Adsorption applications of synthetically prepared PANI-CuO based nanocomposite material

In this work, we have used a polyaniline and cupric oxide-based nanocomposite material (PANI-CuO) for the adsorption of Pb²⁺, Cd²⁺, and Cr⁶⁺ ions from contaminated water. FTIR, FESEM, EDX and XRD methods were used in the characterisation of PANI-CuO. The maximum percentage removal of Pb²⁺, Cd²⁺, and Cr⁶⁺ ions was found to be 79.9%, 78.9% and 82.1% at 1 g of PANI-CuO for 100 mL of contaminated water. The suitability order of the isotherm model was observed as Langmuir > Freundlich > Elovich, whereas the pseudo first order model was best fitted as compared to the pseudo second order model. The rate constants were evaluated as 1.441, 1.801 and 1.661 g mg^?1 min ^?1, respectively. The values of ΔG⁰ were calculated to be ?287.4, ?849.6, and ?728.9 kJ mol^?1 for Pb²⁺, Cd²⁺ and Cr⁶⁺ ions, respectively.     

Comparison of sorption of Pb<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> on Kaolinite clay and polyvinyl alcohol-modified Kaolinite clay

Kaolinite clay obtained from Ubulu-Ukwu, Delta state in Nigeria was modified with polyvinyl alcohol (PVA) reagent to obtain PVA-modified Kaolinite clay adsorbent. Scanning Electron Microscopy (SEM) of the PVA-modified adsorbent suggests that Kaolinite clay particles were made more compact in nature with no definite structure. Modification of Kaolinite clay with PVA increased its adsorption capacity for 300 mg/L Pb²⁺ and Cd²⁺ by a factor of at least 6, i.e., from 4.5 mg/g to 36.23 mg/g and from 4.38 mg/g to 29.85 mg/g, respectively, at 298 K. Binary mixtures of Pb²⁺ and Cd²⁺ decreased the adsorption capacity of Unmodified Kaolinite clay for Pb²⁺ by 26.3% and for Cd²⁺ by 0.07%, respectively. In contrast, for PVA-modified Kaolinite clay, the reductions were up to 50.9% and 58.5% for Pb²⁺ and Cd²⁺, respectively. The adsorption data of Pb²⁺ and Cd²⁺ onto both Unmodified and PVA-modified Kaolinite clay adsorbents were found to fit the Pseudo-Second Order Kinetic model (PSOM), indicating that adsorption on both surfaces was mainly by chemisorption and is concentration dependent. However, kinetic adsorption data from both adsorbent generally failed the Pseudo-First order Kinetic model (PFOM) test. Extents of desorption of 91% Pb²⁺ and 94% Cd²⁺ were obtained, using 0.1 M HCl, for the Unmodified Kaolinite clay adsorbent. It was found that 99% Pb²⁺ and 97% Cd²⁺, were desorbed, for PVA-modified Kaolinite clay adsorbents within 3 min for 60 mg/L of the metal ions adsorbed by the adsorbents.     

Insight into the performance of novel kaolinite-cellulose/cobalt oxide nanocomposite as green adsorbent for liquid phase abatement of heavy metal ions: Modelling and mechanism

