Removal Rate Of Pb Research Articles

Model test of in-situ remediation for heavy metal-contaminated clayey soil by artificial freezing and shaft washing

The low permeability of clayey soil and the pressure of liquid extraction and injection tend to form preferential flow paths in the soil, diminishing the remediation efficiency of shaft washing. Therefore, a new in-situ repair method combining artificial freezing and shaft washing is proposed. Using Pb and Cd contaminated clayey soil as the research object, in-situ model tests of different eluent types, concentrations, and suction modes were conducted to investigate the removal rate of heavy metals and the distribution of temperature and water field. The results demonstrated that the artificial freezing method can effectively induce the water (eluent) migration from the unfrozen zone to the freezing front. Besides, it effectively resolved the issue of poor washing efficiency caused by preferential flow between the extraction and injection wells during the extraction process. After five freeze-thaw cycles, the removal rate of Pb and Cd reached 46.16 % and 59.04 %, respectively. The combination of artificial freezing and plastic drainage plate technology merges artificial freezing and shaft washing methods to achieve the remediation of heavy metal-contaminated soil, providing a reference for the in-situ remediation of heavy metal-contaminated clayey soil.

Study on the enhancement of citric acid chemical leaching of contaminated soil by modified nano zero-valent iron.

This study aimed to evaluate the effect of modified nanoscale zero-valent iron (SAS-nZVI) on chemical leaching of lead and cadmium composite contaminated soil by citric acid (CA). The synthesized SAS-nZVI was used as a leaching aid to improve the removal rate of soil heavy metals (HMs) by CA chemical leaching. The effects of various factors such as SAS-nZVI dosage, elution temperature and elution time were studied. At the same time, the effect of chemical leaching on the basic physical and chemical properties of soil and the morphology of HMs was evaluated. The results show that when the SAS-nZVI dosage is 2.0g/L, the leaching temperature is 25°C, and the leaching time is 720min, the maximum removal rates of Pb and Cd in the soil are 77.64% and 97.15% respectively. The experimental results were evaluated using elution and desorption kinetic models (Elovich model, double constant model, diffusion model). The elution and desorption process of Pb and Cd in soil by SAS-nZVI-CA fitted well with the double-constant model, indicating that the desorption kinetic process of Pb and Cd is a heterogeneous diffusion process, and the elution process is controlled by diffusion factors. After leaching with SAS-nZVI-CA, the physical and chemical properties of the soil changed little, the mobility and toxicity of HMs in the soil were reduced, and the HMs content in the leaching waste liquid was reduced. It can be concluded that SAS-nZVI enhances the efficiency of CA in extracting Pb and Cd from soil, minimizes soil damage resulting from chemical leaching technology, and alleviates the challenges associated with treating leaching waste liquid.

Adsorption behavior of Mg–Al layered double hydroxide on Pb(Ⅱ), Zn(Ⅱ), Cd(Ⅱ), and As(V) coexisting in aqueous solution

MgAl-layered double hydroxide（MgAl-LDH）was synthesized via hydrothermal method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption, energy dispersive spectrum (EDS). The results proved that the prepared MgAl-LDH exhibited a well-defined layered structure and mesoporous morphology with a large specific surface area, which endowed them with abundant adsorption sites and diffusion mass transfer channels for heavy metal ions. Subsequently, the MgAl-LDH was used to evaluate the adsorption efficiency for Pb(Ⅱ), Zn (Ⅱ), Cd (Ⅱ), and As(V) coexisting in aqueous solutions by batch equilibrium experiments. The results showed favorable adsorption performance of MgAl-LDH toward four coexisting ionic species, with competitive adsorption among the heavy metal ions. Under the experimental conditions, the removal rates of Pb(Ⅱ), Zn (Ⅱ), Cd (Ⅱ), and As(V) ions were 96.7%, 97.1%, 65.2%, and 98.7%, respectively, and the selective order for cation adsorption followed Pb(Ⅱ) > Zn (Ⅱ) > Cd (Ⅱ). Furthermore, the adsorption mechanisms of Pb(Ⅱ), Zn (Ⅱ), Cd (Ⅱ) and As(V) by MgAl-LDH were detailed conducted by XRD, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis, and could be ascribed to the surface complexation, precipitation and isomorphic replacement for Pb(Ⅱ), Zn (Ⅱ), Cd (Ⅱ) while surface complexation, ion exchange and electrostatic adsorption for As(V).

