Efficient Removal of Pb(II) from Aqueous Medium Using Chemically Modified Silica Monolith

The adsorptive removal of lead (II) from aqueous medium was carried out by chemically modified silica monolith particles. Porous silica monolith particles were prepared by the sol-gel method and their surface modification was carried out using trimethoxy silyl propyl urea (TSPU) to prepare inorganic–organic hybrid adsorbent. The resultant adsorbent was evaluated for the removal of lead (Pb) from aqueous medium. The effect of pH, adsorbent dose, metal ion concentration and adsorption time was determined. It was found that the optimum conditions for adsorption of lead (Pb) were pH 5, adsorbent dose of 0.4 g/L, Pb(II) ions concentration of 500 mg/L and adsorption time of 1 h. The adsorbent chemically modified SM was characterized by scanning electron microscopy (SEM), BET/BJH and thermo gravimetric analysis (TGA). The percent adsorption of Pb(II) onto chemically modified silica monolith particles was 98%. An isotherm study showed that the adsorption data of Pb(II) onto chemically modified SM was fully fitted with the Freundlich and Langmuir isotherm models. It was found from kinetic study that the adsorption of Pb(II) followed a pseudo second-order model. Moreover, thermodynamic study suggests that the adsorption of Pb(II) is spontaneous and exothermic. The adsorption capacity of chemically modified SM for Pb(II) ions was 792 mg/g which is quite high as compared to the traditional adsorbents. The adsorbent chemically modified SM was regenerated, used again three times for the adsorption of Pb(II) ions and it was found that the adsorption capacity of the regenerated adsorbent was only dropped by 7%. Due to high adsorption capacity chemically modified silica monolith particles could be used as an effective adsorbent for the removal of heavy metals from wastewater.     

A novel green synthesis of Fe3O4 magnetic nanorods using Punica Granatum rind extract and its application for removal of Pb(II) from aqueous environment

We described a novel and eco-friendly approach to remove toxic heavy metal of Pb(II) by using dimercaptosuccinic acid (DMSA) anchored Fe₃O₄ magnetic nanorods (MNRs) which were synthesized via facile method utilizing Punica Granatum rind extract which was a non toxic waste material. The DMSA@Fe₃O₄ MNRs were characterized by X-ray diffraction (XRD), Fourier transformed infrared analysis (FT-IR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and desorption techniques, and vibrating sample magnetometer (VSM). These DMSA@Fe₃O₄ MNRs have been used for the removal of Pb(II) from aqueous solution. The adsorption isotherm data fitted well with Langmuir isotherm and Freundlich model, the monolayer adsorption capacity was found to be 46.18 mg/g at 301 K. The experimental kinetic data fitted very well with the pseudo-second-order model. The results indicate that the biogenic synthesized DMSA@Fe₃O₄ MNRs act as significant adsorbent material for removal of Pb (II) from aqueous environment.     

Adsorption of Pb(II) and Ni(II) From Aqueous Solution by a High-Capacity Industrial Sewage Sludge-Based Adsorbent

In the present study, adsorption of Ni(II) and Pb(II) from aqueous solution was investigated using activated carbon synthesized with industrial wastewater sludge. The synthesized adsorbent was analyzed using nitrogen adsorption–desorption and Fourier transfer infrared (FTIR) techniques. Batch adsorption mode was used to evaluate the effect of solution pH, contact time, adsorbent dose, initial metal ion concentration, and temperature on the adsorption capacity of the synthesized adsorbent. The kinetic data were analyzed using different kinetic models. The pseudo-second-order equation gave the best fit to the experimental data for both metal ions. The equilibrium isotherm data were analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models. The results showed that the data obtained for the Ni(II) and Pb(II) adsorption are in good agreement with the Langmuir model. The Langmuir mono-layer maximum adsorption capacities for Ni(II) and Pb(II) ions were estimated to be 74.06 and 88.76 mg g^?1 at 25°C, respectively. In addition, the thermodynamic studies proved that the adsorption process of both metals could be considered endothermic.     

