Adsorption of Hg(II) ions by PAMAM dendrimers modified attapulgite composites

Folic acid conjugated poly (Amidoamine) dendrimer grafted magnetic chitosan as a smart drug delivery platform for doxorubicin: In-vitro drug release and cytotoxicity studies

This study reports the development of a magnetic and pH-responsive nanocarrier for targeted delivery and controlled release of doxorubicin (DOX). A multifunctional magnetic chitosan nanocomposite (FA-PAMAMG2-MCS) was fabricated by grafting poly(amidoamine) dendrimer and folic acid onto the MCS surface for active targeting. DOX was loaded into this core-shell bio-nanocomposite via adsorption. Structural and morphological characterization of the prepared nanomaterials was performed using XRD, FT-IR, VSM, TGA, BET, FE-SEM/EDX, and TEM techniques. Adsorption capacity of the FA-PAMAMG2-MCS was optimized by changing diverse parameters, such as pH, initial drug concentration, temperature, contact time, and adsorbent dosage. The maximum adsorption capacity for DOX was 102.85 mg g-1 at 298 K. The in-vitro drug release curve at pHs 5.6 and 7.4 manifested a faster drug release from the prepared nanocarrier in acidic environments and, conversely, a slower release in neutral environments over 48 h. The release kinetics followed Peppas-Sahlin models, showing non-Fickian behavior. Moreover, the in-vitro cytotoxicity studies against the human breast cancer (MDA-MB 231) cell line demonstrated the remarkable anticancer activity of the DOX@FA-PAMAMG2-MCS and declared its potency for nanomedicine applications. This multifunctional system could overcome limitations of conventional chemotherapeutic agents through pH-triggered drug release, enabling targeted cytotoxicity against cancer cells.

Synthesis of salicylaldehyde tailored PAMAM dendrimers/chitosan for adsorption of aqueous Hg(II): Performance and mechanism

Water pollution caused by Hg(II) exerts hazardous effect to environmental safety and human health. Herein, a family of salicylaldehyde tailored poly(amidoamine) (PAMAM) dendrimers/chitosan composites (G0-S/CTS, G1-S/CTS, and G2-S/CTS) were prepared and used for the removal of Hg(II) from water solution. The adsorption performance of the as-prepared composites for Hg(II) was thoroughly demonstrated by determining various influencing factors. G0-S/CTS, G1-S/CTS and G2-S/CTS exhibited competitive adsorption capacity and good adsorption selective property for Hg(II). The maximum adsorption capacity of G0-S/CTS, G1-S/CTS and G2-S/CTS for Hg(II) were 1.86, 2.18 and 4.47 mmol‧g-1, respectively. The adsorption for Hg(II) could be enhanced by raising initial Hg(II) concentration and temperature. The adsorption process was dominated by film diffusion processes with monolayer adsorption behavior. The functional groups of NH2, CONH, CN, OH, CO and CN were mainly responsible for the adsorption of Hg(II). G0-S/CTS, G1-S/CTS and G2-S/CTS displayed good regeneration property and the regenerate rate maintained 95.00 % after five adsorption-desorption cycles. The as-prepared adsorbents could be potentially used for the efficient removal of Hg(II) from aqueous solution.

Synthesis of hyperbranched polyamine dendrimer/chitosan/silica composite for efficient adsorption of Hg(II)

