Order Of Pb Research Articles

Seasonal Dynamics of Heavy Metal Concentrations in Water and Fish from Hakaluki Haor of Bangladesh

Food safety is currently a serious concern due to the health risks associated with food intake, particularly due to heavy metal contamination. Therefore, the present study was conducted to investigate the heavy metals concentration in water and fishes collected from Hakaluki haor, Bangladesh. Three important fish species, Labeo rohita, Cirrhinus cirrhosis, and Labeo calbasu, together with water samples, were analyzed for heavy metals (Pb, Cr, and Cd), respectively. Considering four seasons, namely the monsoon, post-monsoon, winter, and pre-monsoon, a total of 72 fish samples were collected from three fishing stations from June 2017 to May 2018. The results showed that the total mean concentration of metals in water (mg L−1) was found to be in the order of Pb (0.125 ± 0.058) > Cr (0.026 ± 0.012) > Cd (0.001 ± 0.0002) within the maximum permissible limits set by the EU and WHO, except for Pb concentrations. Similarly, the total mean concentrations of Pb in fish (µg g−1) were found in order of L. rohita (0.388 ± 0.291) > Cirrhinus cirrhosus (0.334 ± 0.236) > L. calbasu (0.251 ± 0.117) greater than the maximum permissible limits (0.3 µg g−1) set by FIQC, except for L. calbasu. However, the mean concentrations of Cr and Cd in fish were found to be below the maximum permissible limits of FAO and FIQC, respectively. The quantity of heavy metal contamination in this haor indicates that the situation is worrying for the region’s biota and residents. However, to protect public health and reduce environmental risk, the appropriate authorities should oversee and monitor it with strong hands.

Seasonal Variations in Bioaccumulation and Translocation of Toxic Heavy Metals in the Dominant Vegetables of East Kolkata Wetlands: a Case Study with Suggestive Ecorestorative Strategies.

In recent times, East Kolkata Wetlands (EKW), a designated Ramsar site in the eastern part of megacity Kolkata, has been threatened by toxic heavy metal (HM) pollution. Besides being a natural wetland supporting biodiversity, EKW serves as a significant food basket for the city. For assessing the magnitude of HM pollution in this wetland, the three most cultivated food crops of EKW, namely Lagenaria siceraria (bottle gourd), Abelmoschus esculentus (ladies’ fingers), and Zea mays (maize), as well as the ambient soil samples, were collected during premonsoon, monsoon, and postmonsoon for 2 consecutive years (2016 and 2017). Predominant HMs like cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb) were analyzed in the roots and edible parts of these plants, as well as in the ambient soil to evaluate the bioaccumulation factor (BF) and translocation factor (TF) of each HM in the three vegetables. It was observed that the HM content in the food crop species followed the order Z. mays > L. siceraria > A. esculentus. HMs accumulated in all three vegetables as per the order Pb > Cd > Cr > Hg. Monsoon seems to be threatening in terms of bioaccumulation and translocation of HMs as both BF and TF were highest in this season irrespective of the plant species. Hence it demands critical monitoring of HM pollution levels in this wetland and subsequent ecorestoration through distinctive plant growth-promoting rhizobacteria (PGPR)-assisted co-cultivation of these food crops with low-metal-accumulating, deep-rooted, high-biomass-yielding, and bioenergy-producing perennial grass species for minimizing HM intake.

Dual-Modified Lignin-Assembled Multilayer Microsphere with Excellent Pb2+ Capture.

With the continuous research on lignin-based sorbents, there are still limitations in the research of spherical sorbents with a high adsorption capacity for Pb2+. In order to solve the problem of low adsorption effect, alkali lignin (AL) was modified and assembled to increase the adsorption active sites. In this work, we used dual-modified lignin (DML) as a raw material to assemble a singular lignin-based multilayer microsphere (LMM) with sodium alginate (SA) and dopamine. The prepared adsorbent had various active functional groups and spherical structures; the specific surface area was 2.14 m2/g and the average pore size was 8.32 nm. The adsorption process followed the Freundlich isotherm and the second-order kinetic model. Therefore, the LMM adsorbed Pb2+ ascribed by the electrostatic attraction and surface complexation; the adsorption capacity was 250 mg/g. The LMM showed a selective adsorption performance for Pb2+ and the adsorption capacity followed the order Pb2+ (187.4 mg/g) > Cu2+(168.0 mg/g) > Mn2+(166.5 mg/g). After three cycles, the removal efficiency of Pb2+ by the LMM was 69.34%, indicating the reproducibility of LMM.

