Adsorption Behavior Of Pb Research Articles

Enhanced adsorption of Pb(II) ions using a magnetic mesoporous molecular sieves derived from coal fly ash and Nano-Fe3O4 particles

The synthesis of high-performance adsorption materials from coal fly ash presents a promising approach to mitigating environmental pollution in wastewater treatment processes. A novel magnetic mesoporous molecular sieve (MMS) was synthesized through hydrothermal methods utilizing coal fly ash and nano-Fe3O4 particles. The resultant MMS was characterized using XRD, FT-IR, SEM, TEM, and BET analysis. The adsorption performance of MMS for Pb(II) was evaluated by examining thermodynamic and adsorption models. The results show that MMS exhibited mesoporous structures with embedded Fe3O4 nanoparticles, possessing a surface area of 22.94 m2/g and a pore size of 28.47 nm, favorable for applications in aqueous adsorption. The adsorption behavior of Pb(II) onto MMS adhered well to both pseudo-first-order kinetic model and Langmuir isotherm, with a maximum adsorption capacity of 236.97 mg/L. Further insights into the adsorption mechanism were provided by zeta potential and XPS analysis, which revealed that lead is effectively adsorbed onto MMS, with the lead existing predominantly in the form of oxides on the MMS surface. The adsorption process was primarily governed by physical adsorption, accompanied by chemical adsorption. This study presents an innovative approach to converting coal fly ash into highly efficient magnetic adsorbents, thereby offering a sustainable solution for wastewater treatment.

Interaction of Pb(II) with microplastic-sediment complexes: Critical effect of surfactant

In this study, the impact of surfactants on the adsorption behavior of Pb(II) onto microplastics-sediment (MPs-S) complexes was investigated. Firstly, virgin polyamide (VPA) and polyethylene (VPE) were placed in Xiangjiang River sediment for six months to conduct in-situ aging. The results indicated that the biofilm-developed polyamide (BPA) and polyethylene (BPE) formed new oxygen-containing functional groups and different biofilm species. Furthermore, the adsorption capacity of Pb(II) in sediment (S) and MPs-S complexes was in the following order: S > BPA-S > VPE-S > VPA-S > BPE-S. The addition of sodium dodecyl benzenesulfonate (SDBS) promoted the adsorption of Pb(II), and the adsorption amount of Pb(II) increased with the higher concentration of SDBS, while adding cetyltrimethylammonium bromide (CTAB) showed the opposite result. The adsorption process of MPs-S complexes to Pb(II) was dominated by chemical adsorption, and the interaction between MPs-S complexes and Pb(II) was multilayer adsorption involving physical and chemical adsorption when the surfactants were added. Besides, the pH exerts a significant effect on Pb(II) adsorption in different MPs-S complexes, and the highest adsorption amount occurred at pH 6. Noteworthy, CTAB promoted the adsorption ability of Pb(II) when the exogenous FA was added. The binding characteristic of sediment endogenous DOM components and Pb(II) was influenced by the addition of MPs and surfactants. Finally, it confirmed that adsorption mechanisms mainly involve electrostatic and hydrophobic interaction. This study provides a new perspective to explore the environmental behaviors of Pb(II) by MPs and sediments with the addition of surfactants, which was conducive to evaluating the ecological risks of MPs and heavy metals in aquatic environments.

Experimental and statistical physics illumination of Pb(II) adsorption on magnetic chitosan-graphene oxide surface

Adsorption stands for a promising technique for heavy metal remediation. Herein, a high efficiency adsorbent based on magnetic chitosan-graphene oxide (MCGO) was prepared via a simple co-precipitation procedure. Afterwards, adsorption behaviour of Pb(Ⅱ) on MCGO surface was illuminated via batch adsorption experiment and statistical physics calculation. Result presents, MCGO reaches adsorption percent and adsorption quantity 93.06 % and 372.24 mg·g−1 for Pb(Ⅱ) in 44 min, showcasing favorable remediation efficiency. Statistical physics calculation proposes multi-ionic adsorption mechanism. With the increase of temperature, adsorption site density is increased to yield ameliorated adsorption capacity. Moreover, calculation result of the thermodynamic functions designates exothermic, randomness increasing, spontaneous and energy releasing feature. Kinetic fitting based on various models assigns chemical interaction as the rate controlling step. Finally, adsorption mechanism was clarified in atomic level via spectroscopic inspection. Specifically, C=O, C–O, O–H, N+ and –C(=O)NH– contribute to Pb(Ⅱ) adsorption via donating lone pair electrons. This work provides both experimental and statistical physics insights for understanding the adsorption behaviour of typical heavy metal pollutants onto the surface of bio adsorbent like magnetic chitosan-graphene oxide.

