Mechanism Of Pb Research Articles

Selective adsorption of oxidized yeast glucan for Pb2+: Influencing factors, adsorption site and mechanism

This work investigated the influencing factors and mechanism of Pb2+ adsorbed by oxidized yeast glucan (OYG). Firstly, OYG showed greater Pb2+ adsorption performance than yeast glucan, and the adsorption capacity was greater with the oxidation degree increased. The optimal pH range for Pb2+ adsorption was 6–7. The adsorption capacity of Pb2+ reached its maximum of 86.68 and 96.88 mg/g for 20 mg of OYG1 and OYG2, respectively. In addition, OYG exhibited selective adsorption, with adsorption capacity in the order: Pb2+ > Cd2+ > Cu2+ > Ca2+. Then adsorption isotherm was established by fitting Langmuir and Freundlich isotherm adsorption models. Freundlich model could better fit the adsorption process of lead by OYG, indicating that the adsorption process was heterogeneous. According to the Langmuir model, the maximum lead adsorption capacities of OYG1 and OYG2 at 298 K were 100.70 and 131.06 mg/g, respectively. Thermodynamic data indicated a spontaneous endothermic process (ΔG < 0, ΔH > 0), accompanied by increased system disorder (ΔS > 0), involving physical and chemical adsorptions. Finally, FT-IR and XPS results revealed -COOH and -OH were the primary adsorption sites in OYG, and the interaction between these groups and Pb2+ was mainly achieved by electrostatic interaction (or ion-dipole interaction).

Comparative kinetic study of Pb(II) and Cd(II) metal ions removal from aqueous solutions by Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactiplantibacillus pentosus

ABSTRACT In this study, selected lactic acid bacteria, including Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactiplantibacillus pentosus, were evaluated for their potential to remove Pb(II) and Cd(II) ions from aqueous solutions. The highest removal efficiency was achieved at a pH value of 4. Kinetic modeling using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models demonstrated that the intraparticle diffusion model provided the best fit for describing the adsorption process. The results of the study indicated that among the three bacteria tested, L. fermentum exhibited the highest maximum adsorption capacity for Pb(II) at 4.95 mg g−1, followed by L. helveticus at 4.91 mg g−1 and L. pentosus at 4.08 mg g−1. In contrast, for Cd(II) adsorption, L. helveticus showed the highest maximum adsorption capacity at 4.38 mg g−1, followed by L. pentosus at 3.45 mg g−1 and L. fermentum at 2.86 mg g−1. The mechanism of Pb(II) and Cd(II) ions removal by LAB strains involves adsorption onto the bacterial cell surfaces, where interactions such as ion exchange, electrostatic attraction, and complexation play crucial roles. Overall, L. helveticus, L. fermentum, and L. pentosus hold promising potential for various applications in wastewater treatment, particularly in the removal of heavy metal ions.

Effect of Polystyrene Microplastics on Pb(II) Adsorption onto a Loessial Soil (Sierozem) and Its Mechanism.

Microplastics (MPs) have received significant attention recently. However, their influence on soil heavy metal adsorption remains unclear. The effect of polystyrene (PS) MPs on the adsorption of Pb(II) onto a loessial soil (sierozem) was studied by batch experiments in single soil (S), soil with 1 mm PS (S-PS1), and soil with 100 μm PS (S-PS100) systems. The mechanisms of Pb(II) adsorption reduction were investigated. The adsorption of Pb(II) reached equilibrium within 12 h, and the pseudo-second-order model fitted the adsorption processes best. The Langmuir adsorption model provided a better fit to the isotherms, compared to the Freundlich one. The presence of PS decreased the level of adsorption of Pb(II). Larger PS particle size, dose, and fulvic acid (FA) concentration inhibited Pb(II) adsorption onto the soil. The solution pH value showed a positive correlation with the adsorption amount. The adsorption amounts (q e) of Pb(II) in binary metal systems (Cu-Pb and Cd-Pb) were lower than those in single Pb systems, indicating the competitive adsorption among the ions. The adsorption amount presented a trend of S > S-PS100 > S-PS1. The primary mechanism on which PS reduced the adsorption of Pb(II) was the "dilution effect" of MPs. Conclusively, the presence of MPs might elevate the availability of heavy metals by reducing the soil's adsorption capacity for them and then amplifying the risk of heavy metal contamination and migration.

