Alumina physically loaded by thiosemicarbazide for selective preconcentration of mercury(II) ion from natural water samples

Development of a Toxic Lead Ionic Sensor Using Carboxyl-Functionalized MWCNTs in Real Water Sample Analyses

Functional multiwall carbon nanotubes (f-MWCNTs) are of significant interest due to their dispersion ability in the aqueous phase and potential application in environmental, nanotechnology, and biological fields. Herein, we functionalized MWCNTs by a simple acid treatment under ultra-sonification, which represented a terminal or side-functional improvement for the fabrication of a toxic lead ion sensor. The f-MWCNTs were characterized in detail by XRD, Raman, XPS, BET, UV/vis, FTIR, and FESEM-coupled XEDS techniques. The analytical performance of the f-MWCNTs was studied for the selective detection of toxic lead ions by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of the f-MWCNTs was evaluated using several metal ions such as Cd²⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺, and Zn²⁺ ions. Lastly, the newly designed ionic sensor was successfully employed to selectively detect lead ions in several environmental water samples with reasonable results. This approach introduced a new technique for the selective detection of heavy metal ions using functional carbon nanotubes with ICP-OES for the safety of environmental and healthcare fields on a broad scale.

Versatile Porous Poly(arylene ether)s via Pd-Catalyzed C-O Polycondensation

Porous organic polymers (POPs) with strong covalent linkages between various rigid aromatic structural units having different geometries and topologies are reported. With inherent porosity, predictable structure, and tunable functionality, POPs have found utility in gas separation, heterogeneous catalysis, sensing, and water treatment. Poly(arylene ether)s (PAEs) are a family of high-performance thermoplastic materials with high glass-transition temperatures, exceptional thermal stability, robust mechanical properties, and excellent chemical resistance. These properties are desirable for development of durable POPs. However, the synthetic methodology for the preparation of these polymers has been mainly limited in scope to monomers capable of undergoing nucleophilic aromatic substitution (S_NAr) reactions. Herein, we describe a new general method using Pd-catalyzed C-O polycondensation reactions for the synthesis of PAEs. A wide range of new compositions and PAE architectures are now readily available using monomers with unactivated aryl chlorides and bromides. Specifically, monomers with conformational rigidity and intrinsic internal free volume are now used to create porous organic polymers with high molecular weight, good thermal stability, and porosity. The reported porous PAEs are solution processable and can be used in environmentally relevant applications including heavy-metal-ion sensing and capture.

In situ remediation efficacy of hybrid aerogel adsorbent in model aquatic culture of Paramecium caudatum exposed to Hg(II)

Silica-gelatin hybrid aerogel of 24 wt% gelatin content is an advanced functional material suitable for the high performance selective adsorption of aqueous Hg(II). The remediation efficacy of this adsorbent was tested under realistic aquatic conditions by exposing cultures of Paramecium caudatum to Hg(II) and monitoring the model cultures by time-lapse video microscopy. The viability of Paramecium was quantified by analyzing the pixel differences of the sequential images caused by the persistent movement (motility) of the cells. The viability of Paramecium displays a clear exposure-response relationship with Hg(II) concentration. Viability decreases with increasing Hg(II) concentration when the latter is higher than 125 μg L^-1. In the presence of 0.1 mg mL^-1 aerogel adsorbent, the viability of the cells decreases only at Hg(II) concentrations higher than 500 μg L^-1, and 220 min survival time was measured even at 1000 μg L^-1 Hg(II). The effective toxicity of Hg(II) is lower in the presence of the aerogel, because the equilibrium concentration of aqueous Hg(II) is low due to adsorption, thus Paramecium cells do not uptake as much Hg(II) as in the un-remediated cultures. Video imaging of Paramecium cultures offers a simple, robust and flexible method for providing quantitative information on the effectiveness of advanced materials used in adsorption processes for water treatment.

