Heavy Metal Chelating Agent Research Articles

Preparation of a New Heavy Metal Chelating Agent and Its Removal of Copper Ions in Wastewater

In this study, a new type of dithiocarbamate (DTCs) heavy metal chelating agent MF-DTC was prepared by carbon disulfide modified melamine formaldehyde resin prepolymer, and the structure of the chelating agent and chelating products was characterized by infrared, ultraviolet, elemental analysis, thermogravimetry, scanning electron microscopy and other means: the process of chelating agent Cu was studied, and the results showed that MF-DTC chelating agent had a higher adsorption capacity, and compared with the traditional chelating agent SDD and Na2S, it had higher chelating capacity under acidic conditions, it can be directly used to treat heavy metals in acidic wastewater. Moreover, the environmental stability of heavy metals after chelation is high. Heavy metals are not easy to be leached again after treatment.

Effects of cadmium and zinc interactions on the physiological biochemistry and enrichment characteristics of Iris pseudacorus

Compound pollution with cadmium (Cd) and zinc (Zn) is common in nature. The effects of compounded Cd and Zn on the growth and development of Iris pseudacorus in the environment and the plant’s potential to remediate heavy metals in the environment remain unclear. In this study, the effects of single and combined Cd and Zn stress on I. pseudacorus growth and the enrichment of heavy metals in I. pseudacorus seedlings were investigated. The results showed that under Cd (160 μM) and Zn (800 μM) stress, plant growth was significantly inhibited and photosynthetic performance was affected. Cd+Zn200 (160 μM + 200 μM) reduced the levels of malondialdehyde, hydrogen peroxide, and non-protein thiols by 31.29%, 53.20%, and 13.29%, respectively, in the aboveground tissues compared with levels in the single Cd treatment. However, Cd+Zn800 (160 μM + 800 μM) had no effect. Cd and Zn800 inhibited the absorption of mineral elements, while Zn200 had little effect on plants. Compared with that for Cd treatment alone, Cd + Zn200 and Cd+Zn800 reduced the Cd content in aboveground tissues by 54.15% and 49.92%, respectively, but had no significant effect on Cd in the root system. Zn significantly reduced the Cd content in subcellular components and limited the content and proportion of Cd extracted using water and ethanol. These results suggest that a low supply of Zn reduces Cd accumulation in aboveground tissues by promoting antioxidant substances and heavy metal chelating agents, thus protecting the photosynthetic systems. The addition of Zn also reduced the mobility and bioavailability of Cd to alleviate its toxicity in I. pseudacorus.

Sodium dimethyl dithiocarbamate, as a capable heavy metal chelating agent: Production and applications

Sodium dimethyl dithiocarbamate (SDDC) is a universal heavy metal precipitant/chelating agent, which is widely used in the treatment of heavy metals in industrial wastewater and fly ash from waste incineration. It can be utilized as a heavy metal precipitant, fungicide, agricultural insecticide, rubber vulcanization accelerator, styrene-butadiene rubber polymerization terminator, polymerization inhibitor, mineral processing reagent, etc. This review article focuses on the research of the production and application of SDDC in heavy metal chelation. The following three benefits of using SDDC as a heavy metal chelating agent are: (1) it can chelate with various heavy metal ions at room temperature to generate insoluble chelate salts and precipitates, which can be easily removed; (2) SDDC can perform chelation reaction with varies heavy metal ions at the same time; (3) as a heavy metal chelating agent, SDDC is simple to use and low costs, which is significantly better than other heavy metal chelating agents and precipitants. This review paper presents novel ideas for the performance enhancement based on SDDC in removing heavy metals and is a prospect for the research, development, production, and applications of SDDC.

Novel Silanized Graphene Oxide/TiO2 Multifunctional Nanocomposite Photocatalysts: Simultaneous Removal of Cd2+ and Photodegradation of Phenols under Visible Light Irradiation.