Surface modification of date palm activated carbonaceous materials for heavy metal removal and CO2 adsorption

In this study, high surface area activated carbon (AC) was prepared from a local palm tree (Phoenix Dactylifera) using a variety of metal carbonates activators and finally achieved an excellent S_BET of 2700 m²/g when Cs₂CO₃ was used as an activating agent at a temperature of 600 °C. Surface modification of AC was carried out using various nitrogen transporting agents, resulting in N-doped ACs with nitrogen content varying from 4.0 to 11.4 %, depending on the functionalizing agents and activators used. The bimodal (presence of micro- as well as meso-porosity) ACs with such excellent surface properties were studied for their CO₂ uptake capacity at two different temperatures (0 and 25 °C) by isotherms recorded at pressure 1 bar and showed a remarkable uptake ability of 3.52 mmol/g (at 25 °C) and 5.6 mmol/g (at 0 °C), respectively. Also, batch experiments with variable pH, contact time, adsorbate concentrations, adsorbent dose, and temperatures were evaluated to understand the mechanism of sorption phenomena of Cr(VI) and Pb(II) achieving > 99.9 % removal capacity by the prepared ACs. Depending on the heavy metal ions being investigated, it was revealed that the pH of the solution and the amount of adsorbent had a direct impact on the total adsorption ability. Nitrogen atoms doped into the carbon frameworks were found to enhance the adsorption in the case of Pb(II) while the removal of Cr(VI) appeared to be unaffected. Maximum adsorption for Cr(VI) was observed at pH 2 and was determined to follow Freundlich isotherm while that of Pb(II) was observed at pH 7 and follows Langmuir isotherm. Best adsorption was found at an adsorbate concentration of 10 ppm and an adsorbent dose of 10 g/L. Kinetic modeling parameters showed the applicability of pseudo-second-order model perfectly.     

Fabrication of renewable palm-pruning leaves based nano-composite for remediation of heavy metals pollution

The palm-pruning leaves considered as valuable source for low cost adsorbent materials. Such application, enhance the environmental conditions by reducing the bad effects from un-managed palm-pruning leaves such as spreading insects. Herein, the palm-pruning leaves were treated with by water and acid washing to produce cleaned palm leaves (CPL) and then impregnation with iron(III) chloride and thermally treated to produce palm leaves/iron oxide- nanocomposite (PL/IO-NC). The prepared materials were applied for adsorption of some toxic metal ions from solutions. The original palm-pruning leaves as well as the treated adsorbent were characterized by SEM, EDS, FTIR, XRD. Results showed the formation of spots iron oxide nanoparticles onto the palm-pruning leaves. The efficiency of the treated adsorbent for uptake of Mn(II), Co(II) and Pb(II) was studied in term of kinetic, isotherm and thermodynamic to optimize and evaluate the effectiveness of the palm-pruning leaves treatment. The adsorption data was found to be more comfortable with Second order kinetic-model while the isotherm of Langmuir wasn’t suitable and the adsorption data was in agreement with Freundlich assumption. The values of ΔG° in the range (−5.8 to −3.5 kJ/mol) for Mn(II), (−4.2 to −2.1 kJ/mol) for Co(II), (−3.4 to −2.3 kJ/mol) for Pb(II), confirm the confirm the spontaneous and physical nature of the adsorption process.     

Polyethyleneimine-grafted polyphosphazene microspheres for rapid and efficient capture of anionic dyes from wastewater