NanoPOP: Solution-Processable Fluorescent Porous Organic Polymer for Highly Sensitive, Selective, and Fast Naked Eye Detection of Mercury

Fluorescence-based detection is one of the most efficient and cost-effective methods for detecting hazardous, aqueous Hg²⁺. We designed a fluorescent porous organic polymer (TPA-POP-TSC), with a "fluorophore" backbone and a thiosemicarbazide "receptor" for Hg²⁺-targeted sensing. Nanometer-sized TPA-POP-TSC spheres (nanoPOP) were synthesized under mini-emulsion conditions and showed excellent solution processability and dispersity in aqueous solution. The nanoPOP sensor exhibits exceptional sensitivity (K_sv = 1.01 × 10⁶ M^-1) and outstanding selectivity for Hg²⁺ over other ions with rapid response and full recyclability. Furthermore, the nanoPOP material can be easily coated onto a paper substrate to afford naked eye-based Hg²⁺-detecting test strips that are convenient, inexpensive, fast, highly sensitive, and reusable. Our design takes advantage of the efficient and selective capture of Hg²⁺ by thiosemicarbazides (binding energy = -29.84 kJ mol^-1), which facilitates electron transfer from fluorophore to bound receptor, quenching the sensor's fluorescence.

Sulfone-modified chitosan as selective adsorbent for the extraction of toxic Hg(II) metal ions

In this study, a new category of sulfone-modified chitosan derivatives as surface-selective adsorbents for the extraction of toxic Hg(II) metal has been synthesized in good yield. Sulfone-modified chitosan/5–20 based on variable loading of the corresponding phenacyl bromide (5, 10, 15, and 20% with respect to the original weight of the pure chitosan) was synthesized. The β-ketosulfone derivative, namely 1–(4-bromophenyl)-2-(phenylsulfonyl)ethanone, was first prepared by treatment of the corresponding phenacyl bromide with a sufficient amount of sodium benzene sulfinate; its chemical structure was confirmed by spectral analyses, including Fourier transform infrared spectroscopy, 1H-NMR, 13C-NMR, and mass spectrometry. Then, sulfone-modified chitosan/5–20 derivatives were synthesized by the interaction of chitosan with a freshly prepared p-bromo-β-ketosulfone derivative in a mildly acidic aqueous solution using the solution-blending technique. Sulfone-modified chitosan/5–20 derivatives were identified and characterized using common characterization techniques, including Fourier transform infrared spectroscopy, field-emission scanning electron microscope, powder X-ray diffraction, and thermal behaviour. A strong interaction was displayed between chitosan and its corresponding β-ketosulfones in powder X-ray diffraction, which was confirmed by significant 2θ shifts. Sulfone-modified chitosan/5–20 derivatives were detected as catalysts, which efficiently increased the thermal decomposition of pure chitosan. More particularly, the efficiency of sulfone-modified chitosan/5–20 derivatives for Hg(II), Pb(II), Ni(II), Al(III), Sr(II), Cr(III), Fe(III), Zn(II), and Mn(II) detection and adsorption was also investigated using inductively coupled plasma optical emission spectrometry. The sulfone-modified chitosan/5 derivative exhibited the highest adsorption efficiency. The most effective quantitative adsorption onto the sulfone-modified chitosan/5 surface was detected at pH = 2. In addition to that, the adsorption isotherm showed that the adsorption capacity of sulfone-modified chitosan/5 for Hg(II) was 122.47 mg g−1 and that its adsorption isotherm was in agreement with the Langmuir adsorption isotherm.

Investigation of an eco-friendly aerogel as a substrate for the immobilization of MoS2 nanoflowers for removal of mercury species from aqueous solutions

An adsorbent that exhibits high affinity for inorganic mercury (Hg²⁺) with a high removal efficiency of methylmercury (MeHg⁺) has been developed. The adsorbent demonstrates a symbiotic relationship between its two components, molybdenum disulphide nanoflowers (MoS₂NFs) and a poly (vinyl alcohol) (PVA) aerogel. Furthermore, we modified the distribution and loading of the MoS₂NFs, which was possible due to the stable porous support, and investigated the biocompatibility of the aerogel-support adsorbent. The performance of the optimized material exhibited a distribution coefficient of 9.71 × 10⁷ mL g^-1. In addition, the adsorbent was effective over a wide pH range and could efficiently purify both contaminated lake and sea water. The key motivation for using an aerogel support was to stabilise the MoS₂NFs during purification of the water (resulting in improved performance compared to using freestanding MoS₂NFs) and the ability to regenerate the used adsorbent. In addition, animal tests confirmed an extremely low toxicity of the adsorbent to fish, along with the excellent purification results.

