Extraction Of Heavy Metal Ions Research Articles

Development of a dispersive liquid–liquid microextraction procedure based on a natural deep eutectic solvent for ligand-less preconcentration and determination of heavy metals from water and food samples

In the current study, a ligand-less dispersive liquid–liquid microextraction technique assisted ultrasound and vortex equipment (DLLME-A-US-V) procedure was used for the simultaneous preconcentration and extraction of heavy metal ions. The proposed method was done by a natural hydrophobic deep eutectic solvent for the extraction of arsenic, cadmium, lead, and mercury ions without a complexing agent. The natural deep eutectic solvent was prepared from l-menthol (M) and salicylic acid (SA). The precursor of deep eutectic solvents strongly affects the extraction of metal ions. Among the studied solvents, hydrophobic deep eutectic solvents showed the highest extraction recovery. Under optimal experimental conditions, the method linearity, limits of detection (LOD), limits of quantification (LOQ), relative standard deviations (RSD %), enrichment factors (EF), and extraction recovery (% ER) were equal to 0.005–14 µg/L, 0.0043–0.0088 µg/L, 0.0143–0.0294 µg/L, 1.66–2.83 %, 112–120, and 90–96 %, respectively. The obtained coefficients of determination (r2) were also higher than 0.991. This method was successfully applied to determine some heavy metals in food samples in the ultra-trace range with the recovery values of real samples being 93–108 %.

Surface implantation of ionically conductive polyhydroxyethylaniline on cation exchange membrane for efficient heavy metal ions separation

Extraction of heavy metal ions from aqueous could enable recycling of wastewater and reusing of high-value ion resources. Recently, electrodialysis (ED) technology has been applied in the removal of heavy metal ions from wastewater, however, developing high-efficient and stable heavy metal ions selective cation exchange membrane (CEM) remains an elusive challenge. Herein, we demonstrate the fabrication of high-efficient cations selective CEM with the surface implantation of ionically conductive polyhydroxyethylaniline (PANI-OH) on a commercial CEM membrane (CTG) containing sulfonic acid groups via the electrostatic attraction. Implanted hydrophilic and positively charged PANI-OH facilitates fast and selective transfer of Cu2+ over Zn2+ cations through the membrane. Meanwhile, the synergistic effect of rigid conjugate structure and hydrogen-bond interaction of PANI-OH renders the resultant membrane CTG-PANI-OH with stable structure and separation performance. As such, the Cu2+/Zn2+ permselectivity of CTG-PANI-OH membrane is ~1.70, which is about 190 % of that of the pristine CTG membrane. This work provides a facile design and strategy for the construction of high-efficient cations selective CEMs with great application prospects in the purification and extraction of heavy metal ions from wastewater.

Development of ligandless dispersive micro-solid-phase extraction method based on NH2-UiO-66 (Zr) MOF using DES eluent in determination of Cd(II) and Cu(II) ions in water and fruit juice samples

ABSTRACTA metal–organic framework (MOF) was synthesised and used for dispersive micro-solid-phase extraction of heavy metal ions from fruit juice and water sample without adding an additional complexing agent. In this work, 9 mg of the synthesised adsorbent (NH2-UiO-66 (Zr) MOF) was dispersed into 6 mL of sample solution containing Cu(II) and Cd(II) ions. Then, a synthesised deep eutectic solvent was used to elute and desorb the analytes from the surface of the sorbent. The effect of important parameters such as sorbent amount, sample solution volume, extraction time, elution solvent type and volume, desorption time, pH and salt addition on the extraction efficiency of the method was investigated. The developed procedure had linear ranges of 1–100 and 0.5–150 µg L−1 with the limits of detection of 0.37 and 0.19 µg L−1, for Cu(II) and Cd(II) ions, respectively, with flame atomic absorption spectrometry determination. To study the validity of the procedure, the concentration of the analytes was determined in a certified reference material (SPS-WW2) by the proposed method. Finally, the proposed procedure was used for the determination of the concentrations of Cu(II) and Cd(II) ions in different fruit juice and water samples.

