Removal Of Heavy Metal Contaminants Research Articles

人工湿地去除非点源重金属污染物的研究进展

人工湿地去除非点源重金属污染物的研究进展

Thioether-functionalized covalent organic framework for mercury removal

Post-synthetic modification of COFs via pendant groups or secondary functional groups of the skeleton structure is an important strategy to introduce new properties or enhance existing properties of COFs. Herein, we take advantage of the inherent advantages of COFs and introduce thioether functional groups into a reasonably designed novel COF (TAPA-TFPD) through a post-synthetic modification strategy to create a promising thioether functionalized adsorbent for mercury removal. The thioether functionalized COF material, TAPA-TFPD-S-S, exhibited high mercury removal efficiency from aqueous solution, and the adsorption capacity of Hg2+ was up to 593 mg/g. This efficient mercury removal performance can be attributed its well-defined pore channel sufficient to facilitate Hg2+ diffusion together with high concentration of sulfide chelating sites distributed uniformly throughout the pore wall. The strong interaction between Hg2+ and the thioether groups of TAPA-TFPD-S-S was confirmed by XPS. In addition, TAPA-TFPD-S-S also has the ability to capture Hg0 from the air. The efficient capture of mercury species from aqueous solution and air and the excellent reusability make the prepared thioether-functionalized COFs have great development potential in practical applications. Our work not only demonstrates the utilization of thioether-functionalized COFs in the removal of heavy metal contaminants, but also highlights the exceptional potential of post-synthetic modification strategies in the development of environmental remediation materials.

3D Wood Microfilter for Fast and Efficient Removal of Heavy Metal Ions from Water.

Adsorption is an effective method for the treatment of heavy metal ions in water; however, the existing adsorbents are complicated to prepare, and costly and difficult to recover. In this work, a 3D wood microfilter was prepared by modifying wood for the removal of heavy metal contaminants from water. First, a green deep eutectic solvent was used to remove lignin from beech wood. Then citric acid and l-cysteine were sequentially used to graft carboxyl and sulfhydryl groups (-SHs) on the surface of cellulose. Finally, a three-dimensional wood microfilter with an abundant porous structure and adsorption sites was formed. The adsorption kinetics and adsorption isotherms of heavy metal ions on the 3D wood microfilter were systematically investigated using Cu2+ and Cd2+ as model species. The results showed that the 3D wood microfilter had a fast adsorption rate and high saturation capacity for both Cu2+ and Cd2+. Based on the advantages of easy processing and multilayer assembly and stacking, a three-layer wood microfilter was designed to achieve high flux rate (1.53 × 103 L m-2 h-1) and high efficiency (>98%) for the removal of heavy metal ions in water. The enhancement mechanism of the adsorption process of Cu2+ and Cd2+ by the 3D wood microfilter was investigated using SEM and EDS, FTIR, and XPS characterization. The simple synthesis method and high adsorption efficiency of this wood microfilter provide a new strategy for the preparation of cheap, efficient, and recyclable adsorbents for heavy metal ions in water.

Preparation of hydrogels based on poplar cellulose and their removal efficiency of Cd(II) from aqueous solutions.

Industrial heavy metal-contaminated wastewater is one of the main water pollution problems. Adsorbents are a promising method for the removal of heavy metal contaminants. Herein, polyaspartic acid/carboxymethyl poplar sawdust hydrogels (PASP/CMPP) and ascorbic acid/carboxymethyl poplar sawdust hydrogels (VC/CMPP) were prepared by aqueous polymerization using alkalized poplar sawdust (CMPP) as the substrate and PASP and vitamin C (VC) as modifiers. The effective results, provided by the characterization analysis of SEM and BET, indicate that the surface of the PASP/CMPP hydrogel has a larger number of loose pores and a larger pore volume than the VC/CMPP hydrogel. The treatment effects of the two hydrogels on simulated wastewater containing Cd(II) were investigated by a batch of experiments. The results showed that PASP/CMPP had a better adsorption effect than VC/CMPP under the same adsorption conditions. Interestingly, the solid concentration effect was found in the process of sorption kinetics and sorption isotherms. The sorption kinetic curves of Cd(II) on PASP/CMPP were well-fitted by the quasi-second-order kinetics under different adsorbent concentrations. The adsorption conforms to Langmuir and Freundlich adsorption isotherm models. More importantly, PASP/CMPP composites are expected to be used as a new kind of environmental adsorbent for wastewater treatment.