Reduced graphene oxide (RGO)-TiO2 nanocomposites have exhibited effective photocatalytic degradation of various organic pollutants. However, their poor solubility could limit their application in water and other organic solvents. In this study, new graphene-based cross-linked ethylenediaminetetraacetic acid (EDTA)-RGO-TiO2 (ERGT) nanocomposites were synthesized for the removal of Cd(II) and photodegradation of phenol from wastewater by surface-functionalized cross-linking heavy metal chelating agent sodium edetate (EDTA) and photocatalyst titanium dioxide. The structural properties of fabricated nanocomposites were characterized using SEM, TEM, XPS, FTIR, XRD, UV–vis, gas sorption, and Raman spectroscopy analyses. Moreover, the adsorption of Cd(II) and the degradation of phenol under different conditions were studied. The experimental results revealed that the optimal catalytic degradation and adsorption performance could be achieved at pH 5.5, and the maximum absorption ratio of cadmium ions and the degradation efficiency of phenol can reach 178.2 mg/g and 90%, respectively. The results suggested that ERGT is a potential material for the removal of threatening pollutants from wastewater.

Performance and mechanism of copper removal from wastewater by sodium tetraethylenepentamine-N,Nʹ,Nʹʹ,Nʹʹʹ,Nʹʹʹʹ-pentadithiocarboxylic acid

Dithiocarboxylic(DTC)-type heavy metal chelating agents have received increasing attention since they can be used to treat wastewater for heavy metal removal efficiently. In this article, we used some of them, such as a conventional single-DTC chelating agent-sodium dimethyl dithiocarbamate (SDD), a new multi-DTC chelating agent-sodium tetraethylenepentamine-N, Nʹ, Nʹʹ, Nʹʹʹ, Nʹʹʹʹ-pentadithiocarboxylic acid (TEPA-5DTC). We observed that the residual concentration of Cu2+ treated by TEPA-5DTC can be low than the limitation(0.3 mg⋅L-1) at pH 5~10 while the wastewater treated by SDD cannot meet the limitation at overall pH, which means TEPA-5DTC has better efficiency of heavy metal removal and pH-resistance. According to the binding force by UV, XPS and FTIR methods and the microscopic shape of the chelating products by TEM and AFM observation, we found that the advantage of TEPA-5DTC strongly depended on the number of functional groups and the structure of molecules. The mechanistic studies suggested that TEPA-5DTC and Cu2+ can form a two-dimensional flat-type super molecule complex that increased the chelating efficiency and improved the settleability of the dregs compared to SDD. Furthermore, depending on the result of XRD analysis on the product of low temperature incineration of dregs formed by chelating agents and Cu2+, it showed a great potential of recycling copper through smelting. Given that TEPA-5DTC have much greater ability of copper removal and stability in different pH condition than SDD, this work urges the development of TEPA-5DTC for efficient elimination of copper.

Enhanced coagulation coupled with heavy metal capturing for heavy metals removal from coal gasification brine and a novel mathematical model

The wastewater reuse and industrial salt recovery from coal gasification brine (CGB) is the last step for the zero liquid discharge (ZLD) of coal chemical wastewater, and the heavy metals removal is the key limiting factor for the ZLD process. In this research, heavy metals were removed by using the enhanced coagulation coupled with heavy metal capturing technology. Step by step, the optimal type and dosage of chelating agent and flocculant, as well as the optimal coagulant dosage was determined via the single-factor method. Additionally, the impacts of critical water quality parameters (temperature, pH, salinity and organics, etc.) on the removal of heavy metals were also investigated. Finally, the model targeted the removal of total arsenic (As) was constructed by four-factor quadratic regression orthogonal rotation combination design. The initial heavy metal concentration, the amount of heavy metal chelating agents (HMCAs), the amount of flocculant and the amount of coagulant were taken as independent variables, while the total As concentration of effluent was taken as the dependent variable, obtaining the significant regression equation: Y =0.1165 + 0.04187x1-0.01829x3+0.00941x22+0.0116x32-0.00719x2x3 (F2 = 264.22380, p＜0.01). The results demonstrated that appropriate amount of HMCAs and flocculant determined removal efficiency of heavy metals.

