Adsorption Of Pb Research Articles

Comparison of the Effects of Different Organic Amendments on the Immobilization and Phytoavailability of Lead

Organic materials, such as straw, animal manure, and their processed product biochar, are known to exhibit agronomic effects and the ability to remediate heavy metal contamination. However, knowledge regarding the relative effects of different organic amendments in soils on heavy metal immobilization and phytoavailability remain limited. Consequently, the effects of maize straw (MS), chicken manure (CM), mushroom cultivation waste (MW), and sawdust biochar (SB) on the immobilization and phytoavailability of lead (Pb) in wheat plants were investigated in this study using pot experiments. The results showed that the artificial application of Pb reduced soil pH, while increasing the total organic carbon (TOC) and cation exchange capacity (CEC) to various extents. Furthermore, the Pb treatment increased the adsorption of Pb by wheat grains (0.83 mg∙kg−1), resulting in decreased above-ground dry biomass (43.16 g∙pot−1) during the maturity growth period when compared with the control check (CK) treatment. The MS + Pb and CM + Pb treatments increased the exchangeable Pb fractions in the soil, but had a limited effect on Pb accumulation in wheat grains compared with the Pb treatment. In contrast, the SB + Pb treatment effectively increased soil pH and TOC, while decreasing the fraction of exchangeable Pb forms and increasing the oxidizable and residual Pb fractions, compared with the Pb treatment. Moreover, the MW + Pb treatment also increased the soil pH and CEC, displaying the potential to increase soil TOC, in addition to substantially modifying the portioning of Pb from exchangeable forms to less bioavailable fractions. Both the MW and SB amendments significantly reduced Pb concentrations in wheat grains (0.49 and 0.70 mg∙kg−1,∙respectively), resulting in increased above-ground dry biomass (51.59 and 54.12 g∙pot−1, respectively). In summary, the application of organic amendments, especially MW, could be an effective measure for enhancing Pb immobilization in polluted soils, thereby reducing its uptake and translocation to crops.

A novel green synthesis of MnO2-Coal composite for rapid removal of silver and lead from wastewater

The presence of Ag(I) and Pb(II) ions in wastewater poses a significant threat to human health in contemporary times. This study aims to explore the development of a novel and economical adsorbent by grafting MnO2 particles onto low-rank coal, providing an innovative solution for the remediation of water contaminated with silver and lead. The synthesized nanocomposites, referred to as MnO2-Coal, underwent thorough characterization using FTIR, XRD, BET, and SEM to highlight the feasibility of in-situ surface modification of coal with MnO2 nanoparticles. The adsorption of Ag(I) and Pb(II) from their respective aqueous solution onto MnO2-Coal was systematically investigated, with optimization of key parameters such as pH, temperature, initial concentration, contact time, ionic strength, and competing ions. Remarkably adsorption equilibrium was achieved within a 10 min, resulting in impressive removal rates of 80–90 % for both Ag(I) and Pb(II) at pH 6. The experimental data were evaluated using Langmuir, Freundlich, and Temkin isotherm models. The Langmuir isotherm model proved to be more accurate in representing the adsorption of Ag(I) and Pb(II) ions onto MnO2-Coal, exhibiting high regression coefficients (R2 = 0.99) and maximum adsorption capacities of 93.57 and 61.98 mg/g, along with partition coefficients of 4.53 and 71.92 L/g for Ag(I) and Pb(II), respectively, at 293 K. Kinetic assessments employing PFO, PSO, Elovich, and IPD models indicated that the PFO and PSO models were most suitable for adsorption mechanism of Pb(II) and Ag(I) on MnO2-Coal composites, respectively. Moreover, thermodynamic evaluation revealed the spontaneous and endothermic adsorption process for Ag(I), while exothermic behavior for adsorption of Pb(II). Importantly, this approach not only demonstrates cost-effectiveness but also environmental friendliness in treating heavy metal-contamination in water. The research suggests the potential of MnO2-Coal composites as efficient and sustainable adsorbents for water purification applications.

