Self-Assembled Three-Dimensional Microporous rGO/PNT/Fe3O4 Hydrogel Sorbent for Magnetic Preconcentration of Multi-Residue Insecticides

Removal of methylene blue using MnO2@rGO nanocomposite from textile wastewater: Isotherms, kinetics and thermodynamics studies

In this study, the adsorptive removal of methylene blue dye, which is commonly used in textile industries, was investigated using the MnO₂@reduced graphene oxide (rGO) adsorbent. The sonication-assisted synthesis from rGO nanosheets and MnO₂ nanoparticles resulted to the MnO₂@rGO nanocomposite with improved physicochemical properties. The characterization results showed the improved surface area, porous structure and adsorption sites from the nitrogen adsorption-desorption studies, improved morphology from the Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) and the improved crystal structure from X-ray powder diffraction (XRD). The improved physicochemical properties on the MnO₂@rGO nanocomposite played a significant role in enhancing the dye removal in textile wastewater. The equilibrium experimental data was best described by the Langmuir isotherm model with a maximum adsorption capacity of 156 mg g^-1, suggesting a monolayer adsorption. The kinetic data best fitted the pseudo-second order kinetic model, suggesting a chemisorption adsorption process. The thermodynamic data (ΔG°, ΔH° and ΔS°) confirmed the feasibility, randomness and spontaneous nature of the adsorption process. The mechanism of adsorption involved the hydrogen bonding, π-π interactions and electrostatic interactions. The removal of methylene blue using MnO₂@rGO nanocomposite in spiked textile wastewater yielded a 98-99% removal. The method demonstrated competitiveness when compared with literature reported results, paving way for further investigations towards industrial scale applications.

Recent progress in organic-inorganic hybrid materials as absorbents in sample pretreatment for pesticide detection

Sample pretreatment is essential for trace analysis of pesticides in complex food and environment matrices. Recently, organic-inorganic hybrid materials have gained increasing attention in pesticide extraction and preconcentration. This review highlighted the common organic-inorganic hybrid materials used as absorbents in sample pretreatment for pesticide detection. Furthermore, the preparation and characterization of organic-inorganic hybrid materials were summarized. To obtain a deep understanding of adsorption toward target analytes, the adsorption mechanism and absorption evaluation were discussed. Finally, the applications of organic-inorganic hybrid materials in sample pretreatment techniques and perspectives in the future are also discussed.

Three dimensional graphene materials doped with heteroatoms for extraction and adsorption of environmental pollutants in wastewater

Environmental pollution by heavy metal ions, organic pollutants, oils, pesticides or dyes is a ubiquitous problem adversely affecting human health and environmental ecology. Development and application novel adsorbents in full-scale treatment systems with effectiveness properties could effective ways to facilitate the extraction and adsorption of environment pollutants from wastewater. Graphene materials have drawn much attention due to their extraordinary electron mobilities, high surface areas, good thermal conductivities, and excellent mechanical properties. Three-dimensional graphene materials can provide the inherent advantages of 2D graphene sheets and exhibit micro/nanoporous structures, increased specific surface areas, high electron conductivities, fast mass transport kinetics, and strong mechanical strength. Potential applications for 3D graphene materials include environmental remediation, chemical and biological sensing, catalysis, and super capacitors. Recent advances in the applications of 3D functionalized graphene materials (3D FGMs) doped with heteroatoms for the extraction and adsorption of environmental pollutants in wastewater are summarized in this review.

A functionalized carbon nanotube nanohybrids-based QuEChERS method for detection of pesticide residues in vegetables and fruits

A self-separating, analyte-compatible, and efficient clean-up method for QuEChERS extracts was designed and developed based on dispersive solid-phase extraction using a branched polyethylenimine and nanoscale CaSO₄ functionalized carboxylated multi-walled carbon nanotubes (MWCNTs) nanohybrids as sorbent. The feasibility of using a self-separating strategy based on the functionalization of sorbent in a purification procedure was analyzed for the first time in this study. Compared to the traditional QuEChERS method, the proposed method is rapid and convenient without centrifugation of numerous samples in the clean-up process. The use of nanohybrids overcame the issue of low recoveries for planar pesticides, which are easily adsorbed using MWCNTs. A better clean-up capability of the nanohybrids to remove matrix interferences and reduce matrix effect was demonstrated compared with that of traditional clean-up sorbent primary secondary amine. The method was validated by determining twenty-eight pesticides in cucumber, cabbage, apple, and orange. Limits of detections were in the range of 0.0001-0.0026 mg/kg. Spike recoveries of pesticides were within 75.3 - 113.6%, with relative standard deviations less than 14.3% at levels 0.01 mg/kg and 0.1 mg/kg. The developed method was successfully applied to monitor the multi-residues.