Efficient extraction of heavy metals from aqueous solution by novel hybrid material based on silica particles bearing new Schiff base receptor

Removal, mechanistic and kinetic studies of Cr(VI), Cd(II), and Pb(II) cations using Fe3O4 functionalized Schiff base chelating ligands

The Schiff base chelating ligands; (E)-2-(3,3-dimethoxy-2-oxa-7,10-diaza-3-silaundec-10-en-11-yl)phenol (L1), (E)-N-(2-((pyridine-2ylmethylene)amino)ethyl)-3-(trimethoxysilyl)propan-1-amine (L2) and (E)-N-(2-((thiophen-2-ylmethylene)amino)ethyl)-3-(trimethoxysilyl)propan-1-amine (L3) were immobilized on Fe3O4 magnetic nanoparticles (MNPs) and utilized in the extraction of Cr(VI), Cd(II) and Pb(II) metal cations from aqueous solutions. The compounds synthesized, denoted as L1@ Fe3O4, L2@Fe3O4, and L3@Fe3O4, were characterized using FT-IR spectroscopy, TEM-SEM, VSM, and BET/BHJ techniques for analysis of functional groups, surface morphology, magnetic properties, and degree of porosity of the adsorbents, respectively. BET/BHJ technique confirmed the mesoporous nature of the compounds as their pore diameters ranged between 15 and 17 nm. The initial optimization conditions of pH, adsorbent dosage, initial metal concentration, and contact time on adsorption were studied using L1@ Fe3O4. The optimum efficiencies recorded were 68% and 46% for Cr(VI) and Cd(II), respectively, obtained at pH 3, and a metal concentration of 20 ppm while an efficiency of 99% was recorded for Pb(II) cations at pH 7 and a metal concentration of 100 ppm. Compounds L2@Fe3O4 and L3@ Fe3O4 were also used in the extraction of metal cations from aqueous solution and gave efficiencies of 22%, 56%, and 78% for L2@ Fe3O4 and 19%, 90%, and 59% using L3@ Fe3O4 for Cr(VI), Cd(II), and Pb(II), respectively. The maximum adsorption capacities of L1@ Fe3O4 for Cr(VI), Cd(II), and Pb(II) cations were obtained from the Langmuir isotherm as 32.84, 41.77, and 450.45 mg/g, respectively. The experimental data was analyzed using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models. Both linear and non-linear forms of kinetic isotherms; Langmuir, Freundlich, Redlich-Peterson, and Temkin were utilized to investigate the nature of adsorption on L1@Fe3O4. The mechanistic studies deduced that the Langmuir isotherm and pseudo-second-order kinetic model better described the adsorption process both yielding high correlation coefficient values (R2 > 0.98).

Kinetic control aspects and mechanisms in oriented membrane processes for extraction and recovery of ascorbic acid compound

Ascorbic acid comprises four enantiomers, with only one of them, L-ascorbic acid, recognized as vitamin C. The modern industries place significant importance on obtaining this compound in its purest form. The challenge is to recover L-ascorbic acid, which requires specific processes within these industries. To satisfy this condition, purification is needed, a process that requires large quantities of solvents and high energy consumption. To overcome these limitations, we conducted a study on the facilitated extraction of L-ascorbic acid using three affinity polymer membranes, including supported liquid membrane (SLM), polymer inclusion membrane (PIM), and grafted polymer membranes (GPM) with cholic acid as the extractive agent. Following the characterization of the membranes using IR spectroscopy and SEM techniques, we investigated various parameters associated with substrate diffusion through the organic membrane phase. Regarding the biologically active L-ascorbic acid, our research findings indicated that kinetic factors drove the mechanisms of the studied processes.

Synthesis, Crystal Structures, Genotoxicity, and Antifungal and Antibacterial Studies of Ni(II) and Cd(II) Pyrazole Amide Coordination Complexes

In this study, we synthesized two coordination complexes based on pyrazole-based ligands, namely 1,5-dimethyl-N-phenyl-1H-pyrazole-3-carboxamide (L1) and 1,5-dimethyl-N-propyl-1H-pyrazole-3-carboxamide (L2), with the aim to investigate bio-inorganic properties. Their crystal structures revealed a mononuclear complex [Ni(L1)2](ClO4)2 (C1) and a dinuclear complex [Cd2(L2)2]Cl4 (C2). Very competitive antifungal and anti-Fusarium activities were found compared to the reference standard cycloheximide. Additionally, L1 and L2 present very weak genotoxicity in contrast to the observed increase in genotoxicity for the coordination complexes C1 and C2.