The pollution of water system with Hg(II) exerts hazardous effect to ecosystem and public health. Adsorption is considered to be a promising strategy to remove Hg(II) from aqueous solution. Herein, hyperbranched polyamine dendrimer/chitosan/silica composite (SiO₂-FP) was synthesized for the adsorption of aqueous Hg(II). The adsorption performance of SiO₂-FP was comprehensively determined by considering various influencing factors. SiO₂-FP displays good adsorption performance for Hg(II) with the adsorption capacity of 0.79 mmol·g^-1, which is higher than the corresponding chitosan functionalized silica (SiO₂-CTS) by 46.30 %. The optimal solution pH for the adsorption of Hg(II) is 6. Adsorption kinetic indicates the adsorption for Hg(II) can reach equilibrium at 250 min. Adsorption kinetic process can be well fitted by pseudo-second-order (PSO). Adsorption isotherm reveals the adsorption for Hg(II) can be promoted by increasing initial Hg(II) concentration and adsorption temperature. The adsorption isotherm indicates the adsorption process can be described by Langmuir model and the adsorption is a spontaneous, endothermic and entropy-increased process. SiO₂-FP displays excellent adsorption selectivity and can 100 % adsorb Hg(II) with the coexisting of Ni(II), Zn(II), Pb(II), Mn(II), and Co(II). Adsorption mechanism demonstrates -NH-, -NH₂, CN, CONH, -OH, and CO participated in the adsorption. SiO₂-FP exhibits good regeneration property and the regeneration rate can maintain approximately 90 % after five adsorption-desorption cycles.

Selective removal of Hg(II) by UiO-66-NH2 modified by 4-quinolinecarboxaldehyde: from experiment to mechanism

In wastewater, heavy metal Hg causes serious harm to ecology, so it needs to be removed. In this paper, a novel MOF adsorbent (UiO-66-QU) was prepared by modifying UiO-66-NH₂ with 4-quinolinecarboxaldehyde, which was used to selectively remove Hg(II) from water. The adsorbent was characterized using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), zeta potentiometer, and X-ray photoelectron spectroscopy (XPS). In order to investigate the Hg(II) adsorption performance of UiO-66-QU, the effect of time, initial concentration, pH, and temperature were carried out. Langmuir model fitting shows that the maximum adsorption capacity of UiO-66-QU for Hg(II) is 556 mg/g at 298 K. The experimental results show that UiO-66-QU has better Hg(II) adsorption capacity than UiO-66-NH₂. The isotherm is in accordance with pseudo-second-order models. It is indicated that the adsorption process is mainly monolayer chemical adsorption. The thermodynamic parameters also indicate that the adsorption process is spontaneous and endothermic. It has excellent reusability and selectivity. XPS and the zeta potential showed that the adsorption mechanism was the complex reaction of Hg(II) with nitrogenous group. Therefore, the adsorbent has potential application prospects in removal of Hg(II) from wastewater.

Preparation and oil absorption performance of ATP/P(MMA-BMA-St)/Fe

In this paper, oil-in-water-in-oil (O/W/O) double Pickering emulsions were prepared by purified and modified attapulgite (ATP), and modified nano-Fe3O4 as stable particles. By using the Pickering emulsion as a template and using methyl methacrylate (MMA), butyl methacrylate ester (BMA) and styrene (St) as monomers, ATP/P(MMA-BMA-St)/Fe3O4 composite porous resins were then prepared. The oil absorption performance of the composites was investigated. The results showed that the composite materials prepared by the double Pickering emulsion template method exhibited a three-dimensional (3D) porous structure. When using the optimal conditions (mMMA:mBMA = 3:2, m(MMA+BMA):mSt = 1:2, initiator = 5.33%, crosslinking agent = 20%, modified attapulgite = 0.33% and oil phase/water phase = 1:4), the prepared porous material had the best oil absorption performance, resulting in a diesel oil absorption rate and oil retention rate of 897.29 and 84.76% respectively. This study provides a simple, economic and environmentally friendly method for the preparation of inorganic–organic composite porous materials, which has great application potential in the field of oil treatment.

