Monodisperse superparamagnetic nanoparticles separation adsorbents for high-yield removal of arsenic and/or mercury metals in aqueous media

Magnetic dispersive solid-phase extraction of some pesticides from fruit juices using monodisperse nanosorbent combined with dispersive liquid-liquid micro-extraction

In this study, the new synthesized magnetic nanoparticles based on amorphous carbon have been used as a sorbent in magnetic dispersive solid-phase extraction prior to dispersive liquid-liquid micro-extraction. The developed method was applied for analysis of ten pesticides from different fruit juice samples by gas chromatography-flame ionization detection. In this work, a few mg of the sorbent is added into an aqueous solution containing the analytes. Adsorption and desorption of the compounds of interest are accelerated by vortexing and sonication, respectively. To achieve high enrichment factors, a suitable organic solvent (iso-propanol) is used to elute the target analytes from the nanosorbent. The obtained iso-propanol is phased and 1,1,2-trichloroethane are employed as the disperser and extraction solvents, respectively, in the following micro-extraction procedure. The synthesized magnetic nanoparticles were characterized by scanning electron microscope, X-ray diffraction, vibrating sample magnetometer, and Fourier-transform infrared spectrophotometer. To achieve the high extraction efficiency and optimum conditions, all parameters that could affect the extraction yield were investigated. Under optimum conditions, the method had broad linear ranges with a proper linearity (r² ≥ 0.9987). Limits of detection and quantification for analysis of the selected pesticides were found in the ranges of 0.5-1.0 and 1.7-3.3 µg L^-1, respectively. High enrichment factors and extraction recoveries were obtained in the ranges of 321-438 and 64-88%, respectively. To evaluate repeatability of the method, it was performed on two sets of standard solutions at the concentrations of 10 and 50 µg L^-1 (each analyte). Relative standard deviations varied in the ranges of 2-6% and 4-7% for intra- (n = 6) and inter-day (n = 5) precisions, respectively.

Understanding the adsorption of iron oxide nanomaterials in magnetite and bimetallic form for the removal of arsenic from water

Arsenic decontamination is a major worldwide concern as prolonged exposure to arsenic (>10 µg L-1) through drinking water causes serious health hazards in human beings. The selection of significant, cost-effective, and affordable processes for arsenic removal is the need of the hour. For the last decades, iron-oxide nanomaterials (either in the magnetite or bimetallic form) based adsorptive process gained attention owing to their high arsenic removal efficiency and high regenerative capacity as well as low yield of harmful by-products. In the current state-of-the-art, a comprehensive literature review was conducted focused on the applicability of iron-based nanomaterials for arsenic removal by considering three main factors: (a) compilation of arsenic removal efficiency, (b) identifying factors that are majorly affecting the process of arsenic adsorption and needs further investigation, and (c) regeneration capacity of adsorbents without affecting the removal process. The results revealed that magnetite and bimetallic nanomaterials are more effective for removing Arsenic (III) and Arsenic (V). Further, magnetite-based nanomaterials could be used up to five to six reuse cycles, whereas this value varied from three to six reuse cycles for bimetallic ones. However, most of the literature was based on laboratory findings using decided protocols and sophisticated instruments. It cannot be replicated under natural aquatic settings in the occurrence of organic contents, fluctuating pH and temperature, and interfering compounds. The primary rationale behind this study is to provide a comparative picture of arsenic removal through different iron-oxide nanomaterials (last twelve yearsof published literature) and insights into future research directions.