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Technologies Developing in Heavy Metals' Removal from Water

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: closed (25 February 2020) | Viewed by 39184

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Special Issue Editors

Dr. Manassis Mitrakas

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Guest Editor

Department of Chemical Engineering, Aristotle University of Thessaloniki, GR-54124, Thessaloniki, Greece
Interests: wastewater treatment; membrane bioreactors; activated sludge processes; water quality and treatment; analytical chemistry; removal of toxic parameters from water; chemical engineering
Special Issues, Collections and Topics in MDPI journals

Dr. Konstantinos Simeonidis

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Analytical Chemistry Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: water analysis; nanoparticle synthesis; X-ray analysis; microscopy analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Elevated concentrations of heavy metals in drinking water resources and industrial or urban wastewater pose a serious threat to human health and the equilibrium of ecosystems. During the last few decades, authorities have tended to set more strict regulations on acceptable limits challenging the improvement of conventional treatment technologies or the adoption of innovative processes. However, meeting the technology-based treatment standards, complying with local legislation, and keeping the designed system economically viable are not always easy tasks to fulfil.

In this Special Issue, we invite papers presenting research findings from the fields of adsorption, ion exchange, chemical precipitation, membrane filtering, biological processes, phytoremediation, or any other advanced technology oriented towards the selective removal of soluble forms of heavy metals from polluted water or wastewater below the corresponding regulation limit. Beyond the scientific importance, authors should evaluate the removal efficiency at residual concentrations equal to the regulation limit and should emphasize the potential to implement their technology in large-scale facilities operating under realistic conditions of water or wastewater treatment; furthermore, they are encouraged to analyze the cost impact with respect to the obtained efficiency and the currently applied methods. Both laboratory and pilot-scale experimental works will be included.

Dr. Manassis Mitrakas
Dr. Konstantinos Simeonidis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Heavy metals
Drinking water
Wastewater
Removal mechanism
Pilot unit
Cost analysis
Regulation compliance

Published Papers (10 papers)

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Editorial

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3 pages, 173 KiB

Open AccessEditorial

Technologies Developing in Heavy Metals’ Removal from Water

by Konstantinos Simeonidis and Manassis Mitrakas

Water 2021, 13(6), 860; https://doi.org/10.3390/w13060860 - 22 Mar 2021

Cited by 3 | Viewed by 1827

Abstract

Elevated concentrations of heavy metals in drinking water resources and industrial or urban wastewater pose a serious threat to human health and the equilibrium of ecosystems [...] Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

Research

Jump to: Editorial

18 pages, 3303 KiB

Open AccessArticle

Application of Composite Pre-Polymerized Coagulants for the Treatment of High-Strength Industrial Wastewaters

by Athanasia K. Tolkou and Anastasios I. Zouboulis

Water 2020, 12(5), 1258; https://doi.org/10.3390/w12051258 - 28 Apr 2020

Cited by 23 | Viewed by 2902

Abstract

The aim of this study was the investigation of alternative pre-polymerized coagulants for the treatment of high-strength industrial wastewaters, such as those created by tanneries, or by yeast production industries. The novel inorganic composite coagulant examined in this study (as well as variations of it) was denoted as PSiFAC_1.5-10-15. The contribution of a typical polyelectrolyte to improve the effectiveness of the coagulation/flocculation (C/F) process was additionally studied, either by adding it separately (i.e., as a flocculant aid) or by co-polymerizing it within the structure of inorganic coagulant (denoted as PAPEFAC_1.5-10-15). It was found that the PSiFAC_1.5:10:15 coagulant, either with or without the addition of polyelectrolyte, can provide better efficiency for the C/F process than the conventional coagulants. For example, the addition of 80 mg Al/L in yeast production wastewater samples resulted in a 56% reduction of COD, 40% of turbidity, and 43% of phosphates, regarding the pre-treated anaerobically wastewater samples and reduced by an extra 22%, 14%, and 38% for the pre-treated anaerobically plus aerobically wastewater samples, respectively. The residual aluminum concentration in the treated wastewaters was found to be below the legislation limit of 200 μg Al/L. The characterization of coagulants showed the relatively higher Al₁₃ content of 51% and 43% for the cases of PSiFAC_1.5-10-15 and PAPEFAC_1.5-10-15, respectively, accompanied by the high zeta-potential measurements (50.5 and 39.5 mV). Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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10 pages, 1103 KiB