Sorption of copper (II) ions by a composite sorbent based on chitosan and montmorillonite

A composite sorbent based on chitosan and montmorillonite has been developed for the extraction of heavy metal ions from aqueous solutions. The optimal chitosan / montmorillonite ratio for obtaining sorbent granules has been determined. Equilibriumkinetic studies of the process of copper (II) ions extraction in the heterophase system "aqueous solution of metal sulphate - modified sorbent" have been carried out.The treatment of sorption isotherms of copper (II) ions by the initial chitosan and a chitosan based composite according to the Langmuir equation made it possible to determine the maximum sorption capacities of these materials (А∞). It has been established that A∞ of the chitosan/montmorillonite composite sorbent exceeds the maximum sorption capacity for the original chitosan by more than two times.The effect of pH on the sorption of copper ions by chitosan-based sorbents is due to the competition of metal cations and protons for sorption sites. In the course of competitive chemisorption, protons deactivate amino groups - the main sorption centers, converting them into an inactive, H-salt form, which leads to a decrease in the sorption capacity of chitosan in relation to copper ions.Changes in the composition of the modified sorbent compared to the original chitosan are confirmed by infrared spectroscopy data. Microscopic studies using the method of scanning electron microscopy show the presence of changes in the surface structure of chitosan granules when montmorillonite is introduced into the composition of the sorbent.

Covalent organic frameworks based hierarchical porous hybrid monolithic capillary: Synthesis, characterization, and applications in trace metals analysis

The preparation of hierarchical porous monolithic column with high covalent organic frameworks (COF) loading and micropores accessibility is challenging due to the easy aggregability and sedimentation of COFs. Herein, a novel strategy based on high internal phase emulsion (HIPE) polymerization was proposed for preparing COF hybrid capillary monolithic column with hierarchical porosity. COFs with different frameworks including imine COFs (COF-OMe, COF-F and COF-SH), triazine COF (CTF-1) and boron-based COF (COF-5) were selected to investigate the universality of the preparation strategy. The presence of COF in the monolithic capillary was confirmed by scanning electron microscope, X-ray diffraction and fourier transform infrared spectroscopy. Nitrogen adsorption/desorption experiments and thermogravimetric analysis showed that the prepared COF hybrid monolithic capillary exhibited high COF loading (e.g., 28.7% for COF-SH) and accessibility (e.g., 98.5% for COF-SH), mainly due to the thin walls of void-window structures originated from polymerization of HIPE. The successful preparation of water-stable COF-F, COF-OMe, COF-SH and CTF-1 hybrid monolithic columns demonstrated the proposed synthesis strategy is universal to water-stable COF without tedious optimization of dispersion system, effectively avoiding the sedimentation of COF in pre-polymerization solution. Then, the sulfhydryl-modified COF hybrid polymer (poly(COF-SH-HIPE)) monolithic column was evaluated for the extraction of heavy metal ions, and a method based on poly(COF-SH-HIPE) monolithic capillary microextraction on-line coupled with inductively coupled plasma mass spectrometry detection was developed for analysis of trace Cd, Hg and Pb in human fluid samples.

Effect of chemical modification of cotton cellulose by anthranilic acid on the sorption of Cu(II) and Fe(II) ions

The authors modified cotton cellulose with anthranilic acid to obtain a new sorbent capable of efficient extraction of heavy metal ions from aqueous solutions. We conducted the modification in two stages: at the first stage, we obtained dialdehyde cellulose by oxidation of cellulose with sodium metaperiodate; at the second stage, we treated dialdehyde cellulose with anthranilic acid to obtain a ready-made sorbent. The authors determined the optimum conditions for modifying cotton cellulose to achieve maximum sorption of iron(II) and copper(II) ions. We studied the equilibrium-kinetic characteristics of the original and modified cotton cellulose. Also, we have processed the results of the kinetic experiment within the framework of pseudo-first- and pseudo-second-order kinetics models. We selected sorption isotherms, processed them within the framework of the Langmuir model, and determined the values of the ultimate sorption capacity (A∞). The modification of cotton cellulose enables to increase its sorption capacity significantly. According to the results, the A∞ of the modified sorbent is about 4-5 times higher than the ultimate sorption capacity of native cotton cellulose to Cu(II) and Fe(II) ions. In contrast, we obtained and compared the IR spectra of anthranilic acid-modified cellulose and native cellulose. Additionally, we obtained SEM images of the modified sorbent and the native cotton cellulose surface structure.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution.

