capacity toward Methylene Blue (MB) significantly increased. The biochar-bound SDS introduced functional groups and negative charges to the biochar surface, which could thus enhance the adsorption of MB via hydrogen bonding and electrostatic interaction. The results can shed light on the underlying mechanism of the influence of anionic surfactants on the adsorption of MB by biochar.