Appraisal of heavy metal pollution in the water resources of Western Uttar Pradesh, India and associated risks

The ponds are the important water resources for the developing nations including rural India. They not only supply the water during the non-monsoon period but also acts as a flood absorber during the monsoon period. However, with the increase in population, modernization, and alternate water supply schemes, the ponds are getting polluted mainly due to the discharge of wastewater from residential areas, sewage outlets, solid waste dump sites, livestock rearing sites (e.g., dairy, poultry), and fertilizers and pesticides from farmers’ fields. The sludge accumulated in these water bodies may contain an appreciable amount of toxic metals that may leach to the groundwater and long-term use of contaminated water, either directly from these water bodies or the nearby handpumps or tubewells, can cause serious threats to human health. This study investigated nine heavy metal (Pb, Cu, Ni, Zn, Cr, Cd, Fe, As, and Mn) contamination in the pond sludge, pond soil, and groundwater at twenty-one villages in Western Uttar Pradesh (India), and provides a sound case for examining the toxic metal accumulation in the terrestrial water bodies. The mean concentration of Pb, Cu, Ni, Zn, Cr, Cd, Fe, As and Mn in pond sludge was 0.64, 0.53, 0.94, 3.34, 0.62, 0.010, 151.70, 0.32, and 35.02 mg/kg sludge, respectively, and in pond soil the concentration of Pb, Cu, Ni, Zn, Cr, Cd, Fe, As and Mn were 0.13, 0.45, 1.21, 0.82, 3.22, 0.06, 2055.04, 0.16, and 457.84 mg/kg soil, respectively. The geo-accumulation index (I-geo) in the pond sludge and soil ranged from unpolluted to extremely polluted. The average I-geo values of metals in pond sludge and soil were in order Pb (4.93) > Zn (4.36) > Ni (0.70) > Cu (0.40) > As (0.32) > Cd (-0.58) > Cr (-1.96) > Fe (-4.24) > Mn (-5.28) and Cu (2.76) > Cr (2.35) > Pb (2.17) > Ni (2.01) > Zn (1.53) > Cd (-0.22) > Fe (-0.49) > As (-0.78) > Mn (-1.41), respectively. The combined ecological risk due to metal accumulation extended from low risk to very high risk. The groundwater samples were observed to non-comply the drinking water standards due to high levels of Pb, Cu, Ni, Fe, and Mn, and the human health hazard index ranged from 0.831 to 21.76. This study highlights the value of baseline monitoring and provides a sound case for examining the pond ecosystem for heavy metal toxicity before and during the rejuvenation of such water bodies in India and other sub-tropical countries.

In situ Functionalized Mesoporous Silicas for Sustainable Remediation Strategies in Removal of Inorganic Pollutants from Contaminated Environmental Water.

