Effective adsorption of Pb(II) ion from aqueous solution onto ZSM-5 zeolite synthesized from Vietnamese bentonite clay

ZSM-5 zeolite was successfully synthesized from bentonite clay sourced from Lam Dong Province, Vietnam, using the hydrothermal method at 170 °C for 18 h. The synthesized ZSM-5 (SiO2/Al2O3 ratio ~ 34) exhibited a single phase with high crystallinity (91.8%), and a clear and uniform shape. In a detailed examination of the synthesized material's Pb(II) adsorptive capacity, various factors were taken into account, including pH, interaction time, ionic strength, and the amount of adsorbent. Isotherms and kinetics were examined to elucidate the uptake behavior. Study results suggested that Pb(II) ion uptake by ZSM-5 was most appropriately described by the Sips isotherm and intraparticle diffusion kinetic models. The calculated maximum monolayer adsorption capacity according to the Langmuir isotherm model was 48.36 mg/g. Furthermore, the adsorption mechanisms of Pb(II) on ZSM-5 involving electrostatic interactions, ion exchange, and diffusion into pores were demonstrated using the analytical techniques before and after Pb(II) adsorption. These findings demonstrate that ZSM-5 synthesized from bentonite clay exhibits an excellent adsorption capacity for Pb(II), resulting in promising applications for treating drinking water or aqueous industrial waste containing Pb(II) ions.

An MXene-Grafted Terpolymer Hydrogel for Adsorptive Immobilization of Toxic Pb(II) and Post-Adsorption Application of Metal Ion Hydrogel

Toxic metal ions present in industrial waste, such as Pb(II), introduce deleterious effects on the environment. Though the adsorptive removal of Pb(II) is widely reported, there is a dearth of research on the suitable utilization and disposal of the Pb(II)-adsorbed adsorbent. In this work, an MXene-grafted terpolymer (MXTP) hydrogel has been designed for the adsorption of Pb(II) under ambient conditions of pH and temperature. The hydrogel MXTP was synthesized by facile one-pot polymerization in aqueous solvent, and the detailed structural characterization of terpolymer (TP), MXTP, and Pb(II)-loaded MXTP, i.e., Pb(II)-MXTP, was carried out by a combination of proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometric (XRD), thermogravimetric/differential thermogravimetric (TG/ DTG), and field emission scanning electron microscopic (FESEM) analyses. The specific capacitance and conductivities of Pb(II)-MXTP were studied with cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS), which unambiguously indicate successful post-adsorption application. The specific capacitance of MXTP decreased after Pb(II) adsorption, whereas the conductivity increased significantly after Pb(II) adsorption, showing that MXTP can be successfully deployed as a solid electrolyte/anode after Pb(II) adsorption. This study covers the synthesis of a novel MXene-grafted terpolymer hydrogel for adsorptive exclusion of Pb(II) and assessment of the as-adsorbed Pb(II)-loaded hydrogel as a solid electrolyte/anode material and is the first demonstration of such post-adsorptive application.

Chitosan cross-linked and grafted with epichlorohydrin and 2,4-dichlorobenzaldehyde as an efficient adsorbent for removal of Pb(II) ions from aqueous solution

Epichlorohydrin-modified chitosan-Schiff base composite (CS/24Cl/ECH) prepared via the one-pot reaction as characterized by Fourier transform Infra-Red spectroscopy (FT-IR), X-ray powder diffraction (XRD), Differential scanning calorimetry (DSC) and Scanning electron microscope (SEM). Its removal ability of Pb(II) ions from aqueous solution was investigated. The adsorption of Pb(II) ions carried out at different initial pH, dose of CS/24-Cl/ECH, contact time and co-existing ions. The maximum adsorption capacity of Pb(II) ions was 170 mg/g. Finally, based on the absorption results, the adsorption of Pb(II) ions was fitted by single-layer Langmuir isotherm model and the pseudo-second-order (PSO) kinetics model. The absorption mechanism of Pb(II) ions was controlled by chemical coordination Pb(II) ions with the active sites on the surface of CS/24Cl/ECH composite. Also, CS/24Cl/ECH showed excellent recyclable efficiency up to 5 cycle and potential sorbent for other heavy metal ions.