The Effect of Chitosan of Ark Clam Shells to Reduce Pb and Hg Level and Amount of Bacteria in the Blood Cockles Meatball

Chitosan of ark clams shell is regarded as untapped waste; it has potential as a heavy metal chelating agent and anti-bacterial. The objective of this research is to examine the effect of chitosan of the ark clams shell as a chelating agent to decrease of Pb and Hg level in the blood cockles meatball. This research is also aimed at exploring the capability of chitosan of the shell in decreasing the bacteria within blood cockle meatball. This research conducted complete randomized design with the provision of five-level of chitosan concentration, i.e., 0%, 0.5%, 1%, 1.5%, 2.0%. Atomic-Absorbent Spectrophotometric (AAS) method used to examine the level of Pb and Hg within the meatball, while the total of bacteria was determined by using Total Plate Count (TPC) method. The data were analyzed by using Analysis of Variance (ANOVA) and Least Significant Difference (LSD) test. The results reveal that the administration of chitosan of ark clam on blood cockle meatballs reduced Pb levels from 0.195 ppm to 0.168 ppm, while Hg levels reduced from levels of 0.018 to 0.008 ppm, and the number of bacteria from 2.4 × 102 to 1.4 × 102 colony/g. In conclusion, the chitosan of the ark clams shell can ensure the safety of the meatball product.

Ecotoxicity assessment of sodium dimethyldithiocarbamate and its micro-sized metal chelates in Caenorhabditis elegans

Sodium dimethyldithiocarbamate (SDDC) is a widely used heavy metal chelating agent in harmless treatment of wastewater and hazardous waste, but SDDC and its heavy metal chelates may leak into the environment and bring potential ecological risks. In this study, the model organism Caenorhabditis elegans was used to evaluate the toxic effect of SDDC and its heavy metal Cu, Pb chelates. Multiple endpoints were investigated by subacute exposure to SDDC (0.01–100 mg/L) and micro-sized Cu, Pb chelates of SDDC (1–100 mg/L). Our data indicated that the LC50 value of SDDC was 139.39 mg/L (95% Cl: 111.03, 174.75 mg/L). In addition, SDDC was found that concentration of 1 mg/L is a safe limit value for nematode C. elegans, and concentration above 1 mg/L caused adverse effects on the survival, growth, locomotion behaviors and reactive oxygen species (ROS) production of exposed nematodes. Furthermore, all tested SDDC-Cu and SDDC-Pb chelates had obviously lower toxic effect than untreated Cu, Pb metals. These two chelates also had a lower toxic effect than SDDC agent due to its more stable structure. Moreover, SDDC-Cu had a higher toxic effect than SDDC-Pb at the same concentration. Thus, our results suggest that SDDC as a kind of chelating agent applied in harmless treatment of heavy metals, the safe addition limit should not be exceeded.

Stabilization of heavy metals in MSWI fly ash with a novel dithiocarboxylate-functionalized polyaminoamide dendrimer

A novel heavy metal chelating agent, dithiocarboxylate-functionalized polyaminoamide dendrimer (PAMAM-0G-DTC), was evaluated for the stabilization of heavy metals from municipal solids waste incineration (MSWI) fly ash. PAMAM-0G-DTC achieved overall stabilization performance at a lower dosage (3% w/w) and a wider pH range (2–13) compared to conventional chelating agents such as sodium dimethyl dithiocarbamate (SDD) and dithiocarboxylate-functionalized tetraethylenepentamine (TEPA-DTC). The leaching toxicity of Pb and Cd in the MSWI fly ash by PAMAM-0G-DTC stabilization met the landfill requirements but could not be achieved by SDD and TEPA-DTC even at a 10 wt% concentration. Sequential chemical extraction of fly ash before and after stabilization shows that PAMAM-0G-DTC can be combined with active heavy metals in water-soluble, interchangeable, and carbonate states to form more stable heavy metals in organic and residual states. Mechanistic studies show that multiple PAMAM-0G-DTC molecules can combine with multiple heavy metals to form three-dimensional network-like super-molecular compounds with an infinite extension of space size. This makes the heavy metals more stable and embedded in the network-like super-molecular structure, thus minimizing the potential risk of leaching. Overall, by forming more geochemically stable phases, the treatment of fly ash with PAMAM-0G-DTC has a strong ability to reduce the toxic leaching of heavy metals at a lower dosage and suppress the risk of secondary pollution in a landfill at a wide range of pH values (2–13).

