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12 pages, 3087 KiB

Open AccessArticle

Functionalized PET Waste Based Low-Cost Adsorbents for Adsorptive Removal of Cu(II) Ions from Aqueous Media

by Oana Ionela Ungureanu, Dumitru Bulgariu, Anca Mihaela Mocanu and Laura Bulgariu

Water 2020, 12(9), 2624; https://doi.org/10.3390/w12092624 - 19 Sep 2020

Cited by 18 | Viewed by 3114

The widespread use of polyethylene terephthalate (PET) in the packaging industry has led to the discharge of huge amounts of such waste into the environment and is an important source of pollution. Moreover, because the degradation of PET waste requires a very long [...] Read more.

The widespread use of polyethylene terephthalate (PET) in the packaging industry has led to the discharge of huge amounts of such waste into the environment and is an important source of pollution. Moreover, because the degradation of PET waste requires a very long time (over 180 years), the recycling of this waste is the only solution to reduce environmental pollution in this case. The solution proposed in this study, is the transformation of PET waste into granular adsorbent materials by functionalization with different phenolic compounds (phenol, p-chlor-phenol, and hydroxyquinone), and then their use as adsorbent materials for removing metal ions (ex. Cu(II) ions) from aqueous solutions. The functionalization of PET waste was done with different amounts (2–8 g) of each phenolic compound. The adsorption capacity of obtained materials was tested at different initial Cu(II) ions concentrations, in batch systems, at room temperature (20 ± 1 °C). The experimental results have shown that the adsorbent material obtained by the functionalization of PET waste with 8 g of phenol has the best adsorptive performances (q = 12.80 mg g⁻¹) at low initial concentrations of Cu(II) ions, while the adsorbent material obtained by the functionalization of PET waste with 2 g of hydroxyquinone is more efficient in removal of high concentrations of Cu(II) ions (q = 61.73 mg g⁻¹). The experimental isotherms were modeled using Langmuir and Freundlich isotherm models, to highlight the adsorptive performances of these new adsorbents and their potential applicability in environmental decontamination processes. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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13 pages, 6356 KiB

Open AccessEditor’s ChoiceArticle

Adsorption Properties of Magnetic Magnetite Nanoparticle for Coexistent Cr(VI) and Cu(II) in Mixed Solution

by Jin Zhang, Shuang Lin, Meiling Han, Qing Su, Lianqiu Xia and Zhaocong Hui

Water 2020, 12(2), 446; https://doi.org/10.3390/w12020446 - 07 Feb 2020

Cited by 70 | Viewed by 4462

Abstract

The adsorption properties of coexistent Cr(VI) and Cu(II) in mixed solution on magnetic magnetite (Fe₃O₄) nanoparticle were studied in batch experiments. The influences of various factors, such as pH, adsorbent dose, temperature, initial concentration of metal ions, and coexisting [...] Read more.

The adsorption properties of coexistent Cr(VI) and Cu(II) in mixed solution on magnetic magnetite (Fe₃O₄) nanoparticle were studied in batch experiments. The influences of various factors, such as pH, adsorbent dose, temperature, initial concentration of metal ions, and coexisting ions in water were investigated. At the same time, the adsorption kinetics and adsorption isotherms were studied. The mechanism of adsorption for Cr(VI) and Cu(II) was investigated through the study of surface properties of Fe₃O₄, the presence of ions, and the influence of pH and zeta potential. The results indicate that pH has an influence on adsorption for Cr(VI) and Cu(II), and the optimal pH value for Cr(VI) and Cu(II) adsorption is 4.0. The adsorption efficiency increased with the increase of the adsorbent dose. Temperature under experimental design had no obvious effect. With 2.0 g/dm³ Fe₃O₄, the maximum adsorption capacity for Cr(VI) and Cu(II) reached 8.67 mg/g and 18.61 mg/g in mixed solution of 80 mg/dm³ Cr(VI) and Cu(II), respectively. Phosphorus had some influence on the adsorption for Cr(VI), and other coexisting anions and cations had no influence on the adsorption for Cr(VI) and Cu(II). The adsorption data for Cr(VI) and Cu(II) were nicely fit to the Langmuir adsorption equation and the pseudo-second-order model. As a multifunctional material, nano-Fe₃O₄ exhibited good adsorption performance for coexistent Cr(VI) and Cu(II) and could easily be separated and recovered under magnetic field. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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16 pages, 2489 KiB