Tetraethylenepentamine-Grafted Amino Terephthalic Acid-Modified Activated Carbon as a Novel Adsorbent for Efficient Removal of Toxic Pb(II) from Water.

In this study, a new composite, tetraethylenepentamine (TEPA), was incorporated into amino terephthalic acid-modified activated carbon (ATA@AC) through a one-pot integration of TEPA with the COOH moiety of ATA@AC. This process resulted in the creation of a TEPA@ATA@AC composite for Pb(II) removal from an aquatic environment. Several techniques, including SEM, EDX, FT-IR, TGA, XRD, and Zeta potential, were employed to emphasize the chemical composition, morphology, and thermal durability of the as-synthesized TEPA@ATA@AC composite. The impact of experimental variables on the adsorption of Pb(II) ions was studied using batch adsorption. The uptake assessment suggested that the TEPA@ATA@AC composite exhibited superior Pb(II) removal performance with high removal efficiency (97.65%) at pH = 6.5, dosage = 0.02 g, equilibrium time = 300 min, and temperature = 298 K. The isotherm data exhibited good conformity with the Langmuir isotherm model, whereas the kinetics data displayed strong agreement with both pseudo-first-order and pseudo-second-order kinetics models. This reflected that the Pb((II) uptake by the TEPA@ATA@AC composite was caused by physisorption coupled with limited chemisorption. The greatest monolayer uptake capacity of the TEPA@ATA@AC composite was 432.8 mg/g. The thermodynamic findings indicated that the Pb(II) uptake on the TEPA@ATA@AC composite was an exothermic and feasible process. After five adsorption-desorption runs, the TEPA@ATA@AC composite maintained a superior uptake capacity (83.80%). In summary, the TEPA@ATA@AC composite shows promise as a potent adsorbent for effectively removing Cr(VI) from contaminated water, with impressive removal efficiency.

Fe3O4/Graphene Oxide/Chitosan Nanocomposite: A Smart Nanosorbent for Lead(II) Ion Removal from Contaminated Water.

A new graphene oxide (GO) nanocomposite that contains chitosan, a biological polymer, combined with a magnetic nanoparticle inorganic material (Fe3O4) was successfully prepared and applied for the adsorption of Pb(II) from aqueous solutions. The structural and morphological properties of the GO/Fe3O4/CS (GFC) nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Influent factors for Pb(II) adsorption, including the contacting time, pH of the working medium, working temperature, and adsorbent dosage on the adsorption efficiency, have been optimized. Under optimized conditions, the adsorption isotherm results indicated that the Langmuir model provided a better description for the adsorption of Pb(II) onto the GFC nanosorbent than the Freundlich model. The maximum adsorption capacity (qmax) was 63.45 mg g-1. The pseudo-second-order kinetic model (R2 = 0.999) was fitted with the experimental results, implying that the adsorption of Pb(II) onto GFC is a chemical process. The thermodynamic studies demonstrated the exothermic nature of the adsorption process. Another advantage of the GFC nanosorbent for Pb(II) removal is its capability to be easily recovered under the use of an external magnet and subsequently regenerated. Our work demonstrated that the removal efficiency was stable after several regeneration cycles (i.e., approximately 12% reduction after four successive adsorption-desorption cycles), implying that the GFC nanosorbent exhibits satisfactory regeneration performance. Therefore, with high removal efficiency, high adsorption capacity, and stable reusability, the GFC nanocomposite is a remarkable application potential adsorbent for the in situ treatment of Pb(II) ion-containing aqueous solutions.