Stability of bentonite colloid carried with kaolin-supported nanoscale zero-valent iron together as composite remediation materials and its adsorption property onto multi-heavy metals

In order to improve the defects of fast sedimentation rate and poor mobility of kaolin-supported nano-zero-valent iron (K-nZVI), bentonite colloid with strong suspension and adsorption was selected as the carrier in this study, and the stability and adsorption of bentonite colloid carried with K-nZVI (B-K-nZVI) were studied. The sedimentation tests as well as viscosity tests were prepared to determine the best solid mass ratio of the stable suspension fluid. The adsorption tests combined with adsorption kinetics and isotherm models were conducted to reveal the adsorption and reduction properties of B-K-nZVI to remove chromium, zinc and lead ions. The results showed that B-K-nZVI greatly presented superior stability and determined 5 % of bentonite and 0.2 % of K-nZVI as the best solid mass ratio. The removal rate of Pb and Zn exceeded 90 % within 30 minutes; meanwhile, the removal efficiency was Pb(II) > Zn(II) > Cr(total), indicating that the effect of B-K-nZVI on cations was significantly better than that on anions. In addition, the adsorption capacity of Pb(II), Zn(II) and Cr(total) by B-K-nZVI were 19.11 mg·g−1, 17.33 mg·g−1 and 1.03 mg·g−1 after 30 minutes of reaction, respectively. Compared to K-nZVI, the new composite remediation material has achieved significant improvements in stability and adsorption performance. This study has great significance for demonstrating B-K-nZVI as potential remediation materials to reduce the levels of some heavy metals in groundwater and providing reliable theoretical basis for remediation material design.

A novel combined process for enhancing soluble salt recovery and reducing pollutant diffusion in municipal solid waste incineration fly ash

There is a limited body of research on the recovery of soluble salts from municipal solid waste incineration fly ash (MSWI-FA), with challenges stemming from the effective management of residual heavy metals and dioxins. In this investigation, we propose using water-washing treatment for fly ash dechlorination and using CO2 aeration carbonation combined with ceramic membrane filtration to recover soluble salt resources from fly ash. This study investigated the impact of combined processes on fly ash soluble salt recovery, carbon dioxide capture and sequestration, heavy metal removal, and dioxin diffusion reduction. The findings revealed that the combined process can significantly enhance the rate of carbonation and the removal of heavy metals. Specifically, the removal rates of Pb and Zn reach 100%. The resulting CaCO3 precipitation particle size is smaller, averaging only approximately 4 μm, with greater surface porosity, higher heavy metal and dioxin content, and dioxin toxic equivalents as high as 8.11 ng TEQ/kg. Moreover, the dioxin content in the recovered mixed salt decreased, and its dioxin toxic equivalent was only 3.228.11 ng TEQ/kg. Consequently, the combined process of CO2 aeration combined with ceramic membrane filtration was used in conjunction to significantly reduce pollutants (heavy metals and dioxins) in the MSWI-FA recovered salt. This approach enhances the recyclable resource utilization of MSWI-FA and reduces the risk of pollution dispersal during MSWI-FA disposal and resource utilization.