Adsorptive performance and mechanism exploration of l-lysine functionalized celluloses for enhanced removal of Pb(II) from aqueous medium

In this study, two novel biosorbents of l-lysine grafted cellulose (L-PCM, L-TCF) were prepared for Pb(II) removal from aqueous solutions. Various adsorption parameters were surveyed, such as adsorbent dosages, initial concentration of Pb(II), temperature and pH, using adsorption techniques. At normal temperature, less adsorbent can achieve better adsorption capacity (89.71 ± 0.27 mg g^-1 with 0.5 g L^-1 of L-PCM, 16.84 ± 0.02 mg g^-1 with 3.0 g L^-1 of L-TCF). The pH range of application for L-PCM was 4-12 and that of L-TCF was 4-13. The adsorption of Pb(II) by biosorbents went through the boundary layer diffusion stage and void diffusion stage. The adsorption mechanism was chemisorption based on multilayer heterogeneous adsorption. The pseudo-second-order model fitted the adsorption kinetics perfectly. The Freundlich isotherm model adequately described Multimolecular equilibrium relationship between Pb(II) and biosorbents; the predicted maximum adsorption capacities of the two adsorbents were 904.12 and 46.74 mg g^-1, respectively. The results showed that the adsorption mechanism was the electrostatic attraction between Pb(II) and -COOH and the complexation between Pb(II) and -NH₂. This work demonstrated that l-lysine modified cellulose-based biosorbents have great potential in the field of Pb(II) removal from aqueous solutions.

Adsorption of lead ions by activated carbon doped sodium alginate/sodium polyacrylate hydrogel beads and their in-situ recycle as sustainable photocatalysts

In this study, sodium alginate (SA), sodium polyacrylate (PAAS) and powdered activated carbon (PAC) were cross-linked by calcium ions [(Ca(II)] to form SA/PAAS/PAC (SPP) hydrogel beads. The hydrogel-lead sulfide (SPP-PbS) nanocomposites were successfully synthesized by in-situ vulcanization after the lead ions [(Pb(II)] adsorption. SPP showed an optimal swelling ratio (600% at the pH value of 5.0) and superior thermal stability (206 °C of heat-resistance index). The adsorption data of Pb(II) was compatible with the Langmuir model, and the maximum adsorption capacity of SPP was 391.65 mg/g after optimizing the mass ratio of SA to PAAS (3:1). The addition of PAC not only enhanced the adsorption capacity and stability, but also promoted photodegradation. The significant dispersive capacity of PAC and PAAS resulted in PbS nanoparticles with particle sizes of around 20 nm. SPP-PbS showed good photocatalysis and reusability. The degradation rate of RhB (200 mL, 10 mg/L) was 94% within 2 h and maintained above 80% after 5 cycles. The treatment efficiency of SPP was more than 80% in actual surface water. The results of quenching experiments and electron spin resonance (ESR) experiments revealed that the superoxide radicals (O₂^-) and holes (h⁺) were the main active species in the photocatalytic process.

Efficient Removal of Pb(Ⅱ) by Highly Porous Polymeric Sponges Self-Assembled from a Poly(Amic Acid)

Lead (II) (Pb(II)) is widespread in water and very harmful to creatures, and the efficient removal of it is still challenging. Therefore, we prepared a novel sponge-like polymer-based absorbent (poly(amic acid), PAA sponge) with a highly porous structure using a straightforward polymer self-assembly strategy for the efficient removal of Pb(II). In this study, the effects of the pH, dosage, adsorption time and concentration of Pb(II) on the adsorption behavior of the PAA sponge are investigated, revealing a rapid adsorption process with a removal efficiency up to 89.0% in 2 min. Based on the adsorption thermodynamics, the adsorption capacity increases with the concentration of Pb(II), reaching a maximum adsorption capacity of 609.7 mg g^-1 according to the Langmuir simulation fitting. Furthermore, the PAA sponge can be efficiently recycled and the removal efficiency of Pb(II) is still as high as 93% after five adsorption-desorption cycles. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses reveal that the efficient adsorption of Pb(II) by the PAA sponge is mainly due to the strong interaction between nitrogen-containing functional groups and Pb(II), and the coordination of oxygen atoms is also involved. Overall, we propose a polymer self-assembly strategy to easily prepare a PAA sponge for the efficient removal of Pb(II) from water.

