Adsorption of Pb(II) from aqueous solution by silica-gel supported hyperbranched polyamidoamine dendrimers

Efficient removal of low concentrations of copper and lead ions in water using chitosan-condensed tannin composite microspheres

Condensed tannin was solidified onto chitosan microspheres to prepare chitosan-tannin (CT) composite microspheres with a simple preparation method to study its performance in adsorbing copper (Cu2+) and lead ions (Pb2+) in aqueous media. The study investigated the influence of the mass ratio of tannin and chitosan, pH value, adsorption time, and initial concentrations of Cu2+ and Pb2+ on the adsorption capacity of Cu2+ and Pb2+ ions. Additionally, the study examined the adsorption isotherms and kinetics of Cu2+ and Pb2+ on CT composite microspheres. The adsorption process aligns more closely with the fitting results of the Langmuir model. The maximum capacity for saturated monolayer adsorption of CT composite microspheres for Cu2+ and Pb2+ was 37.6 and 52.9 mg/g, respectively. The adsorption process of CT composite microspheres for Cu2+ and Pb2+ was primarily driven by single-layer chemical adsorption. In addition, metal ions adsorbed onto CT composite microspheres can be released by treating them with a dilute solution of strong acid. Furthermore, the CT composite microspheres exhibited impressive removal efficiencies of 82 % and 95 % for Cu2+ and Pb2+ respectively, even at low concentrations of 2 mg/L. The CT composite microspheres have the ability to easily separate the adsorbed Cu2+ and Pb2+ ions.

Selective immobilization of Pb(II) by biogenic whewellite and its mechanism

The development of bio-adsorbents with highly selective immobilization properties for specific heavy metals is a great challenge, but has important application value. Biogenic whewellite (BW) with high selectivity for Pb(II) was synthesized by mineral microbial transformation. The selective immobilization properties and mechanism of BW for Pb(II) were analyzed by combining mineral characterization technology and batch adsorption research methods. The results indicated that BW can efficiently and selectively immobilize Pb(II) in single or composite heavy metal adsorption solutions, and the immobilized Pb(II) is difficult to desorb. BW undergoes monolayer adsorption on Pb(II), Qmax ≈ 1073.17 mg/g. The immobilization of Pb(II) by BW is a physico-chemical adsorption process with spontaneous heat absorption and an accompanying increase in entropy. In addition, the sequestration of Pb(II) by BW remains around 756.99 mg/g even at pH = 1. The excellent selective immobilization properties of BW for Pb(II) are closely related to its smaller Ksp, electrostatic repulsion effect, organic-inorganic composite structure, acid resistance and the formation of Pb(II) oxalate. This study provides beneficial information about the recycling of lead in acidic lead-containing wastewater and composite heavy metal contaminated water bodies.

Chloride converts lead slag into a bifunctional material to remove heavy metals

Efficient and safe removal of arsenic and lead from industrial wastewater is essential for ecological protection. In this study, we developed a novel method using lead slag as a purifying agent and sodium chloride as a reinforcing agent to remove arsenic and lead from industrial wastewater. Through a combination of experiments and simulations, we elucidated the mechanisms involved in this reaction. The initial concentrations of As and Pb ions in the industrial wastewater were 4333 and 188 mg/L, respectively. After the reaction at 25 °C and a pH ranging from 9.7 to 10, the concentrations of arsenic and lead were reduced to 4.9 mg/L and 0.008 mg/L, respectively, achieving a removal rate of 99.9%. Our experimental results demonstrated that Pb2+ and AsO43- ions released from the lead slag and industrial wastewater reacted with Cl- ions to form Pb5(AsO4)3Cl precipitates, thus effectively eliminating a significant amount of As and Pb species. Simulation studies indicated that Pb5(AsO4)3Cl exhibited exceptional stability below 400 °C and could be directly stored. Additionally, the lead slag, which is rich in silica, played a crucial role in removing and stabilizing As and Pb ions. Under alkaline conditions, silica encapsulated the As and Pb species, adhering to the surface of the Pb-As co-precipitates and forming dense, irregular, small particles with internal and external structures that impeded the efflux of As and Pb ions. This phenomenon was confirmed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The kinetics of As and Pb ion removal was consistent with the pseudo-second-order kinetic model, indicating that the removal process was primarily governed by chemical interactions. Lead slag exhibits significant potential and advantages in the removal of As and Pb. This innovative method offers an effective approach to address heavy metal contamination in industrial wastewater, thus contributing to ecological protection.