From speciation study to removal of Pb2+ from natural waters by a carnosine-based polyacrylamide/azlactone copolymer

A deep speciation study on L-carnosine (CAR) and Pb²⁺ system was performed in aqueous solution with the aim to assess its potential use as a sequestering agent of metal cation. To determine the best conditions for Pb²⁺ complexation, potentiometric measurements were carried out over a wide range of ionic strength (0.15 ≤ I/≤ 1 mol/L) and temperature (15 ≤ T/°C ≤ 37), and thermodynamic interaction parameters (logβ, ΔH, ΔG and TΔS) were determined. The speciation studies allowed us to simulate sequestration ability of CAR toward Pb²⁺ under different conditions of pH, ionic strength and temperature and to establish a priori the conditions for the best removal performance, i.e., pH > 7 and I = 001 mol/L. This preliminary investigation was very useful in optimizing removal procedures and limiting subsequent experimental measurements for adsorption tests. Therefore, to exploit the binding ability of CAR for Pb²⁺ removal from aqueous solutions, CAR was covalently grafted on an azlactone-activated beaded-polyacrylamide resin (AZ) using an efficient click coupling reaction (78.3% of coupling efficiency). The carnosine-based resin (AZCAR) was analyzed by ThermoGravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). Morphology, surface area and pore size distribution were studied through a combination of Scanning Electron Microscope (SEM) and adsorption/desorption of N₂ analyses according to the Brunauer-Emmett-Teller (BET) and Barret-Johner-Halenda (BJH) approaches. The adsorption capacity of AZCAR toward Pb²⁺ was investigated under conditions simulating the ionic strength and pH of different natural waters. The time needed to reach equilibrium in the adsorption process was 24 h, and the best performance was obtained at pH > 7, typical of most natural waters, with removal efficiency ranging from 90.8% (at I = 0.7 mol/L) to 99.0 (at I = 0.001 mol/L).

A Review: Adsorption and Removal of Heavy Metals Based on Polyamide-amines Composites

In recent years, the problem of heavy metal pollution has become increasingly prominent, so it is urgent to develop new heavy metal adsorption materials. Compared with many adsorbents, the polyamide-amine dendrimers (PAMAMs) have attracted extensive attention of researchers due to its advantages of macro-molecular cavity, abundant surface functional groups, non-toxicity, high efficiency and easy modification. But in fact, it is not very suitable as an adsorbent because of its solubility and difficulty in separation, which also limits its application in environmental remediation. Therefore, in order to make up for the shortcomings of this material to a certain extent, the synthesis and development of polymer composite materials based on PAMAMs are increasingly prominent in the direction of solving heavy metal pollution. In this paper, the application of composites based on PAMAMs and inorganic or organic components in the adsorption of heavy metal ions is reviewed. Finally, the prospects and challenges of PAMAMs composites for removal of heavy metal ions in water environment are discussed.

Kinetics, thermodynamics, equilibrium, surface modelling, and atomic absorption analysis of selective Cu(ii) removal from aqueous solutions and rivers water using silica-2-(pyridin-2-ylmethoxy)ethan-1-ol hybrid material

The removal of heavy metals is attracting considerable attention due to their undesirable effects on the environment. In this investigation, a new adsorbent based on silica functionalized with pyridin-2-ylmethanol (SiPy) was successfully synthesized to yield to a hybrid material. FTIR, SEM, TGA, and specific surface area analysis were used to characterize the structure and morphology of the SiPy hybrid material. Various heavy metal ions such as Cu(ii), Zn(ii), Cd(ii), and Pb(ii) were selected to examine the adsorption efficiency of the newly prepared adsorbent, optimized at varying solution pH, contact time, concentration, and temperature. The adsorbent SiPy displayed good adsorption capacity of 90.25, 75.38, 55.23, and 35.12 mg g⁻¹ for Cu(ii), Zn(ii), Cd(ii), and Pb(ii), respectively, at 25 min and pH = 6. The adsorption behaviors of metal ions onto the SiPy adsorbent fitted well with the pseudo-second-order kinetic mode and the isotherm was better described by the Langmuir isotherm. The thermodynamic studies disclose spontaneous and endothermic adsorption process. Furthermore, the SiPy adsorbent retained good selectivity and regeneration properties after five adsorption–desorption cycles of Cu(ii). A computational investigation of the adsorption mechanism indicates that the N-pyridine, O-hydroxyl, and ether O-atoms play a predominant role during the capture of Cu(ii), Zn(ii), Cd(ii), and Pb(ii). This study proposes the SiPy adsorbent as an attractive material for the selective removal of Cu(ii) from real river water and real industrial wastewater.

The removal of heavy metals is attracting considerable attention due to their undesirable effects on the environment.