A cost-efficient kaolinite-cellulose/cobalt oxide green nanocomposite (Kao-Cel/Co₃O₄ NC) was successfully synthesized, and utilized as a promising material for removing Pb²⁺ and Cd²⁺ from aqueous solution. The fabricated nanocomposite has been characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analysis. The batch methodology was exploited for optimization of process parameters and the optimized conditions were found to be adsorbent dosage (2.0 g/L), extraction time (50 min), initial concentration (60 mg/L), and initial solution pH (6). Kao-Cel/Co₃O₄ NC displayed excellent adsorption properties and achieved maximum saturation capacity (Q_m) of 293.68 mg Pb²⁺/g and 267.85 mg Cd²⁺/g, with an equilibration time of 50 min at 323 K. The Langmuir model best expressed the isotherm data recommending the adsorption onto energetically homogeneous NC surface, while the compatibility of kinetics data with pseudo-second-order model revealed the dependency of adsorption rate on adsorption capacity, and probable involvement of chemisorption in the rate-controlling step. Electrostatic interaction and ion exchange mechanism were responsible for the uptake of Pb²⁺ and Cd²⁺ by Kao-Cel/Co₃O₄ NC as demonstrated by Fourier transform infrared spectroscopy and pH studies. Thermodynamic parameters confirmed the physical, spontaneous, and endothermic sequestration processes. Real water investigation specified that the present adsorbent could be effectively used for liquid phase decontamination of Pb²⁺ and Cd²⁺. The nanocomposite exhibited high reusability, which could be utilized efficiently for five runs with sustainable results. In summary, this study portrayed the present nanocomposite as an emerging material for the adsorption of heavy metal ions particularly Pb²⁺ and Cd²⁺.     

Competitive heavy metal removal by poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐itaconic acid)

The competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solutions by the copolymer of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and itaconic acid (IA), P(AMPS‐co‐IA), was investigated. Homopolymer of AMPS (PAMPS) was also used to remove these ions from their aqueous solution. In the preparation of AMPS–IA copolymer, the molar percentages of AMPS and IA were 80 and 20, respectively. In order to observe the changes in the structures of polymers due to metal adsorption, FTIR spectra by attenuated total reflectancetechnique and scanning electron microscopy (SEM) pictures of the polymers were taken both before and after adsorption experiments. Total metal ion removal capacities of PAMPS and P(AMPS‐co‐IA) were 1.685 and 1.722 mmol Me²⁺/g_polymer, respectively. Experimental data were evaluated to determine the kinetic characteristics of the adsorption process. Competitive adsorption of Pb²⁺, Cu²⁺, and Cd²⁺ ions onto both PAMPS and P(AMPS‐co‐IA) was found to fit pseudo‐second‐order type kinetics. In addition, the removal orders in the competitive adsorption of these metal ions onto PAMPS and P(AMPS‐co‐IA) were found to be Cd²⁺ > Pb²⁺ > Cu²⁺ and Pb²⁺ > Cd²⁺ > Cu²⁺, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of macroreticular chelating resins containing mercapto groups from 2,3-epithiopropyl methacrylate/divinylbenzene copolymer beads and their adsorption capacity

Macroreticular chelating resins containing mercapto groups were prepared by the reaction of 2,3-epithiopropyl methacrylate/divinylbenzene macroreticular copolymer beads with ethanolic potassium hydrogensulfide solution for 1 h at 50°C. The adsorption capacities of this resin for Ag⁺, Hg²⁺, Pb²⁺ and Cd²⁺ were determined at various pH values. In the acidic region, the resin shows a high affinity for Ag⁺ and Hg²⁺ and high resistance against air oxidation. Cadmium is readily eluted with 1 mol dm^?3 hydrochloric acid; silver, mercury and copper ions can be eluted with 1 mol dm^?3 hydrochloric acid containing 5% (w/v) thiourea. The proposed resin appears to be useful for the removal of As³⁺ from aqueous solutions.     

Cysteine functionalized poly(hydroxyethyl methacrylate) monolith for heavy metal removal