Preparation of polyamidoamine dendrimer-functionalized chitosan beads for the removal of Ag(I), Cu(II), and Pb(II)

Chitosan bead grafted by third-generation dendrimers (CB-G3) with a diameter of 1.40 mm was synthesized to investigate their performance in recovering Ag(I), Cu(II), and Pb(II) ions in aqueous media. The prepared adsorbents were characterized by XRD, FT-IR, elemental analysis, TGA, and SEM, and the effects of pH, contact time, concentration, and temperature were examined. The results showed that the adsorbents were successfully fabricated. The optimum pH value was 5, and the increased generation number contributed to adsorption capacity improvement, indicating that electrostatic interactions between amine groups and metal ions are the governing mechanism of adsorption by the CB-G3. The kinetics, isotherms, and thermodynamics of Ag(I), Cu(II), and Pb(II) adsorption onto the CB-G3 were investigated. The adsorption processes can be described using pseudo-second-order kinetic and Langmuir models. The maximum monolayer adsorption capacities were 105.62, 88.82, and 97.87 mg·g^-1 for Ag(I), Cu(II), and Pb(II) at 30 °C within 210 min, respectively. Electrostatic interactions and hydrogen bonds are the main mechanisms between metal ions and N atoms. Therefore, the CB-G3 is a promising candidate for Ag(I), Cu(II), and Pb(II) adsorption owing to its splendid ability in easy separation, good adsorptivity, and reusability for efficiently adsorbing Ag(I), Cu(II), and Pb(II) ions.

Preparation and evaluation of celite decorated iron nanoparticles for the sequestration performance of hexavalent chromium from aqueous solution

The increasing usage of an important heavy metal chromium for industrial purposes, such as metallurgy, electroplating, leather tanning, and other fields, has contributed to an augmented level of hexavalent chromium (Cr(VI)) in watercourses negatively impacting the ecosystems and significantly making Cr(VI) pollution a serious environmental issue. In this regard, iron nanoparticles exhibited great reactivity in remediation of Cr(VI)-polluted waters and soils, but, the persistence and dispersion of the raw iron should be improved. Herein, this article utilized an environment-friendly celite as a modifying reagent and described the preparation of a novel composites namaly celite decorated iron nanoparticles (C-Fe⁰) and evaluation of C-Fe⁰ for the sequestration performance of Cr(VI) from aqueous solution. The results indicated that initial Cr(VI) concentration, adsorbent dosage, and especially solution pH are all critical factors to control C-Fe⁰ performance in Cr(VI) sequestration. We demonstrated that C-Fe⁰ could achieve a high Cr(VI) sequestration efficiency with an optimized adsorbent dosage. Fitness of the pseudo-second-order kinetics model with data indicated that adsorption was the rate-controlling step and chemical interaction controlled Cr(VI) sequestration on C-Fe⁰. The adsorption isotherm of Cr(VI) could be the best depicted by Langmuir model with a monolayer adsorption. The underlying sequestration path of Cr(VI) by C-Fe⁰ was then put forward, and the combined effect of adsorption and reduction implied the potentials of C-Fe⁰ in Cr(VI) removal.

Experimental Insights into Mesoporous Polyaniline-Based Nanocomposites for Anionic and Cationic Dye Removal

