Removal of chelated heavy metals from aqueous solution: A review of current methods and mechanisms
TL;DR: This review summarizes the various treatment methods applied to the removal of heavy metal complexes, with a summary of the mechanisms of action and recent research progress, and comprehensively analyzes future prospects and developments in methods for removal of chelated heavy metals.
About: This article is published in Science of The Total Environment.The article was published on 2019-08-15. It has received 222 citations till now.
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TL;DR: In this article, the authors discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal.
Abstract: Water pollution is one of the global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water pollutants. In this work, we discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal. Anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in aquatic environments. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, mercury, and arsenic, are outlined. We also give some perspectives about several techniques used to detect heavy metals, as well as about the factors that could affect the contaminant removal. The advantages and drawbacks of conventional and non-conventional heavy metal removal methods are critically discussed, given particular attention to those related to adsorption, nanostructured materials and plant-mediated remediation. Some of the commercial products currently used to eliminate heavy metals from water are also listed. Finally, we point out some the requirements and opportunities linked to developing efficient methods for heavy metal removal, such as the ones that exploit nanotechnologies.
294 citations
TL;DR: In this article, the effect of process conditions, such as temperature, pH value, and coexisting ions, on adsorption performance are combed, and the universal guidance law is obtained.
Abstract: Heavy metal contamination has been a serious threat to environment and human health Carbon-based materials, from biochar/activated carbon to modified materials (ie carbon nanotubes-based materials, and graphene-based materials), have been widely studied as efficient adsorbents for the heavy metal removal from aqueous solutions This review discussed the recent achievements in adsorption isotherms, adsorption kinetics and adsorption mechanism according to the existing forms of heavy metals in water The effect of process conditions, such as temperature, pH value, and coexisting ions, on adsorption performance are combed, and the universal guidance law is obtained The physical adsorption, electrostatic interaction, ion exchange, surface complexation, and precipitation/coprecipitation play important roles in heavy metals adsorption process In addition to the common activated carbon(AC), biochar(BC) and the emerging carbon nanotubes(CNTs) and graphene(GN) adsorbent show good development potentials Meanwhile, though the modified carbonaceous materials can achieve high adsorption capacity and removal efficiency of heavy metals, the modification operation is complex, especially chemical modification Acid and alkali solution are often used to regenerate spent materials in desorption, however, further studies of other desorption reagent are really needed This review highlights the removal of heavy metal ions from aqueous solution using carbon-based materials as adsorbents, and discusses the existing deficiencies and suggestions on further study
232 citations
TL;DR: In this article, a review of wastewater treatment and its respective benefits/applications in field scale were discussed and the difficulties in the enhancement of treatment methodologies for pragmatic commercial application are recognized and the future viewpoints are introduced.
190 citations
TL;DR: In this article, a magnetic chitosan/Al2O3/Fe3O4 (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cd and Zn(II) metal ions from aqueous solution.
160 citations
TL;DR: In this paper , a magnetic chitosan/Al2O3/Fe3O4 (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn (II) metal ions from aqueous solution.
Abstract: In this study, a magnetic chitosan/Al2O3/Fe3O4 (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.
150 citations
References
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TL;DR: In this article, the photocatalytic degradation of azo dyes containing different functionalities has been reviewed using TiO2 as photocatalyst in aqueous solution under solar and UV irradiation.
Abstract: The photocatalytic degradation of azo dyes containing different functionalities has been reviewed using TiO2 as photocatalyst in aqueous solution under solar and UV irradiation. The mechanism of the photodegradation depends on the radiation used. Charge injection mechanism takes place under visible radiation whereas charge separation occurred under UV light radiation. The process is monitored by following either the decolorization rate and the formation of its end-products. Kinetic analyses indicate that the photodegradation rates of azo dyes can usually be approximated as pseudo-first-order kinetics for both degradation mechanisms, according to the Langmuir–Hinshelwood model. The degradation of dyes depend on several parameters such as pH, catalyst concentration, substrate concentration and the presence of electron acceptors such as hydrogen peroxide and ammonium persulphate besides molecular oxygen. The presence of other substances such as inorganic ions, humic acids and solvents commonly found in textile effluents is also discussed. The photocatalyzed degradation of pesticides does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Thus, the study focuses also on the determination of the nature of the principal organic intermediates and the evolution of the mineralization as well as on the degradation pathways followed during the process. Major identified intermediates are hydroxylated derivatives, aromatic amines, naphthoquinone, phenolic compounds and several organic acids. By-products evaluation and toxicity measurements are the key-actions in order to assess the overall process.
3,692 citations
TL;DR: A review of recent applications of biochars, produced from biomass pyrolysis (slow and fast), in water and wastewater treatment, and a few recommendations for further research have been made in the area of biochar development for application to water filtration.
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TL;DR: Results from this study indicated that dairy manure can be converted into value-added biochar as effective sorbent for metal and/or organic contaminants.
Abstract: Biochar (BC) produced from agricultural crop residues has proven effective in sorbing organic contaminants. This study evaluated the ability of dairy-manure derived biochar to sorb heavy metal Pb and organic contaminant atrazine. Two biochar samples were prepared by heating dairy manure at low temperature of 200 degrees C (BC200) and 350 degrees C (BC350). The untreated manure (BC25) and a commercial activated C (AC) were included as controls. Sorption of Pb by biochar followed a dual Langmuir-Langmuir model, attributing to Pb precipitation (84-87%) and surface sorption (13-16%). Chemical speciation, X-ray diffraction, and infrared spectroscopy indicated that Pb was precipitated as beta-Pb9(PO4)6 in BC25 and BC200 treatment, and as Pb3(CO3)2(OH)2 in BC350. Lead sorption by AC obeyed a single Langmuir model, attributing mainly to surface sorption probably via coordination of Pb d-electron to C==C (pi-electron) and --0--Pb bonds. The biochar was 6 times more effective in Pb sorption than AC, with BC200 being the most effective (up to 680 mmol Pb kg(-1)). The biochar also effectively sorbed atrazine where atrazine was partitioned into its organic phase, whereas atrazine uptake by AC occurred via surface sorption. When Pb and atrazine coexisted, little competition occurred between the two for sorption on biochar, while strong competition was observed on AC. Results from this study indicated that dairy manure can be converted into value-added biochar as effective sorbent for metal and/or organic contaminants.
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TL;DR: Low-cost adsorbents can be viable alternatives to activated carbon for the treatment of metals-contaminated wastewater and vary, depending on the characteristics of the individual adsorbent, the extent of surface modification and the initial concentration of the adsorbate.
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