Preparation and characterization of calcite/biochar composites fabricated by co-pyrolysis technique

In this study, calcite/biochar (CAL/BC) porous composites were synthesized via the co-pyrolysis of coconut shell (CS) and calcite (CAL) at temperatures ranging from 500°C, 600°C and 700°C. The surface morphology, chemical composition, and electrochemical properties of the CAL/BC composites were characterized using scanning electron microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS), BET analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and electrochemical workstation. The results revealed that CAL/BC composites produced at 700°C exhibited the highest adsorption capacity for Pb solution among all synthesized materials, with a maximum adsorption capacity of 79.8 mg/g. Furthermore, excellent regeneration properties were observed for all CAL/BC composites prepared at 500°C, 600°C, and 700°C, with a high removal rate of Pb maintained after four adsorption-desorption cycles. The CAL/BC composite synthesized at 700°C exhibited the lowest corrosion current density of 6.314×10−6A/cm2, indicating the most outstanding corrosion resistance among all three CAL/BC composites. Conversely, the highest corrosion current density of 8.871×10−5A/cm2 was observed in the CAL/BC composite prepared at 500°C, indicating the most inadequate corrosion resistance of this composite.

Removal of Pb(II), Cu(II), and Ag(I) from aqueous solutions using biochar derived by P-enriched water hyacinth

ABSTRACT A new synthesis was developed to prepare engineered biochar derived from phosphorous-rich water hyacinth. The statistical analysis indicated a significant correlation between P content and the removal rates of Pb (II), Cu (II), and Ag (I), revealing the pivotal role of enrich P in the biochar for heavy metals (HM) removal. SEM-EDX, XRD and FTIR analyses validated the presence of P functional groups on the surface of P-biochar. Batch experiments showed that the strong acidic initial solution negatively affected the adsorption of HM ions, and a similar negative impact was observed during Cu (II) adsorption under the high ionic strength conditions. Competitive adsorption experiment confirmed P-biochar’s resilience against competing metal ions during the adsorption of HM ions. Pb (II) and Ag (I) adsorption were primarily governed by precipitation/reduction, along with complexation reactions involving P functional groups. Cu (II) adsorption was dominated by complexation between Cu (II) and P functional groups.

Sodium alginate/ diatom -based blotting hydrogel material for Pb(II) removal: Effect of crosslinker optimization on its composition, selectivity, and desorption rate

In this study, we report a novel adsorption material (SAD-IIP), which is used for the directional adsorption of Pb (II), the polymerization time, the amount of crosslinking agent and the crosslinking time were optimized by response surface design, and the effect of the amount of crosslinking agent on the adsorption of lead on SAD-IIP was analyzed. The numerical control of cross-linking agent directly determines the number of effective imprinting sites, which affects the orientation selectivity of target ions and the desorption rate of the adsorbent. The results showed that the best adsorption performance was obtained when the polymerization temperature was 59.14 ° C, the amount of glutaraldehyde was 1.20 ml, and the crosslinking time was 92.55 min. The adsorption amount and imprinting factor were 244.09 mg/G and 9.90, respectively, the self-polymerization and self-crosslinking of the adsorbent in the imprinting process are effectively avoided. The adsorption mechanism of SAD-IIP is ion exchange with Ca2+ and chelation coordination of sulfhydryl, hydroxy, carboxyl with lead ion. After 10 cycles, the removal rate of Pb (II) and desorption rate of SAD-IIP were 92.75% and 70.43%, respectively. These results indicate that the rational control of the introduction conditions of cross-linking agent is of theoretical and practical value for the preparation of new hydrogel imprinting materials for selective adsorption of target ions and efficient recovery of Pb (II).

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.