Cu(ii), Ga(iii) and In(iii) complexes of 2-acetylpyridine N(4)-phenylthiosemicarbazone: synthesis, spectral characterization and biological activities

In this paper, synthesis and characterization of metal complexes [Cu2(L)3]ClO4 (1), [Ga(L)2]NO3·2H2O (2) and [In(L)2]NO3·H2O (3) (HL = 2-acetylpyridine N(4)-phenylthiosemicarbazone) was carried out, including elemental analysis, spectral analysis (IR, UV-vis, NMR), and X-ray crystallography. Complex 1 contains one S-bridged binuclear [Cu2(L)3]+ unit, where two Cu atoms display diverse coordination geometries: one being square planar geometry and the other octahedral geometry. Both 2 and 3 are mononuclear complexes, and the metal centers in 2 and 3 are chelated by two NNS tridentate ligands possessing a distorted octahedral geometry. Biological studies show that all the complexes possess a wide spectrum of modest to effective antibacterial activities and remarkable cytotoxicities against HepG2 cells, and 1, in particular, with an IC50 value of 0.19 ± 0.06 μM, is 113-fold and 28-fold more cytotoxic than HL and the antitumor drug mitoxantrone, respectively. In addition, 3 exhibits excellent photoluminescence properties. Upon the addition of 1 equiv of In3+ ions, a remarkable fluorescence intensity of HL and fluorescent color change (from transparent to light-green) could be observed with 365 nm light, indicating that this ligand may be used as a promising colorimetric and fluorescent probe for In3+ detection.

Removing lead ions from aqueous solutions by the thiosemicarbazide grafted multi-walled carbon nanotubes

A novel multi-walled carbon nanotubes (MWCNTs) material functionalized with thiosemicarbazide was synthesized successfully and used to remove lead ions from aqueous solutions. The technologies of Fourier Transform Infrared Spectroscopy, scanning electron microscopy and thermal gravimetric analysis were used to characterize the structure and properties of thiosemicarbazide grafted MWCNTs. The adsorption conditions, such as pH, contact time and temperature, were investigated. The results showed pH affected the adsorption process greatly, and the adsorption process reached equilibrium within 60 min. The maximum adsorption capacity was 42.01 mg/g. The adsorption process fitted well with the pseudo-second-order kinetic model and the Langmuir model. The thermodynamic parameters indicated the adsorption process was endothermic and spontaneous in nature.

Combined tween 20-stabilized gold nanoparticles and reduced graphite oxide-Fe3O4 nanoparticle composites for rapid and efficient removal of mercury species from a complex matrix

This study describes a simple method for removing mercuric ions (Hg(2+)) from a high-salt matrix based on the use of Tween-20-stabilized gold nanoparticles (Tween 20-Au NPs) as Hg(2+) adsorbents and composites of reduced graphite oxide and Fe3O4 NPs as NP collectors. Citrate ions adsorbed on the surface of the Tween 20-Au NPs reduced Hg(2+) to Hg(0), resulting in the deposition of Hg(0) on the surface of the NPs. To circumvent time-consuming centrifugation and transfer steps, the Hg(0)-containing gold NPs were collected using reduced graphite oxide-Fe3O4 NP composites. Compared with the reported NP-based methods for removing Hg(2+), Tween 20-Au NPs offered the rapid (within 30 min), efficient (>99% elimination efficiency), durable (>10 cycles), and selective removal of Hg(2+), CH3Hg(+), and C2H5Hg(+) in a high-salt matrix without the interference of other metal ions. This was attributed to the fact that the dispersed Tween 20-Au NPs exhibited large surface-area-to-volume ratio to bind Hg(2+) through Hg(2+)-Au(+) metallophilic interactions in a high-salt matrix. The formation of graphite oxide sheets and reduced graphite oxide-Fe3O4 NP composites was demonstrated using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectrometry, and transmission electron microscopy. The mechanism of interaction between Tween 20-Au NPs and Hg(2+) was studied using visible spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy.