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe3O4 nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe3O4 nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg2+, Pb2+, Co2+ and Cd2+ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1–200 μg L−1 for Hg2+ and 0.05–200 μg L−1 for Pb2+, Co2+ and Cd2+, and high sensitivity with limits of detection (LOD) of 0.018 μg L−1, 0.014 μg L−1, 0.013 μg L−1 and 0.025 μg L−1 for Cd2+, Pb2+, Co2+ and Hg2+, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb2+, Cd2+, Co2+and Hg2+ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Energy-saving technology for processing of exhausted etching solutions with obtaining of ferromagnetic compounds

Exhausted etching solutions are the waste of industrial enterprises and contain toxic pollutants that have a detrimental effect on the environment. Currently, the processing of these solutions to obtain marketable products is important. The paper presents the results of research on the application of the ferritization method for processing of exhausted etching solutions of steel surfaces. Energy-saving activation of the process by alternating magnetic fields was used, which has undeniable advantages compared to traditional thermal activation. The influence of the initial concentration of iron ions in the reaction mixture of ferritization process and the methods of its activation on the treatment quality of exhausted etching solutions was studied. It was established that the best degree of extraction of heavy metal ions from exhausted etching solutions by ferritization is achieved when the reaction mixture is activated by alternating magnetic fields at an initial concentration of iron ions of 6.6 g/dm3 . At the same time, the residual concentration of iron ions in purified solutions does not exceed 0.03 mg/dm3 , that corresponds to degree of purification of solutions of 99.999%. Those solutions can be reused in situ. The qualitative and quantitative composition of ferritization sediments was studied. Phases of ferroxygite δ-FeOОН, magnetite Fe3O4 and maghemite ɣ-Fe2O3 were detected by X-ray phase analysis in the sediments. It was established that at the initial concentration of iron ions of 26.6 g/dm3 with thermal activation of the reaction mixture and 16.6 g/dm3 with alternating magnetic fields activation, the sediment exclusively contains the magnetite phase. The results of the study indicate the possibility of further use of sediments for the production of important industrial products and materials containing ferromagnetic compounds. The implamitation of improved ferritization process in industrial enterprises will allow to achieve decrease of energy consumption compared to known technologies of exhausted etching solutions processing.

Separation of heavy metals by amino acid functionalized polymer: Experimental and theoretical insights

A chloromethylated polystyrene resin was chemically functionalized with glycine molecules to introduce metal ions chelating sites. The functionalized resin (PsGly) was loaded in a glass column and successfully used for the extraction of heavy metal ions. Several experimental parameters like solution pH, sample flow rate, adsorbent dose and breakthrough volume was studied and optimized. The adsorption capacity observed for Ni(II), Cu(II) and Zn(II) were 0.72, 0.68 and 0.60 mmol g−1, respectively. The chelating mechanism for metal ion adsorption was studied by density functional theory. The metal-ligand interaction energy, entropy, and Gibbs energy were estimated by employing the B3LYP basis set of density functional theory and suggest that the studied metal ions form strong complexes with the adsorbent. The column procedure was employed for the extraction of heavy metal ions from wastewater with detection limit of 0.2 μg L−1.

Simulation of sorption processes of wastewater treatment by modified zeolites

Based on the results of experimental studies of sorption wastewater treatment, a regression-type mathematical model has been developed that adequately describes the effect of all parameters of the ongoing process on the sorption activity of zeolite: initial concentration, sorption time, process temperature, and medium pH. For the first time in research, a generalized criterion for the consistency of behavior and the width of the domain of definition of the model was used. The processes of involving large-tonnage wastes of chemical production to obtain adsorption materials effective for the extraction of heavy metal ions from industrial wastewater have been studied. Natural zeolites were used as the initial matrix, the main component of which is klinoptilolite. A sulfur polymer obtained from epichlorohydrin production wastes with the main component 1,2,3-trichloropropane is proposed as a modifier. Fixation of the modifier on the surface of the zeolite, as well as the effective adsorption of metal ions, have been proven by IR spectroscopy and energy dispersive analysis.