Developing novel adsorbent to capture organic contaminants from wastewater rapidly and efficiently is highly desirable for waste treatment and environmental restoration. Herein, we reported a new amino-rich spherical adsorbent (PZS-PEI) for highly-efficient uptake of anionic dyes from aqueous solution. The PZS-PEI adsorbent was fabricated through a two-step process including synthesis of PZS-Cl microspheres via room temperature polymerization of hexachlorocyclotriphosphazene with bis(4-hydroxyphenyl) sulfone and subsequent surface grafting reaction of PZS-Cl microspheres using branched polyethyleneimine (PEI). The microstructure of as-obtained PZS-PEI microspheres was fully characterized by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, zeta potential, and N₂ adsorption test. The adsorption performance of the PZS-PEI microspheres towards organic dyes was evaluated through carrying out a series of studies including various influence factor analysis, adsorption isotherm, kinetics, and thermodynamics. Results show that the PZS-PEI adsorbent owned good adsorption selectivity towards anionic dyes, and the maximum adsorption capacities for methyl orange (MO), acid chrome blue K, eosin-Y reached 190.29, 152.90, and 92.34 mg/g at 25 °C, respectively. In addition, the uptake behavior of organic dye by the PZS-PEI adsorbent conformed to Freundlich isotherm and pseudo-second order kinetic model, and the adsorption process followed a three-stage intraparticle diffusion mode with an endothermic and spontaneous characteristic. Electrostatic interaction and hydrogen bonding were responsible for the highly-efficient adsorption of the PZS-PEI adsorbent towards typical anionic dye MO.     

The starch modified montmorillonite for the removal of Pb(II), Cd(II) and Ni(II) ions from aqueous solutions

In the present study, we attempted to synthesize a novel sorbent from the starch modified montmorillonite for the removal of Pb(II), Cd(II), and Ni(II) ions from aqueous solutions. Structure and properties of the adsorbent were characterized by Fourier-transformed infrared(FT-IR) spectroscopy, X-ray diffraction (XRD), and Field emission scanning electron microscopic (FE-SEM) techniques. Batch experiments were confirmed through the effect of different conditions including pH, contact time, initial metal concentration and adsorbent dose. Specifically, the optimum value of adsorbent dose was achieved as 20 g/l for the removal of almost metal ions. The adsorption data was fitted with the optimum pH value as 5 for all experiments. The contact time at which the uptake of maximum metal adsorption was observed within 45 min for Pb(II), 90 min for Cd(II), and 60 min for Ni(II). In addition, it was revealed in our study that the equilibrium data obeyed the Langmuir model, and the adsorption kinetic followed a pseudo second-order rate model. Obtained results were noticeable for a modified phyllosilicate adsorbent, and with such a simple and low-cost modification for montmorillonite, the potential of this material as an economical and effective adsorbent for the removal of metal ions from aqueous solution was considerably elevated.     

Kinetics and equilibrium studies of adsorption of chromium(VI) ion from industrial wastewater using Chrysophyllum albidum (Sapotaceae) seed shells

A new biosorbent has been prepared by coating Chrysophyllum albidum (Sapotaceae) seed shells with chitosan and/or oxidizing agents such as sulfuric acid. This study investigated the technical feasibility of activated and modified activated C. albidum seed shells carbons for the adsorption of chromium(VI) from aqueous solution. The sorption process with respect to its equilibria and kinetics as well as the effects of pH, contact time, adsorbent mass, adsorbate concentration and particle size on adsorption was also studied. The most effective pH range was found to be between 4.5 and 5 for the sorption of the metal ion. The pseudo-first-order rate equation by Lagergren and pseudo-second-order rate equation were tested on the kinetic data, the adsorption process followed pseudo-second-order rate kinetics, also, isotherm data was analyzed for possible agreement with the Langmuir and Freundlich adsorption isotherms, the Freundlich and Langmuir models for dynamics of metal ion uptake proposed in this work fitted the experimental data reasonably well. However, equilibrium sorption data were better represented by Langmuir model than Freundlich. The adsorption capacity calculated from Langmuir isotherm was 84.31, 76.23 and 59.63 mg Cr(VI)/g at initial pH of 3.0 at 30 °C for the particle size of 1.00–1.25 mm with the use of 12.5, 16.5 and 2.1 g/L of CACASC, CCASC and ACASC adsorbent mass, respectively. This readily available adsorbent is efficient in the uptake of Cr(VI) ion in aqueous solution, thus, it could be an excellent alternative for the removal of heavy metals and organic matter from water and wastewater.     