The aim of this study was to investigate the performance of monoliths composed of hydroxyethyl methacrylate (HEMA) to which N-methacryloyl-(L)-cysteine methyl ester (MAC) was polymerized for removal of heavy metal ions. Poly(HEMA-MAC) monolith was produced by bulk polymerization. Poly(HEMA-MAC) monolith was characterized by FTIR and scanning electron microscopy (SEM). The poly(HEMA-MAC) monolith with a swelling ratio of 89%, and containing 69.4 μmol MAC/g were used in the adsorption studies. Adsorption capacity of the monolith for the metal ions, i.e., Cu²⁺, Cd²⁺, Zn²⁺, Hg²⁺, and Pb²⁺ were investigated in aqueous media containing different amounts of the ions (10–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(HEMA-MAC) monolith were 68.2 mg/g for Zn²⁺, 129.2 mg/g for Cu²⁺, 245.8 mg/g for Pb²⁺, 270.2 mg/g for Hg²⁺, and 284.0 mg/g for Cd²⁺. pH significantly affected the adsorption capacity of MAC incorporated monolith. The competitive adsorption capacities were 587 μmol/g for Zn²⁺, 1646 μmol/g for Cu²⁺, 687 μmol/g for Pb²⁺, 929 μmol/g for Hg²⁺, and 1993 μmol/g for Cd²⁺. The chelating monolith exhibited the following metal ion affinity sequence on molar basis: Cd²⁺ > Cu²⁺ > Hg²⁺ > Pb²⁺ > Zn²⁺. The formation constants of MAC–metal ion complexes have been investigated applying the method of Ruzic. The calculated values of stability constants were 5.28 × 10⁴ L/mol for Cd²⁺, 4.16 × 10⁴ L/mol for Cu²⁺, 2.27 × 10⁴ L/mol for Hg²⁺, 1.98 × 10⁴ L/mol for Pb²⁺, and 1.25 × 10⁴ L/mol for Zn²⁺. Stability constants were increased with increasing binding affinity. The chelating monoliths can be easily regenerated by 0.1 M HNO₃ with higher effectiveness. These features make poly(HEMA-MAC) monolith a potential adsorbent for heavy metal removal.     

Cellulose/chitosan composites prepared in ethylene diamine/potassium thiocyanate for adsorption of heavy metal ions

Cellulose/chitosan composites were successfully prepared in a new and basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN), by dissolving cellulose and chitosan in 70/30 (w/w) EDA/KSCN at ?19 °C, and then coagulating in methanol. Wide angle X-ray diffraction studies revealed that the EDA/KSCN solvent system is capable of disrupting the hydrogen bonds in both cellulose and chitosan and increase the amorphous regions. Stability tests proved that the composites are stable in acidic aqueous solution due to the hydrogen bonds formed between cellulose and chitosan. This is the first time to dissolve chitosan in a basic-based solvent system and prepare cellulose/chitosan composites in a straightforward way. The adsorption of heavy metal ions (Cu²⁺, Cd²⁺, and Pb²⁺) onto the cellulose/chitosan composites was investigated. The adsorption capacity is highly dependent on pH and the maximum metal uptake was obtained at pH 5.0. Increasing initial metal concentration enhanced the diffusion of metal ions to the composite surface and therefore the metal removal efficiency. Higher percentage of chitosan in the composites also led to higher metal adsorption. The results indicated that the prepared cellulose/chitosan (1:1) composite can adsorb 0.53 mmol/g Cu²⁺, 0.28 mmol/g Cd²⁺ and 0.16 mmol/g Pb²⁺ ions at pH 5.0. The Freundlich model and the pseudo-second-order model were in good agreement with the adsorption isotherms and kinetics, respectively. X-ray photoelectron spectroscopy studies indicated that the binding of heavy metal ions is attributed to the nitrogen atoms of amino groups in chitosan. The composites can be reused for metal removal.     

Photoactive chemosensors 4: a Cu protein cavity mimicking fluorescent chemosensor for selective Cu recognition

Fluorescent chemosensor 3 can sense Cu²⁺ ions (1-8 μM) even in the presence of elevated levels of Ni²⁺, Cd²⁺, Zn²⁺, Hg²⁺, Ag⁺ and Pb²⁺ (5000 μM). 3 can also analyze for Ag⁺ ions (50-500 μM) in the presence of Ni²⁺, Cd²⁺, Zn²⁺, Hg²⁺ and Pb²⁺ (5000 μM) but Cu²⁺ strongly interferes.     