A Highly Efficient Environmental-Friendly Adsorbent Based on Schiff Base for Removal of Cu(II) from Aqueous Solutions: A Combined Experimental and Theoretical Study

Removal of heavy metals from drinking water sources and rivers is of strategic health importance and is essential for sustainable ecosystem development, in particular in polluted areas around the globe. In this work, new hybrid inorganic-organic material adsorbents made of ortho- (Si-o-OR) or para-Schiff base silica (Si-p-OR) were synthesized and characterized in depth. These hybrid adsorbents show a high selectivity to Cu(II), even in the presence of competing heavy metals (Zn(II), Cd(II), and Pb(II)), and also demonstrate great reusability after five adsorption-desorption cycles. Maximum sorption capacity for Cu(II) was found for Si-o-OR (79.36 mg g⁻¹) and Si-p-OR (36.20 mg g⁻¹) in no less than 25 min. Energy dispersive X-ray fluorescence and Fourier transform-infrared spectroscopy studies demonstrate that this uptake occurs due to a chelating effect, which allows these adsorbents to trap Cu(II) ions on their surfaces; this result is supported by a theoretical study for Si-o-OR. The new adsorbents were tested against real water samples extracted from two rivers from the Oriental region of Morocco.

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

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.

Investigation of mercury(II) and copper(II) sorption in single and binary systems by alginate/polyethylenimine membranes

This study investigates Hg(II) and Cu(II) sorption in single and binary systems by alginate/polyethylenimine membranes. Batch experiments are conducted to assess the metal sorption performance. FTIR and SEM-EDX analyses are used to identify metal binding mechanism. The sorption kinetics are better fitted by the pseudo-second-order-equation compared to the pseudo-first-order-equation. Three isotherms are compared for fitting the sorption in mono-component solutions and the Sips model gives the best simulation of experimental data. The competitive-Sips model fits well sorption data in Hg-Cu binary solutions and finds that the Cu uptake is drastically reduced by Hg competition. Copper(II) uptake remains negligible at low pH whereas it increases with pH up to 6 because of material deprotonation. Mercury(II) sorption behaves differently, it slightly changes from pH 1 (q_eq: 0.76 mmol g^-1) to pH 6 (q_eq: 0.84 mmol g^-1) due to chloro-anion formation. Therefore, playing with the pH allows separating Hg(II) from Cu(II).

New hybrid adsorbent based on porphyrin functionalized silica for heavy metals removal: Synthesis, characterization, isotherms, kinetics and thermodynamics studies

The pollution of water resources due to the disposal of toxic heavy metals has been a growing global concern for the last decades. For this purpose, the search for effective and economic material based adsorbents is required, due to the efficiency of the process. In this work, a novel inorganic-organic hybrid material based on silica chemically modified with a porphyrin (SiNTPP), with a high metal removal efficiency, was developed. The new material was characterized using a set of suitable techniques such as ¹³C NMR of the solid state, elemental analysis, FTIR, nitrogen adsorption-desorption isotherm, BET surface area, BJH pore sizes and scanning electron microscopy (SEM). The new material surface exhibits good chemical and thermal stability based on the obtained thermogravimetric curves (TGA). An adsorption study was accomplished to investigate the effect of porphyrin-silica hybrid on the removal of Pb(II), Zn(II), Cd(II) and Cu(II) from aqueous solutions using a batch method. The effect of various parameters, such as initial metal concentration, pH, temperature, as well as the kinetics and thermodynamics for sorption on SiNTPP were investigated. The studies demonstrate that adsorption is fast, as proved by the equilibrium achievement within 25min. The metals removal from aqueous solution are better adapted to the Langmuir isotherm model than to the Freundlich model. The thermodynamic parameters (ΔG°, ΔH° and ΔS°) disclose that the process was endothermic and spontaneous in nature, and the adsorption process follows a pseudo-second order kinetics. The adsorbent can be regenerated continuously without affecting its extraction percentage. Its effectiveness is highly justified compared to previous described materials.

Trace amount determination of Cd(ii), Pb(ii) and Ni(ii) ions in agricultural and seafood samples after magnetic solid phase extraction by MIL-101(Cr)/phenylthiosemicarbazide-functionalized magnetite nanoparticle composite

Herein, a novel nanosorbent consisting of phenylthiosemicarbazide magnetite nanoparticles and MIL-101(Cr) was synthesized, characterized and utilized to magnetic solid phase extraction of some heavy metals in various agricultural and seafood samples.

A novel environment-friendly hybrid material based on a modified silica gel with a bispyrazole derivative for the removal of ZnII, PbII, CdIIand CuIItraces from aqueous solutions

New surface-functionalized with bispyrazole receptor was designed for efficient removal of heavy metals. The architecture of host–guest on the surface was identified.