Bio-waste assisted phase transformation of Fe3O4/carbon to nZVI/graphene composites and its application in reductive elimination of Cr(VI) removal from aquifer

This paper reportsa facile approach for the synthesis of graphene stabilisedzero valent iron (nZVI) via carbothermal reduction method using bio-waste materials. X-ray photoelectron spectroscopy confirmed the formation of nZVI, which was further supported by magnetic susceptibility measurements. The process of Cr(VI) removal was revealed by analysing nZVI/graphene before and after the Cr(VI) adsorption process. nZVI/graphene reduces Cr(VI) to Cr(III), which was adsorbed on the graphene sheet, avoiding the passivation of nZVI. Graphene provides good electrical conductivity, skeletal support, and has long-term electron releasing characteristics, which can accelerate the reduction of Cr(VI) to Cr(III) and demonstrates a quick and high removal capacity of Cr(VI) from an aquifer. The influence of Cr(VI) initial concentration, adsorbent dosages, equilibrium studies, solution pH, kinetics, adsorption isotherms, and thermodynamic parameters was also investigated.Synopsis.The green synthesis of nZVI/graphene compositesfor Cr(VI) reduction has not been well investigation. This paper reports a facile eco-friendly synthesis of nZVI/graphene composites for the removal of heavy metal contaminants from aquifers.

One-pot synthesis of iron oxides decorated bamboo hydrochar for lead and copper flash removal

A novel one-pot codeposition strategy was developed by employing bamboo hydrochar as precursors to fabricate magnetic porous char (MPC) with Fe 3 O 4 or α-Fe loading. The synthesized MPC with well dispersed magnetic phase and high thermal stability displayed excellent adsorption capacities and flash adsorption rate for Cu(II) and Pb(II). The batch sorption experiments showed that MPC had the best performance with Langmuir adsorption capacities as high as 125.06 mg/g for Cu(Ⅱ) and 153.85 mg/g for Pb(Ⅱ), respectively. More importantly, the short time of adsorption reaching 90 % equilibrium within 10 min was considerably beyond previous study. Also, a synergistic mechanism of the chemical complexation and physical adsorption for the higher adsorption capabilities and flash removal rate of the synthesized MPC was proposed. The regeneration investigation revealed that the sorption efficiencies remained at high level with above 92.4 % for Cu(II) and 94.1 % for Pb(II) after five cycles. Thus, the MPC were expected to be a promising candidate for high-efficient and rapid removal of heavy metal contaminants from wastewater in future practical utilization . • Highly porous and thermal stable magnetic biochar were synthesized by one-pot method. • The adsorption capacities were 125.06 mg/g for Cu(Ⅱ) and 153.85 mg/g for Pb(Ⅱ), respectively. • The adsorption reached 90 % of the adsorption equilibrium within 10 min. • The sorption efficiencies of regeneration remained above 92.4 % for Cu(II) and 94.1 % for Pb(II) after five cycles.

Bio-Inspired Eco-Friendly Superhydrophilic/Underwater Superoleophobic Cotton for Oil-Water Separation and Removal of Heavy Metals.