A Review on Biochar as an Adsorbent for Pb(II) Removal from Water

Heavy metal contamination in drinking water is a growing concern due to its severe health effects on humans. Among the many metals, lead (Pb), which is a toxic and harmful element, has the most widespread global distribution. Pb pollution is a major problem of water pollution in developing countries and nations. The most common sources of lead in drinking water are lead pipes, faucets, and plumbing fixtures. Adsorption is the most efficient method for metal removal, and activated carbon has been used widely in many applications as an effective adsorbent, but its high production costs have created the necessity for a low-cost alternative adsorbent. Biochar can be a cost-effective substitute for activated carbon in lead adsorption because of its porous structure, irregular surface, high surface-to-volume ratio, and presence of oxygenated functional groups. Extensive research has explored the remarkable potential of biochar in adsorbing Pb from water and wastewater through batch and column studies. Despite its efficacy in Pb removal, several challenges hinder the real application of biochar as an adsorbent. These challenges include variability in the adsorption capacity due to the diverse range of biomass feedstocks, production processes, pH dependence, potential desorption, or a leaching of Pb from the biochar back into the solution; the regeneration and reutilization of spent biochar; and a lack of studies on scalability issues for its application as an adsorbent. This manuscript aims to review the last ten years of research, highlighting the opportunities and engineering challenges associated with using biochar for Pb removal from water. Biochar production and activation methods, kinetics, adsorption isotherms, mechanisms, regeneration, and adsorption capacities with process conditions are discussed. The objective is to provide a comprehensive resource that can guide future researchers and practitioners in addressing engineering challenges.

Adsorption mechanism of Cs+ and Pb2+ on the N-A-S-H surface under the different Si/Al ratio and temperature

The application of low-calcium alkali-activated geopolymers has significantly enhanced the removal of Pb2+ and Cs+ from the contaminated soils and water. However, the adsorption mechanisms of Pb2+ and Cs+ influenced by the temperature and Si/Al at the molecular scale remain unclear, which were the two critical factors influencing the adsorption capacity. This study employed molecular dynamics simulation to elucidate the effects of temperature and Si/Al ratio on the adsorption mechanism and behavior of Pb2+ and Cs+ on the N-A-S-H surface. Research findings demonstrate that the adsorption of Pb2+ and Cs+ on the N-A-S-H surface is attributed to chemical adsorption. Increasing temperature can regulate the removal ratio of heavy metal ions by enhancing the quantity of cation exchange (correlation coefficient of 0.88). Temperature also influences the removal ratio by changing in adsorption energy, potential of mean force, and controlling the maximum adsorption capacity, hydration, and diffusion ability of the heavy metals (correlation coefficient of 0.67, 0.55, 0.6, and 0.57). While the Si/Al ratio influences the adsorption of heavy metals by enhancing the negative charge density of N-A-S-H gel and strengthening the interaction between heavy metals and oxygen atoms on the N-A-S-H surface (correlation coefficient of 0.96 and 0.52). Additionally, temperature exhibits a more pronounced effect on enhancing in the removal ratio of heavy metals. The heavy metal removal was maximally increased by 435 % (for Cs+) and 439 % (for Pb2+) via elevated temperature, while it was increased by 63 % (for Cs+) and 98 % (for Pb2+) via decreased Si/Al ratio. This study can not only provide a new perspective on the removal of heavy metals by N-A-S-H gel, but also can contribute to the achievement of green and sustainable development goals.

A new insight into the surface adsorption in the solution phase: A modification of the Langmuir isotherm.

The Langmuir isotherm, originally developed to study the adsorption of gases, has been modified in this research to investigate the adsorption of solutes in the solution phase. The modification considers the adsorption of solvent molecules and the interactions between adsorbed particles and the species in the solution. Three equations have been obtained to calculate the contribution of these additional effects on the Gibbs free energy, enthalpy, and entropy of solute adsorption based on the new isotherm. The study evaluated the efficiency of the new isotherm in the adsorption of some metal ions in an aqueous solution and found that it is more accurate than the Langmuir isotherm and provides a deeper insight into the adsorption process in the solution phase. PRACTITIONER POINTS: Modification of the Langmuir isotherm for adsorption in solution. Comparison of the efficiency of the Langmuir and modified Langmuir isotherms. Accurate determination of and for Pb(II), Cd(II), and Ni(II) adsorption.