Adsorptive removal of Pb(II) using nanostructured γ-alumina in a packed bed adsorber: Simulation using gPROMS

In this work, convective-dispersive and pore volume and surface diffusion models have been used to analyze Pb(II) adsorption from an aqueous solution over a nanostructured γ-alumina adsorbent in a packed bed adsorber. The models encompassing partial differential equation and a linear algebraic equation coupled with isotherm have been simulated in gPROMS using the backward finite difference approach. The predicted breakthrough curves of Pb(II) adsorption concerning flow rate, initial metal concentration, and bed height were matched with the experimental data. The accuracy of model predictions was analyzed through statistical measures such as coefficient of determination (R²), root mean square error, and chi-squared value. The simulation results also predicted the axial dispersion, distribution coefficient, mass transfer coefficient, pore volume, and surface diffusion coefficient, which are, otherwise, difficult to measure experimentally and, in turn, have been used to assess the mass transfer characteristics of continuous Pb(II) adsorption. Additionally, the values of breakthrough time, exhaustion time, adsorption column capacity, and mass transfer zone were determined as a function of flow rate, bed height, and initial metal concentration. Surface and pore volume diffusions (10^-11-10^-10 m²/s) apparently controlled the continuous adsorption process, with surface diffusion being dominant. The transport parameters evaluated in the current study could be beneficial for the large-scale Pb(II)/nanostructured γ-alumina adsorption system. As evident from the successful simulation, the developed gPROMS program can also be applied to other adsorbate/adsorbent systems with a slight modification concerning the operating parameters.

Preparation of Citric Acid-Sewage Sludge Hydrochar and Its Adsorption Performance for Pb(II) in Aqueous Solution

In order to seek the value-added utilization method of sewage sludge and develop low-cost and high-efficient adsorbents, a hydrochar was prepared by the co-hydrothermal carbonization of sewage sludge and citric acid and then characterized. The differences in Pb(II) adsorption performance between the citric acid–sewage sludge hydrochars (AHC) and the hydrochar prepared solely from sewage sludge (SSHC) were also investigated. When citric acid dose ratio (mass ratio of citric acid to dry sewage sludge) is 0.1, the obtained hydrohcar (AHC0.1) has the highest specific surface area (59.95 m²·g⁻¹), the most abundant oxygen-containing functional groups, the lowest pH_pzc (5.43), and the highest equilibrium adsorption capacity for Pb(II). The maximum adsorption capacity of AHC0.1 for Pb(II) is 60.88 mg·g⁻¹ (298 K), which is approximately 1.3 times that of SSHC. The potential mechanisms can be electrostatic attraction, co-precipitation, complexation, and cation-π interaction. It was demonstrated that by incorporating citric acid into the hydrothermal carbonization, resource utilization of sewage sludge can be accomplished effectively.

Ultra-deep removal of Pb by functionality tuned UiO-66 framework: A combined experimental, theoretical and HSAB approach

A specific functionality in the adsorbent materials plays a significant role for the selective capture of heavy metals based on Pearson's Hard-Soft-Acid-Base (HSAB) concept. Herein, we introduced single and double amino- and thiol-functionalities into the UiO-66 framework, which acted as hard and soft base sites for heavy metal adsorption, respectively. The synthesized adsorbents (labelled as NH₂-UiO-66, (NH₂)₂-UiO-66, SH-UiO-66 and (SH)₂-UiO-66) were applied for the selective removal of lead (Pb) ions from contaminated water. The removal efficiency of Pb was about 64, 85, 75 and 99% (pH = 6, T = 30 °C, sample dosage = 10 mg, Pb concentration = 100 mg L^-1), respectively, based on available number of interacting sites in the respective adsorbent. To elaborate HSAB concept, the interacting sites of these functional groups towards Pb were explored by identifying their possible types of interactions in terms of soft acid-base affinity, coordinate and covalent bonding, chelation, π-π interactions and synergetic effect of bonding. Density functional theory (DFT) simulation was used to confirm these interactions and to help the better understanding of adsorption mechanism. Model fitting and characterization of Pb-sorbed adsorbents were also performed to reveal kinetics, order of adsorptive reaction, thermodynamics and adsorption mechanism. Moreover, the optimization of adsorptive removal was performed by controlled parameters including time, initial concentration, pH and temperature. The reusability and selectivity of these adsorbents along with recovery of Pb(II) were also assessed. This study presents the conceptual framework for the design of functional adsorbents in the removal of heavy metals using the HSAB principle as an intended guideline.