Open AccessArticle

Adsorption of Cu(II) Ions on Adsorbent Materials Obtained from Marine Red Algae Callithamnion corymbosum sp.

by Alina Roxana Lucaci, Dumitru Bulgariu, Maria-Cristina Popescu and Laura Bulgariu

Water 2020, 12(2), 372; https://doi.org/10.3390/w12020372 - 30 Jan 2020

Cited by 43 | Viewed by 2882

Abstract

In recent years, studies on the more efficient use of natural materials in adsorption processes have increased significantly. Thus, obtaining new adsorbents from marine algae biomass with higher adsorptive performance will ensure a better use of these renewable resources. In this study, the [...] Read more.

In recent years, studies on the more efficient use of natural materials in adsorption processes have increased significantly. Thus, obtaining new adsorbents from marine algae biomass with higher adsorptive performance will ensure a better use of these renewable resources. In this study, the adsorption of Cu(II) ions from aqueous solution was done using three types of adsorbent materials obtained from marine red algae biomass (Callithamnion corymbosum sp.), namely: alginate (Alg), algae waste biomass resulted after alginate extraction (AWB) and iron nanoparticles functionalized with alginate (Fe-NPs-Alg), compared to raw marine red algae biomass (RAB). FTIR spectra and SEM images recorded for each type of adsorbent indicate a porous structure and the presence of various superficial functional groups who may be involved in the retention of Cu(II) ions. The biosorption experiments were performed in a batch system, at different initial Cu(II) ion concentrations and contact times, maintaining a constant initial solution pH (4.4), adsorbent dose (2.0 g/L), and temperature (25 ± 1 °C). The obtained results indicate that the retention of Cu(II) ions requires a maximum of 60 min to reach equilibrium, and the maximum adsorption capacity increases in order: RAB (47.62 mg/g) < Fe-NPs-Alg (52.63 mg/g) < AWB (83.33 mg/g) < Alg (166.66 mg/g). The quantitative removal of Cu(II) ions from aqueous effluents can be done in two successive adsorption stages, using AWB (in the first stage) and Fe-NPs-Alg (in the second stage), when the treated solution has a Cu(II) ions concentration below the maximum permissible limit. The quantitative recovery of retained Cu(II) ions (over 97%) can be done by treating these exhausted adsorbent materials with 0.1 N HNO₃ solution. Therefore, the extraction of alginate from marine red algae biomass could be a viable solution to obtain efficient adsorbent materials for Cu(II) ions removal from aqueous media, and allow for a better valorisation of marine red algae biomass. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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11 pages, 2176 KiB

Open AccessArticle

Implementation of Modified Acacia Tannin by Mannich Reaction for Removal of Heavy Metals (Cu, Cr and Hg)

by Lorena Lugo, Alison Martín, John Diaz, Alejandro Pérez-Flórez and Crispin Celis

Water 2020, 12(2), 352; https://doi.org/10.3390/w12020352 - 28 Jan 2020

Cited by 22 | Viewed by 3316

Abstract

The modified tannin by Mannich reaction was investigated for wastewater treatment. The removal of heavy metals, such as copper, chromium and mercury, in industrial wastewater was evaluated through the coagulation–flocculation technique, using modified Acacia tannin (MAT) as a coagulant agent. The successful tannin [...] Read more.

The modified tannin by Mannich reaction was investigated for wastewater treatment. The removal of heavy metals, such as copper, chromium and mercury, in industrial wastewater was evaluated through the coagulation–flocculation technique, using modified Acacia tannin (MAT) as a coagulant agent. The successful tannin modification was evaluated by infrared spectopometry (FTIR), nuclear magnetic resonance (NMR); monitoring the removal of heavy metals was performed by atomic absorption (AA) and a direct mercury analyzer (DMA). Additionally, the parameters of water quality, total suspended solids (TSS), turbidity and chemical oxygen demand (COD) were assessed. Different doses of MAT were evaluated (375 ppm, 750 ppm, 1250 ppm and 1625 ppm) and three different levels of pH (4, 7 and 10). The highest percentages of removal obtained were copper 60%, chromium 87%, mercury 50%–80%, COD 88%, TSS 86% and turbidity 94%, which were achieved with the dose of 375 ppm of MAT at pH 10. The coagulation–flocculation process with the modified Acacia tannin is efficient for the removal of conventional parameters and for a significant removal of the metals studied. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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13 pages, 6050 KiB