A method for the efficient removal of Pb(II) by D001 resin in a rotating packed bed

The treatment of Pb(II) is a challenging problem. In this study, a new approach for removal of Pb(II) using D001 resin in a rotating packed bed (RPB) is proposed, and the adsorption behaviors and mechanisms are investigated. The results reveal that under optimal conditions (initial Pb(II) concentration c0 = 100 mg L−1, high-gravity factor β = 36.33, liquid flow rate QL = 60 L h−1, initial solution pH = 5.0, and temperature T = 303 K), the removal rate of Pb(II) in RPB is 95.54 % at 120 min, which is 12.18 % and 9.81 % higher than that in thermostatic shaker (TS) and stirred tank reactor (STR). The adsorption of Pb(II) by D001 resin can be well described by the Langmuir adsorption isotherm and the adsorption heat is 13.24 kJ mol−1, and it is a typical monomolecular layer adsorption. It is also found that the adsorption mechanism of Pb(II) by D001 resin in RPB follows the pseudo-first-order kinetics, and the rate constant k1 is 1.72 and 1.64 times that in TS and STR. The R-SO3Na is the dominant group and Na+ undergoes ion exchange with Pb (II) on the surface of D001 resin. This study provides a new method for the treatment of Pb(II).

Recovery of lead and chlorine via thermal co-treatment of municipal solid waste incineration fly ash and lead-rich waste cathode-ray tubes: Analysis of chlorination volatilization mechanism

In this study, a new lead (Pb) and chlorine (Cl) recovery process via the thermal co-treatment of Municipal solid waste (MSW) incineration fly ash (FA) and waste cathode-ray tubes (CRT) was developed and the synergistic effects under different CRT ratios, temperatures, and residence times were comprehensively investigated. Thermogravimetric experiments revealed that the co-processing of FA and CRT exhibited a remarkable synergistic effect as evidenced by the considerable increase in mass loss and mass-loss rate when compared with the theoretical values. When the mixtures with 50% CRT addition was treated at 1200 °C for 60 min, Pb removal rate reached the maximum value of 98.67%, and the Cl removal rate considerably increased by 37.32% compared to that with FA treatment alone. Additionally, the Cl content in the residue was < 2%. It was mainly attributed to the volatilization of chlorides, such as PbCl2, NaCl, and KCl. CaCl2 generated from the decomposition of CaClOH in FA was conducive to improve Pb removal in CRT through indirect chlorination and destroying the glass structure in CRT. Co-processing of FA and CRT demonstrates promising potential for several benefits, including the reduction in melting temperature, recovery of Pb and Cl from secondary fly ash, and the reutilization of calcium-rich slag.

Adsorption performance of groundnut and sheanut shells biochars in ternary system of toxic metals

The choice of biomass is influenced by its availability, potential characteristics such as abundance of functional groups and large surface area. This study explored the removal of toxic metal ions from aqueous solution using groundnut and sheanut shells biochars. Groundnut and sheanut shells biochars pyrolysed at 350 ± 5ºC and 700 ± 5°C and used to remove lead (Pb), cadmium (Cd) and mercury (Hg) in ternary systems. Initial toxic metal concentrations and residual concentrations after the biochars application were measured using atomic absorption spectrophotometer. The adsorption efficiency of groundnut and sheanut shells biochars pyrolysed at 350 ± 5ºC and 700 ± 5°C in the ternary system ranged from 81.28% to 100% for lead, cadmium ranged from 43.66% to 100% and mercury ranged from 96.38% to 100%. The higher removal rates of Pb, Cd and Hg by the biochars showed the pH solutions were favourable for the adsorption. Langmuir isotherm was the model that best fit the adsorption of toxic metal ions. Groundnut and sheanut shells biochars qualify as a feasible and economic option for toxic metals removal. Hence, studies should be conducted in real polluted water to ascertain the actual effectiveness of these biochar treatments.