Chemically modified kapok fiber for fast adsorption of Pb2+, Cd2+, Cu2+ from aqueous solution

Kapok fiber, a natural hollow fiber with thin shell and large cavity, has rarely been used as adsorbent for heavy metal ions. In this paper, kapok fibers were modified with diethylenetriamine pentaacetic acid (DTPA) after hydrophilicity treatment. The adsorption behavior of the resultant kapok-DTPA influenced by pH, adsorption time and initial concentration of metal ion was investigated. The results demonstrate that adsorption equilibrium was reached within 2 min for Pb²⁺ and Cd²⁺. Adsorption kinetics showed that the adsorption rate was well fitted by pseudo-second-order rate model. The adsorption isotherms were studied, and the best fit was obtained in the Langmuir model. The maximum adsorption capacities of kapok-DTPA were 310.6 mg g^?1 for Pb²⁺, 163.7 mg g^?1 for Cd²⁺, 101.0 mg g^?1 for Cu²⁺, respectively. After eight desorption and re-adsorption loops, the lost adsorption capacities for Pb²⁺ and Cu²⁺ were less than 10 %. Because of the large specific area derived from the hollow fiber structure, kapok-DTPA exhibited much better adsorption capacity compared with many other reported adsorbents based on natural materials.     

Heavy Metal Removal from Synthetic Solutions with Magnetic Beads Under Magnetic Field

The aim of this study is to prepare magnetic beads which can be used for the removal of heavy metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate‐vinyl imidazole) [m‐poly(EGDMA‐VIM)] beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ nano‐powder. The specific surface area of the m‐poly(EGDMA‐VIM) beads was found to be 63.1 m²/g with a size range of 150–200 µm in diameter and the swelling ratio was 85%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA‐VIM) beads was 12.4%. The maximum binding capacities of the m‐poly(EGDMA‐VIM) beads were 32.4 mg/g for Cu²⁺, 45.8 mg/g for Zn²⁺, 84.2 mg/g for Cd²⁺and 134.5 mg/g for Pb²⁺. The affinity order on mass basis is Pb²⁺>Cd²⁺>Zn²⁺>Cu²⁺. Equilibrium data agreed well with the Langmuir model. pH significantly affected the binding capacity of the magnetic beads. Binding of heavy metal ions from synthetic wastewater was also studied. The binding capacities were 26.2 mg/g for Cu²⁺, 33.7 mg/g for Zn²⁺, 54.7 mg/g for Cd²⁺ and 108.4 mg/g for Pb²⁺. The magnetic beads could be regenerated up to about 97% by treating with 0.1 M HNO₃. These features make m‐poly(EGDMA‐VIM) beads a potential candidate for support of heavy metal removal under magnetic field.     

Quenching effect of some heavy metal ions on the fast peroxyoxalate-chemiluminescence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane as a novel fluorophore

The fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. The relationships between the chemiluminescence intensity and concentrations of TCPO, imidazole, hydrogen peroxide and L are reported. In the presence of imidazole as catalyst, the entire CL signal was completed in less than 3 s. The quenching effect of Cu²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Ag⁺ ions on the chemiluminescent system was investigated, the resulting Stern–Volmer plots were obtained and the K_Q values were calculated. It was found that the quenching effect of metal ions on the chemiluminescence of L decreases in the order Cu²⁺ > Pb²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺.     

Evaluation of PANI-Averraoha bilimbi leaves activated carbon nanocomposite for Cd2+ and Pb2+ removal from wastewater