Low-cost mesoporous silicas of the SBA-15 family were prepared, aimed for removal of a broad spectrum of both cationic and anionic forms of hazardous metal pollutants (Cr(III, VI), Mn(II, VII), Pb(II), Cd(II), and Cu(II)) from environmental water. Series of mono- and bifunctional materials with immobilized ethylenediaminetriacetic acid (EDTA), primary amine (NH2), and quaternary ammonium (QAS) groups were prepared in a cost-efficient one-step synthesis using two silica sources, low-cost sodium metasilicate (Na2SiO3 9H2O) and the conventional source—tetraethylorthosilicate (TEOS). The functionalized SBA-15 samples obtained from both silica sources were highly ordered, as evidenced by TEM and SAXS data. All obtained materials were mesoporous with high surface area values of up to 745 m2/g, pore volumes from 0.99 to 1.44 cm3/g, and narrow pore distributions near 7 nm. The adsorption affinity of the EDTA-functionalized samples followed the common order Pb(II)> Cd(II)> Cu(II)> Cr(III)> Mn(II), which could be explained based on the Pearson theory. The highest adsorption capacities were observed for samples functionalized by EDTA groups using TEOS for synthesis (TEOS/EDTA): 195.6 mg/g for Pb(II), 111.2 mg/g for Cd(II), 58.7 mg/g for Cu(II), 57.7 mg/g for Cr(III), and 49.4 mg/g for Mn(II). Moreover, organic matter (humic acid up to 10 mg/L) and inorganic (Na(I), K(I), Mg(II), Ca(II), etc) macrocomponents present in environmental water had almost negligible effect on the removal of these cations. The NaSi/EDTA/NH2 sample revealed a better selectivity compared to the NaSi/NH2 sample towards such species as Cr(III), Mn(II), Cd(II), and Cu(II). The chromate-ions uptake at pH 7.5 by the TEOS/QAS sample turned practically unaffected by the presence of doubly charged anions (CO32–, SO42–). The content of functional groups on the surface of MS decreased only slightly (∼1–5%) after several regeneration cycles. The complete desorption of all heavy metal ions can be achieved using 1 mol/L EDTA solution. Reusability tests demonstrated the complete stability of the adsorbent for at least five to six consecutive adsorption/desorption cycles with no decrease in its adsorption characteristics compared to those obtained by 0.05 mol/L HNO3 treatments. The synthesized mesoporous materials were evaluated for removal of the heavy metal ions from drinking and different natural water samples, proving their potential as sustainable, effective, and cost-efficient adsorbents.

An Investigation for Heavy Metals’ Contamination in Farmers’ Fingernails: Case Study in Libya

This study aims to assess the concentration levels of heavy metals, which are associated with health hazards: arsenic (As), cadmium (Cd), and lead (Pb) among Libyan farmers using fingernails as a biomarker. Factors that may contribute for accumulation of these toxic heavy metals in the farmers’ fingernails were also evaluated. This cross-sectional study involved 127 farmers and 25 high school teachers living in the same geographical area as the farmers (served as the control group). Fingernail samples of the participants were collected, treated, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for As, Cd, and Pb contents after microwave acid digestion. Results of this study indicated that the concentration levels of the investigated heavy metals in fingernail samples of both participating farmers and control group were in order of Pb > Cd > As. Also, the results showed that As, Cd, and Pb levels in the farmers’ fingernails were found to be higher than in the control group by about 9-, 5-, and 2-fold, respectively. This difference for all heavy metals analyzed was found to be statistically significant P < 0.05 . As a conclusion, the results of this study clearly indicated that Libyan farmers have been exposed to high levels of toxic heavy metals as a result of their agricultural activities compared with the general population living in the same geographical area as farmers, which, in turn, pose a high risk to their health. Thus, toxicological, epidemiological, and clinical studies for the Libyan farmers are strongly recommended.

Heavy metal concentration in water, soil and cultivated vegetables at the edge of Kashaf Roud River, Mashhad, Iran: ecological risk assessment and bioaccumulation factor

ABSTRACT The entrance of heavy metals through human activities causes pollution of water, soil, and plants. The aim of this study was to measure the heavy metals concentration (Hg, Pb, As, and Cd) and their ecological impacts on water, soil, and vegetables in the Kashaf Roud River basin. Hence, 72 samples of irrigation water, 72 samples of soils, and 216 samples of vegetables (dill, leek, and basil) were collected. The contamination levels were evaluated by several ecological indices including Ecological Risks index (ERI), Heavy Metal Evaluation Index (HEI), Contamination factor (Cf), Pollution Index (PI), geo-accumulation index (Igeo), Potential ecological risk index (RI), Pollution load index (PLI), and modified degree of contamination (MDC). Based on obtained results, concentrations of heavy metals in water and soil samples were in the order of Pb>As>Cd>Hg. In addition, Pb and As had the highest concentration in vegetables with the mean total concentrations of 1.60 and 0.08 mgkg−1 wet weight, respectively. According to ERI value (238), water sampling site no. 3 had higher pollution than other places and was classified in the considerable ecological risk. Among the soil samples, the Cf average values followed the declining order of Cd (7.78)>Pb (6.91)>Hg (4.26)>As (2.68), so that Pb and Cd presented high contamination levels. Moreover, all soil samples of the studied region possessed PLI>1, which confirms their contamination with heavy metals. Finally, the trends in the BAF values for heavy metals in various vegetables were in order of Hg>Cd≈Pb>As for Leek and Hg>As> Pb>Cd for Dill and Basil. Concentrations of heavy metals in soil and water samples were within the national and international standard ranges. However, the concentrations of these metals in some vegetable samples exceeded the national and international levels. The utilisation of standard quality effluent for agricultural irrigation requires control measures and good organisational performance.