Effective integrated methods for oil-water separation and water remediation have signifi-cance in both energy and environment fields. Materials with both superlyophobic and superlyophilic properties toward water and oil have aroused great attention due to their energy-saving and high-efficient advantages in oil-water separation. However, in order to fulfill the superlyophobicity, low surface tension fluorinated components are always being introduced. These constituents are environmentally harmful, which may lead to additional contamination during the separating process. Moreover, the heavy metal ions, which are water-soluble and highly toxic, are always contained in the oil-water mixtures created during industrial production. Therefore, material that is integrated by both capacities of oil-water separation and removal of heavy metal contamination would be of significance in both industrial applications and environmental sustainability. Herein, inspired by the composition and wettability of the shrimp shell, an eco-friendly chitosan-coated (CTS) cotton was developed. The treated cotton exhibits the superhydrophilic/underwater superoleophobic property and is capable of separating both immiscible oil-water mixtures and stabilized oil-in-water emulsions. More significantly, various harmful water-soluble heavy metal ions can also be effectively removed during the separation of emulsions. The developed CTS coated cotton demonstrates an attractive perspective toward oil-water separation and wastewater treatment in various applications.

PVA-integrated graphene oxide-attapulgite composite membrane for efficient removal of heavy metal contaminants.

Graphene oxide (GO) is an excellent membrane-forming material with unique two-dimensional transport channels and excellent adsorption properties for heavy metal contaminants. However, swelling under cross-flow conditions and long-term water immersion leads to poor separation performances. To improve the stability of GO membrane materials, we propose a PVA-integrated graphene oxide/attapulgite membrane (GOAP) with a 3D microstructural arrangement of "brick-mortar-brick." The addition of PVA as mortar reinforces the strength of the structures via induced hydrogen bonding within the 3D water transport network. Furthermore, the Al2O3 ceramic substrate pre-treated with (3-aminopropyl) triethoxysilane (APTES) provided high mechanical stability to the composite membrane, extending the membrane's stability beyond a month of immersion without swelling or shedding. The PVA-integrated GO/ATP composite membrane maintained a rejection rate of 99% for Cu2+ solution (100mg/L) in a 26-h continuous with nearly 100% rejection for various metals ions such as Cu2+, Ni2+, Pb2+, and Cd2+. The membrane exhibited a water flux of 20.7 L·m-2·h-1, which was 15.9-fold high than the pure GO membrane (GOM). The high water flux and heavy metal filtration rate with superior stability proved the practical suitability of the composite film for removing heavy metal ions.

Remediation of chromium contaminated soil by soil washing using EDTA and N-acetyl-L-cysteine as the chelating agents

The use of chelating agents in soil washing has been known to be an efficient, eco–friendly, and inexpensive treatment process for the removal of heavy metal contamination. In this study, statistically designed lab-scale soil washing experiments were carried out using two chelating agents i.e., ethylene diamine tetraacetic acid (EDTA) and N-acetyl-L-cysteine (NAC). The effects of pH, contact time and dosage of wash solution on chromium (Cr+6) removal efficiency (RE) was investigated and optimized using response surface methodology (RSM). The ANOVA analysis of the experimental design for both the chelating agents revealed that pH is the key influencing parameter in Cr+6 removal. The optimum conditions were found to be: pH - 5.5, contact time - 216 h, dosage of EDTA - 4128 mg/kg and dosage of NAC - 300 mg/kg. The projected Cr+6 RE under these optimum conditions was 14.3% and 65.7%, for EDTA and NAC, respectively. The results from this investigation indicated that soil washing with NAC could be a better alternative to EDTA for Cr+6 removal from soil.

Examining the Effect of a Chitosan Biopolymer on Alkali-Activated Inorganic Material for Aqueous Pb(II) and Zn(II) Sorption.

