Ultra-thin graphene oxide membrane deposited on highly porous anodized aluminum oxide surface for heavy metal ions preconcentration

Simultaneous extraction of five heavy metal ions from root vegetables via dual-frequency ultrasound-assisted enzymatic digestion

The dual-frequency ultrasound-assisted enzymatic digestion (DUED) technique was developed for synchronous green extraction of five heavy metal ions in root vegetables. The combination of α-amylase, cellulase, and papain showed significant advantageous in extracting heavy metal ions. Under optimized dual-frequency ultrasonic conditions, the extraction rates of Cr, As, Cd, Pb, and Hg in carrots reached 99.04%, 105.88%, 104.65%, 104.10%, and 103.13% respectively. And the extraction process is highly efficient, completing in just 15 min. Compared to conventional microwave-assisted acid hydrolysis method, this technique eliminates the need for high-temperature concentrated acid, enhancing its environmental sustainability while maintaining mild reaction conditions, making it ideal for biosensors application. Additionally, simultaneous extraction and detection of four heavy metals in lotus roots were successfully achieved by using DUED and a fluorescent paper-based microfluidic chip. The obtained results are consistent with those obtained using conventional methods.

Ionic liquid-immobilized silica gel as a new sorbent for solid-phase extraction of heavy metal ions in water samples

In the current study, we have developed a solid-phase extraction (SPE) method with novel C18-alkylimidazolium ionic liquid immobilized silica (SiO₂–(CH₂)₃–Im–C₁₈) for the preconcentration of trace heavy metals from aqueous samples as a prior step to their determination by inductively coupled plasma mass spectrometry (ICPMS). The material was characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray Spectroscopy (EDS), and Brunauer–Emmett–Teller (BET) analysis. A mini-column packed with SiO₂–(CH₂)₃–Im–C₁₈ sorbent was used for the extraction of the metal ions complexed with 1-(2-pyridylazo)-2-naphthol (PAN) from the water sample. The effects of pH, PAN concentration, length of the alkyl chain of the ionic liquid, eluent concentration, eluent volume, and breakthrough volume have been investigated. The SiO₂–(CH₂)₃–Im–C₁₈ allows the isolation and preconcentration of the heavy metal ions with enrichment factors of 150, 60, 80, 80, and 150 for Cr³⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Pb²⁺, respectively. The limits of detection (LODs) for Cr³⁺, Ni²⁺, Cu²⁺, Cd²⁺, and Pb²⁺ were 0.724, 11.329, 4.571, 0.112, and 0.819 μg L⁻¹, respectively with the relative standard deviation (RSD) in the range of 0.941–1.351%.

Novel C18-alkylimidazolium ionic liquid immobilized silica (SiO₂–(CH₂)₃–Im–C₁₈) was synthesized through a four-step procedure. It showed high efficiency for the separation/preconcentration of trace heavy metal ions from aqueous samples.

Systematic study of physicochemical and electrochemical properties of carbon nanomaterials

Carbon nanomaterials exhibit exceptional properties and broad horizon applications, where graphene is one of the most popular allotropes of this family due to its astounding performance in every stratum vis-à-vis other classical materials. The large surface area of 2630 m² g⁻¹, high electrical conductivity, and electron mobility of non-toxic graphene nanomaterials serve as the building blocks for supercapacitor studies. In this article, comparative studies are carried out between electrochemically exfoliated graphene sheets (GSs), solvothermally synthesized graphene quantum dots (GQDs) and acid refluxed carbon nanotubes (CNTs) as an energy storage electrode nanomaterial through cyclic voltammetry (CV). The electrochemical properties of the materials are well correlated with the physicochemical characteristics obtained from Raman, Fourier-transform infrared, and absorption spectroscopy. Thin GSs (0.8–1 nm) and small size (6–10 nm) GQDs fabricated by using laboratory-grade 99% purity graphite rods resulted in promising low-cost materials at mass scale as compared to conducting CNTs. The 0D graphene quantum dots proved to be an excellent energy electrode material in an alkaline electrolyte solution compared to other carbon nanomaterials. The distinct characteristic features of GQDs, like superior electrical properties, large surface area, and abundant active sites make them an ideal candidate for utilization in supercapacitors. The GQDs exhibited an enhanced specific capacitance of 113 F g⁻¹ in 6 mol L⁻¹ KOH through cyclic voltammetry.