Preparation of poly(lactic acid) (PLA)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/graphene oxide (GO) polymeric composites for the selective removal of lead ions (Pb(II)) in water

AbstractLead pollution in water has risen globally, due to industrialization and globalization. In this study, this problem was addressed by preparing poly (lactic acid) (PLA)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/graphene oxide (GO) composites and addressing their effectiveness in absorbing water, and adsorbing Pb(II) ions in water. In water absorption studies, increasing the GO content to above 1 wt.% (3 and 5 wt.%) resulted in the degradation of the composites. All blends, and composites with 1 wt.% GO loading showed good water intake properties, with the composites having the highest. Pb (II) ion intake analyses showed that all the materials adsorb Pb(II) ions significantly in 24 h contact time, but the composites with 1 wt.% GO loadings adsorbed the greatest (81.3%–86.5%). For the effect of pH on adsorption, the adsorption of Pb(II) ions increased with an increase in pH from acidic to basic. This was attributed to the abundance of hydroxyl ions in basic media, that will not compete with Pb(II) ions for adsorption sites. Conclusions were that the 49.5/49.5/1 w/w PLA/PHBV/GO composite was the most optimal adsorbent of Pb(II). This composite could be used in industrial water purification processes like membranes, to remove lead ions from water while conserving the environment.Highlights Melt mixed PLA/PHBV/GO composites for removing lead ions from water. 1 wt.% GO contents in the composites sufficiently absorbed water. 3 and 5 wt.% GO contents resulted in the hydrolytic degradation of composites. Contact time is directly proportional to the degree of lead ion adsorption. Basic pH media resulted in the optimal adsorption of lead ions from water.

Synthesis of MgO nanomaterials using ultrasonic electrodeposition and their adsorption performance for Pb(II)

This study reports the successful synthesis of MgO nanomaterials while employing ultrasonic electrodeposition and heat treatment procedures. The capability and mechanism of these materials for removing Pb (II) from industrial soil were then investigated under ultrasonic powers of 100 W, 150 W, and 200 W. The surface morphology and phase composition of the nanomaterials were analyzed through SEM and XRD. The MgO nanomaterials prepared at 150 W displayed a high adsorption capacity for Pb (II), reaching up to 68.9 mg g−1, under conditions of pH 4.5, temperature 30 °C, Pb (II) concentration of 50 mg/L, and an optimal reaction time of 20 min. The maximum adsorption capacity of MgO nanomaterials prepared at 150 W ultrasonic power was observed to be 43.7 mg g−1 under the condition of 30 °C, Pb (Ⅱ) concentration of 50 mg/L, the optimal deposition time of 20 min, and pH 7. Analysis of the Pb (II) adsorption process on the surface of MgO nanomaterials was carried out using the pseudo-second-order kinetic and Langmuir models. The results revealed that Pb (II) adsorption on MgO nanomaterials exhibited distinct monolayer and chemical adsorption properties. Moreover, the Pb (II) adsorption capacity on MgO nanomaterials was found to be significantly influenced by temperature. The highest adsorption amount of Pb (II) by MgO nanomaterials was observed at a temperature of 30 °C. Further, the Langmuir model revealed the adsorption properties of MgO for Pb (II), with a correlation coefficient higher than 0.99. Therefore, the results confirm that ultrasonic power affects the adsorption performance of MgO nanomaterials prepared by ultrasonic electrodeposition, with the adsorption performance of MgO nanomaterials prepared at 150 W being the best.

Adsorption of Pb (II) ions on variable charge oxidic calcined substrates with chemically modified surface.