Use of municipal waste incineration fly ashes (MSWI FA) in metakaolin-based geopolymer.

The solidification/stabilization (S/S) through geopolymer is regarded as the ideal approach for the disposal of municipal waste incineration fly ashes (MSWI FA). This work aims to investigate the S/S behaviors of MSWI FA (up to 20 wt.% incorporations) in metakaolin-based geopolymer (MKG), with a focus on the effect of MSWI FA dosage on the performance of geopolymer. Results show that MSWI FA participates in the geopolymerization and alters the reaction products of geopolymer. MSWI FA imposes a dual effect on the performance of geopolymers. A dosage of MSWI FA lower than 5 wt.% can enhance the strength development of geopolymer, mainly due to the formation of C-A-S-H gels in the framework. However, an MSWI FA addition higher than 5 wt.% significantly decreases the strength of geopolymer. The efficiency of immobilization increases with the ionic radius of heavy metals, following the order of Pb > Zn > Cr > Cu. Heavy metals are immobilized in geopolymer framework through ions exchange and coordination to the nonbridging Si-O- and Al-O-. These results help to further understand the use of metakaolin-based geopolymer as an MSWI FA S/S binder.

Evaluation of the Immobilization of Coexisting Heavy Metal Ions of Pb2+, Cd2+ , and Zn2+ from Water by Dairy Manure-Derived Biochar: Performance and Reusability.

Heavy metals including Cd, Pb, and Zn are prevalent stormwater and groundwater contaminants derived from natural and human activities, and there is a lack of cost-effective treatment for their removal. Recently, biochar has been increasingly recognized as a promising low-cost sorbent that can be used to remediate heavy metal contaminated water. This study evaluates the immobilization/release performance of dairy manure-derived biochar (DM-BC) as a sustainable material for competitive removal of coexisting heavy metal ions from water and explains the underlying mechanism for regeneration/reusability of biochar. Results showed that the metal ions exhibited competitive removal in the order of Pb2+ ≫ Zn2+ > Cd2+. The pH played a decisive role in influencing metal ion speciation affecting the electrostatic attraction/repulsion and surface complexation. Higher pH led to greater removal for Pb2+ and Cd2+, whereas Zn2+ showed maximum removal at pH ≈ 7.5. Diffuse reflectance infrared spectroscopy, scanning electron microscopy, and X-ray diffraction confirmed the interactions and precipitation reactions of oxygen-containing functional groups (e.g., ─OH, , and Si─O) as key participants in metal immobilization. Langmuir, Freundlich, and Redlich-Peterson isotherm modeling data showed varied and unique results depending on the metal ion and concentration. The removal kinetics and model fitting showed that the three steps of intraparticle diffusion might be more representative for describing the immobilization processes of metal ions on the external surface and internal pores. In the flow-through columns, DM-BC effectively retained the mixed metal ions of Cd2+, Pb2+, and Zn2+ showing 100% removal for the duration of the column run over three cycles of regeneration and reuse.

Cadmium, lead and arsenic contamination in an abandoned nonferrous metal smelting site in southern China: Chemical speciation and mobility