THE USE OF ALUMINOSILICATE CLAYS AS SORBENTS IN THE PURIFICATION OF MEDIA FROM HEAVY METAL IONS

Shown that galvanic production, which is engaged in the application of protective or decorative coatings on metal and non-metal products (galvanizing, nickel plating, oxidation), can also be attributed to enterprises that pollute the environment with wastewater. Subject to all the norms of the technological process, despite the various methods of surface treatment of products, a certain amount of wastewater of complex composition is still formed. With an inferior degree of purification, they are one of the sources of pollution of aquatic environments. The main toxic components polluting this kind of wastewater are heavy metal ions such as chromium-6, cadmium-2, lead-2 and other toxic substances. Shown that in wastewater treatment the main place belongs to the sorption method, which uses natural sorbents such as activated carbons, zeolites, bentonite clays, and other natural materials. Searched for natural raw materials to obtain effective sorbents during decontamination of industrial effluents. The chemical-mineralogical composition of a number of deposits of aluminosilicate rocks in Azerbaijan has been studied. An analysis of the results obtained made it possible to establish the optimal variant of the synthesis of sorbents. Based on a frame-type aluminosilicate zeolite (clinoptilolite) and layered aluminosilicate (bentonite) with a high content of montmorillonite, their Na-forms were obtained. The results of the physicochemical analysis of the natural material and its modified Na-form are presented. Sorption treatment of wastewater from some heavy metal ions on modified forms of bentonite and clinoptilolite was carried out. It has been established that, in terms of sorption properties, the obtained sorbents based on natural raw materials Na-clinoptilolite and Na-bentonite can be recommended instead of synthetic industrial KU-2-8 in the sorption extraction of heavy metal ions from wastewater

Layer-by-Layer Assembly of Polyelectrolytes on Urchin-like MnO2 for Extraction of Zn2+, Cu2+ and Pb2+ from Alkaline Solutions

Three-dimensional (3D) urchin-like MnO2@poly (sodium 4-styrene sulfonate) (PSS)/poly (diallyl dimethylammonium chloride) (PDDA)/PSS particles were prepared via the layer-by-layer (LBL) assembly of polyelectrolytes for the extraction of Zn2+ from alkaline media. The adsorption performance of Zn2+ on MnO2, MnO2@PSS/PDDA/PSS, and MnO2@(PSS/PDDA)3/PSS was investigated in batch experiments. The adsorption of Zn2+ on MnO2@PSS/PDDA/PSS has been studied under various conditions, such as initial Zn2+ concentration, adsorbent dosage, the solution’s pH, and reaction time. The Zn2+ adsorption process is well represented by the pseudo-second-order kinetic model, and the equilibrium data fit the Freundlich isotherm well. MnO2@PSS/PDDA/PSS also showed high efficiency for Pb2+ and Cu2+ removal from slightly alkaline water. Thus, our research provides a deep insight into the preparation of 3D manganese oxides with polyelectrolyte films for the extraction of heavy metal ions, such as Pb2+, Cu2+, and Zn2+, from slightly alkaline wastewater.

Selective extraction of heavy metals (Fe, Co, Ni) from their aqueous mixtures by Task-Specific salicylate functionalized imidazolium based ionic liquid

Iron (Fe), cobalt (Co) and nickel (Ni) together are known as the iron triad exhibiting similar chemical and physical affinities in the periodic table. We have developed a green, efficient, highly selective, environmentally benign, water-IL biphasic solvent extraction system for the selective extraction of iron triad elements from their aqueous mixtures at room temperature using a new salicylate functionalized imidazolium based task specific ionic liquid (TSIL) i.e. 1,3-dioctylimidazolium 2-hydroxybenzoate [DOIM][OHB]. Co2+ was extracted within 5 min as a blue complex while the residual mixture was allowed to stand overnight. In the meantime, Fe2+ was oxidized to Fe3+ without using any additional oxidants and was extracted as a red coloured complex. Ni2+ was not observed visibly, however atomic absorption spectroscopy (AAS) indicated the presence of less than 1% Ni2+. The extraction of heavy metal ions follows neutral extraction mechanism elucidated through UV visible spectroscopy.