This work presents the preparation of inorganic-organic hybrid nanocomposites, namely three-dimensional polyaniline (Pani)/activated silica gel (ASG) (3D Pani@ASG), their characterization, and in removing application as a potential adsorbent for cationic brilliant green (BG), crystal violet (CV), and anionic Congo red (CR), and methyl orange (MO) dyes. Pani@ASG nanocomposites have been prepared by the in situ polymerization method and characterized using various techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction, thermogravimetric analysis with derivative thermogravimetry, zeta potential analyses, and Brunauer-Emmett-Teller (BET). The scanning electron microscopy (SEM) study confirms the average particle size of the Pani@ASG nanocomposite is in the range of 5 nm. FESEM, TEM, FTIR, and XRD analysis proved the successful decoration of ASG over Pani. The BET result of Pani@ASG shows a mesoporous nature with a pore diameter of less than 3 nm and a surface area of 423.90 m² g^-1. Both SEM and TEM analyses show the proportional distribution of ASG over Pani's surface. The adsorption trend of BG and MO on the studied materials at pH 7 was found as follows: Pani@ASG > Pani > ASG. The highest sorption capacities of MO and BG on Pani@ASG were 161.29 and 136.98 mg/g (T = 298.15 K, and Pani@ASG dose: 0.04 g for MO and 0.06 g for BG), which were greater compared with bare Pani and bare ASG, respectively. The interaction mechanism behind the adsorption of BG and MO dyes onto the Pani@ASG nanocomposite includes electrostatic interaction, π-π interaction, and hydrogen bonding. The mechanistic pathway and the interactions between the targeted dyes and Pani@ASG were further studied using adsorption isotherm, adsorption kinetics, and thermodynamics.

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.

In situ growth of ZIF-8 on carboxymethyl chitosan beads for improved adsorption of lead ion from aqueous solutions

In this study, a method for the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on carboxymethyl chitosan beads (BCMC) to produce a composite adsorbent (BCMC@ZIF-8) for the removal of Pb²⁺ from water is proposed. The results revealed that the utilization of the BCMC as a framework enhanced the stability of ZIF-8, and the presence of the latter in the composite improved the removal efficiency of Pb²⁺ from water. Data from X-ray photoelectron spectroscopy analysis and adsorption kinetics revealed that the adsorption mechanism included diffusion and the sharing/transfer of electrons between BCMC@ZIF-8 and Pb²⁺. The maximum adsorption capacity of BCMC@ZIF-8 fitted using the Langmuir model was 566.09 mg/g. Results of the experiments on the regeneration of the adsorbent and its stability in water further indicated that BCMC improved the stability of ZIF-8. This study demonstrated that the stability of metal-organic framework (MOF) materials, which exhibited high efficiencies for the removal of heavy metals in water can be improved through fixation of the polymer skeleton. Thus, the present study offers practical and theoretical guidance for the application of MOF materials in water treatment.

Biomass-derived porous carbon with high drug adsorption capacity undergoes enzymatic and chemical degradation

Degradability is a key safety issue when choosing materials for biomedical applications and environmental protection. This factor greatly limits the application of porous carbon in these areas due to the inert and stable nature of carbon network. In this work, this conflict could be well-resolved by rational designing a mesoporous carbon (MC) with biomass as a carbon source. The retained oxygen-containing species simultaneously increase drug adsorption capacity and the degradability of MC. The maximum adsorption quantity for doxorubicin over MC can reach 395.3 mg/g, about 3-fold over carbon nanotubes. The detailed analysis reveals that the degradation of MC occurs via a radical mediated oxidation process. The high electron density feature of MC facilitates the electrophilic addition reaction in the presence of HO. During this process, the carbon network is gradually degraded into fragments, carbon nanodots and ultimately to CO₂. This work opens up a new way to fabricate degradable porous materials and provides a promising material for the practical application in biomedical and environmental field.

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.

Simultaneous removal of organic and inorganic pollutants from water by Ni/NiO/SnO2 nanoparticles

Herein, we report a facile synthesis of Ni/NiO/SnO₂ hybrids where the core-shell-type Ni/NiO nanoparticle is decorated with the SnO₂ nanoparticle to make a heterojunction and their potential evaluation for simultaneous removal of organic and inorganic pollutants. The metallic nickel core of the nanoparticle helps to separate easily from water magnetically and restricts the possible secondary contamination. The formation of semiconductor-semiconductor heterojunction enhances the photocatalytic activity to degrade the organic pollutants. The nanomaterial was characterized using microscopic, spectroscopic, and BET analyses. Results indicated an efficient degradation of ~ 94% of crystal violet in 40 min. An adsorption capacity of ~ 530 mg g^-1 and ~ 650 mg g^-1 of cadmium and lead ions, respectively, was found for single-component adsorption experiments, and ~ 520 mg g^-1 and ~ 720 mg g^-1 of cadmium and lead ions, respectively, were found for multi-component experiments. This observation suggested that the lead and cadmium ion adsorption process is affected by the synergistic and antagonistic effects, respectively. However, no significant change in the photocatalytic activity was observed for multi-component experiments. Results indicated that the process followed the Langmuir isotherm and pseudo-second-order kinetics irrespective of the number of pollutants present. An excellent adsorption capacity of metal ions and photodegradation capability of organic dye in multi-component solution, and possible reusability of the nanoparticle, make the Ni/NiO/SnO₂ a potential material for simultaneous removal of organic and inorganic pollutants.