The paper describes lead ion adsorption on variable charge oxidic calcined substrates with chemically modified surfaces. Amphoteric oxides of iron, aluminum, titanium, and manganese, change their surface electric charge after acid or alkaline treatment, letting cationic or anionic adsorption reactions from aqueous solutions. This property allows using them as adsorbing substrate for heavy metals retention in water treatment systems. Substrate was prepared by extruding cylindrical strips from a saturate paste of the oxidic lithological material-OLM; dries it up and thermally treated by calcination. The study was performed by triplicated trial, on batch mode, using 2 grams samples of treated with NaOH 0.1N and non-treated substrate. Lead analysis was performed by AAS-GF. Freundlich and Langmuir models were used to fit results. Comparing differential behavior between treated and non-treated substrates showed the variable charge nature of the OLM. Results show L-type isotherms for the adsorption of Pb(II) ions on the activated substrate, suggesting good affinity between Pb(II) ions and OLM's surface. Average value of adsorption capacity ( K) for activated substrate (1791.73±13.06), is around four times greater than the non-activated substrate (491.54±31.97), during the adsorption reaction, 0.35 and 0.26 mmolH + of proton are produced on the activated and non-activated substrate respectively using a 1 mM Pb(II) solution and 72.2 and 15.6 mmolH + using a 10 mM Pb(II) solution. This acidification agrees with the theoretic model of transitional metals chemisorption on amphoteric oxides, present in lithological material used for the preparation of adsorbent substrates, confirming the information given by the L-type isotherms. Results suggest that these variable charge oxidic adsorbent substrate show great potential as an alternative technique for water treatment at small and medium scale using granular filtration system. The easiness and low price make them suitable to apply in rural media where no treating water systems is available.

Carboxymethyl cellulose aerogel decorated MOF-808 with defects via mixed-metallic center and etching for enhanced Pb(II) removal

Pb(II) removal from water is essential for human health due to their high toxicity and carcinogenicity. Metal-organic frameworks (MOFs) have potential to remove heavy metal ions because of their adjustable structure and tunable pore size. However, the microporous structure limits their removal performance because Pb(II) mainly exists in water as hydrated ion, which is larger than the pore size of MOFs. Defect engineering is promising to form suitable pore to capture Pb(II). Herein, we developed an etched Cu0.3Zr0.7-MOF-808 MOF by a mixed-metal strategy followed with an etching process. We replaced part of Zr4+ in the MOF-808 skeleton with Cu2+ through competition between Zr4+/Cu2+ for coordinating with –COOH on 1,3,5-Benzenetricarboxylic acid (H3BTC) to increase its specific surface area. Then H3PO4 and EDTANa2·2H2O as etchants were used to break the coordinate bond between Zr4+/Cu2+ and –COOH on H3BTC to achieve macroporous structure to inhabit Pb(II). The powder property of MOFs limits their practical applications due to their poor recyclability. We crosslinked the MOF on CMC by coordinating Zr4+ on the MOF with –COOH on CMC to form aerogel to facilitate its recyclability. The maximum adsorption capacity for Pb(II) was 542.77 mg/g at 45 °C. The adsorption of Pb(II) conformed to the intra-particle diffusion model and the Langmuir model, illustrating that the adsorption process was monolayer adsorption and affected by intra-particle diffusion. The electrostatic attraction and chelation between Pb(II) and –COOH accounted for the effective Pb(II) removal performance. This work provides a novel idea for the removal of heavy metal ions from water.

Preparation of high-efficient KMnO4 modified biochar for heavy metal removal from municipal wastewater

KMnO4-modified biochar (KM/biochar) derived from cotton stem is prepared with different cotton stem/KMnO4 ratios for Pb(II) removal from wastewater. The characterization analysis indicates that KM/biochar has abundant surface functional groups and large surface area, contributing to Pb(II) removal. Pb(II) adsorption on KM/biochar can be accurately analyzed using the Pseudo-second order and Hill model. The maximum Pb(II) adsorption capacity of KM/biochar is 144.49 mg/g at pH of 5. Pb(II) adsorption on KM/biochar is spontaneous based on thermodynamics analysis with the enthalpy value of the 8.54 kJ/mol. Coexisted ions such as Na+, K+, Ca2+ and Mg2+ have slightly influenced on Pb(II) adsorption process. The regeneration experiment analysis indicates that KM/biochar shows excellent Pb(II) adsorption capacity after three cycles. The existence of CO2 can contribute to Pb(II) removal from wastewater. Pb(II) adsorption mechanism includes precipitation, cation exchange, electrostatic attraction and π-π interaction. These above analysis results indicate that the waste cotton stem can be converted into the high-efficient KM/biochar for Pb(II) removal from wastewater.