Open AccessArticle

Nanoscale Zero Valent Iron Supported by Biomass-Activated Carbon for Highly Efficient Total Chromium Removal from Electroplating Wastewater

by Bo Zhang, Bo-Hong Zhu, Xiong Wang and Song-Bai You

Water 2020, 12(1), 89; https://doi.org/10.3390/w12010089 - 26 Dec 2019

Cited by 15 | Viewed by 3765

Abstract

The application potential of nanoscale zero valent iron (nZVI) in wastewater treatment is huge and has attracted a lot of attention. In this study, the composite material BC-nZVI was prepared by emulsion of nZVI and biomass-activated carbon (BC) under the mechanical agitation condition, [...] Read more.

The application potential of nanoscale zero valent iron (nZVI) in wastewater treatment is huge and has attracted a lot of attention. In this study, the composite material BC-nZVI was prepared by emulsion of nZVI and biomass-activated carbon (BC) under the mechanical agitation condition, and was characterized by SEM-EDX, XRD, XPS, and FTIR. The decontamination abilities of BC-nZVI were tested by the removal of total chromium (Cr) from electroplating wastewater. The results showed that the removal efficiencies of Cr in the electroplating wastewater by nZVI particles can be effectively improved when supported with BC, but cannot be improved in its storage capacity. The chemical adsorption process between the Cr and BC-nZVI is the main rate-limiting step in the removal of total Cr from wastewater, and multiple parameters such as dosage, pH, and initial concentration of Cr was found to affect the rate. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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14 pages, 1554 KiB

Open AccessArticle

Recovering Metals from Aqueous Solutions by Biosorption onto Hydrolyzed Olive Cake

by Rafael Fernández-González, María Ángeles Martín-Lara, Gabriel Blázquez, Antonio Pérez and Mónica Calero

Water 2019, 11(12), 2519; https://doi.org/10.3390/w11122519 - 28 Nov 2019

Cited by 12 | Viewed by 2641

Abstract

Olive cake obtained as a by-product from the olive oil industry has been evaluated as biosorbent of heavy metals from aqueous solutions in batch and continuous systems (fixed-bed columns). First, a complete study of effect of hydrothermal treatment with water on biosorption capacity [...] Read more.

Olive cake obtained as a by-product from the olive oil industry has been evaluated as biosorbent of heavy metals from aqueous solutions in batch and continuous systems (fixed-bed columns). First, a complete study of effect of hydrothermal treatment with water on biosorption capacity of resulting solid was performed. Results showed that the values of biosorption capacity increased when the particle size of material decreased and the temperature of treatment increased. Then, hydrolyzed olive cake was treated by common chemicals (hot water, nitric acid, and sodium hydroxide) and the impact of chemical treatment was analyzed. The results were well reproduced by Langmuir and Freundlich isotherm models, getting maximum experimental biosorption capacities that changed between 42.34 mg/g obtained for the solid material modified by NaOH and 14.27 mg/g obtained for the solid material modified by nitric acid. Finally, laboratory tests in fixed-bed columns were performed with four different heavy metals and at three different inlet concentrations. The biosorption capacity increased from 2.83 mg/g (Cr), 4.51 mg/g (Cu), 12.30 mg/g (Pb), and 4.10 mg/g (Zn) to 3.08 mg/g (Cr), 5.17 mg/g (Cu), 13.21 mg/g (Pb), and 5.51 mg/g (Zn) when the concentration of metal ions increased, from 50 mg/L to 200 mg/L, respectively. Also, the experimental data obtained was successfully correlated with the Thomas, Yoon–Nelson, and dose–response models. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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15 pages, 2391 KiB

Open AccessArticle

Potential Use of Biochar from Various Waste Biomass as Biosorbent in Co(II) Removal Processes

by Alina Roxana Lucaci, Dumitru Bulgariu, Iftikhar Ahmad, Gabriela Lisă, Anca Mihaela Mocanu and Laura Bulgariu

Water 2019, 11(8), 1565; https://doi.org/10.3390/w11081565 - 29 Jul 2019

Cited by 70 | Viewed by 3923

Abstract

The removal of Co(II) ions from aqueous media was done using three types of biochars obtained from algae waste biomass, mustard waste biomass, and soy waste biomass. The biochar samples were obtained by pyrolysis of waste biomass resulted from biofules production, at relative [...] Read more.