Efficient Removal of Pb(II) from Aqueous Systems Using Spirulina-Based Biohybrid Magnetic Helical Microrobots

Wastewater remediation toward heavy metal pollutants has attracted considerable attention, and various adsorption-based materials were employed in recent years. However, it is still challenging to explore low-cost and high-efficient adsorbents with superior removal performance, nontoxicity, flexible operation, and good reusability. Herein, Fe3O4- and MnO2-loaded biohybrid magnetic helical microrobots (BMHMs) based on Spirulina cells were presented for the first time, and their performance on Pb(II) removal was studied in detail. Intracellular synthesis of Fe3O4 and MnO2 nanoparticles into Spirulina cells was successively conducted to obtain the BMHMs with superparamagnetism and high surface activity. The BMHMs could be flexibly propelled under magnetic actuation, and collective cork-screw spinning was performed to enhance fluidic diffusion with intensive adsorption. Rapid and significant removal of Pb(II) in wastewater was achieved using the swarming microrobots, and a high adsorption capacity could be reached at 245.1 mg/g. Moreover, the BMHMs could be cyclically reutilized after simple regeneration, and good specificity toward Pb(II) was verified. The adsorption mechanism was further studied, which revealed that the pseudo-second-order kinetics dominated in the adsorption process, and the Langmuir isothermal model also fitted the experimental results well. The intriguing properties of the BMHMs enable them to be versatile platforms with significant potentials in wastewater remediation.

Facile preparation of sulfhydryl modified montmorillonite nanosheets hydrogel and its enhancement for Pb(II) adsorption

In the work, sulfhydryl functionalized montmorillonite nanosheets based hydrogel balls were firstly synthesized for Pb(II) adsorption, and then characterized by scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), surface area analyzer (BET), thermogravimetry (TG), and zeta potential. Effects of initial solution pH, adsorbent dosage, contact time, temperature on Pb(II) adsorption of the resulting hydrogel balls were investigated systematically. The experimental results showed that the increase amount of sulfhydryl functionalized montmorillonite nanosheets (MMTNs-SH) maintained the hydrogel balls a better porous structure and bigger specific surface area, endowing it a bigger adsorption capacity. The adsorption process was fitted well with pseudo-second-order kinetics model and Freundlich model, and more than 97% of Pb(II) could be removed under the optimum conditions. Moreover, hydrogel spheres have a certain cycle performance. In addition, the interactions between Pb(Ⅱ) ions and the oxygen atoms in the hydroxyl groups and the sulfur atoms in the sulfhydryl groups, and the ion exchange in MMTNs-SH dominated the adsorption.

Facile preparation of MoS2@Kaolin composite by one-step hydrothermal method for efficient removal of Pb(II)

MoS₂@Kaolin was prepared by facile one-step hydrothermal method for the efficient adsorption of Pb(II) from aqueous solution. XRD, TG, SEM, BET, XPS and FTIR were used to characterize the phase and structure of composite before and after the adsorption of Pb(II). The results showed that MoS₂ nanosheets were successfully assembled on kaolinite surface to form MoS₂@Kaolin, and the adsorption capacity of the MoS₂@Kaolin is 1.74 and 16.95 times than that of single MoS₂ and kaolinite, respectively. MoS₂@Kaolin composite exhibited a fast adsorption rate for Pb(II) and an excellent adsorption efficiency for Pb(II) in a wide pH range (2-5.5). The adsorption process followed the Langmuir isotherm model and maximum adsorption capacity was 280.39 mg/g. The adsorption kinetics of MoS₂@Kaolin composite to Pb(II) fitted well with the pseudo-second-order kinetics models, which showed that the adsorption process was controlled by chemical sorption. MoS₂@Kaolin showed excellent regeneration and maintained high selectivity adsorption with co-existence metal ions. The adsorption mechanism was that the Pb(II) reacted with the S atoms on surface of MoS₂@Kaolin under oxidation conditions provided by molybdenum disulfide to form the insoluble compound β-Pb₃O₂SO₄ in aqueous solution. MoS₂@Kaolin was an adsorbent for Pb(II) in aqueous solution with excellent adsorption properties and application potential.