An easily organic–inorganic hybrid optical sensor based on dithizone impregnation on mesoporous SBA‐15 for simultaneous detection and removal of Pb(II) ions from water samples: Response‐surface methodology

In this study, a novel organic–inorganic hybrid adsorbent for single‐step detection and removal of Pb(II) ions based on dithizone (DZ) anchored on mesoporous SBA‐15 was fabricated. The designed solid optical sensor revealed rapid colorimetric responses and high selectivity. Central composite design (CCD) combined with desirability function (DF) was applied to evaluate the interactive effects and optimization of important variables such as pH value, mesoporous SBA‐15 dosage, contact time and initial concentration of Pb(II) ions and optimum conditions for each of the factors were obtained 6.0, 25 mg, 30 min and 20 μg ml^{− 1}, respectively. This adsorbent or solid optical chemo sensor exhibited a linear range of 1.0 to 100.0 μg ml⁻¹ of Pb(II) ion concentration with a detection limit of 0.07 μg ml⁻¹. This adsorbent was applied to determine and remove the Pb(II) in spiked samples. Various isotherm models such as Langmuir, Freundlich, Temkin and Dubinin–Radushkevich were studied for fitting the experimental equilibrium data. Langmuir model was chosen as an efficient model. Various kinetic models such as pseudo‐first, second order intraparticle, diffusion models were studied for analysis of experimental adsorption data and the pseudo second order model was chosen as an efficient model.     

Removal of heavy metal ions from water by using poly(ethyleneglycol dimethacrylate-co-acrylamide) beads

Poly(ethyleneglycol dimethacrylate-co-acrylamide) (poly(EDGMA-co-AAm)) copolymer beads have been prepared for use in the separation Pb(II), Hg(II), and Cd(II), metal ions in aqueous solution by a batch equilibration technique. Adsorption capacity were increased with pH for Pb(II), Cd(II) and Hg(II) and then reached almost plateau value around 6.0. The high initial rate of metal ions uptake (<10 min) suggests that the adsorption occurs mainly at the bead surface. The metal uptake results show that poly(EGDMA-co-AAm) can be used for the adsorption of the following metals in the indicated order: Pb(II) > Cd(II) > Hg(II) expressed on a molar basis. However, when the uptake was expressed in terms of the amount of metal removed from solution was as follows: Pb(II) > Hg(II) > Cd(II). The beads still showed preference toward Pb(II) when this metal was in a mixture with Hg(II) and Cd(II). A linearized form of the Freundlich and the Langmuir isotherm model fits the experimental equilibrium concentration data of Hg(II) and Cd(II) better than isotherm type model of Pb(II). The recovery of the metal ions after adsorption and the regeneration of the adsorbent can be carried out by treatment of the loaded beads with either 0.5 M NaCl, or 1 M HNO₃.     

Glutaraldehyde cross-linked epoxyaminated chitosan as an adsorbent for the removal and recovery of copper(II) from aqueous media

A novel glutaraldehyde cross-linked epoxyaminated chitosan (GA-C-ENCS) prepared through chemical modification was used as an adsorbent for the removal and recovery of Cu(II) from aqueous media. The adsorbent was characterized by FTIR, SEM-EDS, ESR, TG/DTG, BET-surface area and potentiometric titration. The Cu(II) adsorption process, which was pH dependent showed maximum removal at pH 6.0. Adsorption equilibrium was achieved within 3 h. The adsorption of Cu(II) followed a reversible-first-order kinetics. The equilibrium data were evaluated using the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The best interpretation for the equilibrium data was given by the Dubinin–Radushkevich isotherm. The adsorption capacity of the adsorbent increased from 3.11 to 3.71 mmol g⁻¹ when the temperature was increased from 20 to 50 °C. The complete removal of 20.7 mg L⁻¹ Cu(II) from electroplating industry wastewater was achieved by 0.4 g L⁻¹ GA-C-ENCS. Regeneration experiments were tried for four cycles and the results indicate a capacity loss of <7.0%.     