Biopolymers and alkali-activated materials have attracted a great deal of attention as adsorbents for the removal of heavy metal contaminants from aqueous solutions. Both materials are sustainable and feature unique properties, but biopolymers are relatively more expensive or difficult to prepare and exhibit low mechanical and surface properties, a narrow pH range, and thermal stability. In this study, hybrid adsorbents were prepared from both types of material, by alkali activation of low-cost fly ash precursors accompanied by incorporation of 0-2%mass chitosan biopolymer. Two types of alkaline activating solutions, NaOH and Na2SiO3, were employed to generate two sets of hybrid adsorbents with varying chitosan contents. The effect of the chitosan dosage on the aqueous Pb(II) and Zn(II) sorption efficiency was also investigated. The adsorbents exhibited 98-100% removal efficiencies for both metals, but the sorption of Zn(II) was generally higher than that of Pb(II). The addition of 0.1-2.0%mass chitosan resulted in very little improvement in the overall efficiency of the adsorbents. In contrast, 0.05%mass chitosan led to a decrease in the sorption efficiency; this was linked to the decrease in the adsorbents' ζ potential. The Na2SiO3-activated materials featured larger BET surface areas and better overall sorption performance, while the NaOH-activated materials showed the worst Pb(II) sorption performance and hence more noticeable improvement upon addition of chitosan. Mechanistic investigation shows that the sorption process follows second-order kinetics and is a chemisorption-driven process.

Mechanistic insight into the removal of aqueous Cd using an immobilized ZIF-8 and microflora cooperative composite

Biotechnology and metal-organic-frameworks (MOFs) materials have been investigated intensively for the removal of heavy metal from wastewater. However, the cooperative effect of bacteria and MOFs on heavy metal adsorption was less reported. Considering this, this study has screened out microflora with cadmium (Cd) adsorption ability. Furthermore, it was combined with zeolitic imidazolate framework-8 (ZIF-8) to form a ZIF-8 and microflora complex (ZMC). Moreover, ZMC was further immobilized to improve its Cd adsorption effect and reusability. Results revealed that the immobilized ZMC exhibited 99.91% and 78.83% Cd adsorption rate for 20 mg L−1 and 300 mg L−1 Cd, respectively. Meanwhile, the immobilized ZMC maintained a relatively stable adsorption effect under varied external pH. The reaction mechanism was summarized as covalent binding accompanied with a small amount of electrostatic attraction. Microflora could enhance the surface electronegativity of ZIF-8. ZIF-8 could strengthen the response of antioxidant activity of microflora and augmented the affinity of microflora secretions for Cd. This proposed method may provide a new insight for the removal of heavy metal contaminants in water.

Biogenic Synthesis of Iron Oxide Nanoparticles Using Enterococcus faecalis: Adsorption of Hexavalent Chromium from Aqueous Solution and In Vitro Cytotoxicity Analysis.

The biological synthesis of nanoparticles is emerging as a potential method for nanoparticle synthesis due to its non-toxicity and simplicity. In the present study, a bacterium resistant to heavy metals was isolated from a metal-contaminated site and we aimed to report the synthesis of Fe3O4 nanoparticles via co-precipitation using bacterial exopolysaccharides (EPS) derived from Enterococcus faecalis_RMSN6 strains. A three-variable Box–Behnken design was used for determining the optimal conditions of the Fe3O4 NPs synthesis process. The synthesized Fe3O4 NPs were thoroughly characterized through multiple analytical techniques such as XRD, UV-Visible spectroscopy, FTIR spectroscopy and finally SEM analysis to understand the surface morphology. Fe3O4 NPs were then probed for the Cr(VI) ion adsorption studies. The important parameters such as optimization of initial concentration of Cr(VI) ions, effects of contact time, pH of the solution and contact time on quantity of Cr(VI) adsorbed were studied in detail. The maximum adsorption capacity of the nanoparticles was found to be 98.03 mg/g. The nanoparticles could retain up to 73% of their efficiency of chromium removal for up to 5 cycles. Additionally, prepared Fe3O4 NPs in the concentration were subjected to cytotoxicity studies using an MTT assay. The investigations using Fe3O4 NPs displayed a substantial dose-dependent effect on the A594 cells. The research elucidates that the Fe3O4 NPs synthesized from EPS of E. faecalis_RMSN6 can be used for the removal of heavy metal contaminants from wastewater.

