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A novel electrochemical sensor based on nitrogen doped graphene (NGE) and palygorskite (Pal) for the simultaneous detection of hydroquinone (HQ) and catechol (CT) has been proposed. Pal is particularly pointed out for its appreciable specific surface area and reactive-OH groups on its surface. Acid treatment Pal demonstrated better physico-chemical properties, which are propitious to electrochemical sensor construction. The introduction of NGE not only improved the poor conductivity of Pal but also served as an excellent adherent matrix. The modified electrode demonstrated the enhanced redox peak currents of HQ and CT with good discrimination. Under optimized conditions, the linear ranges for HQ and CT were 2–50 μM and 1–50 μM, with detection limit (LOD) of 0.8 μM and 0.13 μM, respectively. The result designates that the Pal/NGE composite promises to be a new eco-friendly modified material for sensor fabrication. [ABSTRACT FROM AUTHOR]

Abstract Herein, we reported the adsorption and desorption of Pb(II) on l -lysine modified montmorillonite (L-Mt) with molecular dynamics simulation. l -lysine (Lys) modified montmorillonite (L-Mt) was prepared, characterized by various analytical techniques, and the simulation studies were performed to evaluate the interlayer structure and interaction properties of l -lysine and L-Mt. The results of X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectrum suggested that Lys+ was intercalated into the interlayer of Na-montmorillonite (Na Mt) successfully. The batch adsorption experiments were implemented to study the adsorption capacity of Pb(II) on L-Mt in water. The maximum adsorption capacity of Pb(II) on the L-Mt (up to 43.3 mmol/100 g) were considerably higher than that on Na Mt (up to 15.3 mmol/100 g), at room temperature. The adsorption isotherms of both, L-Mt and Na Mt can fit the Langmuir isotherm. The adsorption experiments showed that Pb(II) removal efficiency of L-Mt is better than Na Mt in acidic solution. The simulation results revealed the micro-mechanism of Lys+ inserted into the interlayer gallery of Na Mt. It can be deduced that lysine interacted with montmorillonite surface mainly through the protonated side-chain amino group rather than through the protonated main-chain amino group or deprotonated carboxyl group. These consequences are expected to elucidate the adsorption mechanisms occurring at the water/clay minerals interface at atom level, providing significant insight into the adsorption and retention of Pb(II) on L-Mt composite, and lead to relevant engineering applications while treating heavy metals of wastewater. Graphical abstract Unlabelled Image Highlights • l -lysine modified montmorillonite (L-Mt) has higher adsorption capacity for Pb(II) than Na Mt. Their maximum adsorption capacity is 43.3 mmol/100 g and 15.3 mmol/100 g, respectively. • L-Mt is more efficient on the retention of Pb(II) than Na Mt. When pH 3.0, the desorption ratio of Pb(II) is 16.08% and 58.31%, respectively. • The microstructure and interaction between lysine and Na Mt has been revealed by molecular dynamic simulation. [ABSTRACT FROM AUTHOR]

A novel multi amine-containing Gemini surfactant (including four positively charged N) modified organo-montmorillonite (GMt) was prepared and served as adsorbents of phenol, o-chlorophenol (2-CP) and 2,4,6-trichlorophenol (2,4,6-TCP). The structure and morphology of GMt were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), N 2 adsorption/desorption isotherms (BET) and thermo gravimetric analysis (TGA). A batch technique was applied to investigate the influence of various factors, and the results illustrated that the saturated intercalation concentration of the modifier was 0.8 times to the cation exchange capacity (CEC) of the original Na-Mt and the adsorption was pH dependent, the optimum adsorption occurred at pH = 10, 7, 5 for phenol, 2-CP and 2,4,6-TCP, respectively. At the same conditions, the adsorption capacities of original Na-Mt were only 8.29 mg/g, 26.20 mg/g and 39.13 mg/g for three phenolic pollutants, while the maximum equilibrium adsorption amounts were 81.68 mg/g, 336.59 mg/g and 535.49 mg/g for phenol, 2-CP and 2,4,6-TCP, respectively. The adsorption kinetics of all the three phenols was in good agreement with the pseudo-second order kinetics model. The adsorption isotherm of 2,4,6-TCP was abided by Langmuir and Freundlich isotherm, however, phenol and 2-CP were better modeled by Freundlich isotherm. The negative values of ∆ G ° and positive values of ∆ H ° got from thermodynamic study confirmed that the adsorption of 2-CP and 2,4,6-TCP on GMt was a physical, spontaneous and endothermic process. The adsorption process of phenol was an exothermic process. Both adsorption and partition contributed to the adsorption of these three phenols to organo-montmorillonite. [ABSTRACT FROM AUTHOR]