Adsorption Behaviour of Pb and Cd on Graphene Oxide Nanoparticle from First-Principle Investigations.

Graphene oxide (GO) is considered as a promising adsorbent material for the removal of metal from aqueous environments. Here, we have used the density functional theory (DFT) approach and a combination of parameters to characterise the interactions of GO with lead (Pb) and cadmium (Cd), i.e., typical harmful metals often found in water. Our model systems consist of a singly and doubly adsorbed neutral (Pb0, Cd0) and charged (Pb2+, Cd2+) atoms adsorbed on the GO nanoparticle of the chemical formula C30H14O15. We show that a single charged metal ion binds more strongly than a neutral atom of the same type. Moreover, to determine the possibility of multiple adsorptions of the GO nanoparticle, two metal atoms of the same species were co-adsorbed on its surface. We found a site-dependent adsorption energy such that when two atoms of the same specie are adsorbed at sites Si and Sj, the binding energy per atom depends on whether one of the two atoms is adsorbed firstly on the Si or Sj sites. Furthermore, the binding energy per atom for the two co-adsorbed atoms of the same specie (i.e., neutral or charged) is less than the binding energy of a singly adsorbed atom. This suggests that atoms may become less likely to be adsorbed on the GO nanoparticle when their concentration increases. We adduce the origin of this observation to be interplay between the metal-metal interaction on the one hand and GO-metal on the other, with the former resulting in less binding for the charged adsorbed metals in particular, due to repulsive interaction between two positively charged ions. The frontier molecular orbitals analysis and the calculated global reactivity descriptors of the respective GO-metal complexes revealed that all the GO-metal complexes have a smaller HOMO-LUMO gap (HLG) relative to that of pristine metal-free GO nanoparticle. This may indicate that although the GO-metal complexes are stable, they are less stable compared to metal-free GO nanoparticles. The negative values of the chemical potentials obtained for all the GO-metal complexes further confirm their stability. Our work differs from previous experimental studies in that those lacked details of the interaction mechanisms between GO, Pb and Cd, as well as previous theoretical studies which used limited numbers of parameters to characterise the GO-metal interactions. Rather, we present a set of parameters or descriptors which provide comprehensive physical and electronic characterisation of GO-metal systems as obtained via the DFT calculations. These parameters, along with those reported in previous studies, may find applications in rational design and high-throughput screening of graphene-based materials for water purification, as an example.

Coal gasification fine slag based multifunctional nanoporous silica microspheres for synergistic adsorption of Pb(II) and Congo red

The discharge of large-scale industrial solid waste and wastewater has caused severe damage to environmental health. In this study, the adsorption behaviors of Pb(II) and Congo Red (CR) dye in single and binary aqueous systems were investigated using novel functionalized nanoporous glass microspheres (NGM). The NGM material was fabricated from coal gasification fine slag (CGFS) by a simple treatment and characterized using TG, BET, XRD, TEM, FT-IR, and XPS to analyze its physicochemical properties. The adsorption experiments showed that the adsorption amounts of DMA-NGM for Pb(II) and CR were 302.39 mg/g and 342.74 mg/g for the single systems, and 372.73 mg/g and 412.93 mg/g for the binary systems, respectively. The increased adsorption capacity was attributed to the synergistic effect of electrostatic attraction and chelation. Furthermore, the pseudo-second-order model and Elovich model could reasonably describe the adsorption of Pb(II) and CR on DMA-NGM. Pb(II) adsorption on DMA-NGM was monolayer adsorption and CR adsorption was multilayer adsorption. In summary, the results demonstrate the potential of efficient and environmentally friendly adsorbents for the resource recovery of CGFS and the processing of printing and dyeing wastewater.