The Adsorption of Heavy Metal Ions by Poly (Amidoamine) Dendrimer-Functionalized Nanomaterials: A Review

Rapid industrialization has resulted in serious heavy metal pollution. The removal of heavy metal ions from solutions is very important for environmental safety and human health. Poly (amidoamine) (PAMAM) dendrimers are artificial macromolecular materials with unique physical and chemical properties. Abundant amide bonds and amino functional groups provide them with a high affinity for heavy metal ions. Herein, PAMAM-functionalized adsorbents are reviewed in terms of different nanomaterial substrates. Approaches in which PAMAM is grafted onto the surfaces of substrates are described in detail. The adsorption isotherms and kinetics of these adsorbents are also discussed. The effects of PAMAM generation, pH, adsorbent dosage, adsorption time, thermodynamics, and ionic strength on adsorption performance are summarized. Adsorption mechanisms and the further functionalization of PAMAM-grafted adsorbents are reviewed. In addition to the positive results, existing problems are also put forward in order to provide a reference for the optimization of PAMAM-grafted adsorbents of heavy metal ions.

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.

Preparation of PAMAM modified PVDF membrane and its adsorption performance for copper ions

As one of the main pollutants of water pollution, the potential toxicity of heavy metal ions always threatens the safety of human and nature. Therefore, how to effectively remove heavy metal ions has become an important research topic in environmental protection. In the existing research, adsorption method is outstanding from many methods because of its high adsorption efficiency and easy operation. In this study, different generations of hyperbranched polyamide-amine (PAMAM) were grafted onto PVDF membrane to obtain the membrane with high adsorption capacity for heavy metal ions. The structure and physicochemical properties of the membranes were evaluated by means of fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FE-SEM), element analyzer and X-ray photoelectron spectroscopy (EDX). At the same time, various factors affecting the adsorption process were studied, and it was found that the adsorption behavior of copper ion (Cu²⁺) on the membrane conformed to the pseudo-first-order kinetic model and Langmuir isotherm model. Moreover, after comparing the adsorption effect of the modified membranes grafted with different generations of PAMAM, it was found that the membrane grafted with the third generation PAMAM had the best adsorption when the solution pH was 5, and its maximum adsorption capacity could reach 153.8 mg/g. After five adsorption-desorption cycles, its adsorption capacity can reach 72.83% of the first test, indicating that it has good recycling performance. The results show that the adsorption membrane has good application potential and research value.

Adsorption of Hg(II) in solution by mercaptofunctionalized palygorskite

In the past 10 years, the treatment and restoration of soil and water bodies contaminated by mercury and other heavy metals have received unprecedented attention and support from China's environmental protection authorities. The search for low-cost and high-efficiency adsorbents has become one of the research hotspots in this field. In this paper, a simple and environment-friendly method was used to graft 3-mercaptopropyl trimethoxysilane on the surface of palygorskite. The synthesized mercaptofunctionalized palygorskite (M-PAL) was characterized by XRD, FT-IR, BET and SEM-EDS, respectively, and its adsorption conditions, adsorption models and thermodynamic parameters for Hg2+ were systematically investigated. The experimental results indicated that the saturated adsorption capacity of Hg2+ on the M-PAL could reach 203.4 mg·g-1, within 120 min at pH 4 and 298 K. By analyzing the experimental data of adsorption kinetics and thermodynamics, it was found that the adsorption process of Hg2+ conformed to the pseudo-second-order kinetic model, which belonged to chemical adsorption of the rate-controlled step; the Langmuir model better described the adsorption isotherm. The thermodynamic parameters obtained (ΔH=29.95 kJ·mol-1, ΔS=103.09 J·mol-1·K-1 and ΔG<0) show that the whole process is a spontaneous endothermic process. When the concentration of Na+, K+, Ca2+, Mg2+, Cl-, NO3-, H2C2O4 and C6H8O7 was 200 times that of Hg2+, although these organic acids had a slightly greater effect on the adsorption of Hg2+ on mercaptofunctionalized palygorskite than inorganic ions, the adsorption capacity remained above 185 mg·g-1. The adsorption products could be still stable in simulated acid rain with pH 3, 4, 5, 6, 7 and oxalic acid solution with concentration of 1, 2, 3, 4 and 5 mmol·L-1, and the desorption rates were about 3%. Through XPS analysis, the specific coordination of Hg2+ with the S atom on the surface of M-PAL was confirmed.