Adsorption Capability and Mechanism of Pb(II) Using MgO Nanomaterials Synthesized by Ultrasonic Electrodeposition

Adsorption Capability and Mechanism of Pb(II) Using MgO Nanomaterials Synthesized by Ultrasonic Electrodeposition

Adsorption Kinetics and Mechanism of Pb(II) and Cd(II) Adsorption in Water through Oxidized Multiwalled Carbon Nanotubes

Toxic heavy metals are ubiquitous in the aquatic environment and show a significant danger to human health. Carbon nanotubes have been extensively used in treating the contamination of groundwater due to their porous multi-layer nature. Batch tests revealed that oxidized multiwalled carbon nanotubes (O-MWCNTS) offer better removal of Pb(II). The removal rate of Pb(II) was 90.15% at pH 6 within 24 h, which was ~58% more than that of Cd(II). The removal rate decreased to 55.59% for Pb(II) and to 16.68% for Cd(II) when the initial concentration of Pb(II)/Cd(II) ranged from 5 to 15 mg·g−1. The removal rate in the competitive tests was about 60.46% for Pb(II) and 9.70% for Cd(II). The Langmuir model offered better description of the adsorptive data for both ions. And the Qm of Pb(II) was 5.73 mg·g−1, which was 2.39 mg·g−1 more than that of Cd(II) in a single-icon system, while Qm was 7.11 mg·g−1 with Pb(II) and 0.78 mg·g−1 with Cd(II) in competitive water. And thermodynamic tests further indicated that the activating energy of Pb(II) and Cd(II) was 83.68 and 172.88 kJ·mol−1, respectively. Lead and cadmium adsorbed on the surface of O-MWCNTS are antagonistic in the competitive system. Based on XPS analyses, it was concluded that the absorbed lead/cadmium species on O-MWCNTS were (-COO)2Pb, (-COO)Pb(-O)/(-COO)2Cd, and (-COO)Cd(-O). Additionally, they offered theoretical evidence supporting the practicality of using nanocomposite membranes as a means to remove cadmium and lead.

Efficient lead removal from aqueous solutions using a new sulfonated covalent organic framework: Synthesis, characterization, and adsorption performance

The aim of removing Pb(II) from water is to minimize the potential harm posed by toxic metals to both human health and the environment. To achieve this, a covalent organic framework adsorbent called TFPOTDB-SO3H was developed using a condensation process involving 2,5-diaminobenzenesulfonic acid and 2,4,6-tris-(4-formylphenoxy)-1,3,5-triazine. This adsorbent exhibited excellent properties such as high repeatability, selectivity, and easy solid–liquid separation. Under conditions of pH = 6.0 and 298 K, the TFPOTDB-SO3H demonstrated impressive capability of adsorbing Pb(II). In a brief span of 10 min, it attained a special elimination rate of 99.40 % and shown its capacity to adsorb up to 500.00 mg/g. The adsorbent presented effective removal of Pb(II) from a solution that had a mixture of various ions, showcasing its proficiency in capturing the contaminant, with a partition coefficient (Kd) of 3.99 × 106 mL/g and an adsorption efficiency of 99.75 % among six coexisting ions. The pseudo-second-order kinetic model was observed to govern the adsorption process kinetics, while the Langmuir isotherm model confirmed monolayer chemisorption as the mechanism for Pb(II) removal. Thermodynamic analysis indicated that the uptake process was both exothermic and spontaneous. Furthermore, the adsorbent maintained a significant adsorption efficiency of 89.63 % for Pb(II) even after undergoing four consecutive adsorption–desorption cycles. These findings collectively suggest that TFPOTDB-SO3H has excellent potential for effectively adsorbing and removing Pb(II) heavy metal ions from wastewater.