Immature persimmon residue as a novel biosorbent for efficient removal of Pb(II) and Cr(VI) from wastewater: Performance and mechanisms

Owing to the powerful affinity of tannin toward heavy metal ions, it is frequently immobilized on adsorbents to enhance their adsorption properties. However, natural adsorbents containing tannin have been overlooked owing to its water solubility. Herein, a novel natural adsorbent based on the immature persimmon residue (IPR) with soluble tannin removed was fabricated to eliminate Pb(II) and Cr(VI) in aquatic environments. The insoluble tannin in IPR endowed it with prosperous properties for eliminating Pb(II) and Cr(VI), and the IPR achieved maximum Pb(II) and Cr(VI) adsorption quantities of 68.79 mg/g and 139.40 mg/g, respectively. Kinetics and isothermal adsorption analysis demonstrated that the removal behavior was controlled by monolayer chemical adsorption. Moreover, the IPR exhibited satisfactory Pb(II) and Cr(VI) removal efficiencies even in the presence of multiple coexisting ions and showed promising regeneration potential after undergoing five consecutive cycles. Additionally, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analysis unveiled that the elimination mechanisms were primarily electrostatic attraction, chelation and reduction. Overall, the IPR, as a tannin-containing biosorbent, was verified to possess substantial potential for heavy metal removal, which can provide new insights into the development of novel natural adsorbents from the perspective of waste resource utilization.

Promoting the circular economy: Valorization of a residue from industrial char to activated carbon with potential environmental applications as adsorbents

Pyrolysis of residues enriched with carbon, such as in agroforestry or industrial activities, has been postulated as an emerging technology to promote the production of biofuels, contributing to the circular economy and minimizing waste. However, during the pyrolysis processes a solid fraction residue is generated. This work aims to study the viability of these chars to develop porous carbonaceous materials that can be used for environmental applications. Diverse chars discharged by an industrial pyrolysis factory have been activated with KOH. Concretely, the char residues came from the pyrolysis of olive stone, pine, and acacia splinters, spent residues fuel, and cellulose artificial casings. The changes in the textural, structural, and composition characteristics after the activation process were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, FTIR, elemental analysis, and XPS. A great porosity was developed, SBET within 776–1186 m2 g−1 and pore volume of 0.37–0.59 cm3 g−1 with 70–90% of micropores contribution. The activated chars were used for the adsorption of CO2, leading to CO2 maximum uptakes of 90–130 mg g−1. There was a good correlation between the CO2 uptake with microporosity and oxygenated surface groups of the activated chars. Moreover, their ability to adsorption of contaminants in aqueous solution was also evaluated. Concretely, there was studied the adsorption of aqueous heavy metals, i.e., Cd, Cu, Ni, Pb, and Zn, and organic pollutants of emerging concern such as caffeine, diclofenac, and acetaminophen.

Characterization Analysis of Mudstone and Study of Its Pb (II) Adsorption Characteristics in Polluted Water Bodies

In order to explore a medium material for the efficient treatment of Pb(II) pollutants in groundwater, in this paper, mudstone is selected as the medium material, and the morphological structure of the mudstone is characterizes via X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyses to study the feasibility of the mudstone adsorbing Pb(II) ions. Then, static adsorption experiments are carried out to investigate the removal effect of mudstone on Pb(II) in aqueous solutions under different conditions and to determine the optimal adsorption conditions. Finally, the results are fitted and analyzed using a thermodynamic model to explore the adsorption mechanism of the mudstone. The main results of this study are as follows. The main mineral composition of the mudstone used in the experiments includes CaCO3, SiO2, CaAl2O4·10H2O, and CaFe4O7. The specific surface area of the mudstone is as high as 23.027 m2·g−1, the pore size is 9.145 nm, and its surface structure is rough, with pores and fissures developed. The pore space and adsorption capacity of the mudstone were enhanced. When 1 g·L−1 of mudstone was added, the pH value of the solution was 6, the reaction time was 60 min, and the initial concentration of Pb(II) was 30 mg·L−1. The removal efficiency of Pb reached 84.5%, and the adsorption amount was 25.352 mg·g−1. For the removal of Pb(II) from the aqueous solution by the mudstone under different concentrations of Pb(II), the reaction was in accordance with the Langmuir adsorption isotherm model, and the maximum adsorption amount reached 54.975 mg·g−1. The relationship between the removal of Pb(II) and the reaction time was in accordance with the pseudo-second-order rate model. The results of this study suggest that mudstone can be used for the removal of Pb(II) from aqueous media.