Simultaneous adsorption of mercury species from aquatic environments using magnetic nanoparticles coated with nanomeric silver functionalized with l-Cysteine

We introduce a novel, efficient and fast method for the total and simultaneous removal of monomethylmercury, dimethylmercury, ethylmercury and Hg (II) from aquatic environments using magnetic core nanoparticles, coated with metallic nanomeric silver and functionalized with l-Cysteine. As far as the authors know, simultaneous removal has not been achieved previously. The experimental design was based on exploring a wide range of experimental conditions, including pH of the medium (2-12), contact time (up to 20 min), adsorbent dose (50-800 μL) and temperature (293-323 K), in order to achieve the highest adsorption efficiency. The results show that, for a pH equal to 6.2 at room temperature, 400 μL of nanoparticles is sufficient to achieve 100% adsorption efficiency for all the studied Hg species after a contact time of 30 s. The adsorbent was characterized by means of Scanning Electron Microscopy, Energy Dispersive X-ray Analysis, Fourier-Transform Infrared Spectroscopy and a BET test. Moreover, the procedure allows the total recovery and recycling of the nanoparticles using 50 μL of 0.01 M KI. As regards reuse, the adsorbent exhibits no loss of adsorption capacity during the first three adsorption cycles. Thermodynamics reveals that adsorption is of a physicochemical nature, the equilibrium isotherms being described by a Langmuir model for all the Hg species. The ability of the method to simultaneously adsorb all species of mercury present in water, achieving full adsorption in just a few seconds, along with the simple experimental conditions and its cost-effectiveness, strongly support the approach as an alternative to current procedures.

Phosphorous-functionalized PAMAM dendrimers supported on mesoporous silica for Zr(iv) and Hf(iv) separation

To overcome the urgency of zirconium and hafnium separation, a novel mesoporous silica sorbent (PS-G1.0-MSNs) modified with phosphorous-functionalized G1.0 PAMAM dendrimers was prepared. The adsorption and separation behaviors of PS-G1.0-MSNs adsorbent on Zr(iv) and Hf(iv) were perfromed as a function of acidity, contact time, temperature, and ion concentrations by batch sorption methods. The maximum adsorption capacities for Zr(iv) and Hf(iv) were 25.7 mg g⁻¹ and 5.36 mg g⁻¹ under optimal experimental conditions, respectively, and the separation factor β_Hf/Zr = 2.0 > 1 demonstrated that the prepared sorbent had preferential selectivity for Hf(iv) in rich Zr(iv) solution. Moreover, kinetic data indicated that the sorption process on Zr(iv) and Hf(iv) achieved equilibrium within 120 min, and followed the pseudo-first-order model with a rate-determining step. The adsorption amount increased as temperature raised from 283 K to 303 K and the isothermal data plotted with the Langmuir model was better than the Freundlich model with monolayer behavior. Thermodynamic data analysis indicated that the sorption process was spontaneous and endothermic. Furthermore, XPS analysis revealed that the metal ion adsorption was mainly induced by the chemical coordination of Zr(iv) and Hf(iv) ions with N, O, P atoms of amide and phosphate groups. The present work provides good guidelines on the design of high efficient sorbent for the separation of Hf(iv) from Zr(iv) solutions.

The adsorption and separation process of PS-G1.0-MSNs on Zr(iv) and Hf(iv).

Facile Synthesis of Cross-linked Hyperbranched Polyamidoamines Dendrimers for Efficient Hg(Ⅱ) Removal From Water