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).

Waste-to-wealth application of wastewater treatment algae-derived hydrochar for Pb(II) adsorption

Hydrochar, as an energy-lean solid waste, is generated from an advanced biofuel conversion technique hydrothermal liquefaction (HTL) and always leads to environmental pollution without appropriate disposal. In this study, HTL-derived hydrochar is recycled and prepared as adsorbent used for Pb(Ⅱ) removal from wastewater. As the original porous structure of hydrochar is masked by oily volatiles remained after HTL, two types of oil-removal pretreatment (Soxhlet extraction and CO₂ activation) are explored. The result shows that CO₂ activation significantly enhances the adsorption capacity of Pb(Ⅱ), and the maximum adsorption capacity is 12.88 mg g⁻¹, as evaluated using Langmuir adsorption model. Further, apart from oily volatiles, most inorganic compounds derived from wastewater-grown algae is enriched in hydrochar, causing a smaller surface area of hydrochar. An ash-removal alkali treatment following CO₂ activation is introduced to dramatically increase the adsorption capacity to 25.00 mg g⁻¹ with an extremely low Pb(II) equilibrium concentration of 5.1×10^-4 mg L⁻¹, which is much lower than the maximum level of Pb concentration in drinking water (set by World Health Organization). This work introduces an approach to reuse HTL-hydrochar as an inexpensive adsorbent in Pb-contaminated water treatment, which not only provides another possible renewable adsorbent candidate applied in the field of lead adsorption, but also finds an alternative route to reduce solid waste effluent from HTL process.

Biosorption capacity of Mucor circinelloides bioaugmented with Solanum nigrum L. for the cleanup of lead, cadmium and arsenic

The biosorption and bioaugmentation performances of Mucor circinelloides were investigated under different contact time, initial metal(loid) concentration and species. The microbe-plant interaction appeared synergistic with enhancing plant growth and alleviating oxidative damages induced by lead, cadmium and arsenic. The bioaugmentation with M. circinelloides led to significant immobilization on lead, cadmium and arsenic as indicated by the decreases of metal(loid) transfer and bioavailability in plant-microbe aqueous system. Lead, cadmium and arsenic were mainly allocated on cell wall and a few parts entered into intercellular system, suggesting cell wall adsorption and intracellular bioaccumulation served as the main mechanisms of M. circinelloides. The adsorption kinetics and isotherms on lead, cadmium and arsenic were fitted well with the pseudo-second-order and Langmuir models, with the maximum adsorption capacities of 500, 15.4 and 29.4 mg·g^-1 fungal biomass at pH 6.0 and 25 ℃. The optimum initial concentration and contact time were 300-10-20 mg·L^-1 and 2 h. This study provides a basis for M. circinelloides as a promising adsorbent and bioaugmented agent for the cleanup of soil/aqueous environment contaminated with lead, cadmium and arsenic.

Magnetite nanoparticles grafted with murexide-terminated polyamidoamine dendrimers for removal of lead (II) from aqueous solution: synthesis, characterization, adsorption and antimicrobial activity studies

In this study, new, efficient, eco-friendly and magnetically separable nanoadsorbents, MNPs-G1-Mu and MNPs-G2-Mu, were successfully prepared by covalently grafting murexide-terminated polyamidoamine dendrimers on 3-aminopropyl functionalized silica-coated magnetite nanoparticles, and used for rapid removal of lead (II) from aqueous medium. After each adsorption process, the supernatant was successfully acquired from reaction mixture by the magnetic separation, and then analyzed by employing ICP-OES. Chemical and physical characterizations of new nanomaterials were confirmed by XRD, FT-IR, SEM, TEM, and VSM. Maximum adsorption capacities (q_m) of both prepared new nanostructured adsorbents were compared with each other and also with some other adsorbents. The kinetic data were appraised by using pseudo-first-order and pseudo-second-order kinetic models. Adsorption isotherms were found to be suitable with both Langmuir and Freundlich isotherm linear equations. The maximum adsorption capacities for MNPs-G1-Mu and MNPs-G2-Mu were calculated as 208.33 mg g^-1 and 232.56 mg g^-1, respectively. Antimicrobial activities of nanoparticles were also examined against various microorganisms by using microdilution method. It was determined that MNPs-G1-Mu, MNPs-G2-Mu and lead (II) adsorbed MNPs-G2-Mu showed good antimicrobial activity against S. aureus ATTC 29213 and C. Parapsilosis ATTC 22019. MNPs-G1-Mu also showed antimicrobial activity against C. albicans ATTC 10231.