A novel magnetic Fe3O4/cellulose nanofiber/polyethyleneimine/thiol-modified montmorillonite aerogel for efficient removal of heavy metal ions: Adsorption behavior and mechanism study

To efficiently remove heavy metals from wastewater, designing an adsorbent with high adsorption capacity and ease of recovery is necessary. This paper presents a novel magnetic hybridized aerogel, Fe3O4/cellulose nanofiber/polyethyleneimine/thiol-modified montmorillonite (Fe3O4/CNF/PEI/SHMMT), and explores its adsorption performance and mechanism for Pb2+, Cu2+, and Cd2+ in aqueous solutions. The hybrid aerogel has a slit-like porous structure and numerous exposed active sites, which facilitates the uptake of metal ions by adsorption. Pb2+, Cu2+, and Cd2+ adsorption by the hybridized aerogel followed the second-order kinetics and the Langmuir isotherm model, the maximum adsorption of Pb2+, Cu2+, and Cd2+ at 25 °C, pH = 6, 800 mg/L was 429.18, 381.68 and 299.40 mg/g, respectively. The adsorption process was primarily attributed to monolayer chemical adsorption, a spontaneous heat-absorption reaction. FTIR, XPS and DFT studies confirmed that the adsorption mechanisms of Fe3O4/CNF/PEI/SHMMT on Pb2+, Cu2+, and Cd2+ were mainly chelation, coordination, and ion exchange. The lowest adsorption energy of Pb2+ on the hybrid aerogel was calculated to be −2.37 Ha by DFT, which indicates that the sample has higher adsorption affinity and preferential selectivity for Pb2+. After 5 cycles, the adsorption efficiency of the aerogel was still >85 %. The incorporation of Fe3O4 improved the mechanical properties of the aerogel. The Fe3O4/CNF/PEI/SHMMT has fast magnetic responsiveness, and it is easy to be separated and recovered after adsorption, which is a promising potential for the treatment of heavy metal ions.

Phosphogypsum/titanium gypsum coupling for enhanced biochar immobilization of lead: Mineralization reaction behavior and electron transfer effect

The hazards caused by Pb pollution have received worldwide attention. Phosphogypsum (PG) and titanium gypsum (TG) have the disadvantage of limited adsorption capacity and poor dispersion when used as heavy metal adsorbents on their own. The excellent pore and electron transfer capacity of biochar makes it possible to combine with PG and TG to solidify/stabilize Pb2+. In this study, the mechanism of Pb2+ adsorption/immobilization by rice husk biochar (BC) combined with PG/TG was investigated in terms of both mineral formation and electron transfer rate. The removal rate of Pb2+ by BC composite PG (BC/PG-Pb) or TG (BC/TG-Pb) was as high as 97%–98%, an increase of 120.9% and 122.5% over BC. Adsorption kinetics and mineral precipitation results indicate that the main removal of Pb2+ from BC/PG-Pb and BC/TG-Pb is achieved by PG/TG induced Pb-sulfate and Pb-phosphate formation. The addition of PG/TG significantly enhances the formation of stable Pb-minerals on the biochar surface, with the proportion of non-bioaccessible forms exceeding 50%. The four-step extraction results confirm that P and F in PG/TG are key in facilitating the conversion of Pb minerals to pyromorphite. The rich pore structure of biochar not only disperses the easily agglomerated PG/TG onto the biochar surface, but also attracts Pb2+ for uniformly dispersed precipitation. Furthermore, the excellent electrical conductivity and smooth electron transfer channels of biochar facilitate the reaction rate of Pb2+ mineralization. Overall, the use of biochar in combination with PG/TG is a promising technology for the combination of solid waste resourceisation and Pb remediation.

Bimodal interferences of Pb(II) induced by parallel deposition in Pb(II)-Cu(II) electrochemical detections: Voltammetric signals analysis combined with numerical simulations on transient interfacial phenomena

The perplexity of double peaks in Pb(II) detections has been a threat to the reliability of Pb(II) electroanalysis results for a long term. For the complexity of electrode interfaces, rare studies were taken on mechanisms of Pb(II) double peaks through interfacial kinetics. In this work, analyses on experimental signals and interfacial simulations were working together to reveal that the generation of Pb(II) double peaks in Pb(II)-Cu(II) systems is the deposition of Pb(II) on Cu deposits occurring in parallel. By applying anode stripping voltammetry and cyclic voltammetry, a parallel deposition reaction was found to influence the shape of Pb(II) peaks, and the existence of the second peak was controlled through the adjustment of experimental conditions. A kinetic model was built to reveal the interference of electroanalysis signals caused by a parallel deposition reaction and simulations based on the model were combined with experiments to illustrate that double peaks of Pb(II) were caused by the parallel deposition on Cu(II) deposits. This work proposes another insight of Pb(II) double peaks from macroscale kinetics and pays more attention on the dynamic procedure of electroanalysis interfaces, which makes the study on environmental electroanalysis interface phenomena more clear and is enlightening to develop efficient electrical methods for pollutant monitoring.