Synthesis of dimercaptosuccinic acid (DMSA) coated magnetic nanoparticles: feasibility on dye decolorization and heavy metal adsorption

As highlighted in UN sustainable development goals 2030 report, one of the important challenge in future is to provide clean water. Thus, enormous efforts have been made to improve water quality from recalcitrant pollutants such as organic dyes, heavy metal and others. Magnetic nanoparticles is one of viable candidate to degrade the above pollutants due to its unique properties such bifunctional (catalytic and adsorption) capability & ease for magnetic separation. However, one of the main challenge is to maintain its colloidal stability to exploit its advantages for water remediation. Thus, this work explored its colloidal stability by coating it with heavy metal chelating agent namely Dimercaptosuccinic Acid (DMSA). The resultant clustered magnetic nanoparticles were evaluated its feasibility by using Rhodamine B dye and lead (Pb) heavy metal as model system. It is revealed that DMSA-coated magnetic nanoparticles is a viable candidate for this model system.

Heavy metal waste treatment product as semiconductor: Efficient visible light photocatalytic activity of the Bismuth(III) chelates

Trithiocyanuric acid trisodium salt hydrate (Na3TMT) has been proved an excellent heavy metal chelating agent and widely applied for heavy metal ions elimination in industrial wastewater. In this work, the chelating products of Bismuth(III) ion with this effective agent were prepared by solid state and liquid phase reactions, and proved as a new kind of n-type semiconductor. For full utilization of resource, the green and low-cost massive Bismuth chelate with good crystallinity, distinctive morphology, appropriate band structure and high stability was applied for photoelectrochemical application and photocatalytic organic pollutants degradation upon visible light. Results indicated that OH radicals were the main reactive specie in the photodegradation process. The combination of heavy metals and organic contaminants removal was achieved by a waste-to-wealth route.

Evaluation of Jeffamine® Core PAMAM Dendrimers for Simultaneous Removal of Divalent Heavy Metal Ions from Aqueous Solutions by Polymer Assisted Ultrafiltration

Different generations (G3-G4) of amine-terminated Jeffamine® T-403 core poly(amidoamine) PAMAM dendrimers (JCPDs) were used as new macromolecular heavy metal chelating agent templates in polymer assisted ultrafiltration (PAUF) for the investigation of their removal ability for some of the divalent metal ions: Cu, Co, Ni, Cd, and Zn from aqueous solutions under competitive conditions. The effects of pH and generation size of JCPDs were also investigated. Extent of binding (EOB) data can be appropriately expressed by a tetradentate coordination for JCPDs at pH 9 where the maximum removal of metal ions was observed. At pH 9.0, the affinity of both generations towards heavy metal ions was also observed in the decreasing order of Zn(II) > Co(II) > Ni(II) > Cu(II) > Cd(II). Results revealed that the highest total binding capacity was observed for G3-NH2 (262.79 ± 1.62 mg/g) as a little bit higher than that of G4-NH2 (257.27 ± 2.57 mg/g). EOB studies also proved the active contribution of amide groups to metal binding ability of PAMAMs. Both generations were selective towards Cu(II) ions at lower pH 5 and pH 7. From these results, it was concluded that studied JCPDs have the desired technical properties to be used for the removal of toxic metals from wastewaters.

KADMİYUM TOKSİSİTESİ OLUŞTURULAN SIÇANLARDA TANNİK ASİTİN, AĞIR METAL GİDERİMİ VE BAZI BİYOKİMYASAL DEĞERLER ÜZERİNE ETKİSİNİN ARAŞTIRILMASI

OBJECTIVE: Cadmium (Cd), one of the major environmental pollutants used intensively in the industrial field and could causes a variety of vital threats due to our exposure in our daily lives. Having a long half-life, Cd causes direct or indirect toxicity to respiratory, urinary, cardiovascular, gastrointestinal, nervous system and bones. It is known that Cd that accumulates in the body causes many diseases such as osteoporosis, anemia, eosinophilia, anosmia and chronic rhinitis. In our study, we aimed to investigate the role of tannic acid (TA), an antioxidant substance with a high content of flavonoids and heavy metal chelating agents, in order to investigate its role in protecting from Cd toxicity.

Two 8-Hydroxyquinolinate Based Supramolecular Coordination Compounds: Synthesis, Structures and Spectral Properties.