In current investigation, we synthesized new Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposites and utilized as cost effectual for the elimination of Cd²⁺ and Pb²⁺ ions from the wastewater. The synthesized nanocomposite was confirmed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX), Fourier Transform-Infrared (FT-IR) spectroscopy and X-Ray Diffraction (X-RD) techniques. A batch adsorption study carried in wastewater containing different concentrations of Cd²⁺ and Pb²⁺ ions in the temperature range of 303–343 K. The results show that, around 80% of Cd²⁺ and Pb²⁺ ions from the wastewater was successfully isolated by using PANI-ABLC nanocomposite. Attempts were made to fit adsorption to different isotherm models. The PANI-ABLC nanocomposite complied Langmuir adsorption model (R² = 0.999) and pseudo-second order kinetics. Further, maximum adsorption efficiency observed at 0.5 g of Polyaniline-Averraoha bilimbi leaves activated carbon nanocomposites. AC- Impedance Spectroscopy (IS) technique shows that, Polyaniline-Averraoha Bilimbi Leaves Activated Carbon (PANI-ABLC) nanocomposite is suitable for removal of Cd²⁺ and Pb²⁺ ions from the wastewater. AC impedance spectroscopy technique study shows that, the process of adsorption was controlled by charge transfer process.     

In-situ electrochemical and piezogravimetric studies on the application of macrocyclic resorcinarene tetramer in the development of chemically-modified heavy metals ions detection platform in aqueous media

The new application of C-dec-9-enylcalix[4]resorcinarene (R₁), as an ionophore to detect heavy metals (HMs) cations (Cd²⁺, Hg²⁺, Cu²⁺, and Pb²⁺) in the aqueous media has been investigated through the preparation of an effective mass-sensitive sensor via the exploitation of a flow-type QCM-I technique. By adjusting the ions’ amounts in model solutions over a wide range of concentrations, acquired changes in the oscillating frequency related to the loading of metal ions on the sensor’s surface were gained, and thus favorable metrological parameters displaying the lowest detection limit (LOD) associated with copper ions (10 ppb). Simultaneously, a novel voltammetric sensor was prepared by modifying gold screen-printed electrodes (SPEs) with R₁. Electrochemical characterization employing CV, SWV, and EIS was carried out, showing the success of the electrode modification. Then, the experimental conditions of supporting electrolyte, pH, accumulation time, and accumulation potential were optimized to achieve an enhanced detection. The R₁@SPE sensor simultaneously detected the HMs (Cd²⁺, Hg²⁺, Cu²⁺, Pb²⁺), and the lowest LOD was associated with Pb²⁺ (0.19 ppb). The selectivity evaluation of the electrochemical sensor was performed by studying the effect of interferences majorly present in water sources (Mg²⁺, Ni²⁺, Zn²⁺, Al³⁺, and K⁺) on the SWV detection signals, and it was revealed that the interfering ions did not affect the simultaneous detection of the studied HMs (RSD less than 5%), the voltammetric sensors also presented excellent repeatability and reproducibility (RSD less than 5%).     

Impacts of calcium-alginate density on equilibrium and kinetics of lead(II) sorption onto hydrogel beads

Chronic exposure to Pb²⁺ above the 15-μg/L US Environmental Protection Agency action level for drinking water has been shown to cause a host of health problems in humans. Thus, it is important to study new methods available for the treatment and removal of Pb²⁺ from drinking water and wastewater, where elevated levels of heavy metals are found. Alginate-based beads represent one such possible method for heavy metal removal. The impact of alginate density on the equilibrium and kinetics of Pb²⁺ sorption onto hydrogel beads was investigated using Ca-alginate beads ranging from 1% to 8% (w/v) and exposed to Pb²⁺ concentrations ranging from 100 to 1,000 mg/L. When Ca-alginate beads were characterized using Fourier transform infrared analysis, the carboxylic acid groups of the mannuronate and guluronate residues in alginate were the primary functional groups that interacted with Pb²⁺. Hydration of Ca-alginate beads was also examined and found to decrease as Ca-alginate density increased. A positive correlation was observed between Ca-alginate hydration and Pb²⁺ sorption. Sorption of Pb²⁺ was fast, reaching equilibrium after approximately 4 h, and is well described by the Langmuir adsorption isotherm. Maximum sorption capacities for 1%, 4%, and 8% beads were 500 ± 100, 360 ± 30, and 240 ± 20 mg/g (dry weight), respectively. The kinetics of sorption were best described by the pseudo-second-order Lagergren model, with rate constants determined as 3.2 ± 0.1 × 10⁻⁴, 1.0 ± 0.1 × 10⁻⁴, and 1.6 ± 0.1 × 10⁻⁴ g mg⁻¹ min⁻¹ for 1%, 4%, and 8% beads, respectively.     