Development of a loose powder sintering method for the preparation of porous ceramic from municipal solid waste incineration fly ash

Loose powder sintering was used to prepare porous ceramic from municipal solid waste incineration fly ash (MSWI FA) and waste glass (WG). Sintering experiments at various temperatures, holding times, Al2O3 and SiC were conducted to investigate their effect on the ceramic properties and volatile heavy metal removal efficiency. The results show that increasing temperature from 1100 °C to 1250 °C promoted the transition of the mixtures from loose powder to a densified sintered matrix, with a bulk density increase of 31.10% and an open porosity decrease of 70.41%. The bulk density of the ceramic increased to 2.44 g/cm3 with 3% Al2O3 addition. The removal rates of Pb, Zn, Cu and Cd were higher than 90% at 1200 °C for 90 min, and promoted by the increasing temperature and holding time. Notably, 3% Al2O3 addition inhibited the volatilisation of Zn, Cu and Cd, particularly for Zn, the removal rate of which reduced to 61.66% at 1200 °C. The bulk density of the ceramic decreased to a minimum value of 1.48 g/cm3 with 4% SiC. The ratio of MSWI FA:WG:Al2O3:borax of 28.3:56.7:10:5 was proposed to obtain ceramic with a bulk density of 1.54 g/cm3 and a water absorption rate of 8.59% at 1150 °C. The leaching concentration of the porous ceramic met the Chinese regulatory standard (GB 8978-1996). Preparation of MSWI FA-based porous ceramics using the powder sintering method is a promising route for the harmless utilisation of MSWI FA. The porous ceramic is potentially applicable as a thermal-insulation building material.

Dust removal ash coupled with high-temperature exhaust gas to produce energy gas CO and remove the heavy metals synchronously

In order to solve the utilization problem of dry quenching coke dust removal ash (DRA) and high-temperature exhaust gas (HTEG) at the same time, this study proposes a new technology that combines DRA and high-temperature exhaust gas to produce energy gas CO and realize the removal of heavy metals in dust removal ash. The reaction properties of DRA and high-temperature exhaust gases, as well as the migration law of heavy metals, are preliminarily evaluated using thermodynamic simulation software (FactSage) and a combination of thermogravimetric mass spectrometry (TG-MS). The dropper furnace (DF) experiments are used to verify the feasibility of the new technology by simulating the high-temperature flue gas environment. The findings reveal that as pressure rises, the content of gas products namely CO2 and CH4 rises while the content of gas products CO and H2 falls. At the same time, when the temperature rises, the CO and H2 contents rise. Heavy metals such as Cd, Pb, and Zn are also more volatile, whereas heavy metals such as Ni, Cr, and Cu, require higher temperatures to volatilize. As the temperature increases from 800 to 1200 °C, the Pb removal rate climbs from 34.6% to 92.5%, the Cd removal rate increases from 46.5% to 95.6%, and the Zn removal rate increases from 13.4% to 80.5%. The new technology captures CO2 from high-temperature exhaust gases and converts them into CO energy gases, simultaneously realizing the removal of heavy metals. This provides an innovative solution for the treatment of organic solid waste.

Efficient removal of Pb(II) by iminodiacetic acid modified magnetic mesoporous carbon

Magnetic mesoporous adsorbent carbon modified with iminodiacetic acid (Fe3O4@mC-IDA), was prepared to remove Pb(II). The magnetic mesoporous carbon (Fe3O4@mC) was first synthesized by in-situ growing carbon layers on the surface of ferrosoferric oxide, which exhibited large specific surface area and mesoporous structure, and the template molecule and carbon source are both from rich and cheap magnesium citrate. Then, iminodiacetic acid (IDA) was attached to Fe3O4@mC by a ring opening reaction. Multiple characterization techniques were applied to demonstrate the synthesis of the adsorbent. The composite could achieve adsorption equilibrium of Pb(II) in 65 min, and had a maximum adsorption capacity of 429.23 mg g−1 for Pb(II). Langmuir isothermal, pseudo-2nd-order kinetics model and Elovich model could be relatively suitable for simulating the adsorption process. In addition, the adsorbent had fine reusability, and the removal rate of Pb (II) reached 90.67% after 5 cycles. The adsorption mechanistic study showed that COO− and tertiary amine formed tridentate chelates with Pb(II), and hydroxyl groups combined with Pb(II) through electrostatic attraction. These results suggested that Fe3O4@mC-IDA was a potential adsorbent for Pb(II) removal with fast adsorption speed, easy separation ability and fine reusability.