Two new Cr(III) complexes based on 2-substituted 8-hydroxyquinoline ligands, namely [Cr(L1)3] (1), (HL1=(E)-2-[2-(4-nitro-phenyl)-vinyl]-8-hydroxy-quinoline) and [Cr(L2)3] (2), (HL2=(E)-2-[2-(4-chloro-phenyl)vinyl]-8-hydroxy-quinoline), were prepared by a facile hydrothermal method and characterized thoroughly by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, TGA, ESI-MS, UV-Visible absorption spectra and fluorescence emission spectra. Single crystal X-ray diffraction analyses showed that the two compounds featured 3D supramolecular architectures constructed from noncovalent interactions, such as π···π stacking, C-H···π, C-H···O, C-Cl···π, C-H···Cl interactions. The thermogravimetric analysis and ESI-MS study of compounds 1 and 2 suggested that the Cr(III) complexes possessed good stability both in solid and solution. In addition, the ultraviolet and fluorescence response of the HL1 and HL2 shown marked changes upon their complexation with Cr(III) ion, which indicated that the two 8-hydroxyquinolinate based ligand are promising heavy metal chelating agent for Cr3+.

Research on magnetic separation for complex nickel deep removal and magnetic seed recycling.

This study investigated the deep removal of complex nickel from simulated wastewater using magnetic separation and magnetic seed recycling. Nano-magnetite (Fe3O4) was used as the magnetic seed. The flocculant applied was N,N-bis-(dithiocarboxy) ethanediamine (EDTC), a highly efficient heavy metal chelating agent included in dithiocarbamate (DTC). Important investigated parameters included hydraulic retention time, magnetic seed dosage, and magnetic field strength. The study also explored the magnetic flocculation mechanism involved in the reaction. The result indicated that the residual Ni concentration was reduced to less than 0.1mg/L from the initial concentration of 50mg/L under optimal conditions. Magnetic seed recovery reached 76.42% after a 3-h stirring period; recycled magnetic seeds were analyzed using scanning electron microscope (SEM) and X-ray diffraction (XRD). The zeta potential results illustrated that magnetic seeds firmly combined with flocs when the pH ranged from 6.5 to 7.5 due to the electrostatic attraction. When the pH was less than 7, magnetic seeds and EDTC were also combined due to electrostatic attraction. Particle size did affect microfloc size; it decreased microfloc size and increased floc volume through magnetic seed loading. The effective binding sites between flocs and magnetic seeds increased when adding the magnetic seeds. This led the majority of magnetic flocs to be integrated with the magnetic seeds, which served as a nucleus to enhance the flocculation property and ultimately improve the nickel complex removal rate.

A novel heavy metal chelating agent sixthio guanidine acid for in situ remediation of soils contaminated with multielements: its synthesis, solidification, biodegradability, and leachability

Purpose The main objectives of the study were to (1) develop a one-step facile procedure for synthesizing a new chemical amendment agent with three chelating groups for solidifying multiple heavy metals, called sixthio guanidine acid (SGA), using guanidine hydrochloride and carbon disulfide as raw reactants and (2) assess its biodegradability, solidification effectiveness, and leachability in remedying soils contaminated with multiple heavy metals of various concentrations compared with other traditional amendment agents.

Assessing the tolerance of immobilized laccase from a salt-tolerant strain of Trichoderma viride Pers NFCCI-2745 to heavy metal ions, detergents and copper chelating agents

The biotreatment of industrial effluents that contain heavy metals, detergents and metal chelating agents represents a great concern to industries as these compounds are either toxic to microbes or they act as non-competitive inhibitors/denaturing agents for several enzymes. So, it is essential to know the effect of various agents usually present in the treatment plant on activity of the enzyme, for extending its applications in in situ treatment processes. This study describes the immobilization conditions of laccase and analysis of the sensitivity of immobilized laccase from Trichoderma viride Pers NFCCI-2745 to heavy metals, detergent and copper chelating agents. The concentrations and combinations of cations influenced the activity of immobilized enzyme and its yield. The immobilized Cu–Ba alginate enzyme showed comparatively higher activity compared to the Cu-alginate enzyme. Most of the metal ions tested enhanced laccase activity at lower concentration. Immobilized laccase retained more than 70 % of its activity even in the presence of 20 mM copper chelating agents like EDTA and sodium thioglycolic acid. Sodium azide, on the other hand, inhibited 80 % of the activity of all the beads even at a very low concentration of 0.5 mM. Cu–Ba and Cu–Ni alginate enzyme exhibited comparatively higher tolerance than Cu-alginate beads to EDTA and sodium thioglycolate. Tween 20 and cetyl trimethyl ammonium bromide significantly increased the activity of all the beads. These properties of the immobilized laccase may be aptly considered and suitably utilized in treating phenolic effluents that may contain heavy metals, detergents and certain copper chelating agents which may otherwise pose a threat to enzymatic activity.