Preparation and metal binding behavior of poly(4-vinylbenzyl 2-hydroxyethyl) sulfoxide and sulfone

In order to explore the reuse properties of oxidized chelating resin containing sulfur after adsorption, two kinds of novel chelating resins, poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfoxide (PVBSO) and poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfone (PVBSO₂), were synthesized using poly[4-vinylbenzyl-(2-hydroxyethyl)] sulfide (PVBS) as material. Their structures were confirmed by FTIR and XPS. The adsorption properties and mechanism for metal ions such as Au³⁺, Pt⁴⁺, Pd²⁺, Hg²⁺, Cu²⁺, Ni²⁺, Fe³⁺, Pb²⁺, Cd²⁺, and Zn²⁺ were investigated. Experimental results showed that PVBSO had good adsorption and selective properties for Au³⁺, Pd²⁺ and Cu²⁺ when the coexisting ion was Pt⁴⁺, Ni²⁺, Pb²⁺ or Cd²⁺. In the aqueous system containing Cu²⁺ and Pb²⁺ or Cu²⁺ and Cd²⁺, PVBSO₂ only adsorbed Cu²⁺. The selective coefficients of PVBSO and PVBSO₂ were α_Au/Pt = 4.8, α_Au/Pd = 11.8, α_Pd/Pt = 10.9, α_Cu/Ni = 2.5, α_Cu/Cd = 41.2, α_Cu/Pb = ∞, α_Cu/Ni = 3.0, α_Cu/Cd = ∞, α_Cu/Pb = ∞, respectively.     

Adsorption of metal ions by microwave assisted grafting of cross‐linked chitosan beads. Equilibrium,isotherm, thermodynamic and desorption studies

Chemical modification of chitosan has become increasingly essential due to chitosan versatility that enables the material to be easily modified in a way of increasing its properties in adsorption processes. In this investigation, chitosan solution was cross‐linked with glutaraldehyde the cross‐linked solution was used in producing the beads and thereafter grafted with ethylene acrylic acid. The chemical functionalities of the beads were obtained by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), X‐ray diffraction (XRD) and Thermogravimetric analysis (TGA). Adsorption of Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cr⁶⁺ and Cd²⁺ ions from single component aqueous mixture by grafted cross‐linked chitosan beads (GXXB) was studied as a function of pH, temperature, initial concentration, contact time, agitation speed and ionic strength. Equilibrium data was obtained from the adsorption experiment, the data were applied in isotherm, thermodynamics and kinetic studies. The Langmuir, Temkin and Dubinin‐kaganer‐Radushkevich (DKR) model were successful in describing the isotherm data for the considered metal ions while the Freundlich model was not efficient in describing the experimental data. Pseudo‐second order and intra‐particle model described the kinetic data quite well. Thermodynamic parameters such as Gibb's free energy change (?G^o), enthalpy change (?H^o) and entropy change (?S^o) were calculated and the results showed the adsorption of Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cr⁶⁺ and Cd²⁺ ions onto GXXB is spontaneous and endothermic in nature. Regeneration of the used adsorbent was effective for the studied metal ions.     