Dendritic Polymers as Promising Additives for the Manufacturing of Hybrid Organoceramic Nanocomposites with Ameliorated Properties Suitable for an Extensive Diversity of Applications

As the field of nanoscience is rapidly evolving, interest in novel, upgraded nanomaterials with combinatory features is also inevitably increasing. Hybrid composites, offer simple, budget-conscious and environmental-friendly solutions that can cater multiple needs at the same time and be applicable in many nanotechnology-related and interdisciplinary studies. The physicochemical idiocrasies of dendritic polymers have inspired their implementation as sorbents, active ingredient carriers and templates for complex composites. Ceramics are distinguished for their mechanical superiority and absorption potential that render them ideal substrates for separation and catalysis technologies. The integration of dendritic compounds to these inorganic hosts can be achieved through chemical attachment of the organic moiety onto functionalized surfaces, impregnation and absorption inside the pores, conventional sol-gel reactions or via biomimetic mediation of dendritic matrices, inducing the formation of usually spherical hybrid nanoparticles. Alternatively, dendritic polymers can propagate from ceramic scaffolds. All these variants are covered in detail. Optimization techniques as well as established and prospected applications are also presented.

Optimal generation number in magnetic-cored dendrimers as Pb(II) and Cd(II) adsorbents

As the generation number of dendrimers increases, more organic branches and terminal groups are synthesized on the surface. However, this may not be actual situations in all generations of dendrimers. Different generations of magnetic cored dendrimer (MCD) terminalized with amine functional groups were compared as adsorbents for heavy metal ions in water. To determine the optimal generation number as adsorbent, the maximal adsorption of lead and cadmium on generation 1, 2, and 3 (G1, G2, and G3) MCDs. Higher generation MCD had more organic contents and possibly terminal groups on its structure. However, G2 MCD was the highest in adsorbing both lead and cadmium. An acid-base titration was performed to quantify the amine functional groups. The active amine sites on G2 are 4.35 times as much as that of G1 and 0.12 times as much as that of G3, which coincided with the adsorption experimental result. Incomplete dendritic structure formation due to steric hindrance caused G2 MCD to be the most efficient among the three generations of MCDs in this research.

Enhanced adsorption of Cr(VI), Ni(II) ions from aqueous solution using modified Eichhornia crassipes and Lemna minor

The environment is seriously affected by the release of hazardous heavy metals from the industries. The transformation of aquatic weeds into valuable nanosorbent has been considered as effective and efficient material in the wastewater treatment process. The aim of the study is to analyze the potential of nano-EC and nano-LM for the removal of chromium(VI) and nickel(II) ions. The characteristics of nanosorbent were analyzed using Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett-Teller analysis (BET), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermo gravimetric analysis (TGA), respectively. Adsorptive performance of nanosorbent was studied with respect to pH, contact time, nano adsorbent dosage, and metal ion concentration. The maximum monolayer adsorption capacity of Cr(VI) and Ni(II) with respect to nano-EC was found to be 79.04 mgg^-1 and 85.09 mgg^-1, respectively. Adsorption isotherm and kinetic studies were performed and it was reported that adsorption isotherm follows Langmuir model with regression coefficient R² > 0.9 for nano-EC and nano-LM respectively. The pseudo-second order model was found to fit well with experimental data. Experimental results suggested that nano-EC can be considered as a suitable nanosorbent for the removal of Cr(VI) and Ni(II) ions from effluents.