Dendrimers as commonly used metal ions adsorption materials have the advantages of good adsorption performance and high reuse rate, but the high cost limits its extensive use. Compared with dendrimers, hyperbranched dendrimers have similar physical and chemical properties and are more economical. Therefore, hyperbranched dendrimers are more suitable for industrial large-scale adsorption. The hyperbranched polyamidoamine (HPAMAM) gels were prepared by cross-linking hyperbranched polyamidoamine (HPAMAM-ECH-x and HPAMAM-EGDE-x) with different amounts of epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE), respectively. The as-synthesized adsorbents were characterized by FT-IR, SEM and XPS. The prepared adsorbents were used to adsorb Hg(Ⅱ) in aqueous solution, and the effects of solution pH, contact time, temperature and initial concentration of metal ion on the adsorption capacity were investigated. The effect of solution pH indicated that the optimum condition to Hg(Ⅱ) removing was at pH 5.0. The adsorption kinetic curves of the two kinds of materials were in accordance with the pseudo-second-order model. For the HPAMAM-ECH samples, the adsorption thermodynamic curves fitted the Langmuir model, while for the HPAMAM-EGDE samples, both Langmuir and Freundlich equations fitted well. The maximum adsorption capacity of HPAMAM-ECH-3 obtained from Langmuir model toward Hg(Ⅱ) was 3.36 mmol/g at pH 5.0 and 35°C.

Corn bracts loading copper sulfide for rapid adsorption of Hg(II) and sequential efficient reuse as a photocatalyst

Hg(II) ions in wastewater are highly toxic to the environment and human health, yet many materials to remove the ions exhibit lower adsorption efficiency, and few studies report the reuse of Hg(II)-loaded waste materials. Here, a cheap and efficient adsorbent was prepared for the removal of Hg(II) based on corn bracts (CB) loading copper sulfide (CuS), and the Hg(II)-adsorbed material was reused as a photocatalyst. By changing the adsorption variables such as pH, adsorbent dosage, Hg(II) concentration, contact time and coexisting ions, the optimum adsorption conditions were obtained. The study indicated the adsorption capacity and removal rate of CB/CuS reached 249.58 mg/g and 99.83% at pH 6 with 20 mg CB/CuS, 50 mL Hg(II) concentration (100 mg/L) and 60 min, and coexisting ions did not affect the uptake of Hg(II). The adsorption behavior of CB/CuS toward Hg(II) followed pseudo-second-order and Langmuir models, with the theoretical maximum adsorption capacity of 316.46 mg/g. Finally, we explored an alternative strategy to dispose of spent adsorbents by converting the CB/CuS/HgS into a photocatalyst for the degradation of rhodamine B, with a removal rate of 98%. Overall, this work not only develops a promising material for the treatment of Hg(II)-containing wastewater, but opens up a new approach for the use of the waste adsorbent.

Design of PAMAM grafted chitosan dendrimers biosorbent for removal of anionic dyes: Adsorption isotherms, kinetics and thermodynamics studies

PAMAM grafted chitosan as biocompatible adsorbent was synthesized through Michael addition of methyl acrylate followed by amidation of ethylenediamine on the chitosan backbone. Then, the adsorption capacity of bioadsorbents were assessed by employing two anionic dyes. The adsorption experiments were carried out using a batch adsorption system. The influence of various operational variables such as different PAMAM generations, pH, adsorbent dosage, contact time, initial dye concentration and temperature on the maximum adsorption capacity (q_m) were investigated. The adsorbent consists of second generation of PAMAM (CS-PAMAM G2) demonstrated high removal efficiency for both dyes. The maximum adsorption capacity of CS-PAMAM G2 for Congo Red at certain operational conditions was 559.3 mg/g; while the maximum adsorption capacity for Amido Black 10B at certain operational conditions was 489.8 mg/g; which revealed endothermic and exothermic nature of adsorption process for Congo Red and Amido Black 10B, respectively. These results were then well confirmed by thermodynamics studies. Also, kinetic studies showed that the dye adsorption process followed a pseudo-second-order kinetic model. Moreover, among various applied isotherms, the experimental data were well-fitted by Sips model. Consequently, CS-PAMAM G2 showed superior potential for the removal of dyes from aqueous phase.