Competitive adsorption of lead and cadmium on soil aggregate at micro-interfaces: Multi-surface modeling and spectroscopic studies

Aggregates are the basic structural units of soils and play a crucial role in metal migration and transformation. Combined contamination of lead (Pb) and cadmium (Cd) is common in site soils, and the two metals may compete for the same adsorption sites and affect their environmental behavior. Herein, the adsorption behavior of Pb and Cd on aggregates of two soils and contributions of soil components in single and competitive systems were studied by combining cultivation experiments, batch adsorption, multi-surface models (MSMs), and spectroscopic techniques. The results demonstrated that < 2 µm size aggregate was the dominant sink for Pb and Cd competitive adsorption in both soils. Compared with Pb, the adsorption capacity and behavior of Cd were affected greatly under competition. MSMs prediction revealed that soil organic matter (SOM) contributed the most to Cd and Pb adsorption on aggregates (> 68.4%), but the dominant competitive effect occurred on different sites for Cd adsorption (primarily on SOM) and Pb adsorption (primarily on clay minerals). Further, 2 mM Pb coexistence caused 5.9 − 9.8% of soil Cd conversion to unstable species (Cd(OH)2). Thus, the competitive effect of Pb on Cd adsorption cannot be ignored in soils with high content of SOM and fine aggregates.

Preparation and Application of a Magnetic Oxidized Micro/Mesoporous Carbon with Efficient Adsorption for Cu(II) and Pb(II).

Water pollution is a worldwide problem that requires urgent attention and prevention and exceeding use of heavy-metal ions is one of the most harmful factors, which poses a serious threat to human health and the ecological environment. In this work, a magnetic oxidized micro/mesoporous carbon (MOMMC) was prepared for the easy separation of Cu(II) and Pb(II) from water. The dual-template method was used to prepare micro/mesoporous carbon using sucrose as the carbon source, silica nanoparticles formed by tetraethyl orthosilicate as the microporous templates, and triblock copolymer F127 as the mesoporous template. MOMMC was obtained by oxidation using potassium persulfate and then magnetized through in situ synthesis of Fe3O4 nanoparticles. FTIR, TG-DSC, XRD, TEM, SEM, nitrogen adsorption-desorption isotherms, zeta potential, and VSM were used to confirm the synthetic process, structure, and basic properties of MOMMC. The high-saturation magnetization (59.6 emu·g-1) of MOMMC indicated its easy and fast separation from water by an external magnetic field. Kinetics studies showed that the adsorption of Cu(II) and Pb(II) on MOMMC fit the pseudo-second-order model well. Isotherm studies showed that the adsorption behavior of Cu(II) was better described by the Langmuir model, and the adsorption behavior of Pb(II) was better described by both Langmuir and Redlich-Peterson models. MOMMC obtained efficient adsorption for Cu(II) and Pb(II) with the large adsorption capacity of 877.19 and 943.40 mg·g-1 according to the Langmuir adsorption isotherm equation, and a better selectivity for Pb(II) was observed in competitive adsorption. MOMMC still possessed a large adsorption capacity for Cu(II) and Pb(II) after three adsorption-desorption cycles. These findings show that MOMMC represents an excellent adsorption material for the efficient removal of heavy-metal ions.

Preparation of efficient heavy metal adsorbent based on walnut shell and adsorption for Pb(II) ions from aqueous solution

An efficient heavy metal absorbent, amino-terminated hyperbranched polymer modified walnut shell (FWNS) was prepared. The adsorption behavior for Pb(II) ions from aqueous solution was also discussed. The FWNS was prepared using an amino-terminated hyperbranched polymer (ATHBP) as modifying agent and glycidyl methacrylate(GMA) as the grafting bridge. The FWNS was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscope (SEM). The adsorption capacity of FWNS for Pb(II) was investigated at different adsorbent dosages (0.25–2.5gL−1) and pH (from 2.0 to 6.0). The result indicated that the absorbent had good adsorption capacity over a wide pH range (2.0–6.0). The maximum Pb(II) ions adsorption capacity (Qm) obtained by a Langmuir fitting model was 1250.00 mg/g at 293 K. The adsorption kinetics fitted the pseudo-second-order equation. The adsorption of FWNS for Pb(II) ions was an endothermic reaction and spontaneous process. Furthermore, the result shows FWNS has excellent regeneration.