Removal of Pb(II) Ions from Wastewater by Using Polyethyleneimine-Functionalized Fe3O4 Magnetic Nanoparticles

A class of polyethyleneimine (PEI)-functionalized Fe3O4 magnetic nanoparticles (MNPs) has been facilely produced through a solvothermal process. The synthetic MNPs have been characterized by multiple technologies and then used for Pb(II) ion sorption from the aqueous media in different conditions. It was found the Pb(II) adsorption behaviors could be well fitted by the pseudo second-order kinetic and Langmuir isotherm models. The maximum Pb(II) adsorption capacity at 25 °C and pH 5.0 was calculated to be 60.98 mg/g. Moreover, effects of temperature, pH, and electrolyte of aqueous phase on the Pb(II) adsorption capacity of MNPs have been carefully examined. The Pb(II) adsorbing capacity was enhanced with temperature or pH rising, but reduced with the addition of various electrolytes. Additionally, the recyclability of synthetic MNPs has been also assessed. The prepared PEI-functionalized MNPs could still maintain good adsorption performance after five cycles of Pb(II) removal. These results indicated that the PEI-functionalized Fe3O4 MNPs could be readily synthesized and served as a desirable and economic adsorbent in Pb(II)-contaminated wastewater treatment.

Synthesis of amino-functionalized magnetic aerobic granular sludge-biochar for Pb(II) removal: Adsorption performance and mechanism studies

In the present study, a novel amino-functionalized magnetic aerobic granular sludge-biochar (NH₂-M-AGS) was successfully fabricated through magnetization and functional modification and applied for Pb(II) sorption. The composite was characterized by using scanning electron microscopy (SEM), energy dispersive spectrum (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Zeta potential analysis, vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The effects of adsorbent dosage, pH value, contact time and initial metal concentration on the adsorption of Pb(II) were investigated by using batch equilibrium experiments. It was concluded that the pseudo-second-order model was better to describe adsorption kinetic of Pb(II) onto NH₂-M-AGS. The Langmuir model was more accorded with the experimental data, and the maximum adsorption capacity of Pb(II) was 127.0 mg/g. A possible adsorption mechanism could be mainly caused by surface complexation, electrostatic attraction and precipitation. In five adsorption-desorption cycles, the desorption efficiency of Pb(II) exhibited a slight decline and still reached at 88.14%. Furthermore, the good reproducibility indicated that NH₂-M-AGS could be used a desirable, economic and recyclable adsorbent in practical metal-contaminated wastewater treatment.

Efficient Removal of Pb(II) and Cd(II) from Industrial Mine Water by a Hierarchical MoS2/SH-MWCNT Nanocomposite

In this study, we investigate the adsorption capability of molybdenum sulfide (MoS₂)/thiol-functionalized multiwalled carbon nanotube (SH-MWCNT) nanocomposite for rapid and efficient removal of heavy metals [Pb(II) and Cd(II)] from industrial mine water. The MoS₂/SH-MWCNT nanocomposite was synthesized by acid treatment and sulfurization of MWCNTs followed by a facile hydrothermal reaction technique using sodium molybdate and diethyldithiocarbamate as MoS₂ precursors. Morphological and chemical features of the nanocomposite material were studied using various characterization techniques. Furthermore, the effects of adsorbent (MoS₂/SH-MWCNT nanocomposite) concentration, contact time, initial concentration of heavy-metal ions, and reaction temperature were examined to determine the efficiency of the adsorption process in batch adsorption experiments. Kinetics and isotherm studies showed that the adsorption process followed pseudo-second-order and Freundlich adsorption isotherm models, respectively. Thermodynamic parameters calculated using van't Hoff plots show the spontaneity and endothermic nature of adsorption. MoS₂/SH-MWCNT nanocomposite demonstrates a high adsorption capacity for Pb(II) (90.0 mg g^-1) and Cd(II) (66.6 mg g^-1) following ion-exchange and electrostatic interactions. Metal-sulfur complex formation was identified as the key contributor for adsorption of heavy-metal ions followed by electrostatic interactions for multilayer adsorption. Transformation of adsorbent into PbMoO_4-x S _x and CdMoO_4-x S _x complex because of the adsorption process was confirmed by X-ray diffraction and scanning electron microscopy-energy-dispersive spectrometry. The spent adsorbent can further be used for photocatalytic and electrochemical applications; therefore, the generated secondary byproducts can also be employed for other purposes.