The investigation of chemical speciation of primary toxic metal(loid)s (Cd, Pb, and As) in soil profile in nonferrous metal smelting site is a key to the assessment of their mobility characteristics and formulation of subsequent remediation strategy. In this study, 74 soil samples were collected at 12 different soil profiles; soil physio-chemical properties and total content of Cd, Pb and As and corresponding chemical speciation were also determined. The results showed that the mean total concentration followed the order of Pb > As > Cd. A large proportion of Pb, Cd and As were accumulated in upper soil profiles (depth < 3 m). Heavy pollution of Pb, Cd and As were observed in the whole soil profile at the area of fuel oil storage tank (ZY6) and lead smelting area (ZY8). The dominant fraction of Cd was exchangeable fraction (F1); Pb was dominant in Fe/Mn oxides-bound fraction (F3) in most cases; Crystallized Fe/Al hydrous oxides bound fraction (F4) generally accounted for a large proportion of As. Mobility factor (MF) followed the order Cd > As > Pb, indicating that Cd was the most mobile element in soil profiles. Pearson correlation analysis found that MFCd was significantly positively correlated to soil silt; the F4 fraction percentage of As was significantly positively correlated to soil redox potential (Eh). Additionally, MFCd/Pb was found to be positively correlated to crystalline iron (Fec), while negatively correlated to amorphous iron (Feo). The findings reported in this study, on the basis of distribution characteristics of chemical speciation could provide a new solution for future soil remediation at the site. Long-term solutions to metal(loid)s pollution might be offered by microbial-assisted soil washing technique that promotes the transformation of Fe/Mn oxides-bound fraction and organic/sulfide-bound fraction.

Ecological and Health Risk Assessment of Heavy Metals in Soils from Recycled Lead Smelting Sites

In this study, 258 soil samples were collected to determine the total content and each speciation fraction of chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in the soil by inductively coupled plasma mass spectrometry (ICP-MS), and their potential ecological and human health risks were assessed using the geo-accumulation index (Igeo), risk assessment code (RAC), and health risk assessment. The results showed that: (1) The mean concentrations of heavy metals (HMs) (mg/kg) in the surface soil of the site were in the order of Pb (1921.77) &gt; Mn (598.21) &gt; Zn (162.29) &gt; Cr (84.65) &gt; Cu (15.16) &gt; Cd (1.8), with the mean values of Cd and Pb exceeding the local background values by 164 and 725 times. (2) In the vertical direction, Cr, Mn, and Pb have no tendency to migrate downward; Cd and Zn demonstrate a strong ability to migrate. (3) The bioavailability of Cd is the highest in the surface soil, followed by Mn and Pb; in the soil below a depth of 0.5 m, the prevalent form of HMs is its residual state (F4). (4) The degree of Igeo pollution of each HMs is: Pb &gt; Cd &gt; Zn &gt; Cr = Mn = Cu, where Pb pollutes the environment to an extremely contaminated level and Cd causes heavy pollution thereof. According to the RAC results, Cd in the surface soil poses a high risk to the environment, and Pb and Mn pose a moderate risk; meanwhile, with the increase of depth, the risk posed by Cd and Mn to the ecosystem shows a tendency to increase. Health risk evaluation indicated that respiratory intake was the main pathway affecting the carcinogenic risk (CR) and hazard quotient (HQ) of HMs, where Pb and Cr were the main hazard factors for non-CR and Cr was the main carcinogenic factor. This study can provide scientific guidance and technical support for soil risk control or remediation of HM-contaminated sites.

Insight into different removal behaviors and mechanism of heavy metals via sulfate-loaded layered double oxide

Sulfur-containing materials with high affinity toward heavy metals have recently aroused great research enthusiasm. Yet the removal differences and mechanisms for various heavy metals remain unclear in view of rarely systematical reports. In this regard, a sulfate-loaded adsorbent (MgAl-LDO@S) synthesized by precursor-calcination strategy was employed for investigating the removal differences of heavy metals (i.e., Pb(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ), typical heavy metals in wastewater). As predicted, a diverse adsorption capability for metals on MgAl-LDO@S was observed, following the order of Pb(Ⅱ) (631.90 mg g−1) > Cd(Ⅱ) (208.27 mg g−1) > Ni(Ⅱ) (119.02 mg g−1). Both adsorption isotherm and kinetic demonstrated that the monolayer, heterogeneous-homogeneous, and multilayer adsorption occurred in Pb(Ⅱ), Cd(Ⅱ) and Ni(Ⅱ), respectively, which were controlled by chemisorption. Furthermore, the removal differences were deeply exploded via the combination of XRD, FT-IR and XPS analyses and contribution calculation. The ion exchange was the main adsorption mechanisms for Pb (II) with 44.77%, while complexation dominated in Cd(II) and Ni(II) removal, with the proportion of 53.36% and 55.89%, respectively. Besides, the solubility constant (Ksp) of precipitate, affinity of sulfate group, as well as the self-characteristic properties contributed to various removal ability for heavy metal ions (e.g., ionic radius, electronegativity, and hard-soft-acid-base attribute) as well.