Industrial alkali lignin-derived biochar as highly efficient and low-cost adsorption material for Pb(II) from aquatic environment

Developing a cost-effective and high-efficiency biochar is critical in various environmental applications. Lignin-based materials are natural and abundant adsorbents to heavy metals benefited from their special polyphenol structure and physicochemical properties. In this study, adsorption capacities to Pb(II) by alkali lignin (AL) and its biochar derivative (ALB) were comparatively discussed, and the latter exhibited superior adsorption performance, with a maximum adsorption capacity almost twice that of the former, and a much faster absorption rate. The q_m value of ALB was significantly superior to that of other reported biochar materials. Pb(II) was mainly adsorbed into ALB in three forms: mineral precipitation, ion exchange, and surface complexation, with complexation and mineral precipitation being the dominant mechanisms of adsorption. This study demonstrates that alkali-lignin derived biochar is a promising material for the remediation of polluted by Pb(II).

Exploring of toxic Pb(II) removal by low-cost bio-adsorbent of camphor leaf forestry waste after camphor oil extraction

Camphor leaf (CL) was widely used to extract camphor oil and thus led to abundant forestry waste. In order to reduce pollution, the waste CL was used to prepare bio-adsorbent for Pb(II) removal after alkali treatment and functional modification. The effects of solution pH, initial Pb(II) concentration, contact time and solution temperature were investigated on adsorption process to evaluate the potential application in heavy metal ions' removal. It was found that the massive hydroxyl groups released and plenty of micro-pores formed after the alkali treatment of CL bio-adsorbent, which obviously increased the Pb(II) adsorption. And the adsorption performance promoted continually after further functional modification by ionized 1,2,3,4-butanetetracarboxylic acid (BTCA). The increase of pH was favourable for the adsorption even though the precipitation effect was deducted. Linear fitting method was more suitable to describe the adsorption process than nonlinear fitting method, including adsorption isotherms and adsorption kinetics research. The adsorption thermodynamics was better to be described by nonlinear fitting method due to its lower root mean square error (RMSE) value and higher R² value. Among which, the adsorption isotherm and adsorption kinetics were fitted well to Langmuir model and pseudo-second-order model, respectively. The adsorption thermodynamics was exothermic in nature and the process was spontaneous at low solution temperature. The adsorption mechanism was revealed as the combination of dominant chemical adsorption and assistant physical adsorption.

Multi-edged molybdenite achieved by thermal modification for enhancing Pb(II) adsorption in aqueous solutions

Thermal modification was simply performed on molybdenite to enhance the adsorption of Pb(II) in aqueous solutions, and the root of this phenomenon was well studied in this work. Various thermal modification temperatures at 300 °C, 400 °C and 500 °C were applied to modify the surface property of molybdenite, producing different degrees of edge defect and surface wettability in molybdenite samples. Contact angle tests, atomic force microscopy (AFM) observations and adsorption tests illustrated that molybdenite thermally modified at 400 °C contained most edge defects and achieved a 147.846 mg/g Pb(II) adsorption, which was almost 10 times of that obtained by natural molybdenite. The adsorption experiment also indicated that the increase of surface hydrophilia of molybdenite would slightly benefit the Pb(II) adsorption. The X-ray photoelectron spectroscope (XPS) exhibited that a strong chemical adsorption existed between Pb(II) and S elements. AFM study further demonstrated that the interaction between Pb(II) and S atoms exposed at the triangular edges of molybdenite were the intrinsic reason for the great enhancement of Pb(II) adsorption. This work provides a new insight to absorb Pb(II) in aqueous solutions using natural molybdenite.