Influence of FeCl3/Fe3(PO4)2/CaO in sludge on the migration pattern of heavy metals during coal slime combustion

The influence of minerals (FeCl3, Fe3(PO4)2, CaO) contained in SS(Sewage Sludge) on the migration and mechanism of Pb, As, Cu, Cr, Cd in CS(Coal Slime) during the co-combustion process was studied by electric heating tube furnace. Studies have shown that the interaction of minerals in SS with minerals and heavy metals in CS is an important factor affecting the migration of heavy metals in the co-combustion process of SS-CS. The heavy metals combine to form volatile heavy metal-Cl compounds. Compared with the single combustion of CS, the retention rates of Pb, As, Cu, and Cd are reduced by 89.6%, 45.1%, 70.4%, and 89.2% at 900 °C. When CS is blended with Fe3(PO4)2, Fe3(PO4)2 decomposes a large amount of Fe2O3 and P with the increase of combustion temperature to react with As, Cu, and Cr in CS, which makes the retention rate of the three heavy metals increase by 30.6%, 194.1%, and 1726.4% under the combustion condition of 900 °C compared with CS alone. When CS was burned with CaO, CaO had a competitive adsorption effect on Pb and Cd, which reduced the retention rate of Pb and Cd by 12.2% and 58.2% at 900 °C compared with CS alone. Meanwhile, CaO reacted with As, which increased the retention rate of As by 1.3% and 38.9% at 700 °C and 900 °C.The effects of Cl on the migration of Pb, Cu, Cr, and Cd were stronger than those of CaO and Fe3(PO4)2, and Fe2O3 and CaO had the greatest effect on the sequestration of As.

Capacity and Mechanisms of Pb(II) and Cd(II) Sorption on Five Plant-Based Biochars

China is a large agricultural country that produces a large amount of crop straw every year. Thus, the development of cost-effective and economic application of invasive plants is warranted. Biochars derived from crop straw have been proven to be promising for adsorbent materials. However, less studies have focused on biochar derived from different types of crop straw as adsorbent under the same conditions to compare their adsorption performance. Here, we characterized the five biochars in the same system (600 °C). In results, GBC has higher ash content, pH, CEC, specific surface area, mineral composition and oxygen-containing functional groups. The adsorption kinetics can be explained adequately by the pseudo-second-order model and the Langmuir model, indicating that the adsorption behavior of the biochar is both physical adsorption and chemical adsorption; the adsorption process includes complexation reaction, cationic π bond, ion precipitation and electrostatic adsorption. In conclusion, GBC exhibited higher metal equilibrium adsorption capacities (125 mg·g−1 for Pb2+, 29 mg·g−1 for Cd2+). The solution pH, biochar dosing, pyrolysis temperature and the properties of these heavy metals were responsible for adsorption capacity, thus showing stronger affinity and better adsorption effect. Our results are important for the selection and utilization of plant-based biochar for different heavy metals.

Removal of Pb2+ in aqueous solutions using Na-type zeolite synthesized from coal gasification slag in a fluidized bed：Hydrodynamic and adsorption

As the heavy metal ion in aqueous solutions, Pb2+ has certain harm to the surrounding natural and ecological environment. To eliminate the pollution of Pb2+ in aqueous solution, Na-type zeolite was prepared from the coal gasification slag by alkaline activation technology, and then the hydrodynamic of fluidized bed with Na-type zeolite granules was studied to achieve fluidization stability. Finally, the adsorption process and mechanism of Pb2+ in aqueous solutions using Na-type zeolite were studied by multiple adsorption experiments in stable fluidized bed. The results showed that: The removal process of Pb2+ using Na-type zeolite is a single-layer adsorption dominated by chemical adsorption, companying with surface electrostatic interaction and ionic exchange processes in the interlayer. Fluidized adsorption process of Pb2+ by Na-type zeolite is mainly affected by rising-water velocity, original concentration of Pb2+, and bed material quantity in fluidized bed. The order of influence significance was as below: Original concentration (co) > Bed material quantity (mo) > Rising-water velocity (vt). Under optimal operating conditions (co=200 mg/L, vt=0.053 m/s, mo =72 g), the fluidized bed have higher adsorption saturation (qs=0.649 g/g) than that of fixed bed (qs=0.501 g/g), promoting the adsorption process of Pb2+ by Na-type zeolite. This research provided a new method for the efficient removal of Pb2+ from aqueous solution.