Cellulose-lanthanum hydroxide nanocomposite as a selective marker for detection of toxic copper

In this current report, a simple, reliable, and rapid method based on modifying the cellulose surface by doping it with different percentages of lanthanum hydroxide (i.e., 1% La(OH)3-cellulose (LC), 5% La(OH)3-cellulose (LC2), and 10% La(OH)3-cellulose (LC3)) was proposed as a selective marker for detection of copper (Cu(II)) in aqueous medium. Surface properties of the newly modified cellulose phases were confirmed by Fourier transform infrared spectroscopy, field emission scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopic analysis. The effect of pH on the adsorption of modified cellulose phases for Cu(II) was evaluated, and LC3 was found to be the most selective for Cu(II) at pH 6.0. Other parameters, influencing the maximum uptake of Cu(II) on LC3, were also investigated for a deeper mechanistic understanding of the adsorption phenomena. Results showed that the adsorption capacity for Cu(II) was improved by 211% on the LC3 phase as compared to diethylaminoethyl cellulose phase after only 2 h contact time. Adsorption isotherm data established that the adsorption process nature was monolayer with a homogeneous adsorbent surface. Results displayed that the adsorption of Cu(II) onto the LC3 phase obeyed a pseudo-second-order kinetic model. Selectivity studies toward eight metal ions, i.e., Cd(II), Co(II), Cr(III), Cr(VI), Cu(II), Fe(III), Ni(II), and Zn(II), were further performed at the optimized pH value. Based on the selectivity study, it was found that Cu(II) is highly selective toward the LC3 phase. Moreover, the efficiency of the proposed method was supported by implementing it to real environmental water samples with adequate results.

Synthesis and application of surface-imprinted activated carbon sorbent for solid-phase extraction and determination of copper (II)

A new Cu(II)-imprinted amino-functionalized activated carbon sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Cu(II) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of Cu(II) were optimized with respect to different experimental parameters using static and dynamic procedures in detail. Compared with non-imprinted sorbent, the ion-imprinted sorbent had higher selectivity and adsorption capacity for Cu(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Cu(II) was 26.71 and 6.86 mg g(-1), respectively. The relatively selectivity factor values (αr) of Cu(II)/Zn(II), Cu(II)/Ni(II), Cu(II)/Co(II) and Cu(II)/Pb(II) were 166.16, 50.77, 72.26 and 175.77, respectively, which were greater than 1. Complete elution of the adsorbed Cu(II) from Cu(II)-imprinted sorbent was carried out using 2 mL of 0.1 mol L(-1) EDTA solution. The relative standard deviation of the method was 2.4% for eleven replicate determinations. The method was validated for the analysis by two certified reference materials (GBW 08301, GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace copper in natural water samples with satisfactory results.

Functionalized nanospheres for efficient sequestration of cadmium ions

This manuscript reports the synthesis, characterization and the subsequent application of thiosemicarbazide functionalized nanosilica spheres in Cd(ii) ion sequestration.

Novel solid-phase extractor based on functionalization of multi-walled carbon nano tubes with 5-aminosalicylic acid for preconcentration of Pb(II) in water samples prior to determination by ICP-OES

New solid-phase extractor (MWCNTs-5-ASA) was synthesized via covalent immobilization of 5-aminsalicylic acid onto multi-walled carbon nanotubes (MWCNs). The success of the functionalization process was confirmed using Fourier transform infrared spectroscopy, scanning electron microscope, and surface coverage determination. Batch experiments were conducted as a function of pH to explore MWCNTs-5-ASA efficiency to extract several metal ions viz., Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II). It was found that Pb(II) exhibits the highest extraction percentage with maximum adsorption capacity 32.75 mg g(-1). Its binding performance was well fitted with Langmuir sorption isotherm. On the other hand, the selective separation and preconcentration of trace Pb(II) under dynamic conditions prior to determination by inductively coupled plasma-optical emission spectrometry was investigated under different parameters. These included the rate of flow and volume of sample solution, in addition to the type of the eluate, its volume and concentration. The effect of a variety of foreign ions on the recovery percentage was also evaluated. Trace Pb(II) ions present in 500 mL aqueous solution adjusted to pH 4.0 were retained on 50 mg of MWCNTs-5-ASA and completely eluted using 4.0 mL of 2 M HNO₃. The limit of detection and the precision of the method were 0.25 ng mL(-1) and 2.8%, respectively (N = 5). This methodology has been applied for the determination of Pb(II) in water samples with good results.