Application of machine learning in prediction of Pb2+ adsorption of biochar prepared by tube furnace and fluidized bed.

Data mining by machine learning (ML) has recently come into application in heavy metals purification from wastewater, especially in exploring lead removal by biochar that prepared using tube furnace (TF-C) and fluidized bed (FB-C) pyrolysis methods. In this study, six ML models including Random Forest Regression (RFR), Gradient Boosting Regression (GBR), Support Vector Regression (SVR), Kernel Ridge Regression (KRR), Extreme Gradient Boosting (XGB), and Light Gradient Boosting Machine (LGBM) were employed to predict lead adsorption based on a dataset of 1012 adsorption experiments, comprising 422 TF-C groups from our experiments and 590 FB-C groups from literatures. The XGB model showed superior accuracy and predictive performance for adsorption, achieving R2 values for TF-C (0.992) and FB-C (0.981), respectively. Contrasting inferior results were observed in other models, including RF (0.962 and 0.961), GBR (0.987 and 0.975), SVR (0.839 and 0.763), KRR (0.817 and 0.881), and LGBM (0.975 and 0.868). Additionally, a hybrid dataset combining both biochars in Pb adsorption also indicated high accuracy (0.972) as obtained from XGB model. The investigation revealed that the influence of char characteristics and adsorption conditions on Pb adsorption differs between the two biochar. Specific char characteristics, particularly nitrogen content, significantly influence lead adsorption in both biochar. Interestingly, the influence of pyrolysis temperature (PT) on lead adsorption is found to be greater for TF-C than for FB-C. Consequently, careful consideration of PT is crucial when preparing TF-C biochar. These findings offer practical guidance for optimizing biochar preparation conditions during heavy metal removal from wastewater.

Synthesis of stable mesoporous Zr-MOFs using pyrazine-containing ligand for efficient capture of Pb(II) in wastewater

By optimizing the reaction conditions, a zirconium-based adsorbent Zr-PzDC with pyrazine-2,5-dicarboxylic acid as the ligand was synthesized for the treatment of lead ions in an aqueous solution. SEM, EDS-Mapping, XRS and FT-IR characterization confirmed the synthesis of Zr-PzDC. Meanwhile, BET results show that Zr-PzDC is a typical mesoporous material. The analysis of the binding process of Zr-PzDC with Pb(II) in water shows that the adsorption kinetics conform to the pseudo-second-order model; The adsorption isotherm data fits well with the Langmuir model, and the maximum adsorption capacity of Pb(II) is 298.39 mg/g; The thermodynamic parameters show that the adsorption of Pb(II) in water is a spontaneous endothermic process. Combined with the XPS spectral results, physical adsorption is the main binding mode, and single-layer chemisorption is the limiting step in the adsorption process. The results of both static and dynamic column adsorption experiments show that Zr-PzDC can treat lead ions quickly and efficiently, and has excellent reusable performance, which makes Zr-PzDC have good application potential in treating lead-containing wastewater of the battery production process.