Removal of heavy metals from fly ash using electrodialysis driven by a bioelectrochemical system: a case study of Pb, Mn, Cu and Cd

ABSTRACT Municipal solid waste incineration (MSWI) fly ash is classified as hazardous waste due to high leachable heavy metals, and incineration leachate belongs to organic wastewater with high biodegradability. Electrodialysis (ED) has shown potential for the removal of heavy metals from fly ash, and bioelectrochemical system (BES) employs biological and electrochemical reactions to generate electricity and remove contaminants from a wide range of substrates. In this study, the ED-BES coupled system was constructed for the co-treatment of fly ash and incineration leachate, where the ED was driven by BES. The treatment effect of fly ash by varying additional voltage, initial pH and liquid-to-solid (L/S) ratio was evaluated. Results showed that the highest removal rates of Pb, Mn, Cu and Cd were 25.43%, 20.13%, 32.14% and 18.87% after 14 days treatment of the coupled system, respectively. These values were obtained under 300 mV of additional voltage, L/S 20 and initial pH3. After the treatment of the coupled system, the fly ash leaching toxicity was lower than the threshold of GB5085.3-2007. The highest energy saving for removed Pb, Mn, Cu and Cd were 6.72, 15.61, 8.99 and 17.46 kWh/kg, respectively. The ED-BES can be considered a cleanliness approach to treating fly ash and incineration leachate simultaneously.

Environmental remediation of Pb–Cd contaminated soil with organic phosphonic acids-saponin: Conditions, effectiveness, ecological risk and recovery

Soil washing is a rapid and efficient method for heavy metals removal. In this study, a kind of novel environmentally friendly eluent is proposed, consisting of ethylenediamine tetra methylene phosphonic acid and saponin (E-S). In a response surface optimization design (RSOD), the operating parameters were optimized and ecological effects were investigated. Additionally, soil microbial diversity and composition were discussed. Finally, an optimal method for chelator recovery was presented. The single-factor and RSOD results showed that E-S had higher remediation efficiency for Pb–Cd contaminated soil with the best parameters of duration 240 min, temperature 40 °C, E/S ratio 1:1. Under these operating conditions, the removal rates of Pb and Cd were (72.2 ± 0.5)% and (61.2 ± 0.4)% for the artificially contaminated soil and (69.2 ± 0.1)% and (65.2 ± 0.2)% for in situ contaminated soil, respectively. The contents of Pb and Cd decreased from 562.36 mg/kg to 180.41 mg/kg and 80.96 mg/kg to 27.2 mg/kg respectively, and the soil ecological risk indexes reduced from 32% to 24% for Pb and 36%–27% for Cd. Owing to the efficient enrichment of Stenotrophomonas in soil, E-S has a potential of simultaneous removal effect on organic pollutants as well. Furthermore, the results revealed that E-S can be effectively recovered (>95%) by sodium sulfide precipitation.

Improving radish phosphorus utilization efficiency and inhibiting Cd and Pb uptake by using heavy metal-immobilizing and phosphate-solubilizing bacteria