Novel route for silylation of silica gel and aliphatic amines immobilization based on microwave-assisted solvent free synthesis and their applications for Cu(II) and Fe(III) removal from natural water samples

This article describes a new route for silica gel silylation and immobilization of aliphatic amines based on microwave-assisted solvent free synthesis to produce new solid phase extractors. The mode of synthesis was optimized under microwave conditions and achieved in a short time without using solvents. The produced phases named: silica gel- monoamine (SG-MA), silica gel- ethylenediamine (SG-EDA) and silica gel- diethylenetriamine (SG-DETA). The selectivity of these phases towards the uptake of Cu(II) and Fe(III) was checked using batch equilibration technique. Microwave radiation power and time of radiation were optimized to obtain the highest metal uptake values. The novel synthesized silica amine phases were characterized using Fourier transform infrared spectra and scanning electron microscope. The effects of different parameters including, hydrogen ion concentration, initial metal ion concentration, mass of the phase and shaking time on binding capacities of both Cu(II) and Fe(III) were explored. Results of sorption isotherms of the phases were better fitted with the Langmuir model (r² ≥ 0.950). In addition, the kinetics data were best fitted with the pseudo-second-order type (r² = 0.999). Application of SG-MA for removal of Cu(II)- and Fe(III)-spiked natural water samples was achieved satisfactorily using batch experiments. The results were found to refer to superior recovery percentages (90.0-97.01 ± 0.010-0.521%) with no significant matrix interferences.

Gold nanoparticle-aluminum oxide adsorbent for efficient removal of mercury species from natural waters

We report a new adsorbent for removal of mercury species. By mixing Au nanoparticles (NPs) 13 nm in diameter with aluminum oxide (Al(2)O(3)) particles 50-200 μm in diameter, Au NP-Al(2)O(3) adsorbents are easily prepared. Three adsorbents, Al(2)O(3), Au NPs, and Au NP-Al(2)O(3), were tested for removal of mercury species [Hg(2+), methylmercury (MeHg(+)), ethylmercury (EtHg(+)), and phenylmercury (PhHg(+))]. The Au NP adsorbent has a higher binding affinity (dissociation constant; K(d) = 0.3 nM) for Hg(2+) ions than the Al(2)O(3) adsorbent (K(d) = 52.9 nM). The Au NP-Al(2)O(3) adsorbent has a higher affinity for mercury species and other tested metal ions than the Al(2)O(3) and Au NP adsorbents. The Au NP-Al(2)O(3) adsorbent provides a synergic effect and, thus, is effective for removal of most tested metal ions and organic mercury species. After preconcentration of mercury ions by an Au NP-Al(2)O(3) adsorbent, analysis of mercury ions down to the subppq level in aqueous solution was performed by inductively coupled plasma mass spectrometry (ICP-MS). The Au NP-Al(2)O(3) adsorbent allows effective removal of mercury species spiked in lake water, groundwater, and seawater with efficiencies greater than 97%. We also used Al(2)O(3) and Au NP-Al(2)O(3) adsorbents sequentially for selectively removing Hg(2+) and MeHg(+) ions from water. The low-cost, effective, and stable Au NP-Al(2)O(3) adsorbent shows great potential for economical removal of various mercury species.

Chemically modified activated carbon with 1-acylthiosemicarbazide for selective solid-phase extraction and preconcentration of trace Cu(II), Hg(II) and Pb(II) from water samples

A new sorbent 1-acylthiosemicarbazide-modified activated carbon (AC-ATSC) was prepared as a solid-phase extractant and applied for removing of trace Cu(II), Hg(II) and Pb(II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The separation/preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. At pH 3, the maximum static adsorption capacity of Cu(II), Hg(II) and Pb(II) onto the AC-ATSC were 78.20, 67.80 and 48.56 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 3.0 mL of 2% CS(NH2)2 and 2.0 mol L(-1) HCl solution. Common coexisting ions did not interfere with the separation. According to the definition of IUPAC, the detection limits (3sigma) of this method for Cu(II), Hg(II) and Pb(II) were 0.20, 0.12 and 0.45 ng mL(-1), respectively. The relative standard deviation under optimum conditions is less than 4.0% (n=8). The prepared sorbent was applied for the preconcentration of trace Cu(II), Hg(II) and Pb(II) in certified and water samples with satisfactory results.