Quantitative Analysis of Heavy Metals in Unbranded Whitening Creams Sold in Karachi

The use of cosmetic products contaminated with toxic heavy metals can cause serious health issues among consumers. Especially, skin whitening products are widely used among women and consumers are completely unaware of the presence of toxic metals in such products. Therefore, the present study is conducted for the first time in Karachi that aims to assess the concentration of selected heavy metals in unbranded skin whitening creams sold in local markets of Karachi using Merck Super Nova60 kits. The findings of the study revealed that the mean concentration of heavy metals was found in the order of Pb &gt; Cr &gt; Ni &gt; Cu &gt; As among all collected samples. Proper monitoring and control of heavy metals must be required during the manufacturing process of the products to avoid serious health impacts among consumers.

Ecological and Health Risk Assessments Based on the Total Amount and Speciation of Heavy Metals in Soils Around Mining Areas

Topsoil and supporting crop samples around a mining area were collected in Longyan City, and the total amounts and speciation of Pb, Cd, and As in the samples were determined. The ecological risk and human health risk assessment of soil heavy metals Pb, Cd, and As were carried out using the Hakanson potential ecological risk assessment method, the ecological risk classification method based on the principle of geochemical statistics, and the health risk assessment method in accordance with the characteristics of human exposure parameters in China. The results indicated that the heavy metal elements in the soil in the study area exceeded the environmental quality standards for Pb and Cd, and the heavy metal contents in cereal grains exceeded the food limit value mainly for Pb. The proportion of the four bioavailable forms except the residue state followed the order of Pb>Cd>As. The ecological risk assessment results based on the total amount of heavy metals and bioavailable forms showed that Cd was the most important ecological risk factor. The single potential ecological risk of Cd and the comprehensive ecological risk of Pb, Cd, and As in the soil based on bioavailable forms were significantly reduced compared with that based on the total amount. The proportion of medium and superior samples decreased from 100% and 50.0% to 17.2% and 7.81%, respectively, and the divided risk zone basically contained all the warning points of exceeding the standard of crops. Oral ingestion was the main carcinogenic and non-carcinogenic exposure route of heavy metals. In terms of carcinogenic risk, the risk of human carcinogenic health exposure to Cd and As was within the acceptable range, regardless of whether bioavailability was considered. Among the non-carcinogenic risks, the non-carcinogenic risk of the heavy metal Cd was negligible. When only the total amount of heavy metals was considered, the non-carcinogenic risk index of Pb and As under the three exposure pathways ranged from 0.14 to 8.65 and from 0.04 to 2.85, respectively. After considering the adjustment of bioavailability, the non-carcinogenic risk of As was greatly reduced and could be considered to no longer have non-carcinogenic risk. Although the non-carcinogenic exposure risk index of Pb was reduced by 84.7%, the maximum value still reached 1.69, which would cause non-carcinogenic harm to the population and was the key to soil remediation in mining areas.

Evaluation of the efficiency of ZnCl2 activated cocoa pod husk charcoal on the removal of Cu2+, Cd2+, and Pb2+ ions from aqueous solution

The efficiency of ZnCl2-activated cocoa pod husk charcoal (ACPHC) in removing Pb(II), Cu(II) and Cd(II) ions from aqueous solution was investigated under different conditions of shaking speed, contact time, adsorbent dose, adsorbate concentration, pH, and temperature with a view to widening the applications of the husk. Adsorption equilibrium, kinetics and desorption studies were conducted. Activated carbon produced at 650 °C was found to give the best desired properties. The optimum shaking time and pH value were 45 min and 6. The shaking speed of 700 rpm gave maximum removal efficiency (mean ± sd) 97.02 ± 0.34%, 96.24 ± 0.19%, and 96.85 ± 0.01% for Pb(II), Cu(II), and Cd(II) ions at the optimum pH, 25 °C, and 0.1 g adsorbent/25 ml solution with adsorption capacities of 2.426, 2.406, and 2.421 mg/g, respectively. While the average capacity at the optimum contact time was 2.290 mg/g. Non-linear Temkin and Redlich–Peterson and linear Langmuir isotherm models gave the best description of the adsorption equilibrium of the metal ions onto ACPHC surface, while pseudo-second order kinetics model gave the best description of the adsorption kinetics. The rate of removal of the metal ions was in the order Pb(II) > Cu(II) > Cd(II). The regeneration of the spent adsorbent was efficient with respect to the considered metal ions. The recovery values were 96.72 ± 0.43%, 92.76 ± 0.49%, and 91.66 ± 0.34% for Pb(II), Cu(II), and Cd(II) ions, respectively. Thus ACPHC was found to be an efficient low-cost material for the removal of the studied metal ions from aqueous solution.