Electrospun Polyacrylonitrile/Lignin/Poly(Ethylene Glycol)-Based Porous Activated Carbon Nanofiber for Removal of Nickel(II) Ion from Aqueous Solution.

The issue of heavy metal contamination has caused a great deal of concern among water quality experts today, as it contributes to water pollution. Activated carbon nanofibers (ACNFs) showed a significant ability in removing heavy metals from the wastewater. In this study, polyacrylonitrile (PAN) was blended and electrospun with an abundant and inexpensive biopolymer, lignin and a water soluble polymer, poly(ethylene glycol) (PEG), by using an electrospinning technique to form nanofibers. The electrospun nanofibers were then investigated as a precursor for the production of porous ACNFs to study the removal of nickel(II) ions by adsorption technique. PEG was added to act as a porogen and to create the porous structure of carbon nanofibers (CNFs). CNFs were prepared by thermal treatment of the electrospun nanofibers and followed by activation of CNFs by thermal and acid treatment on CNFs. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) spectral analysis of the ACNFs showed a strong absorption peak of the C-O functional group, indicating the increase in the oxygenated compound. Field emission scanning electron microscopy (FESEM) images concluded that the ACNFs have more porous and compact fibers with a smaller fiber diameter of 263 ± 11 nm, while the CNFs are less compact and have slightly larger fiber diameter of 323 ± 6 nm. The adsorption study showed that the ACNFs possessed a much higher adsorption capacity of 18.09 mg/g compared with the CNFs, which the amount adsorbed was achieved only at 2.7 mg/g. The optimum adsorption conditions that gave the highest percentage of 60% for nickel(II) ions removal were 50 mg of adsorbent dosage, 100 ppm of nickel(II) solution, pH 3, and a contact time of 60 min. The study demonstrated that the fabrication of ACNFs from PAN/lignin/PEG electrospun nanofibers have potential as adsorbents for the removal of heavy metal contaminants.

Synthesis of Magnetic Pomegranate Biochar Coupled with Yeast As a Novel Metal Adsorbent

Water is the crucial resource for the life on Earth. The water pollution caused by heavy metal has been greatly impacted human health. The removal of heavy metal contaminants in water supply poses a major problem for scientists over the past few decades. Activated carbon is often used as an adsorbent of heavy metals, however the activated carbon is make from charcoal which requires the pyrolysis of wood. Our study used pomegranate peel as an alternative ecofriendly resource for making an effective adsorbent. Biochar amendment on water filtration proves to be a viable option. The surface of pomegranate peel biochar was modified with magnetic nanop-Fe3O4 and baker’s yeast in order to enhance its adsorptive capacity for heavy metals (Pb2+, Cd2+, Cu2+, and As2+) in water as well as improve its reusability. The structure of composite was characterized by using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR), Powder X-Ray Diffraction (P-XRD), and Accelerated Surface Area and Porosimetry System (ASAP). Batch adsorption experiments will be conducted to study the effects of pH, temperature, contact time, adsorbent dosage, and interfering species on heavy metal adsorption.

Reduced graphene oxide supported ZnO/CdS heterojunction enhances photocatalytic removal efficiency of hexavalent chromium from aqueous solution

The removal of toxic and harmful heavy metal contaminants from wastewater is of great importance for global environmental health. The development of efficient photocatalysts is attracting increasing interest with a current focus on material design for improved efficiency. Accordingly, this study aims to optimize the conformation of nanocomposite prepared from a CdS/ZnO heterojunction on reduced graphene oxide (RGO) for boosting the photocatalytic removal of heavy metal contaminants of aqueous systems. Under visible light, the candidate nanocomposites exhibited a range of photocatalytic activity in reducing hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] at room temperature. Among these different nanocomposites, the photocatalytic removal rate constant of Cr(VI) ranged as follows: ZnO/CdS6:5/RGO6 (0.106 min−1) > ZnO/CdS6:5 (0.0630 min−1) > CdS (0.0335 min−1) > ZnO (0.00121 min−1). Moreover, after five cycles of use, the photocatalytic reduction rate of ZnO/CdS6:5/RGO6 was 93.2 %, which signifies its strong re-cycling performance. These results reveal the feasibility of using CdS/ZnO6:5/RGO6 to reduce heavy metal ions from wastewater and provide insights for efficiently removing heavy metal ions without additional chemical trapping agents in the photocatalytic process.