Evaluation of Adsorption Efficiency on Pb(II) Ions Removal Using Alkali-Modified Hydrochar from Paulownia Leaves

In this study, hydrothermal carbonization (HTC) at five temperatures (180, 200, 220, 240, and 260 °C) was applied to transform Paulownia leaves (PL) into a carbonaceous sorbent of Pb(II) from aqueous solutions. To enhance the adsorption efficiency of the obtained hydrochar (PH), subsequent alkali activation was performed using NaOH. Preliminary results of the Pb(II) adsorption (CPb = 200 mg/L) showed removal coefficients after 48 h of 73.44 mg/g, 82.37 mg/g, and 110.9 mg/g for PL, PH-220, and MPH-220, respectively. The selected hydrochar (PH-220) and modified hydrochar (MPH-220) were further investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results revealed that alkali treatment changed the hydrochar structure and, thus, improved its adsorption performance. The kinetic parameters showed that the Pb(II) sorption onto MPH-220 followed a pseudo-second-order model, while the intra-particle diffusion went through two simultaneous stages. The Langmuir isotherm model best described the experimental data and indicated the value of 174.75 mg Pb(II)/g as the maximum adsorption capacity. The two possible mechanisms of Pb(II) binding were complexation and/or Pb-π electron interaction. The obtained results indicate the great potential of MPH-220 for Pb(II) removal from aqueous media and its potential utilization as an effective adsorbent for wastewater purification.

Effective removal of heavy metal-lead and inorganic salts by microporous carbon derived from Zeolitic Imidazolate Framework-67 electrode using capacitive deionization

The available fresh water resources have been polluted by rapid industrialization and urbanization. Several techniques have been developed and practiced for the treatment of wastewater, including physical, thermal, chemical, membrane-based and electrochemical techniques. Still the efficient and effective technique for the wastewater treatment is challenging for researchers over the years. The capacitive deionization (CDI) is an environmentally friendly technology for water purification (desalination) with substantial scope, which works on the principle of electrical double layer (EDL). In this case, salt ions are electrostatically adsorbed on the surface of electrode material. Porous carbon with optimized pore size, hierarchal pore structure and high surface area is preferred for CDI. Herein, we report the detailed study of microporous carbon derived from Zeolitic Imidazolate Framework-67 (PC-ZIF-67) and its application as electrode material in CDI. This setup has been utilized for the removal of monovalent cations (Na+ and K+) and divalent cation (Ca2+) along with heavy metal- lead (Pb2+) from water. The PC-ZIF-67 exhibits typical truncated cubic morphology with microporosity and high gravimetric surface area of 532 m2/g. The as-synthesized PC-ZIF-67 offers salt adsorption capacity (SAC) of 28.1, 30.6, 50.9 mg/g for the removal of Na+, K+ and Ca2+, respectively. Moreover, PC-ZIF-67 shows SAC of 117.2 mg/g for the removal of Pb2+, which is higher than other saline cations. The mechanism of Pb2+ removal is attributed to the electrostatic and π- π interaction between the surface of PC-ZIF-67 and Pb2+. Further, the material displays good cyclic stability during the removal of each cation, retaining 90% of SAC after ten adsorption-desorption cycles. The selectivity of cations is studied by mixed salt electrosorption experiment revealing that there is higher selectivity of PC-ZIF-67 electrode towards divalent cations as compared to monovalent cations. The SAC values have been validated by matching with theoretical adsorption model isotherms. This work promotes future utilization of MOF-derived porous carbon for the effective removal of dissolved Na+, K+, Ca2+ and Pb2+ from aqueous source using CDI.