Adsorption of Lead Ion from Wastewater Using Non-Crystal Hydrated Calcium Silicate Gel

In order to obtain low-cost and excellent adsorption materials, this paper used calcium acetate and water glass as raw materials to synthesis hydrated calcium silicate gel by precipitation method. The performance and structure of hydrated calcium silicate gel were systematically studied by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, specific surface area analyzer and scanning electron microscope. Studies have shown that, non-crystal hydrated calcium silicate gel (CSH) were successfully prepared, and the removal rate of lead ion using CSH reached more than 90%. The adsorption process is consistent with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and the limit adsorption capacity reaches 263.17 mg·g-1. The acid treatment experiment proved that the adsorption capacity of lead ion using CSH was satisfactory, and the adsorption rate remained at >60% after 5 cycles. The research may provide a low-cost, high-efficiency and high stability adsorbent.

Enhanced heavy metal removal from an aqueous environment using an eco-friendly and sustainable adsorbent

Thiol-lignocellulose sodium bentonite (TLSB) nanocomposites can effectively remove heavy metals from aqueous solutions. TLSB was formed by using -SH group-modified lignocellulose as a raw material, which was intercalated into the interlayers of hierarchical sodium bentonite. Characterization of TLSB was then performed with BET, FTIR, XRD, TGA, PZC, SEM, and TEM analyses. The results indicated that thiol-lignocellulose molecules may have different influences on the physicochemical properties of sodium bentonite, and an intercalated-exfoliated structure was successfully formed. The TLSB nanocomposite was subsequently investigated to validate its adsorption and desorption capacities for the zinc subgroup ions Zn(II), Cd(II) and Hg(II). The optimum adsorption parameters were determined based on the TLSB nanocomposite dosage, concentration of zinc subgroup ions, solution pH, adsorption temperature and adsorption time. The results revealed that the maximum adsorption capacity onto TLSB was 357.29 mg/g for Zn(II), 458.32 mg/g for Cd(II) and 208.12 mg/g for Hg(II). The adsorption kinetics were explained by the pseudo-second-order model, and the adsorption isotherm conformed to the Langmuir model, implying that the dominant chemical adsorption mechanism on TLSB is monolayer coverage. Thermodynamic studies suggested that the adsorption is spontaneous and endothermic. Desorption and regeneration experiments revealed that TLSB could be desorbed with HCl to recover Zn(II) and Cd(II) and with HNO3 to recover Hg(II) after several consecutive adsorption/desorption cycles. The adsorption mechanism was investigated through FTIR, EDX and SEM, which demonstrated that the introduction of thiol groups improved the adsorption capacity. All of these results suggested that TLSB is an eco-friendly and sustainable adsorbent for the extraction of Zn(II), Cd(II) and Hg(II) ions in aqueous media.

Preparation of a Novel Zn(II)-Imidazole Framework as an Efficient and Regenerative Adsorbent for Pb, Hg, and As Ion Removal From Water

An outstanding metal-organic framework sorbent (Zn-MOF) was prepared using Zn²⁺ and 3-amino-5-mercapto-1,2,4-triazole to eliminate toxic metal ions from water. Zn-MOF was detected via using Fourier-transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). Zn-MOF is stable and has a very large surface area. The uptake properties of Zn-MOF were investigated. The maximum uptake capacity of Zn-MOF for Pb, Hg, and As ions was 1097, 32, and 718 mg/g, respectively. This was obtained at pH = 4, 5, and 6, respectively. The adsorption data is in good agreement with the Langmuir and pseudo-second-order rate models, indicating that the uptake process of Zn-MOF for toxic metal ions was a single layer uptake on a uniform surface via exchange of valence electrons. Thermodynamics shows that the uptake process is autogenic and endothermic. Zn-MOF can be reused at least 6 times. Mercury and lead strongly coordinated with Zn-MOF. The interaction between arsenic and Zn-MOF is weak chemical coordination and ion exchange. Zn-MOF has wide application prospects for toxic metal ion elimination.