Removal of Pb and Hg from marine intertidal sediment by using rhamnolipid biosurfactant produced by a Pseudomonas aeruginosa strain

Abstract The removal of heavy metal contaminants in marine intertidal sediments is an urgent issue. Heavy metal decontamination with rhamnolipid biosurfactant (RB) is a feasible way of solving this problem. In this paper, two heavy metals, lead (Pb) and mercury (Hg), in marine intertidal sediment were removed by prepared RB in laboratory scale. The results showed that Pb and Hg could be efficiently removed from the intertidal sediment in marine environment by using RB produced by a pseudomonas aeruginosa strain. At a critical micelle concentration of 43.73 mg L−1, 62.50% Pb and 50.20% Hg were removed from the marine intertidal sediment sample containing 520.32 mg ⋅ kg −1 of Pb and 13.15 mg ⋅ kg −1 of Hg (dry weight). The pH affected the Pb and Hg removal by RB, and the alkaline eluent medium was favorable for their removal. A major fraction of removed contaminants comprised organic bound to Pb and Hg during RB solution leaching. The content of exchangeable Pb after leaching treatment in the sediment increased followed by the increase of pH of the RB leaching solution. The removal efficiency increased rapidly during the first two days of leaching process. RB performed better than sodium dodecyl sulfate in terms of Pb and Hg removal. Scanning electron microscopy, zeta potential, and surface tension analysis indicated that leaching by RB solution changed the surface characters of sediment grains and led to high Pb and Hg removal efficiencies from the sediment.

Characterization, bioenergy value, and thermal stability of biochars derived from diverse agriculture and forestry lignocellulosic wastes

In the present study, seven diverse biomasses of Indian origin were characterized and pyrolyzed at 450 °C to produce biochars. The biochars were thoroughly characterized using a variety of techniques to assure their potential energy and environmental and agricultural applications. Biochars derived from crop wastes with low lignin content, viz., rice husk biochar (RHB), rice straw biochar (RSB), maize stover biochar (MSB), and sugarcane biochar (SCB), possessed high ash content, high pH, and low fixed carbon making them suitable for soil amelioration. RSB, RHB, and MSB recorded high cation exchange capacity, making their potential utilization as liming material and removal of heavy metal contaminants. Elemental O/C ratios for all biochars, except maize stover biochar, were in the range of 0.27–0.32, which showed better stability and half-life period. Thermogravimetric analysis (TGA) was carried out to evaluate the thermal stability of biochars up to 900 °C, and the overall mass loss varied in the range of 16–27 wt%. Biochars from eucalyptus (EB), lantana (LB), and pine needle (PNB) were found to have high higher heating values (HHVs) (23–28 MJ/kg), higher fixed carbon, and lower ash content. Correlations were constructed between HHV of biochars and their volatile matter, ash, and fixed carbon content with high but negative correlation with ash content. Rice straw, rice husk, maize stover, and sugarcane trash were poor substrates, as the resultant biochars contained ≤ 60 wt% fixed carbon, high ash, and a relatively low HHV. It is shown that RHB, RSB, MSB, and SCB can be potential materials for soil amendment and plant nutrient, while PNB, LB, and EB are suitable for renewable solid fuel purpose.