The effects of carbon disulfide driven functionalization on graphene oxide for enhanced Pb(II) adsorption: Investigation of adsorption mechanism

The surface properties of graphene oxide (GO) have been identified as the key effects on the adsorption of Pb(II) from aqueous solutions in this study. This study reveals the effect of the surface reactivity of GO via Carbon Disulfide (CS₂) functionalization for Pb(II) adsorption. After successfully preparing CS₂ functionalized GO (GOCS), the specific techniques were applied to investigate Pb(II) adsorption onto GOCS. Results indicated that the new sulfur-containing functional groups incorporated onto GOCS significantly enhanced Pb(II) adsorption capacity on GOCS than that of GO, achieving an improvement of 31% in maximum adsorption capacity increasing from 292.8 to 383.4 mg g^-1. The equilibrium adsorption capacity for GOCS was 280.2 mg g^-1 having an improvement of 83.2% over that of 152.97 mg g^-1 for GO at the same initial concentration of 150 mg L^-1 under the optimal pH of 5.7. Moreover, the results of adsorption experiments showed an excellent fit to the Langmuir and Pseudo-Second-Order models indicating the monolayer and chemical adsorption, respectively. The mechanism for Pb(II) adsorption on GOCS was proposed as the coordination, electrostatic interactions, cation-pi interactions, and Lewis acid-base interactions. The regeneration study showed that GOCS had an appreciable reusability for Pb(II) adsorption with the adsorption capacity of 208.92 mg g^-1 after five regeneration cycles. In summary, GOCS has been proved to be a novel, useful, and potentially economic adsorbent for the high-efficiency removal of Pb(II) from aqueous solutions.

Impacts of carbonization temperature on the Pb(II) adsorption by wheat straw-derived biochar and related mechanism

To determine the quantitative correlations between physicochemical characteristics and Pb(II) adsorption amounts of biochar fractions, we prepared wheat straw-derived biochar under various carbonization temperatures (300-900 °C). The different fractions of the wheat straw-derived biochar, water-soluble material (WM), acid-soluble material (AM), and organic material (OM), were acquired. The ash content, ultimate analysis, pH, ion strength (IS), cation exchange capacity (CEC), and acidic functional groups (AFG) were characterized. The Pb(II) adsorption amounts of different biochars and their fractions were determined. The results revealed that the proportions of biochar fractions (WM, AM, and OM) varied with various carbonization temperatures. The maximum Pb(II) adsorption amount of wheat straw-derived biochar (q_Total) was 157.95 ± 0.13 mg/g obtained at 800 °C, and the quantitative correlations between Pb(II) adsorption amount (q) and carbonization temperature (T) can be elaborated by q_Total = 170.72-336.62exp(-0.0035T) (R² = 0.97), q_WM = 106.18-390.10exp(-0.0046T) (R² = 0.98), q_AM = 496.16-477.74exp(-0.0001T) (R² = 0.79), and q_OM = 1.80 + 34.69exp(-0.0038T) (R² = 0.85). For rate of contribution (RC) for Pb(II) adsorption, when T < 400 °C, the order was AM (60.72 ± 7.33%) > OM (23.41 ± 7.33%) > WM (15.87 ± 0.30%); however, when T ≥ 400 °C, the order was WM (52.31 ± 0.85% - 67.65 ± 2.99%) > AM (29.65 ± 0.46% - 35.77 ± 0.12%) > OM (2.30 ± 0.47% - 12.02 ± 2.43%). Moreover, q_WM and q_AM exhibited significant positive linear correlations with ash (q_WM = 9.92Ash - 123.65, and q_AM = 2.13Ash - 0.49), q_Total was predominantly affected by ash content (q_Total = 10.97 Ash - 95.49). The EDX, XRD, and FTIR analysis results further clarified that ion exchange and precipitation were the main adsorption mechanisms for Pb(II) adsorption by wheat straw-derived biochar.