Phosphate-solubilizing bacteria play a key role in increasing plant growth as potential suppliers of soluble phosphorus and have great potential for the remediation of heavy metal-polluted soils. However, the soil and microbiological mechanisms by which phosphate-solubilizing bacteria prevent heavy metal absorption in radish have not been adequately studied. Here, the mechanisms of phosphorus solubilization, Cd and Pb immobilization, and the inhibition of heavy metal absorption by phosphate-solubilizing bacteria were studied in radish through solution adsorption and pot experiments. Two phosphate-solubilizing bacteria with high Cd and Pb removal rates (46.9–97.12 %), Klebsiella sp. M2 and Kluyvera sp. M8, were isolated. The soluble phosphorus content released by strains M2 and M8 was 265–277 mg L−1, achieved by secreting oxalic acid, ascorbic acid, citric acid, and succinic acid in an inorganic phosphorus medium containing 3 mg L−1 Cd and 5 mg L−1 Pb. Furthermore, these two functional strains induced the formation of Pb2(PO4)2, Cd(PO3)2, Fe2Pb3(PO4)2, CdS, and PbS precipitates that immobilized Cd and Pb in the solution. In general, strains M2 and M8 inhibited the absorption of Cd and Pb by radish by the following mechanisms: i) bacterial cell wall adsorption, ii) induction of Pb2(PO4)2, Cd(PO3)2, Fe2Pb3(PO4)2, CdS, and PbS precipitation in the solution/soil, iii) increases in the Ca2P and FeP contents in the radish rhizosphere, and iv) the promotion of bacterial community enrichment toward phosphorus-solubilizing and plant growth-promoting properties (Ramlibacter, Enterobacter, Bacillus, Gemmatimonas, and Lysinibacillusin) in the radish rhizosphere. These results provide bacterial resources and technical approaches to heavy metal pollution amelioration and efficient phosphorus fertilizer use in farmland.

Design of Zr-MOFs by Introducing Multiple Ligands for Efficient and Selective Capturing of Pb(II) from Aqueous Solutions

The existence of lead ions seriously affects the quality of many metal products in metallurgical enterprises. Currently, the various methods of lead-ion removal tried by researchers will affect valuable metals in the removal process, thus resulting in low economic efficiency. In this study, a novel metal-organic framework adsorbent (UiO-FHD) which efficiently and selectively captures lead ions is developed by introducing multiple ligands. The maximum adsorption capacity of lead ions is 433.15 mg/g at pH 5. The adsorption process accords with the pseudo-second-order kinetic and the Langmuir isotherm models at room temperature. Thermodynamic experiments indicate that the removal of Pb(II) is facilitated by appropriate temperature reduction. The performance tests indicate that UiO-FHD maintains a high removal rate of 90.35% for Pb(II) after four consecutive adsorption-desorption cycles. The distribution coefficient of lead ions (26.7 L/g) shows that UiO-FHD has excellent selective adsorption for lead ions. It is revealed that the chelation of the sulfhydryl groups and the electrostatic interaction of the hydroxyl groups are the dominant factors to improve the removal rate of Pb(II) by density functional theory calculations. This study clarifies the value of self-designed novel organic ligands in metal-organic framework materials that selectively capture heavy-metal ions.

Nanoscale Zero-Valent Iron Dispersed by Sodium Alginate Enables Highly Efficient Removal of Lead (Pb) from Aqueous Solution

Nanozero-valent iron (NZVI) shows great potential in the remediation of water pollution, but its application is limited by its instability and tendency to aggregate. To enhance the dispersibility and antioxidant properties of NZVI, we prepared composites (SN) by wrapping NZVI with sodium alginate (SA) for the removal of Pb(II) from water. Various characterization methods such as SEM-EDS, BET, XPS, and FT-IR were used to study the structure of the materials, and the adsorption properties of Pb(II) in the materials were analyzed using adsorption kinetics and adsorption isotherm experiments. The results showed that SN had a specific surface area of 47.05 m2/g, which was significantly higher than the 7.56 m2/g of NZVI, and the surface passivation was reduced. The maximum adsorption amount of SN on Pb(II) was obtained by fitting the adsorption isotherm model at 70.92 mg/g. After five cycles of adsorption, SN exhibited a removal rate of 95.11% for Pb(II). The mechanism of Pb(II) removal by SN involved the synergistic effect of electrostatic adsorption, redox reaction, ion exchange, and coprecipitation. Notably, even after 90 days of aging, the removal rate of Pb(II) by SN remained high at 95.39%, demonstrating good reactivity. These results indicated that SN is an effective adsorbent to remove Pb(II) contamination.