Adsorption properties of Danthron-impregnated carbon nanotubes and their usage for solid phase extraction of heavy metal ions

Keeping the efficiency of adsorbents in view with devising new solid phase extraction (SPE) methods, this study was aimed at preparation and examination of a new beneficial adsorbent for heavy metal ions. A suitable extractant, 1,8-Dihydroxyanthraquinone (Danthron), was impregnated onto MWCNTs and, firstly, the adsorption properties of Danthron-impregnated MWCNTs (Danthron/MWCNTs) were checked towards some targeted metal ions, i.e. Pb2+, Cu2+, Zn2+, Cd2+, Co2+, and Ni2+ ions. Langmuir isotherm fitted with equilibrium data, kinetic studies vouchsafed the obedience of experimental data from pseudo-second-order model, and thermodynamic appraisals revealed the endothermic nature of adsorption process. Secondly, provided with good sorption properties of the adsorbent, a mini-column packed with Danthron/MWCNTs was recruited for pre-concentration of the interested analytes prior to their determination by inductively coupled plasma (ICP) instrument. The detection limits were in a range between 0.301 and 0.016 µg·L−1 and the new SPE method showed a high efficiency in tackling analysis of natural waters, herbal infusion samples, and certified reference materials. Overall, the results vouchsafed that Danthron/MWCNTs can be regarded as a suitable adsorbent for preconcentration of the targeted metals.

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%.

ВПЛИВ ПОЖЕЖ В ПРИРОДНИХ ЕКОСИСТЕМАХ НА МІГРАЦІЙНУ ЗДАТНІСТЬ ВАЖКИХ МЕТАЛІВ, МЕТОДИ СОРБЦІЙНО-СПЕКТРОФОТОМЕТРИЧНОГО ЇХ ВИЗНАЧЕННЯ

Purpose. Development of methods for sorption-spectrophotometric and atomic-emission determination of hazardous toxicants in order to increase the reliability of monitoring pollution parameters and assess possible future adverse consequences for humans and the environment. Methodology. Sorption-spectrophotometric and atomic-emission determination of Cu (II), Ni (II), Cd (II), Pb (II), Al (III), Fe (III), in soils degraded due to fires, using sorbents based on silica gel, sequentially modified with polyhexamethylene guanidine and arsenazo-I salts, which can be used for simple and fast methods for the determination of heavy and transition metals. Findings. Identification of chemical pollution by heavy metals in degraded soils as a result of tegogenic activity, fires, climate change for making the necessary management decisions. Originality. Sorbents for the group extraction of heavy metal ions were obtained by the method of non-covalent modification of the silica gel surface with polyhexamethylene guanidine and a triphenylmethane sulfonyl dye. Practical value. Techniques have been developed for the sorption-spectrophotometric and atomic-emission determination of Cu (II), Ni (II), Cd (II), Pb (II), Al (III), Fe (III) using silica gel, sequentially modified with salts of polyhexamethylene guanidine and arsenazo I, which can be used for simple, rapid test methods for determining the migration capacity of heavy and transition metals in technogenically polluted ecosystems and will make it possible to make scientifically based decisions on the priority of the implementation of environmental protection measures. To determine the microquantities of the ions under study, it is advisable to use fine-grained silica gel, and coarse-grained silica gel – to determine higher concentrations of the tested ions. Сonclusions. The paper proposes methods for the group sorption - spectrophotometric determination of Cu (II), Ni (II), Cd (II), Pb (II), Al (III), Fe (III) in the main components of the environment (soil and natural waters) on based on sorbents modified with specific analytical reagents, which is one of the promising directions for increasing the sensitivity and selectivity of analysis. References 15, tables 2, figures 5.