Carbon nanomaterials exhibit exceptional properties and broad horizon applications, where graphene is one of the most popular allotropes of this family due to its astounding performance in every stratum vis-à-vis other classical materials.

Determination of the Cadmium Ions from Aqueous Solution Using EDTA Functionalized Prunus Dulcis L. Peels by Solid-Phase Extraction Method

In the present study, Prunus Dulcis L. Peels was modified with ethylenedinitrilo tetraacetic acid and used as the sorbent for the preconcentration of Cd(II) ions from aqueous media. To characterize the sorbent, scanning electron microscopy-energy dispersive X-ray spectrometer and Fourier transform infrared spectrometer analysis were used. The optimum preconcentration conditions such as pH, eluent type, sample volume, sample flow rate and foreign ions effect were determined. The mean recovery and relative standard deviation values were found to be 100.7 ± 1.5 and 4.01% for Cd(II) ions. The capacity of the sorbent was obtained 277.8 mg g^-1 from the Langmuir isotherm model. The limit of detection was calculated as 0.216 µg L^-1 (P.F:40). In order to test the accuracy and applicability of the method, certified reference material and spiked water samples were analyzed. The results demonstrated good agreement with the certified values (relative error < 10%).

Plasma-assisted in-situ preparation of graphene-Ag nanofiltration membranes for efficient removal of heavy metal ions

Graphene-based membranes have been considered as promising separation membranes for water treatments due to their unique two-dimensional confined channels. However, subject to the preparation technology, the effective construction of graphene-based filtration membranes with suitable separation ability on heavy metal ions still face considerable challenges. Herein, we have successfully constructed a kind of graphene-based (reduced graphene oxide, rGO) nanofiltration membranes by adopting a plasma-assisted in-situ photocatalytic reduction method. Graphene oxide-Ag (GO-Ag) composite sheets are prepared firstly and then assembled into membranes by vacuum filtration. With the use of Ag nanoparticles as plasmonic photocatalyst, GO-Ag films can be in-situ reduced, leading to the formation of rGO-based composite membranes. Thanks to the mild in-situ reduction process, the filtration ability on heavy metal ions (Cr(VI), Cr³⁺, Cu²⁺ and Pb²⁺) caused by lamellar structure is well retained in the as-formed rGO-Ag membranes. Especially, when treating the typical toxic Cr(VI) solution, the retention capacity, water flux and stability of rGO-Ag membranes are all improved compared with that of the original GO-Ag ones. In addition, the effectively rejection of Cr(VI) from mixed solutions containing both Cr(VI) and Cr(III) also suggests the good applicability of such rGO-Ag membranes in a complex wastewater system.

Selective Extraction of Trace Arsenite Ions Using a Highly Porous Aluminum Oxide Membrane with Ordered Nanopores

Metal ion extraction and determination at trace level concentration are challenging due to sample complexity or spectral interferences. Herein, we prepared a through-hole aluminum oxide membrane (AOM) by electrochemical anodization of aluminum substrates. The prepared AOM was characterized by scanning electron microscopy, surface area analysis, porosity measurements, and X-ray photoelectron spectroscopy. The AOM with ordered nanopores was highly porous and possess inherent binding sites for selective arsenite sorption. The AOM was used as a novel sorbent for solid-phase microextraction and preconcentration of arsenite ions in water samples. The AOM's sub-micrometer thickness allows water molecules to flow freely across the pores. Before instrumental determination, the suggested microextraction approach removes spectral interferents and improves the analyte ion concentration, with a detection limit of 0.02 μg L^-1. Analyzing a standard reference material was used to validate the procedure. Student's t-test value was less than critical Student's t-value of 4.303 at a 95% confidence level. With coefficients of variation of 3.25%, good precision was achieved.