Removal of Cr(III) from aqueous solution by silica-gel/PAMAM dendrimer hybrid materials

Water pollution caused by Cr(III) is a serious environmental problem which bring adverse effect to environmental protection and public safety. Efficient removal of Cr(III) from aqueous solution is important for the remediation of Cr(III) pollution. Herein, a series of silica-gel/polyamidoamine (PAMAM) dendrimer hybrid materials (SG-G0~SG-G4.0) were used for the removal of Cr(III) from aqueous solution. The factors that affect the adsorption were extensively studied and the adsorption mechanism was demonstrated based on the experimental results and density functional theory (DFT) calculation. Result demonstrates the adsorption capacity of ester-terminated silica-gel/PAMAM dendrimers follow the order of SG-G2.5 > SG-G3.5 > SG-G1.5 > SG-G0.5, while that of amino-terminated ones decrease in the order of SG-G2.0 > SG-G4.0 > SG-G3.0 > SG-G1.0 > SG-G0. The highest adsorption is achieved at pH 4.0 for both ester- and amino-terminated materials. Adsorption kinetic indicates the adsorption equilibrium can be reached at about 240 and 180 min for amino- and ester-terminated hybrids, respectively. Adsorption kinetic can be well fitted by pseudo-second-order kinetic model with film diffusion process as the rate-limiting step. Adsorption isotherm follows Langmuir model with monolayer adsorption behavior. Fourier transform infrared spectra (FTIR) indicate the adsorption of Cr(III) by PAMAM dendrimer mainly involve the participation of N-H and C=O groups. DFT calculation demonstrates the uptake of Cr(III) by ester-terminated adsorbents mainly involves carbonyl oxygen and secondary amine nitrogen atoms to form tetra-coordinated chelate, while that of amino-terminated one tends to form hexa-coordinated chelates by carbonyl oxygen, primary and secondary amine nitrogen atoms.

Novel Chemical Cross-Linked Ionogel Based on Acrylate Terminated Hyperbranched Polymer with Superior Ionic Conductivity for High Performance Lithium-Ion Batteries

A new family of chemical cross-linked ionogel is successfully synthesized by photopolymerization of hyperbranched aliphatic polyester with acrylate terminal groups in an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄). The microstructure, viscoelastic behavior, mechanical property thermal stability, and ionic conductivities of the ionogels are investigated systematically. The ionogels exhibit high mechanical strength (up to 1.6 MPa) and high mechanical stability even at temperatures up to 200 °C. It is found to be thermally stable up to 371.3 °C and electrochemically stable above 4.3 V. The obtained ionogels show superior ionic conductivity over a wide temperature range (from 1.2 × 10^-3 S cm^-1 at 20 °C up to 5.0 × 10^-2 S cm^-1 at 120 °C). Moreover, the Li/LiFePO₄ batteries based on ionogel electrolyte with LiBF₄ show a higher specific capacity of 153.1 mAhg^-1 and retain 98.1% after 100 cycles, exhibiting very stable charge/discharge behavior with good cycle performance. This work provides a new method for fabrication of novel advanced gel polymer electrolytes for applications in lithium-ion batteries.

Facile Fabrication of 3D Graphene⁻Silica Hydrogel Composite for Enhanced Removal of Mercury Ions

Adsorption is a highly promising and widely used approach to remove Hg(II) ions from contaminated water. The key to this technology is exploring the effective adsorbent. The three-dimensional (3D) graphene as reduced graphene oxide hydrogel (rGH)-encapsulated silica gel (SG-PEI/rGH) was prepared by a moderate chemical reduction strategy using ascorbic acid. This composite structure was characterized by FTIR, XRD, and SEM analysis and used as adsorbents for Hg(II) ions. Its adsorption capacity toward Hg(II) ions was 266 mg/g and increased about 32% compared with the silica gel because of reduced graphene oxide hydrogel (rGH). Mechanism study showed that the high adsorption ability was due to the formation of an N–Hg complex with multi-amino groups on the surface of polyethyleneimine-modified silica gel (SG-PEI) and the rapid diffusion of adsorbed ions attributed to the rGH network structure. This composite SG-PEI/rGH would be a promising material for the removal of Hg(II) ions.