Performance and mechanism of Pb2+ and Cd2+ ions’ adsorption via modified antibiotic residue-based hydrochar

This study investigated the hydrochar-based porous carbon prepared by combining the technical route of hydrothermal carbonization (HTC) + chemical activation. The hydrochar morphology was adjusted by changing the activation reaction conditions and adding metal salts. Experiments showed that the activation of KHCO3 significantly increased the specific surface area and pore size of the hydrochar. Besides, oxygen-rich groups on the surface of the activated hydrochar interacted with heavy metal ions to achieve efficient adsorption. The activated hydrothermal carbon adsorption capacity for Pb2+ and Cd2+ ions reached 289 and 186 mg/g, respectively. The adsorption mechanism study indicated that the adsorption of Pb2+ and Cd2+ was related to electrostatic attraction, ion exchange, and complexation reactions. The “HTC + chemical activation” technology was environmentally friendly and effectively implemented antibiotic residues. Carbon materials with high adsorption capacity can be prepared so that biomass resources can be utilized with excessive value, as a consequence presenting technical assistance for the comprehensive disposal of organic waste in the pharmaceutical industry and establishing a green and clean production system.

Natural organic matter changed the capacity and mechanism of Pb and Cd adsorptions on iron oxide modified biochars

Employing Fe-oxide loaded biochars (FBCs) to remediate heavy metal (HM) pollution has been regarded as a promising alternative. However, the removal performance and mechanism of FBCs to compound Pb and Cd in both systems with and without natural organic matter were poorly examined. Here, a series of FBCs were prepared and their adsorption capacity and mechanism for Pb and Cd in dual metal systems affected by humic acid (HA) were studied. The results demonstrated that the pyrolysis temperatures during the FBC preparation significantly affected the physico-chemical properties of FBCs and the specie of Fe-oxides it supported. The FBC300-300 showed the best adsorption performance, with maximum adsorption capacities up to 96.8–151 and 29.1–82.3 mg g−1 for Pb and Cd, respectively. Integrating the findings from adsorption kinetics and isotherm experiments and surface characteristics of the FBCs before and after reaction, the underlying dominated adsorption mechanisms were discussed. The dominant mechanisms and their degrees of action for HM adsorption were significantly different among the FBCs, controlling by the specie of loaded Fe-oxides and other physico-chemical properties of the FBCs (e.g., pH, specific surface area, and functional group). The presence of HA was found that it can distinctly alter HM adsorption process on FBCs, and the alterations depended on the interactions of HM and FBC type. Overall, the findings presented in our study could provide a systematic understanding of the remediation of Pb and Cd compound pollution by the FBCs in a natural environment where natural organic matter were widespread.

Phosphate‐Assisted Remediation of Pb(II) From Jarosite

AbstractJarosite is an essential solid industrial waste material which is generated during the hydrometallurgical processing of zinc in smelters. Besides zinc and iron, Jarosite also contains toxic heavy metals like Pb, Cd, Al, Cr, Cu etc. due to which it is environmentally hazardous. Due to the presence of heavy metals, the useful Zn, Fe components cannot be utilized safely. Therefore, it is necessary to remove Pb(II), a major toxic element, to make it useful. In this report, a green process for immobilization of Pb(II) using phosphate materials (physiochemical adsorption) is discussed. Jarosite was used as a precursor for synthesis of the Zn−Fe binary nano‐composite. Mitigation of Pb(II) by this process was assessed by the batch experiments, which showed significant reduction in leaching of Pb(II). The mechanism of Pb(II) immobilization involve the dissolution of phosphate materials (KH2PO4, NH4H2PO4 and CaH2PO4) to a lower pH≤3 followed by precipitation of Pb(II) in the form of pyromorphite complex. The results indicated that the concentration of Pb(II) was reduced by 90–95 % which was pH dependent with a high uptake (325 ppm) of lead ion in the pH range of 5.5–6.0. This physicochemical process brings new perspectives for reuse of a polluting solid industrial waste.