In situ polymerization of magnetic graphene oxide-diaminopyridine composite for the effective adsorption of Pb(II) and application in battery industry wastewater treatment

The efficient removal of heavy metals from aqueous environment is imperative and challenging. A novel ternary composite constructed of diaminopyridine polymers, graphene oxide, and ferrite magnetic nanoparticles was designed by a facile in situ polymerization strategy for the removal of Pb(II) from aqueous solution. Detailed characterization of morphological, chemical, and magnetic properties was employed systematically to confirm the formation of the composite material. Batch adsorption experiment studies suggested that the composite was an excellent adsorbent for Pb(II) which was easily collected after use via exposure to an external magnetic field for 30 s. The effects of different parameters such as solution pH, adsorbent dosage, contact time, initial Pb(II) concentration, temperature, and co-existing ions were examined. The maximum adsorption capacity at pH = 5 was estimated to be 387.2 mg g^-1 at 298 K by the Langmuir isotherm model, accompanied by favorable adsorption recyclability according to the investigation of regeneration experiments. Thermodynamic studies revealed that the Pb(II) adsorption via our ternary composite was endothermic and spontaneous. The corresponding removal performance for effluent containing Pb(II) from the battery industry was successfully examined. The present results indicated that our designed adsorbent is beneficial to the practical Pb(II) removal in wastewater purification.

Carbonization and ball milling on the enhancement of Pb(II) adsorption by wheat straw: Competitive effects of ion exchange and precipitation

Straw biomass is a promising adsorbent for the removal of heavy metals. To improve its Pb(II) adsorption capacity and elucidate competition of adsorption mechanisms (e.g., ion exchange and precipitation), the Pb(II) adsorption mechanisms for wheat straw (WS-CK), wheat straw-biochar (WS-BC), and ball-milled wheat straw-biochar (WS-BC + BM) samples were investigated in detail by EDX, XRD, and FTIR. The results implied that the Pb(II) adsorption capacities at an adsorbent dosage of 0.2 g/L onto WS-CK, WS-BC, and WS-BC + BM were 46.33, 119.55, and 134.68 mg/g, respectively. This indicates that carbonization and ball milling are efficient techniques for improving the adsorption capacity of Pb(II) onto wheat straw, as WS-BC and WS-BC + BM exhibited adsorption capacities comparable to other commonly used bioadsorbents. Carbonization contributed significantly to precipitation (e.g., PbCO₃ and Pb₃(CO₃)₂(OH)₂). Furthermore, competition existed between ion exchange and precipitation during the Pb(II) adsorption process. With relative lower adsorbent dosages, carbonization and ball milling enhanced ion exchange capacity.

Novel ternary nanohybrids of tetraethylenepentamine and graphene oxide decorated with MnFe2O4 magnetic nanoparticles for the adsorption of Pb(II)

Novel ternary nanohybrids, consisting of tetraethylenepentamine (TEPA), graphene oxide (GO) and manganese ferrite magnetic nanoparticles (TEPA-GO/MnFe₂O₄), were prepared by a facile hydrothermal method and utilized to remove Pb(II) from aqueous solution effectively. The adsorbents were characterized by SEM, TEM, XRD, FTIR, zeta potential analysis, magnetization hysteresis loop, BET and XPS. These nanoparticles exhibited superparamagnetic behavior as well as high removal efficiency for Pb(II). Moreover, numerous amino groups of the functionalized pendant TEPA on GO coupled with the porous structure of TEPA-GO/MnFe₂O₄ contribute to high Pb(II) adsorption capacity. The maximum Pb(II) adsorption capacity of TEPA-GO/MnFe₂O₄ was determined to be 263.2 mg/g at the optimized solution pH of 5.5, much higher than that of GO/MnFe₂O₄ (133.3 mg/g) and GO (196.1 mg/g). The kinetics and isotherm data fitted well with the pseudo-second-order kinetics and the Langmuir isotherm model, respectively. Thermodynamic studies revealed that the Pb(II) adsorption of TEPA-GO/MnFe₂O₄ was a endothermic and spontaneous process. The experimental results corroborated that TEPA-GO/MnFe₂O₄ can be efficaciously reused after washed with HCl, indicative of its potential applications in environmental cleanup.