Effects of Chelating Agent Preparation Conditions on Settlement Formation in Fly Ash Stabilization

AbstractFly ash generated from waste incineration contains hazardous substances such as heavy metals and small amounts of dioxins. Incineration plants in Taiwan stabilized fly ash by mixing it with a heavy-metal chelating agent, cement, and mixing water. Settlement formed in the mixture may adhere to mixers and block transportation pipelines, thereby prolonging processing time and reducing efficiency. Through simulation experiments, it was found that the amount of settlement is low at a mixing speed of 30 rpm, a rotational speed of 50 rpm, a mixing time of 20 min, and a maximum settling time of 30 min. Also, the results of correlation analyses on control parameters showed that settlement formation mainly depended on water hardness level, whereas the other control parameters have trivial effects. Subsequent analysis on the relation between the rate of settlement formation and water hardness showed that an equation obtained from the power method gave the highest correlation; thus, this equation was used for...

Study of Cadmium Wastewater Treatment with Polymer PHA Containing Hydroxamic Acid Groups

Polymer heavy metal chelating agent containing hydroxamic acid groups (PHA) was made in order to observe its effects on the removal rate of Cd2+. The present study reaches the following results: (1) On conditions that pH value is 8.0, the chelating agent is 60mg•L-1and the reaction time is 60min, the highest chelating capacity of the polymer heavy metal chelating agent PHA can reach 341 mg/g. (2) The existence of common cations: K+, Na+and Mg2+can improve PHA’s ability to remove Cd2+. (3) The existence of common anions Cl-, SO42-and NO3-can improve PHA’s ability to remove Cd2+. (4) Co-existing with the turbidity-causing materials, PHA’s removal abilities of Cd2+and turbidity are mutually promotive. (5) The chelating product, Cd-PHA’s amount of leaching of Cd2+is only 1/11 of that in neutralization titration ,having a relatively higher stability and better environmental safety.

Synthesis of heavy metal chelating agent with four chelating groups of N1,N2,N4,N5-tetrakis(2-mercaptoethyl)benzene-1,2,4,5-tetracarboxamide (TMBTCA) and its application for Cu-containing wastewater

A novel heavy metal chelating agent, N1,N2,N4,N5-tetrakis(2-mercaptoethyl) benzene-1,2,4,5-tetracarboxamide (TMBTCA), was designed with four chelating groups, and a facile one-step synthetic procedure was developed with pyromellitic dianhydride (PMDA) and cysteamine hydrochloride (CHC) as raw materials by aqueous acylation. The effects of mole ratio of reactants (CHC/PMDA), reaction temperature, and reaction time on the yield of TMBTCA were studied. Its application for Cu-containing wastewater was investigated. The experimental results showed that the maximum yield of TMBTCA was 75.92%, as the mole ratio of CHC/PMDA reached 4.8, reaction temperature was 5°C, and reaction time was 6h. It was observed that TMBTCA could effectively remove Cu2+ and CuEDTA to much lower than 0.5mg/L (the discharge limit of copper ions in China).Furthermore, TMBTCA showed more affinity for cadmium and copper than some traditional commercial precipitants, such as DTC, TBA and TMT, via comparison of their ability for heavy metal removal, and the precipitates of Cu-TMBTCA and Cd-TMBTCA presented good stability in leaching tests. The results can provide a reference for design and further research on new kind of heavy metal chelating agent with more bonding sites, especially for heavy metal precipitation in PCB wastewater treatment.