Open AccessArticle

Techno-Economic Evaluation of Iron and Aluminum Coagulants on Se(IV) Removal

by Kyriaki Kalaitzidou, Loukas Bakouros and Manassis Mitrakas

Water 2020, 12(3), 672; https://doi.org/10.3390/w12030672 - 01 Mar 2020

Cited by 12 | Viewed by 2736

Abstract

Research on selenium pollution in natural waters is continuous and discouraging. In this study, coagulation/precipitation was applied with the use of Fe(II), Fe(III), and poly-aluminum chloride (PACl) salts for Se(IV) removal at concentration range 10–100 μg Se(IV)/L that is commonly found in drinking waters. Prehydrolyzed Fe(III)-FeCl₃ delivered the best uptake capacity (Q₁₀ = 8.9 mg Se(IV)/g Fe(III) at pH 6) at the residual concentration equal to the drinking water regulation limit of 10 μg/L. This was much higher than the efficiencies achieved when applying the other coagulants: i.e., Q₁₀ = 7.3 mg Se(IV)/g Fe³⁺-FeClSO₄, Q₁₀ = 6.4 mg Se(IV)/g prehydrolyzed Fe(III)-Fe₂(SO₄)₃ and 0.7 mg Se(IV)/g Al-PACl at pH 6, and Q₁₀ = 0.45 mg Se(IV)/g Fe(II) at pH 7.2. Comparing the different sources of Fe(III), it is apparent that Se(IV) uptake capacity is inhibited by the presence of SO₄²⁻ in crystal structure of prehydrolyzed Fe₂(SO₄)₃, while prehydrolyzed FeCl₃ favors Se(IV) uptake. Temperature effect data showed that coagulation/precipitation is exothermic. In techno-economic terms, the optimal conditions for Se(IV) removal are coagulation/precipitation at pH values lower than 7 using prehydrolyzed Fe(III)-FeCl₃, which provides a combination of minimum sludge production and lower operating cost. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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18 pages, 13337 KiB

Open AccessArticle

Removal of Trace Thallium from Industrial Wastewater by Fe⁰-Electrocoagulation

by Xianghui Fu, Li Li, Guochao Yang, Xiangyang Xu, Lihua He and Zhongwei Zhao

Water 2020, 12(1), 163; https://doi.org/10.3390/w12010163 - 05 Jan 2020

Cited by 10 | Viewed by 3331

Abstract

As thallium (Tl) is a highly toxic heavy metal, there are compulsory environmental regulations in many countries on minimizing its release. This research investigated the treatment of real industrial wastewater with low Tl(I) concentration by Fe⁰-electrocoagulation (Fe⁰-EC) in a batch aeration-forced pump cycle reactor. The effects of pH (7–12), current density (8.3–33.3 mA/cm²), dissolved oxygen (DO) in wastewater, and initial Tl(I) concentration (66–165 µg/L) on Tl(I) removal efficiency were investigated. The removal efficiency of Tl(I) is pH-dependent, to be exact, it increases significantly with pH rising from 8 to 11. Initial pH of influent and DO concentration were the key operation parameters which strongly affect Tl(I) removal. After the water sample with initial Tl(I) concentration of 115 µg/L was treated for 12 min by a single-step process at pH of 11 and current density of 16.7 mA/cm², the residual Tl(I) concentration was decreased to beneath the emission limit in China (2 µg/L) with a low energy consumption of 0.82 kWh/m³. By prolonging the operation time, the concentration was further reduced to 0.5 µg/L or even lower. The main composition of the flocculent sludges is iron oxyhydroxide, yet its crystal structure varies dependent on pH value which may result in different Tl(I) removal efficiency. Feroxyhyte nanosheets generate in situ by Fe⁰-EC, which contributes to the rapid and effective removal of Tl(I), while the speedy oxidation under DO-enriched conditions benefits the feroxyhyte formation. The mechanism of Tl(I) removal by Fe⁰-EC is attributed to the combination of electrostatic attraction and the formation of inner-sphere complexes. As shown in the technical and mechanical studies, Fe⁰-EC technology is an effective method for low Tl concentration removal from wastewater. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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11 pages, 4464 KiB

Open AccessFeature PaperArticle

An Optimized Cr(VI)-Removal System Using Sn-based Reducing Adsorbents

by George Papadopoulos, Theopoula Asimakidou, Dimitrios Karfaridis, Ioannis Kellartzis, George Vourlias, Manassis Mitrakas and Konstantinos Simeonidis