The influence of Pb(II) adsorption on (Non) biodegradable microplastics by UV/O3 oxidation treatment

Widely distributed in the natural environment, microplastics (MPs) may serve as carriers for adsorbing and carrying heavy metal. More research is still required to understand the aging process of MPs and interactions between MPs and heavy metals. In this study, we are going to explore the effects of UV/O3 oxidation on the adsorption behavior of Pb(II) on MPs. The MPs that we include in our study are conventional MPs (PE, polyethylene) and biodegradable MPs (PLA, polylactic acid). The results showed that the UV/O3 oxidation significantly increased its specific surface area and oxygen content, thereby enhancing the adsorption capacity of Pb(II) on MPs. Further, the physicochemical properties of PLA are changed much more than PE after UV/O3 oxidation. In this study, the adsorption process conformed to the pseudo-second-order kinetic and the intraparticle diffusion models, and the adsorption order was aged PLA > aged PE > original PLA > original PE. Their maximum adsorption capacities were 0.98 mg/g, 0.83 mg/g, 0.67 mg/g and 0.54 mg/g, respectively. Studies have implied that the oxidation degree and types of MPs have an impact on their interactions with co-existing pollutants. Overall, These studies indicate that oxidation treatment can alter the structural properties of microplastics while also revealing the Pb(II) sorption kinetics and mechanisms onto the MPs, which will help researchers better understand how MPs interact with heavy metals.

Biosorption of Pb and Cd onto Polygonum sachalinense

Adsorption of Pb and Cd onto a biosorbent, carbonized Polygonum sachalinense (CPS) was investigated. The carbonization condition was 1 h at 350ºC. The adsorption behaviors of Pb and Cd onto CPS could be explained by a proposed adsorption model based on the monodentate binding of the divalent metal ions with two types of adsorption sites. The adsorption sites were considered as carboxylic and phenolic groups based on the results of Boehm titration and FT-IR analysis. The maximum adsorption capacity of CPS for the divalent metal ions was determined as 1.22 mmol/g, and it was much larger than the values reported in the previous reports. The binding affinities of Pb of the adsorption sites were considered as much higher than those of Cd based of the adsorption constants. The adsorption constants of Pb and Cd with carboxylic group were about 200–2000 times larger than the of the adsorption constants with phenolic group. The kinetics of Pb and Cd onto CPS were also investigated. It was found that the adsorption of the divalent metal ions onto the phenolic group was a rate limiting step.

Synchronization adsorption of Pb(Ⅱ) and Ce(Ⅲ) by biochar supported phosphate-doped ferrihydrite in aqueous solution: Adsorption efficiency and mechanisms

Biochar facilitate the dispersion of nanoparticles and improve their adsorption capacity. Herein, we prepared a type of biochar-supported phosphate-doped ferrihydrite (P-FH@BC) for simultaneous uptake of Pb(II) and Ce(Ⅲ). P-FH@BC was prepared by mixing P-FH and biochar at different ratios, and the best ratio is 10:1. Acidic conditions inhibit the adsorption of Pb(Ⅱ) and Ce(Ⅲ) onto P-FH@BC, which was consistent with the result of zeta potential. The adsorption processes of Pb(Ⅱ) and Ce(Ⅲ) are competitive in the binary system. The pseudo-second-order kinetic can explain well the adsorption behavior of Pb(Ⅱ) and Ce(Ⅲ) on P-FH@BC, suggesting a complex chemical adsorption process. The adsorption of Pb(II) and Ce(III) by P-FH@BC included physical and chemical processes. The physical process was mainly contributed by electrostatic attraction and pore filling mechanism. The iron-containing groups, phosphorus-containing groups, oxygen-containing groups on the surface of P-FH@BC, as well as phosphate and iron oxide compounds mainly caused the chemical adsorption. Among them, phosphate, -OH and carbonate could combine with Pb and then form low solubility precipitates, such as Pb3(PO4)2, Pb(OH)2, etc., and iron-containing groups could adsorb Pb through ion exchange. The surface functional groups of P-FH@BC could also combine Pb through the surface complexation reaction. The chemisorption mechanism of Ce(III) by P-FH@BC is obviously different from that of Pb(Ⅱ). The adsorption of Ce(III) was mainly contributed by the phosphorus-containing groups on the surface of P-FH@BC due to the surface complexation. These results have important environmental implications for the simultaneous uptake of heavy metals and rare earth elements from solution.