Selective removal of Cd(II), As(III), Pb(II) and Cr(III) ions from water resources using novel 2-anthracene ammonium-based magnetic ionic liquids

Facile synthesis of two 2-anthracene ammonium-based magnetic ionic liquids (MILs), 2-anthracene ammonium tetrachloroferrate (III) ([2A-A]FeCl₄) and 2-anthracene ammonium trichlorocobaltate (II) ([2A-A]CoCl₃) was performed by protonation of 2-aminoanthracene, followed complexation with FeCl₃/CoCl₂. The MILs were tested in the adsorptive removal of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺ from water sources. Upon treatment with 10 mg dosage of MILs in 10 mL aqueous solution of 50 ppm each of Cd²⁺, As³⁺, Pb²⁺ and Cr³⁺, adsorption capacity (mg/g) in the range of 5.73–55.5 and 23.6–56.8 for [2A-A]FeCl₄ and [2A-A]CoCl₃ respectively were recorded. Thus, the optimization, kinetic and isotherms studies were conducted using the [2A-A]CoCl₃ adsorbent. The [2A-A]CoCl₃ was more effective in pH 7–9, and equilibrium adsorption was achieved after 60 min contact time. The adsorption process proceeded via the Pseudo-second order pathway and the Langmuir isotherm model is the best fit for the adsorption process (with q_max = 227 – 357 mg/g) of all the targeted metal ions. The [2A-A]CoCl₃ adsorbent demonstrated practicality with large distribution and selectivity coefficients of the targeted ions, and up to six times regeneration.     

Response surface methodology for optimization of heavy metal removal by magnetic biosorbent made from anaerobic sludge

In this study, optimum conditions for adsorption of heavy metals such as Cu²⁺, Cd²⁺ and Pb²⁺ onto a low-cost, magnetically modified-alkali conditioned anaerobically digested sludge (MADS) adsorbent were obtained. Response Surface Methodology (RSM) incorporating Central Composite Design (CCD) of experiments was applied to optimize four independent process variables. Statistical analysis was executed by ANOVA and the quadratic model developed had regression coefficients of 0.959, 0.957 and 0.95 for Cu²⁺, Cd²⁺ and Pb²⁺, respectively. The independent variables such as pH, time and initial concentration positively influenced adsorption capacity, q_e, whereas the value of q_e decreased with an increase in MADS dosage. Model validation experiments for optimization of adsorption process showed comparable results with predicted values. The adsorption capacity of MADS adsorbent at optimum conditions found through RSM analysis was 29.721 mg L^?1, 28.551 mg L^?1 and 28.601 mg L^?1 for Cu²⁺, Cd²⁺ and Pb²⁺ respectively.     

Silver nanoparticle loaded on activated carbon and activated carbon modified with 2-(4-isopropylbenzylideneamino)thiophenol (IPBATP) as new sorbents for trace metal ions enrichment

The efficiencies and performances of silver nanoparticle loaded activated carbon modified with 2-(4-isopropylbenzylideneamino)thiophenol (IPBATP-Ag-NP-AC) and activated carbon modified with IPBATP (IPBATP-AC), as new sorbents, were evaluated for separation and preconcentration of Cu²⁺, Zn²⁺, Co²⁺, Cd²⁺ and Pb²⁺ ions from real environmental samples. The retained metals content was reversibly eluted using 5?mL of CH₃COOH (6.0?mol?L^?1) and/or 10?mL of 4.0?mol?L^?1 HNO₃ for IPBATP-Ag-NP-AC and IPBATP-AC, respectively. The experimental parameters influence the recoveries of metal ions including pH, amounts of ligand and supports, condition of eluents, sample and eluent flow rates of has been investigated. The preconcentration factors were found to be 100 for Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺ and 50 for Pb²⁺ ions using IPBATP-Ag-NP-AC, and 50 for Zn²⁺, Cd²⁺, Co²⁺, Cu²⁺ and 25 for Pb²⁺ ions using IPBATP-AC. The detection limit of both SPE-based sorbents was between 1.6–2.5?ng?mL^?1 for IPBATP-AC and 1.3–2.5?ng?mL^?1 for IPBATP-Ag-NP-AC. The proposed methods have been successfully applied for the extraction and determination of the understudy metal ions content in some real samples with extraction efficiencies higher than 90% and relative standard deviations (RSD) lower than 2.4%.