Water 2019, 11(12), 2477; https://doi.org/10.3390/w11122477 - 24 Nov 2019

Cited by 7 | Viewed by 3784

Abstract

Despite significant risks to human health due to elevated Cr(VI) concentrations in drinking water, a selective adsorbent capable of purifying water before consumption is still not commercially available. This work introduces an integrated household water filtration setup, for point-of-use applications, loaded with a tin-based Cr(VI)-oriented adsorbent that was tested under various contact times, pH values and Cr(VI) concentrations. The adsorbent comprises a chloride-substituted stannous oxy-hydroxide with a structure resembling that of the mineral abhurite. It demonstrated high reducing capacity that triggered the formation of insoluble Cr(III) hydroxides and the complete removal of Cr(VI) in considerably high volumes of polluted water. Test operation of the filtration system verified its ability to produce Cr(VI)-free water in compliance with the impending drinking water regulation, even for extreme initial concentrations (1000 μg/L). Apart from its high efficiency, the potential of the studied material is enhanced by its minimal-cost synthesis method carried out in a continuous-flow reactor by tin chloride precipitation under acidic conditions. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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12 pages, 2119 KiB

Open AccessArticle

Effect of the Surface Charge on the Adsorption Capacity of Chromium(VI) of Iron Oxide Magnetic Nanoparticles Prepared by Microwave-Assisted Synthesis

by Alvaro Gallo-Cordova, María del Puerto Morales and Eva Mazarío

Water 2019, 11(11), 2372; https://doi.org/10.3390/w11112372 - 13 Nov 2019

Cited by 33 | Viewed by 5053

Abstract

Solid phase extraction using magnetic nanoparticles has represented a leap forward in terms of the improvement of water quality, preventing the contamination of industrial effluents from discharge in a more efficient and affordable way. In the present work, superparamagnetic iron oxide nanoparticles (MNP) with different surface charges are tested as nanosorbents for the removal of chromium(VI) in aqueous solution. Uniform magnetic nanoparticles (~12 nm) were synthesized by a microwave polyol-mediated method, and tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) were grafted onto their surface, providing a variation in the surface charge. The adsorptive process of chromium was evaluated as a function of the pH, the initial concentration of chromium and contact time. Kinetic studies were best described by a pseudo-second order model in all cases. TEOS@MNP barely removed the chromium from the media, while non-grafted particles and APTES@TEOS@MNP followed the Langmuir model, with maximum adsorption capacities of 15 and 35 mg_Cr/g, respectively. The chromium adsorption capacities abruptly increased when the surface became positively charged as the species coexisting at the experimental pH are negatively charged. Furthermore, these particles have proven to be highly efficient in water remediation due their 100% reusability after more than six consecutive adsorption/desorption cycles. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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11 pages, 1724 KiB

Open AccessArticle

Removal of Pb(II) by Pellicle-Like Biofilm-Producing Methylobacterium hispanicum EM2 Strain from Aqueous Media

by Sun-Wook Jeong, Hyo Kyeong Kim, Jung Eun Yang and Yong Jun Choi

Water 2019, 11(10), 2081; https://doi.org/10.3390/w11102081 - 05 Oct 2019

Cited by 12 | Viewed by 3763

Abstract

As concerns are increasing about drinking water contamination with heavy metals, we investigated the possible use of a pellicle (floating biofilm)-like biofilm-producing microorganism as a biosorbent for the treatment of Pb(II) in aqueous solutions. The bacterial pellicle-producing Methylobacterium hispanicum EM2 strain (EM2) was newly isolated from mine tailing soil, and we investigated its use as a biosorbent for treating a Pb(II)-contaminated aqueous solution. The EM2 strain was strongly resistant to Pb(II) up to a concentration of 800 mg/L, and achieved remarkable adsorption performance (adsorption rate and maximum adsorption capacity of 96% ± 3.2% and 79.84 mg/g, respectively) under optimal conditions (pH, biomass content, contact time, and initial Pb(II) concentration of 7.1 g/L, 60 min, and 10 mg/L, respectively). The adsorption of Pb(II) was characterized by scanning electron microscopy-energy dispersive x-ray spectroscopy and Fourier-transform infrared analysis. The equilibrium data matched the Freundlich isotherm model well, indicating the occurrence of multilayer adsorption of Pb(II) onto the heterogeneous surface of the EM2 strain, which was also consistent with the pseudo-second-order kinetic model (R² = 0.98). The high Pb(II) removal efficiency was also confirmed by conducting an adsorption experiment using Pb(II)-contaminated industrial wastewater. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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19 pages, 3761 KiB

Open AccessArticle

Adsorptive Removal of Iron and Manganese from Groundwater Samples in Ghana by Zeolite Y Synthesized from Bauxite and Kaolin

by Bright Kwakye-Awuah, Baah Sefa-Ntiri, Elizabeth Von-Kiti, Isaac Nkrumah and Craig Williams