Hydrothermal synthesis and electrochemical characterization of novel zeolite membranes supported on flat porous clay-based microfiltration system and its application of heavy metals removal of synthetic wastewaters

The present work describes the synthesis and characterization of a zeolite type LTA-clay composite membrane on pre-existing locally organized aluminosilicate in clay support and its application to the removal of heavy metals. X-ray diffraction reveals that the natural clay consists essentially of quartz, kaolinite, illite, dolomite, and calcite phases. Flat discs, membrane supports are prepared by uniaxial pressing of natural clay with 160 ≤ Ф < 250 μm as optimal grain size mixed with 3% w/w activated carbon as porogen agent. Membrane supports are consolidated by sintering to final temperatures of 1000 °C. Zeolite Linde type A (LTA) is deposited on the clay supports using the hydrothermal method. Nitrogen adsorption analysis of the support using Brunauer–Emmett–Teller (BET) theory showed pores with 35.5 nm, which is narrowed to 14.2 nm after zeolite-A deposition. X-ray analysis of the composite membrane (MZA) reveals the growth of new diffraction peaks characteristic of zeolite-A. Prior to water filtration analysis of the MZA composite membrane, the pzc is found to be 9.8 using the titration method. The efficiency of the MZA composite membrane is evaluated by filtration tests of solutions containing heavy metals using a flow loop developed specifically for dead-end filtration. The retention of heavy metals studied follows the order Pb 2+ > Al 3+ > Co 2+ > Cd 2+ > Zn 2+ with 99.7, 99, 89.5, 88.3 and 81.8 retention percent, respectively. The retention mechanism seems to be controlled by the charge of the membrane's surface, which is demonstrated using the linear wave anodic stripping voltammetry (LWASV). • Composite membrane (MZA) is prepared from a natural clay and deposited zeolite A. • Pores' structures and surface properties of the MZA affect the filtration performance. • Pre-existing locally organized aluminosilicate in the clay support enhances the crystallinity of zeolite A. • Selectivity of the MZA towards filtered ions is investigated by linear wave anodic stripping voltammetry. • Retention of heavy metals on MZA reaches 99.7%, 99%, 89.5%, 88.3%, 81.8% for Pb 2+ , Al 3+ , Co 2+ , Cd 2+ and Zn 2+ respectively.

10 years long-term assessment on characterizing spatiotemporal trend and source apportionment of metal(loid)s in terrestrial soils along the west coast of South Korea

Long-term trends in the spatial distributions and sources of metal(loid)s in soils adjacent to the west coastal areas of South Korea have been systematically investigated for 10 years (2010–2019). Monitoring in 17 sites clearly showed site- and region-specific distributions, being associated with land use type (significant differences, as road > agriculture > wild) (P < 0.05), rather than temporal variation. The great concentrations of all metal(loid)s were found near Lake Shihwa (LS) and Geum River (GG), near the road, indicating that transportation activity was the main source of metal(loid)s contamination in soil. Especially, Cd (0.5 mg kg−1), Hg (0.04 mg kg−1), Pb (65 mg kg−1), and Zn (184 mg kg−1), related to the transportation activity near the road, showed twice greater than other land use types, on average. The concentration of metal(loid)s in each site and with the same land use type did not greatly vary over the years, with no significant annual difference (P > 0.05). The degree of metal(loid)s contamination compared to the background levels was identified in the order of Pb > Zn > Cr > Cu > As>Cd > Ni > Hg, with the contaminated hotspots mostly in LS or GG. The potential ecological risk was evidenced for Cd and Hg, but such a trend was temporally irregular over the years, indicating site-specificity. The sources of metal(loid)s were carefully determined as natural (20%), fuel combustion & agricultural pollution (43%), and vehicular emissions (37%) using the Positive Matrix Factorization model. The relative contribution of each source to contamination over the last decade was found to be similar, supporting that site-dependent lesser variation in metal(loid)s contamination in the coastal areas of South Korea. Overall, the distribution of metal(loid)s in the soil near the west coastal areas over the last decade largely depended on land use activities, and contamination degree was associated with non-point sources, such as transportation and fuel combustion.