Removal of Pb (II) and V (V) from aqueous solution by glutaraldehyde crosslinked chitosan and nanocomposites

In this paper, new adsorbents with high mechanical strength chitosan-graphene oxide (CS-GO) and chitosan-titanium dioxide (CS–TiO2) were synthesized by using glutaraldehyde as crosslinking agent, and the adsorption behavior of Pb (II) and V (V) on them were investigated. The materials were characterized by scanning electron microscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The effects of initial metal ion concentration and contact time on the removal of V (V) and Pb (II) by CS-GO and CS-TiO2 were investigated. Characterization results showed that the hydroxyl group of GO/TiO2 reacted with the amino group of chitosan. A comparison of the kinetic models against experimental data showed that the kinetics react system was best described by the pseudo-second-order model. indicating that chemical adsorption was the main adsorption force. the Langmuir adsorption model and Freundlich model agreed well with the experimental data. The removal capacity of Pb (II) by CS-GO and CS-TiO2 were lower than those of V (V). The uncross-linked –OH and CO were the main adsorptive sites for Pb (II) removal, while uncross-linked –OH and –NH2 played an important role in removing V (V). These findings provided insights on the removing lead and vanadium pollution.

Preparation of L-cysteine modified MnFe2O4 nanoparticles based on high-gravity technology and application for the removal of lead

MnFe2O4 nanoparticles, usually applied as a magnetic adsorbent for removing heavy metals in wastewater, have attracted widespread attention for the characteristics of excellent magnetic properties and chemical stability. This study firstly used high-gravity technology coupled with surface modification by L-cysteine to prepare novel L-cysteine modified MnFe2O4 nanocomposite (MnFe2O4-Cys) with small size (< 10 nm), narrow size distribution range and good dispersion in water, and serves as the efficient adsorbent for Pb(II) removal from water. The different preparation conditions were optimized and the obtained products were charactered through a series of characterization methods. As compared to a traditional stirred reactor, the MnFe2O4-Cys prepared via high-gravity technology using impinging stream-rotating packed bed (IS-RPB) reactor (MnFe2O4-Cys-R) has higher crystallinity and saturation magnetization (57.16 emu·g-1). As seen from TEM images and DLS results, the MnFe2O4-Cys-R exhibits a small average size of 7.25 nm and good dispersion in water. Besides, the BET specific surface area of MnFe2O4-Cys-R (169.63 m2·g-1) is 31.2% higher than that of unmodified MnFe2O4 (129.26 m2·g-1) prepared by IS-RPB reactor (MnFe2O4-R). The adsorption behavior of Pb(II) on MnFe2O4-Cys-R is best described by pseudo-second-order kinetic and Temkin isotherm models, respectively, whereas Elovich kinetic and Freundlich isotherm models are best for describing the adsorption of Pb(II) on MnFe2O4-R. The realized experimental maximum adsorption capacity of MnFe2O4-Cys-R is 137.45 mg·g-1, which is 1.98 times that of MnFe2O4-R (69.50 mg·g-1). This study provides a new route for production of small uniform MnFe2O4 nanoparticles with excellent magnetic and adsorption performance for wastewater treatment.

Synthesis of magnetic activated carbon from Citrus hystrix (Kaffir lime or Kolumichai) leaves with excellent Pb(II) adsorption performance towards electroplating wastewater

The adsorption behaviour of Pb(II) ions from aqueous solution has been successfully tested by magnetic activated carbon prepared from novel adsorbent such as Citrus hystrix leaves (MCHLAC) by co-precipitation method and followed by thermal activation. The optimum contact time for the removal Pb(II) ions onto MCHLAC is found to be 90 min, and the optimum pH ranged from 5.0–7.0 respectively. The functionality, surface morphology and elemental composition of MCHLAC have been explored by FTIR, SEM and EDX analysis. The equilibrium data agree well with Langmuir model, which confirm the monolayer coverage of Pb(II) ions onto MCHLAC and the maximum monolayer adsorption capacity is 345.65 mg g-1. The kinetic data follow by pseudo-second order model with film diffusion process. Thermodynamic studies indicate that the process of uptake of lead(II) ions is spontaneous and exothermic. A single –stage batch adsorber is designed using the Langmuir adsorption isotherm equation. The regeneration study show that MCHLAC could be effectively utilized for the removal of Pb(II) ions for seven cycles of operation.