Synthesis of zeolitic imidazolate framework‐8 modified graphene oxide composite and its application for lead removal

AbstractBACKGROUNDThe removal of lead ions (Pb2+) from industrial wastewater can be achieved using adsorption technology. Composites of zeolitic imidazolate framework‐8 (ZIF‐8) and graphene oxide (GO) were prepared via room temperature synthesis (RTS) using RO water as the solvent and by mixing GO with separated parts of ZIF‐8 precursors before its combination. Three weight percentages of GO, 10wt%, 30wt% and 50wt%, were used to synthesize ZGH10, ZGH30 and ZGH50 to determine optimum preparation and application conditions.ResultsZGH30 showed the most outstanding performance as an adsorbent for Pb2+ removal from aqueous solution. As captured by field emission scanning electron microscopy image, ZGH30 showed an adequate amount of ZIF‐8 grown on all surfaces of thr GO sheet, with an appropriate exposure of GO sheet layers for further Pb2+ interaction. The Pb2+ adsorption test revealed that ZGH30 obtained the optimum operating values between pH 5 and 6, using 10 mg dosage and it could remove ≤97% of 100 mg L−1 Pb2+. Additionally, ZGH30 achieved the most rapid equilibrium time within 10 min, similar to ZGH50, as compared to their individual components, ZIF‐8 (240 min) and GO (300 min). The mechanism of Pb2+ adsorption fitted well with a Langmuir isotherm and pseudo‐second‐order kinetic model. The theoretical maximum adsorption capacities obtained through Langmuir isotherm were 200, 454.55, 476.19, 555.56 and 454.55 mg g−1, for GO, ZH, ZGH10, ZGH30 and ZGH50, respectively.ConclusionsTherefore, ZGH30 hybrid successfully unleashed its potential as the adsorbent for wastewater treatment technology with improved performance after modification. © 2023 Society of Chemical Industry (SCI).

Adsorption of Pb(II) and Cd(II) hydrates via inexpensive limonitic laterite: Adsorption characteristics and mechanisms

Industrial heavy metal pollution has been a long-standing concern, and adsorption is an economical and effective measure for treating wastewater containing heavy metal ions. With its low price, large specific surface area, and high surface activity, limonitic laterite is an ideal low-cost adsorbent for the removal of heavy metal ions. In this paper, the adsorption behavior of heavy metal ions on limonitic laterite was studied, and then the mechanism of Pb2+ and Cd2+ hydrate adsorption was described in detail by combining density functional theory (DFT) calculations. The results showed that the removal ratios of Pb2+ and Cd2+ by laterite were 99.1 % and 86.17 %, respectively, which were much higher than the removal efficiencies of Pb2+ and Cd2+ by synthetic goethite. Furthermore, according to isothermal adsorption and kinetic analysis, Pb2+ and Cd2+ were chemically adsorbed on laterite as a single molecular layer. Further mechanistic analysis from DFT indicated that Pb2+ hydrate exhibits bidentate adsorption on the goethite (010) surface, while the Cd2+ hydrate displays monodentate adsorption. Partial density of states (PDOS) and differential charge density analyses indicate that the Pb6d orbital hybridizes with the O1s orbital and the Pb6s orbital with the O2p orbital, forming the Pb-O bond. The Cd5s orbital hybridizes with the O2p orbital, forming the Cd-O bond. Both Pb2+ and Cd2+ undergo stable chemical absorption on the goethite (010) surface.

Efficient lead immobilization by bio-beads containing Pseudomonas rhodesiae and bone char

Mineralization of lead ions (Pb2+) to pyromorphite using phosphorus-containing materials is an effective way to remediate lead (Pb) contamination. Bone char is rich in phosphorus, but its immobilization of Pb2+ is limited by poor phosphate release. To utilize the phosphorus in bone char and provide a suitable growth environment for phosphate-solubilizing bacteria, bone char and Pseudomonas rhodesiae HP-7 were encapsulated into bio-beads, and the immobilization performance and mechanism of Pb in solution and soil by bio-beads were investigated. The results showed that 137 mg/g of phosphorus was released from bone char in the presence of the HP-7 strain. Pb2+ removal efficiency reached 100 % with an initial Pb2+ concentration of 1 mM, bone char content of 6 g/L, and bio-bead dosage of 1 %. Most Pb2+ was immobilized on the surface of the bio-beads as Pb5(PO4)3Cl. The soil remediation experiments showed a 34 % reduction in the acid-soluble fraction of Pb. The bio-beads showed good stability in long-term (30 d) soil remediation. The present study shows that bone char can be turned into an efficient Pb immobilization material in the presence of phosphate-solubilizing bacteria. Thus, bio-beads are expected to be used in the remediation of Pb-contaminated environments.