Adsorption Processing for the Removal of Toxic Hg(II) from Liquid Effluents: Advances in the 2019 Year

Mercury is a toxic metal, thus, it is an element which has more and more restrictions in its uses, but despite the above, the removal of this metal, from whatever the form in which it is encountered (zero valent metal, inorganic, or organic compounds), and from different sources, is of a widespread interest. In the case of Hg(II), or Hg2+, the investigations about the treatment of Hg(II)-bearing liquid effluents (real or in most cases synthetic solutions) appear not to end, and from the various separation technologies, adsorption is the most popular among researchers. In this topic, and in the 2019 year, more than 100 publications had been devoted to this field: Hg(II)-removal-adsorption. This work examined all of them.

Simultaneous enrichment and determination of cadmium and mercury ions using magnetic PAMAM dendrimers as the adsorbents for magnetic solid phase extraction coupled with high performance liquid chromatography

In present study, a sensitive and efficient method based on magnetic PAMAM dendrimers as the sorbents for magnetic solid-phase extraction (MSPE) coupled with high performance liquid-phase chromatography and ultraviolet variable wavelength detector (HPLC-VWD) was developed for simultaneous determination of trace cadmium and mercury ions. Sodium diethyldithiocarbamate (DDTC-Na) was used as the chelating agent during the elution process. Parameters that would affect the extraction efficiency including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and coexisting ions were investigated to achieve the best adsorption efficiency. Under the optimal conditions, good linear relationship was obtained in the range of 0.05-200 μg L^-1 for Cd²⁺ and 0.1-200 μg L^-1 for Hg²⁺, and the limits of detection were 0.016 and 0.040 μg L^-1, respectively. The spiked recoveries of Cd²⁺ and Hg²⁺ were satisfied in the range of 91.5-105% (n = 3). The proposed method was proved to be an alternative and reliable method to determine trace Cd²⁺ and Hg²⁺ in water samples.

Design of l-Cysteine Functionalized UiO-66 MOFs for Selective Adsorption of Hg(II) in Aqueous Medium

Mercury ions can cause a series of hazards to humans and the environment, even in trace amounts. Here, we designed a novel adsorbent (Cys-UiO-66) by functionalizing NH₂-UiO-66 with l-cysteine for selective removal of Hg(II) from solution. The Cys-UiO-66 was characterized by different instruments. The adsorption property of Cys-UiO-66 was evaluated by batch methods. The maximum adsorption capacity was 350.14 mg/g at pH 5.0. Furthermore, the adsorption isotherm and kinetics models were in accord with the Langmuir and pseudo-second-order models, respectively, evidencing that the adsorption behavior was dominated by monolayer chemisorption. The Cys-UiO-66 had better affinity for Hg(II) than other coexisting ions in wastewater and could be regenerated for at least five cycles. The results prove that Cys-UiO-66 is a talented and efficient sorbent for mercury ions.

Fast Removal of Propranolol from Water by Attapulgite/Graphene Oxide Magnetic Ternary Composites

In this work, a novel adsorbent attapulgite/graphene oxide magnetic composite (ATP/Fe₃O₄/GO) was synthesized for removing propranolol (PRO) from aqueous water. The factors affecting the PRO adsorption process onto ATP/Fe₃O₄/GO including pH, ionic strength, sorbent dosage, and humic acid were systematically investigated by batch experiments. Meanwhile, magnetic attapulgite (ATP/Fe₃O₄) and magnetic graphene oxide (GO/Fe₃O₄) were prepared for the comparison of the adsorption performance for PRO. The structural and surface characteristics of the resulting materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential measurements, and scanning electron microscope. The results showed that the adsorption rate of PRO onto ATP/Fe₃O₄/GO was up to 99%, faster and higher than that of other adsorbents involved at neutral pH. Moreover, the adsorption kinetics were better fitted with pseudo-first-order kinetic model than the second-order kinetic model. The adsorption data were fitted well with the Freundlich isotherm equations, implying that the adsorption process was heterogeneous. The adsorption reaction was endothermic and spontaneous according to the thermodynamic parameters. All results indicated that ATP/Fe₃O₄/GO was a promising adsorbent for removing PRO from water.