Adsorption of Pb(II) from Aqueous Solutions onto Humic Acid Modified by Urea-Formaldehyde: Effect of pH, Ionic Strength, Contact Time, and Initial Concentration

Humic acid (HA) and urea-formaldehyde (UF) have been frequently reported as heavy metal adsorbents. However, the literature has never written HA modification by UF to improve the adsorbent’s performance. In this study, a new adsorbent of humic acid-urea formaldehyde (HA-UF) was synthesized. The reaction of the conducted the formation of HA-UF –COOH group of HA with the –NH2 group of UF was evidenced by decreasing total acidity from 549.26 cmol/kg (in HA) to 349.30 cmol/kg (in HA-UF). The success of HA-UF formation was characterized by attenuated total reflection-infrared (ATR-IR), energy dispersive X-Ray (EDX), and X-ray diffraction (XRD). The high stability of HA-UF was shown by 96.8% remaining in solid form at pH 12.4. Adsorption behavior of Pb(II) onto HA-UF was influenced by the ionic strength and pH, which were mainly driven by the ion exchange mechanism (EDR = 9.75 kJ/mol). The higher ionic strength will affect decreasing adsorbed Pb(II) at the optimum pH of 5.5. The effect of initial Pb(II) concentration (isotherm) shows that the data fitted well with the Langmuir-b isotherm model indicated the monolayer adsorption of Pb(II) onto homogenous surfaces of the HA-UF with the adsorption capacity of 2.26 × 10–4 mol/g (which is higher than its original HA of 1.12 × 10–4 mol/g). The Ho (pseudo-second-order) kinetics model represented the effect of contact time (kinetics) was represented by the Ho kinetics model. The synthesized adsorbent is also reusable, with 88.59% of adsorption capacity remaining in the fifth recycle run. Therefore, the adsorbent of HA-UF is suggested to be a promising candidate for adsorption applications.

Production of biochar from the combination of foaming drying and pyrolysis of sludge with the additive of Camellia oleifera shell biochar

In this study, a combination of foaming drying and pyrolysis of sewage sludge (SS) with the additive of Camellia oleifera shell biochar (COSC) process was performed to investigate the effects of process parameters on the foaming drying process, and the properties of the produced biochar. The physical and chemical properties of the products were analyzed and the produced biochar was characterized by FTIR, XPS, and XRD analyses. The produced bio-oil was analyzed by gas chromatography-mass spectrometer (GC–MS). Foamed sludge mixed with Camellia oleifera shell biochar (250−850 μm) (COSC-FS) has a higher drying efficiency. Compared with the dried SS, the dried foamed sludge (FS) has lower HHVs, C, H, N, O content, and higher ash content. The main component of bio-oil was nitrogen-containing aliphatic compounds. Though having a lower specific surface area than unfoaming pretreatment, the biochar obtained from the pyrolysis of foamed sludge mixed with Camellia oleifera shell biochar (COSC-FSC) still has a higher adsorption ability for Pb(II) due to co-precipitation. The addition of NaOH had no effect on the pH of solution from Pb(II) adsorption by COSC-FSC. The adsorption behavior of Pb(II) adsorbed onto the COSC-FSC can be well described by pseudo-second-order kinetic model and Langmuir isotherm model with the improved maximum adsorption capacity of 179.33 mg/g. This work provides a promising method for the disposal and the resource utilization of sludge.

Synthesis and Heavy-Metal Sorption Studies of N,N-Dimethylacrylamide-Based Hydrogels.