Influence of pyrolysis temperature and feedstock biomass on Cu2+, Pb2+, and Zn2+ sorption capacity of biochar

Biochar has attracted significantly growing attention due to its effectiveness in terms of both cost and environmental safety in removing trace metals from soil and water. Its metal sorption capacity depends on its properties, which are in turn governed by pyrolysis temperature and type of biomass. Therefore, this study examines the role of pyrolysis temperature and biomass in biochars sorption capacity of Pb2+, Cu2+ and Zn2+. Biochars produced by pyrolysis of maize (Zea mays L.) cobs at different temperatures were used to assess the effect of temperature, whereas evergreen oak (Quercus ilex L.) pyrolyzed at 500 °C was used to assess the effect of biomass. Sorption isotherms were constructed by batch method and compared with Langmuir and Freundlich models. Most of the sorption isotherms displayed irregular curves and not all of the isotherms fitted the models. Therefore, sorption distribution coefficients and metal removal percentages were used to determine sorption capacities biochars for studied metals. Accordingly, Quercus ilex L. was most effective in sorbing all studied metals, which indicates the role of biomass. The maize biochar pyrolyzed at 500 °C was most effective among maize cob biochars, which revealed the influence pyrolysis temperature. The concentrations of added sorption solutions also played significant role in sorption, and consequently biochar pyrolyzed 350 °C was least effective. The targeted metals also affected the sorption as they compete for sorption sites. Thus, their selective sequence was in the order of Pb2+ ˃ Cu2+ ˃ Zn2+.

The Extent of Heavy Metal Pollution by Chemical Partitioning and Risk Assessment Code of Sediments of Sewage-Fed Fishery Ponds at East Kolkata Wetland, a Ramsar Site, India

Sewage contaminated with toxic metals is being naturally treated in ponds at East Kolkata Wetlands (EKW) for fish cultivation traditionally. From the aquatic phase, these metals get settled on sediment and undergo partitioning. Some fractions are available and may accumulate in the cultivated products. The present study highlights the degree of partition of heavy metals Lead (Pb), Cadmium (Cd) and Chromium (Cr) in these pond sediments. The study reveals that Pb and Cr are significant (39% and 30%, respectively) in Fe-Mn bound fractions. Residual fraction is in the order of Pb > Cr > Cd. The easily available fraction of metals recorded higher in Cd (43.0%) and Cr (42.0%).The risk assessment code (RAC) analysis records that these metals could be considered as potential risk group of metals for higher mobility and availability in these pond ecosystems and is a significant concern for aquaculture products.

Seasonal and Spatial Variation in Dissolved Heavy Metals in Liaodong Bay, China.

Spatial–seasonal variations in dissolved heavy metals in surface seawater were analyzed based on surveys at 87 sampling sites and water samples from six rivers across Liaodong Bay. The concentrations of copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) had ranges of 0.20–40.00 (5.45 ± 5.67), 0.51–33.64 (4.68 ± 3.93), 0.03–13.47 (2.22 ± 2.01), and 0.50–80.09 μg/L (14.22 ± 16.32), respectively, throughout the four seasons of 2020. The trace metal concentration showed a spatial gradient of high to low from river to estuary and from inshore to offshore areas. A combination of pollution levels and marine sensitivity was employed to assess the pollution degree of the heavy metals. As a whole, the single pollution factors of trace metals in Liaodong Bay were ranged in the order Pb > Zn > Cu > Cd. The total pollution degree was relatively high in autumn and summer due to increased riverine inputs after the rainy season, while relatively low in spring and winter. These findings provide baseline data for future targeting policies to protect marine environments in Liaodong Bay.