A Prospect for Environmental Remediation of Perchlorate via Cost-Effective Pinus Leaves and Dandelion Flower Powder-based Layer Double Hydride (LDH) Sorbents

In this study, pine leaves powder (PiP) and dandelion flower powder (DFP) were repurposed to synthesize layered double hydroxides (LDHs) to form a base for sorbents used in perchlorate remediation from wastewater. The effects of the adsorbent dose, pH, thermodynamics, and coexisting ions were evaluated in batch experiments. The results revealed that 0.1 g adsorbent (PiP-LDH and DFP-LDH) removed 97% and 93% of perchlorate contaminants, respectively. In this study, the correlation coefficient of pseudo-second-order was higher than pseudo-first-order for all the LDHs. The kinetic and isotherm studies showed the best uptake of perchlorate in the short time was by PiP-LDH, followed by DFP-LDH (20 min and 40 min, respectively). The calculated and experimental values of adsorption at the equilibrium state also concurred with the pseudo-second-order model. The prepared LDHs were mesoporous. The surface area of PiP-LDH provided more adsorption sites, rendering it more suitable for perchlorate adsorption compared with the other two LDHs. The model suggests Physico-chemical interactions behind the sorption of perchlorate by LDHs. The adsorption was more influenced by anions i.e, PO₄³⁻ > SO₄²⁻ > NO₃ than monovalent anions due to the increase in the charge radius values. The prepared LDHs could be of great benefit to the environmental remediation of wastewater bodies.     

A Simple One-Step Modification of Shrimp Shell for the Efficient Adsorption and Desorption of Copper Ions

Removing toxic heavy metal species from aqueous solutions is a point of concern in our society. In this paper, a promising biomass adsorbent, the modified waste shrimp shell (MS), for Cu (II) removal was successfully prepared using a facile and simple one-step modification, making it possible to achieve high-efficiency recycling of the waste NaOH solution as the modification agent. The outcome shows that with the continuous increase in pH, temperature and ion concentration, the adsorption effect of MS on Cu (II) can also be continuously improved. Adsorption isotherm and adsorption kinetics were fitted with the Langmuir isotherm model and the pseudo-second-order model, respectively, and the maximum adsorption capacity of Cu (II) as obtained from the Langmuir isotherm model fitting reached 1.04 mmol/g. The systematic desorption results indicated that the desorption rate of Cu (II) in the MS could reach 100% within 6 min, where HNO₃ is used as the desorption agent. Moreover, experiments have proven that after five successive recycles of NaOH as a modifier, the adsorption capacity of MS on Cu (II) was efficient and stable, maintaining tendency in 0.83–0.85 mmol/g, which shows that waste NaOH solution can be used as a modification agent in the preparation of waste shrimp shell adsorbent, such as waste NaOH solution produced in industrial production, thereby making it possible to turn waste into renewable resources and providing a new way to recycle resources.     

Removal of Cd(II) and Pb(II) from aqueous solution by modified attapulgite clay

Three low-cost adsorbents (purified raw attapulgite (A-ATP), high-temperature-calcined attapulgite (T-ATP), and hydrothermal loading of MgO (MgO-ATP)) were prepared as adsorbents for the removal of Cd(II) and Pb(II). By evaluating the effect of the initial solution pH, contact time, initial solution concentration, temperature and coexistence of metal ions on Cd(II) and Pb(II) adsorption, the experimental results showed that MgO-ATP was successfully prepared by hydrothermal reaction and calcination as well as appearing to be a promising excellent adsorbent. At an initial pH of 5.0, A-ATP, T-ATP and MgO-ATP reached maximum adsorption amounts of 43.5, 53.9 and 127.6 mg/g for Pb(II) and 10.9, 11.2, and 25.3 mg/g for Cd(II) at 298 K, respectively. The Cd(II) adsorption on A-ATP was fitted by the Freundlich model, while the adsorption of Pb(II) and Cd(II) on T-ATP and MgO-ATP as well as Pb(II) adsorption on A-ATP agreed with the Langmuir model. All kinetic experimental data favored pseudo second-order model. The calculated thermodynamic parameters suggested that Pb(II) adsorption onto MgO-ATP was spontaneous and exothermic. When considering foreign metal ions, the three adsorbents all presented preferential adsorption for Pb (II). Chemical adsorption had a high contribution to the removal of Cd(II) and Pb(II) by modified attapulgite. In summary, the adsorption was greatly enhanced by the hydrothermal loading of MgO. It aimed to provide insights into the MgO-ATP, which could be able to efficiently remove Cd(II) and Pb(II) and serve as an economic and promising adsorbent for heavy metal-contaminated environmental remediation.     