In this work, a hydrogel system was produced via radical polymerization of N,N-dimethylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid in the presence of N,N-methylene-bis-acrylamide as a crosslinker and ammonium persulfate as an initiator. Parameters that impact the conversion of copolymerization (such as initial concentration of monomers, temperature, initiator dose, and time) were studied. The swelling degree of the hydrogel was investigated with the addition of a crosslinker and initiator at different pH levels. A hydrogel with high conversion and high swelling degree was selected to investigate their ability for adsorption of Pb(II) ions from solutions. Adsorption behavior of Pb(II) ions in a hydrogel was examined as a function of reaction time and concentration of lead ions from a solution of Pb(II) ions.

Design and syntheses of functionalized copper-based MOFs and its adsorption behavior for Pb(II)

A novel copper-based MOFs adsorbent (Cu-BTC-Th) was prepared using an one-step method by introducing a new organic ligand of 4-thioureidobenzoicacid (Th) with active groups for selectively adsorbing Pb(II) from aqueous solutions. The chemical composition and structure of the prepared MOFs materials were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS ), Brunner−Emmet−Teller (BET) analysis, and zeta potential measurements. The adsorption capability of the prepared Cu-MOFs was significantly enhanced by introducing the new organic ligand of Th in the materials. The maximum adsorption capacity of the Cu-BTC-Th for Pb(II) attains 732.86 mg/g under the optimal conditions. In addition, the adsorption kinetics and adsorption isotherm analysis showed that the adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption model, indicating that the adsorption of Pb(II) by Cu-BTC-Th was a monolayer chemisorption. The adsorption mechanism of Cu-BTC-Th for Pb(II) was discussed and revealed. On one hand, the adsorption of Pb(II) is mainly through ion exchange with the Cu(II). On the other hand, the −NH2 and −C=S functional groups introduced in the Cu-BTC-Th materials have stronger coordination ability with the Pb(II) ions to enhance the adsorption capability.

Microstructure of Al-substituted goethite and its adsorption performance for Pb(II) and As(V)

Naturally occurring goethite commonly undergoes Al-substitution, while how changes in microstructure induced by Al-substitution affect the interactive reaction of Pb(II) or As(V) at the goethite-water interface remains poorly understood. This study reveals the structural properties of Al-substituted goethite and its adsorption behavior for Pb(II) and As(V) by multiple characterization techniques and Charge Distribution-Multisite Surface Complexation (CD-MUSIC) modeling. Al-substitution caused an obvious decrease in the length-to-width ratio in goethite particles and a slight decrease in the proportion of (110) facets. The presence of Al-O sites and higher surface roughness induced by Al-substitution contributed to a higher inner Stern layer capacitance (C1) and surface charge density of goethite. CD-MUSIC modeling results further revealed that the affinity constant of Pb(II) complex (log KPb) at the goethite-water interface and the adsorption capacity of goethite for Pb(II) decreased with increasing amount of Al-substitution, while an opposite tendency was observed for As(V) adsorption. The dominant species of both Pb(II) and As(V) on goethite were bidentate complexes, and Al-substitution had a minor impact on the abundance of Pb(II) and As(V) complexes on the surface of goethite. Overall, these experimental and modeling results provide new and important insights into the interfacial reactivity of Al-substituted goethite and facilitate the prediction of the environmental fate of heavy metals.

Enhanced Removal of Pb(II) from Aqueous Solution using EDTA‐Modified Magnetic Graphene Oxide

AbstractEthylenediaminetetraacetic acid (EDTA) groups are successfully linked to magnetic graphene oxide (MGO) by a silanization reaction between N‐(trimethoxysilylpropyl) ethylenediaminetriacetic acid and OH on the surface of MGO. The EDTA‐modification enhances the adsorption capacity of MGO because of the chelating ability of EDTA. The adsorption behavior of Pb(II) and the effects of solution conditions such as contact time, initial Pb(II) concentration, and pH (1–9) are investigated. The adsorption capacity for Pb(II) removal is found to be 211.3 mg g−1 and the adsorption process is completed at pH 6.8 within 50 min. The process is shown to follow a pseudo‐second‐order kinetic rate. The isothermal data reveal that the adsorption process of Pb(II) is well‐matched with the Freundlich model. In addition, the magnetic composite can be effectively and simply separated by an external magnetic field. Therefore, MGO‐EDTA can potentially serve as an adsorbent for the separation and removal of Pb(II) from water.