A new alendronate doped HAP nanomaterial for Pb2+, Cu2+ and Cd2+ effect absorption

In this paper, a new nanobiomaterial, alendronate hydroxyapatite (AL-HAP), was synthesized by the conventional co-precipitation method with alendronate (AL) as dopant, and applied in the removal of heavy metal contaminants for the first time. The characterization results showed that the crystallinity of the AL-HAP nanocomposite biomaterials after doping has been greatly deteriorated, and the pore volume and pore size increased. When the doping amount of AL was 10 %, the maximum adsorption capacity of AL-HAP for Pb2+, Cd2+ and Cu2+ can reach 1431.8, 469 and 226.6 mg/g, respectively, which was much higher than that reported in other literature. Meanwhile, the adsorption mechanism of AL-HAP for heavy metal ions was discussed from both the views of experimental and Multiwfn program theoretical calculation based on density functional theory (DFT). Quantitative molecular surface analysis was carried out for the first time to study the minimum points and the positions of electrostatic potential (ESP) and average local ionization energy(ALIE), as well as the exact values, giving more accurate and reliable analysis conclusions for the reaction sites and binding mode. In addition, the independent gradient model (IGM) method was also firstly applied to investigate the interactions between AL and HAP or AL-HAP nanocomposite with metal ions. AL-HAP is a potential adsorption material for heavy metal wastewater treatment and soil remediation because of its advantages such as convenient synthesis, excellent adsorption performance and no secondary pollution.

Interaction of Pb2+ ions in water with two-dimensional molybdenum disulfide

The removal of heavy metal contaminants from water is important for public health, and recently many two-dimensional (2D) materials with high specific surface areas are being studied as promising new active components in water purification. In particular, 2D MoS2 nanosheets have been used for the removal of various heavy metals, but usually in either in complex geometries and composites, or in the chemically exfoliated metallic 1T-MoS2 phase. However, the interaction of heavy metals dissolved in water with unmodified semiconducting 2H-MoS2 is not well studied. In this paper, we report a detailed fundamental investigation of how Pb2+ ions interact with 2H-MoS2. We observe small solid clusters that form on the MoS2 surfaces after exposing them to Pb(NO3)2 aqueous solutions as shown by atomic force microscopy and transmission electron microscopy, and for liquid phase exfoliated MoS2 we observe the nanosheets precipitating out of dispersion along with insoluble solid granules. We use a combination of x-ray photoelectron spectroscopy and x-ray diffraction to identify these solid clusters and granules as primarily PbSO4 with some PbMoO4. We put forth an interaction mechanism that involves MoS2 defects acting as initiation sites for the partial dissolution in aqueous oxygenated conditions which produces MoO42− and SO42− ions to form the solids with Pb2+. These results are an important contribution to our fundamental understanding of how MoS2 interacts with metal ions and will influence further efforts to exploit MoS2 for water remediation applications.

Comparison Between Commercial and Synthesized Fe3O4 Nanoparticles for Removal of Heavy Metal Contaminants in Wastewater

Wastewater polluted with harmful heavy metal presently becomes a crucial environmental issue throughout the world. In this study, commercial and synthesized Fe3O4 nanoparticles were functioned to remove lead, nickel and cadmium ions in single element system. Experimental conditions including pH, contact time and metal ion concentrations were tested. The isothermal equilibrium for single component system was favorable and the maximum uptake of lead, nickel and cadmium ions adsorbed on commercial Fe3O4 were 35.3, 5.18 and 18.16 mg/g respectively while 31.5, 4.36 and 20.56 mg/g on synthesized one at optimum pH 6 for an hour of equilibrium contact time. The isotherm data resulted from both adsorbents fitted well with Freundlich model. The experiments demonstrates that the performance of synthesized nanosorbent which is economically convenient to be used, approaches the effectiveness of commercial Fe3O4. Therefore, prepared nanosorbent form was taken as practical adsorbent and utilized in binary and ternary systems to show the competition of metal contaminants. Results indicated that lead ions had rapid affinity to be sorbed on the nanoparticles while nickel solute had slow attraction. XRF X-ray fluorescence, TEM Transmission electron microscope, FTIR Fourier transfer infrared and XRD X-ray diffraction were also carried out to identify and demonstrate the properties of both nanosorbents.