Determination of influence of pH on reaction mixture of ferritation process with electromagnetic pulse activation on the processing of galvanic sludge

This paper considers prospects for increasing the level of environmental safety of industrial enterprises as a result of the implementation of resource-saving technology of processing galvanic sludge using the ferritization method. The effectiveness of the use of electromagnetic pulse discharges for resource-saving activation of the ferritization process with the extraction of heavy metal ions from sludge (Fe, Ni, Cu, Zn) has been confirmed. The influence of key parameters of the process such as the pH value of the reaction mixture and the initial concentrations of metals in the solution on the quality of processing galvanic sludge by ferritization has been experimentally investigated. It was determined that with an increase in the pH value from 8.5 to 10.5 the residual concentrations of metal ions decrease to the values of 0.1÷0.25 mg/dm3 regardless of the total initial concentrations. It has been established that the technique of electromagnetic pulse activation ensures an adequate degree of extraction of metal ions of 99.9 %; it also has indisputable energy advantages compared to the thermal method: energy costs are reduced by more than 60 %. That indicates the suitability of purified water for reuse in galvanic production in terms of the requirements for the content of heavy metal ions in it. In addition, the structural studies of ferritization sediment samples have been carried out. The sediment is characterized by the maximum content of crystalline ferromagnetic phases of ferrite. It was established that an increase in the pH of the initial reaction mixture leads to an increase in the ferrite phase in sedimentation: at pH=10.5, phases were detected, which are characterized by a maximum ferrite content (exceeding 76 %). The proposed resource-saving ferritization process prevents environmental pollution, ensures efficient and rational utilization of raw materials and energy in the industry; it also makes it possible to obtain commodity products from industrial waste.

Phase Studies and Efficient Recovery of Inorganic Metal Salts from the Microemulsion System Using a Sugar-Based Non-Ionic Surfactant

Abstract In the present work, the phase behaviour of the microemulsion system formulated by using water, organic solvent, and a sugar-based non-ionic surfactant was investigated in detail. We have used a sugar-based non-ionic surfactant for formulation of microemulsion, as it is a greener alternative for the formulation of a microemulsion system, owing to the following aspects: a) better physicochemical properties as compared to that of the conventional non-ionic surfactants, b) non-toxicity, and c) biodegradability. The extraction of heavy metal ions from the metal complexes as well as the recovery efficiency of heavy metal ions using a microemulsion system has been investigated. The maximum absorbance values of metal ions, after recovery from the metal complexes, were measured. Moreover, the UV-Visible spectrophotometric studies revealed that the absorbance increases with an increase in metal ion concentration in the aqueous phase while its value decreases with an increase in the concentration of potassium thiocyanate in the aqueous phase after the extraction of the metal ions from the metal complexes. Furthermore, it has also been evaluated that 4.0 mol/L potassium thiocyanate is the optimum concentration required for efficient recovery of 0.05 mol/L cobalt ion as well as nickel ions. The recovery efficiency of cobalt ions was found to be 97%, whereas that of nickel ions was determined to be 94% respectively. In addition to being an environmentally friendly approach, the present work is an economically viable option too, as it deals with the studies related to the extraction and efficient recovery of metal ions.

Polydopamine-functionalised biosilica derived from diatomite as a porous composite for effective solid phase extraction of heavy metal ions from aqueous samples

ABSTRACT This study aimed to synthesise and apply polydopamine-functionalised biosilica(BS@PDA), derived from diatomite, as a highly porous and biodegradable composite for efficient adsorption of Cu(II), Co(II), Pb(II), and Zn(II) ions from different types of aqueous matrices. The self-polymerisation of dopamine monomers on the treated diatomite’s surface and internal pores was conducted in an aqueous medium at pH = 8.5. The adsorbent’s structural characterisation was evaluated using FT-IR, SEM, EDX, TEM, BET, and BJH confirming a successful synthesis. The effects of critical parameters influencing the quantitative extraction and determination of analytes were optimised. The effects of interfering ions commonly found in industrial and environmental waters were also examined, indicating no severe interference in the extraction process. The calibration curves in the range of 10–500 ng/mL (r ≥ 0.9960) were linear. The relative standard deviations (n = 5) at two different concentration levels were in the range of 2.1–6.2%. The limits of detection of analytes ranged from 0.24 to 1.25 ng/mL. The bio-adsorbent ability to extract the studied analytes was tested in the industrial wastewater, river water, and seawater samples. The recoveries of the spiked analytes in the real samples were above 94%. The results indicated the comparable capacity of the proposed method for both removal and determination of heavy metals in industrial and environmental water samples.