Preparation of novel CS/SiO2-EDTA nanocomposite from ash of rice straw pellets for enhanced removal efficiency of heavy metal ions in aqueous medium

The production valuable materials from waste for environmental treatment have attracted considerable attention worldwide. In this study, porous silica was produced from the ash of rice straw pellets. The porous silica was then modified with chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) to produce novel CS/SiO2-EDTA nanocomposites for the removal of heavy metals in aqueous medium. The adsorption of Pb2+ was investigated to evaluate the effectiveness of the composite and the effects of reaction parameters on the adsorption process were extensively explored. The adsorption is fast in the initial 5 min, then almost reaches equilibrium in 10 min. The conditions for the highest adsorption capacity are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.1 g/L, and a Pb2+ concentration of 100 ppm. The removal efficiency, adsorption capacity, and rate constant are 70.39 %, 703.9 ± 21.1 mg/g, and 0.012 ± 0.003 g/mg·min, respectively. The conditions for the highest adsorption efficiency are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.5 g/L, and a Pb2+ concentration of 40 ppm, where the adsorption efficiency, adsorption capacity, and rate constant are 89.88 %, 71.91 ± 1.86 mg/g, and 0.013 ± 0.002 g/mg·min, respectively. The selectivity of the composite was investigated by using Ni2+, Cu2+ and Fe2+ ions under the same experimental conditions. In multi-metal solutions, the adsorbent showed the highest affinity for Pb2+. In addition, the adsorption isotherms and thermodynamics were investigated and an adsorption mechanism was proposed.

Characterization and use of activated carbon synthesized from sunflower seed shell in the removal of Pb(II), Cd(II), and Cr(III) ions from aqueous solution.

In this work, carbon-based nanomaterials such as active carbon which is prepared from common sunflower (Helianthus annuus) seed shell, and the characterization of the activated carbon NPs were studied using FTIR (Fourier transform infrared spectroscopy), XRD, SEM, EDS, and DTA techniques. Activated carbon NPs have been used in the adsorption of Pb(II), Cd(II), and Cr(III) ions from the aqueous phase. The results showed the highest adsorption efficiency was 99.9%, 92.45%, and 98% for Pb(II), Cd(II), and Cr(III) ions respectively at a temperature of 25 °C, pH = 7-9, and a time of 60 and 180 min, in addition to the accordance of the adsorption models for activated carbon with the Freundlich isotherm model at the value of R2 (0.9976, 0.9756, and 0.9907) and Langmuir isotherm model (0.966, 0.999, and 0.9873) of the Pb(II), Cd(II), and Cr(III) ions, respectively. We conclude the possibility of using activated carbon to have an extremely high sorption capacity across the conditions tested, with the highest adsorption efficiency having been >99% for Pb(II), Cd(II), and Cr(III) ions within the pH range 7-9 and a contact time of 60 to 180 min.

The role of amino acids in facilitating lead accumulation in microalgae: A quantitative analysis of functional group effects

In aquatic ecosystems, dissolved organic matter (DOM) enhances the adsorption of heavy metals onto microalgae by participating in the formation of algae–heavy metal–DOM ternary complexes, thereby increasing environmental risks. The functional groups in the DOM play a crucial role. However, a quantitative description based on these groups is lacking. This study investigates the effects of amino acids (AAs) with varying functional group ratios on the accumulation of lead (Pb) in Chlorella pyrenoidosa (C. pyrenoidosa) using batch experiments. Isotherm model fitting, and Fourier transform infrared spectroscopy (FTIR) are employed for characterisation. Results indicate that the addition of AAs facilitated Pb enrichment in microalgae. In particular, incorporating lysine (Lys) led to maximum accumulation, reaching 1.45 mmol g−1. The adsorption rate decreased after AA addition, particularly with Lys, dropping form 0.0032 g mg−1 min−1 to 0.0009 g mg−1 min−1. The reaction sequence showed carboxyl groups taking precedence over amino groups. The model developed from the data on Pb adsorption by C. pyrenoidosa following AA addition, demonstrated reliability with an R2 of 0.91 and an F-value of 157.6. Notably this study employed two-dimensional correlation spectroscopy (2D–COS), offering novel insights into the key roles of functional groups and their distinct contributions. These valuable insights contribute to intensive research on the ternary complex of algae − heavy metal − DOM and elucidating their ecological risks.