Water 2019, 11(9), 1912; https://doi.org/10.3390/w11091912 - 13 Sep 2019

Cited by 42 | Viewed by 6135

Abstract

Ground water samples from residential homes in three Regions of Ghana: Central, Greater Accra and Ashanti, were analyzed for iron and manganese contamination. The samples were exposed to characterized zeolite Y by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed-infrared spectroscopy and thermos gravimetric-differential thermal analysis. Zeolite Y is able to remove 98% of iron and 97% of manganese within an hour. The adsorption of both iron and manganese followed the Freundlich model, suggesting that the ions were transported onto the zeolite Y surface and subsequently diffused into the zeolite Y framework. The kinetic studies showed that pseudo-first order and intra particle and film diffusion models provided the best fit. The adsorption at 0.2 mg L⁻¹ Fe (

Q_{0.2}

) is calculated to be 0.023 mg g⁻¹ for the Freundlich adsorption model, whilst that of manganese at 0.05 mg L⁻¹ Mn (

Q_{0.05}

) is evaluated to be 0.015 mg g⁻¹. The zeolite retains its adsorption properties when retrieved from the first exposure water sample, washed copiously with distilled water and added to fresh water samples. The results suggest that zeolite Y can be used as a potential adsorbent for the removal of iron and manganese from groundwater. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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13 pages, 2498 KiB

Open AccessArticle

Uptake of As(V) from Groundwater Using Fe-Mn Oxides Modified Kaolin Clay: Physicochemical Characterization and Adsorption Data Modeling

by Rabelani Mudzielwana, Mugera Wilson Gitari and Patrick Ndungu

Water 2019, 11(6), 1245; https://doi.org/10.3390/w11061245 - 14 Jun 2019

Cited by 14 | Viewed by 2989

Abstract

The present study evaluated the effectiveness of Fe-Mn modified kaolin clay in the uptake of As(V) from the solution. The elemental composition was characterized using X-ray fluorescence (XRF), while the surface morphology was characterized using Scanning Electron Microscopy (SEM). The surface area, pore diameter, and pore volume were determined using Brunauer, Emmett, and Teller (BET) and Barrett-Joyner-Halenda (BJH) techniques. The efficiency of the Arsenic removal of the adsorbent was evaluated using batch experiments. The results showed that the percentage of As(V) removal is optimum at acidic pH and decreased as the solution pH becomes more alkaline. The adsorption kinetics data fitted better to pseudo-second-order compared to the pseudo-first-order of reaction kinetics. The adsorption isotherm data fitted to the Langmuir isotherm model showing a maximum adsorption capacity of 2.44 mg/g, adsorbate concentration range of 1–30 mg/L, and adsorbent dosage of 0.4 g/100 mL. The value of ∆G° of the thermodynamic parameter was found to be negative, while ∆H° and ∆S° were found to be positive. For the regeneration-reuse study, the percentage of removal was found to be >85% after the sixth cycle of reuse. The results obtained from this study showed that Fe-Mn modified kaolin (FMK) is suitable for use in the uptake of As(V) from groundwater. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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11 pages, 4214 KiB

Open AccessFeature PaperArticle

Uptake of Sb(V) by Nano Fe₃O₄-Decorated Iron Oxy-Hydroxides

by Konstantinos Simeonidis, Kyriaki Kalaitzidou, Efthimia Kaprara, Georgia Mitraka, Theopoula Asimakidou, Lluis Balcells and Manassis Mitrakas

Water 2019, 11(1), 181; https://doi.org/10.3390/w11010181 - 21 Jan 2019

Cited by 14 | Viewed by 5625

Abstract

The presence of antimony in water remains a major problem for drinking water technology, defined by the difficulty of available adsorbents to comply with the very low regulation limit of 5 μg/L for the dominant Sb(V) form. This study attempts to develop a new class of water adsorbents based on the combination of amorphous iron oxy-hydroxide with Fe₃O₄ nanoparticles and optimized to the sufficient uptake of Sb(V). Such a Fe₃O₄/FeOOH nanocomposite is synthesized by a two-step aqueous precipitation route from iron salts under different oxidizing and acidity conditions. A series of materials with various contents of Fe₃O₄ nanoparticles in the range 0–100 wt % were prepared and tested for their composition, and structural and morphological features. In order to evaluate the performance of prepared adsorbents, the corresponding adsorption isotherms, in the low concentration range for both Sb(III) and Sb(V), were obtained using natural-like water. The presence of a reducing agent such as Fe₃O₄ results in the improvement of Sb(V) uptake capacity, which is found around 0.5 mg/g at a residual concentration of 5 μg/L. The intermediate reduction of Sb(V) to Sb(III) followed by Sb(III) adsorption onto FeOOH is the possible mechanism that explains experimental findings. Full article

(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

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