Shellfish waste-derived mesoporous chitosan for impressive removal of arsenic(V) from aqueous solutions: A combined experimental and computational approach

Novel shellfish waste-derived chitosan (CS) has been developed to adsorb As(V) from simulated wastewater under evaluating adsorption process parameters. The coexistence of some competing ions, like SiO₃^2-, Cl^-, NO₃^– and PO₄^3- as well as the regeneration capacity of the spent adsorbent, was explored. The experimental data were modeled using several kinetics and isotherm models to understand the mechanism related to the uptake process. As(V) uptake was relatively rapid and highly dependent on pH. The Avrami-fractional-order expression supported data best, while the Liu equation described well isotherm data at pH 5.0. The maximum uptake capability (Liu) was 12.32 mg/g, and the highest removal performance (99 %) was obtained at optimum pH 5.0. Molecular dynamics simulations were performed to more clearly illuminate the atomic-level interactions between arsenic species and CS surface in both acidic and basic mediums. After four adsorption–desorption cycles, CS exhibited more than 90 % As(V) removal efficiency. The results of this study indicates that low cost shellfish derived chitosan is promising for efficient removal of As(V) from water body and can be used to remove other pollutants from watewater.     

Biosorption of lead from aqueous solution by seed powder of Strychnos potatorum L.

In the present study, Pb(II) removal efficiency of Strychnos potatorum seed powder (SPSP) from aqueous solution has been investigated. Batch mode adsorption experiments have been conducted by varying pH, contact time, adsorbent dose and Pb(II) concentration. Pb(II) removal was pH dependent and found to be maximum at pH 5.0. The maximum removal of Pb(II) was achieved within 360 min. The Lagergren first-order model was less applicable than pseudo-second-order reaction model. The equilibrium adsorption data was fitted to Langmuir and Freundlich adsorption isotherm models to evaluate the model parameters. Both models represented the experimental data satisfactorily. The monolayer adsorption capacities of SPSP as obtained from Langmuir isotherm was found to be 16.420 mg/g. The FTIR study revealed the presence of various functional groups which are responsible for the adsorption process.     

Isotherm, kinetic and thermodynamic studies of lead and copper uptake by H2SO4 modified chitosan

The kinetic and thermodynamic adsorption and adsorption isotherms of Pb(II) and Cu(II) ions onto H₂SO₄ modified chitosan were studied in a batch adsorption system. The experimental results were fitted using Freundlich, Langmuir and Dubinin–Radushkevich isotherms; the Langmuir isotherm showed the best conformity to the equilibrium data. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models were employed to analyze the kinetic data. The adsorption behavior of Pb(II) and Cu(II) was best described by the pseudo-second order model. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were determined; the adsorption process was found to be both spontaneous and exothermic. No physical damage to the adsorbents was observed after three cycles of adsorption/desorption using EDTA and HCl as eluents. The mechanistic pathway of the Pb(II) and Cu(II) uptake was examined by means of Fourier transform infrared (FTIR) and Energy dispersive X-ray (EDX) spectroscopy. The equilibrium parameter (R_L) indicated that chitosan–H₂SO₄ was favorable for Pb(II) and Cu(II) adsorption.     

Evaluation of an activated carbon from olive stones used as an adsorbent for heavy metal removal from aqueous phases

The performance of a microporous activated carbon prepared chemically from olive stones for removing Cu(II), Cd(II) and Pb(II) from single and binary aqueous solutions was investigated via the batch technique. The activated carbon sample was characterized using N₂ adsorption–desorption isotherms, SEM, XRD, FTIR, and Boehm titration. The effect of initial pH and contact time were studied. Adsorption kinetic rates were found to be fast and kinetic experimental data fitted very well the pseudo-second-order equation. The adsorption isotherms fit the Redlich–Peterson model very well and maximum adsorption amounts of single metal ions solutions follow the trend Pb(II) > Cd(II) > Cu(II). The adsorption behavior of binary solution systems shows a relatively high affinity to Cu(II) at the activated carbon surface of the mixture with Cd(II) or Pb(II). An antagonistic competitive adsorption phenomenon was observed. Desorption experiments indicated that about 59.5% of Cu(II) and 23% of Cd(II) were desorbed using a diluted sulfuric acid solution.     

Preconcentration of trace nickel lons from aqueous solutions by using a new and low cost chelating polystyrene adsorbent

A simple and reliable method has been developed using chelating polymeric adsorbent (PSAHSB) to preconcentration of trace amount of Ni(II) ions from aqueous solutions under static loading conditions, and their determination by Ultraviolet and visible (UV–Vis) absorption spectroscopy. The influences of some analytical adsorption parameters, such as pH, temperature and contact time, the ionization constants of chelating groups in the adsorbent and desorption process were investigated. Maximum adsorption ≥98% was achieved at pH 3–7 after 20 min of contact time and the relative standard-deviation values were ≤5%. Adsorbed metal ions have been desorbed with 10 mL of 2 M HCl acid with the detection limit of 0.0157 μg m⁻¹. The Langmuir and Freundlich isotherm equations were used to describe adsorption behavior of the system at different temperatures. Kinetic and thermodynamic behavior of the adsorbent for Ni(II) ion preconcentration was also studied. The possible adsorption mechanism of Ni (II) ions onto modified adsorbent is also discussed. This method was applied efficiently to remove Ni (II) ions from environmental water samples.     

Surface‐initiated atom transfer radical polymerization of a new rhodanine‐based monomer for rapid magnetic removal of Co(II) ions from aqueous solutions

The present study reports synthesis and characterization of a new acrylamide‐based monomer containing rhodanine moiety, N‐3‐amino‐thiazolidine‐4‐one‐acrylamide (ATA). Poly(ATA)‐grafted magnetite nanoparticles (poly(ATA)‐g‐MNPs) were prepared using surface‐initiated atom transfer radical polymerization of the monomer on Fe₃O₄ nanoparticles. The grafted nanoparticles were characterized by Fourier transform infrared analysis, scanning electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The amount of the grafted polymer was 209 mg g⁻¹, as calculated from thermogravimetric analysis experiment. The capability of poly(ATA)‐g‐MNPs to remove Co(II) cations was shown under optimal conditions of contact time, pH, adsorbent dosage, and initial Co(II) concentration. About 86% of the Co(II) cations were removed over 7 minutes. The adsorption kinetics obeyed the pseudo–second‐order kinetic equation, and the Langmuir isotherm model best described the adsorption isotherm with a maximum adsorption capacity of 3.62 mg g⁻¹. The thermodynamic investigation showed spontaneous nature of the adsorption process (ΔG = −2.90 kJ mol⁻¹ at 25°C ± 1°C). In addition, the poly(ATA)‐g‐MNPs were regenerated by simply washing with an aqueous 0.1M HCl solution. The study of the reusability of the prepared magnetic sorbent revealed that the sorbent can be reused without a significant decrease in the extraction efficiency and be recovered by 95.4% after 7 cycles. These findings suggest that the grafted nanoparticles are stable and reusable adsorbent and can be potentially applied to water treatment in efficient removal of Co(II) cations.