The removal of Co(II) ions from aqueous media was done using three types of biochars obtained from algae waste biomass, mustard waste biomass, and soy waste biomass. The biochar samples were obtained by pyrolysis of waste biomass resulted from biofules production, at relative low temperature (600–650 °C), and this procedure can be considered a suitable alternative to reduce the volume of such waste. FTIR spectra recorded for each type of biochar reveal the presence of several functional groups that can be used as binding sites for Co(II) retention. The batch biosorption experiments were performed as a function of initial Co(II) ions concentration and contact time, at constant solution pH (5.0), sorbent dose (8.0 g/L), and room temperature (25 ± 1 °C). The sorption experiments showed that the Co(II) ions retention reaches the equilibrium in maximum 60 min, and the maximum sorption capacity follows the order: Mustard biochar (MBC—24.21 mg/g) < soy biochar (SBC—19.61 mg/g) < algae biochar (ABC—11.90 mg/g). The modeling of experimental data proves that the retention of Co(II) ions from aqueous solution occurs through electrostatic interactions, and that the sorption process takes place until a monolayer coverage is formed on the outer surface of the biochar. This information is very useful in the design of a suitable desorption system. The desorption results showed that by treating the biochar samples loaded with Co(II) ions with 0.1 mol/L HNO₃ solution, over 92% of Co(II) ions are desorbed and can be recovered, and the biochar samples can be used in at least three sorption/desorption cycles. All the experimental observations sustain the potential use of biochar obtained from different types of waste biomass as a promising alternative sorbent for the removal of Co(II) ions from aqueous media. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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17 pages, 2407 KiB

Open AccessArticle

Batch and Column Scale Removal of Cadmium from Water Using Raw and Acid Activated Wheat Straw Biochar

by Muhammad Asif Naeem, Muhammad Imran, Muhammad Amjad, Ghulam Abbas, Muhammad Tahir, Behzad Murtaza, Ali Zakir, Muhammad Shahid, Laura Bulgariu and Iftikhar Ahmad

Water 2019, 11(7), 1438; https://doi.org/10.3390/w11071438 - 12 Jul 2019

Cited by 87 | Viewed by 5604

Abstract

The present study examined novel wheat straw biochar (WSB) and acid treated wheat straw biochar (AWSB) for cadmium removal from contaminated water. A series of batch and column scale experiments was conducted to evaluate the potential of WSB and AWSB for cadmium removal [...] Read more.

The present study examined novel wheat straw biochar (WSB) and acid treated wheat straw biochar (AWSB) for cadmium removal from contaminated water. A series of batch and column scale experiments was conducted to evaluate the potential of WSB and AWSB for cadmium removal at different biochar dosage (0.5–8 g/L), initial cadmium concentration (5–100 mg/L), solution pH (2–8) and contact time (5–180 min). Results revealed that cadmium adsorption decreased by increasing biochar dosage from 0.5 to 8 g/L; however, optimum dosage for maximum (99%) removal of cadmium was 2 g/L by WSB and 1 g/L by AWSB. Enhanced cadmium removal potential by AWSB is attributed to increased surface area, microporosity and variation in functional groups. Equilibrium experimental data was well described by Freundlich adsorption isotherm whereas kinetic data were better explained with pseudo-second order model. Both WSB and AWSB have shown good adsorption capacity of 31.65 mg/g and 74.63 mg/g, respectively, that is comparable with other costly adsorbents. Columns packed with WSB and AWSB at laboratory scale have also shown good retention of cadmium with excellent reusability. These findings indicate that WSB especially AWSB could be a promising, cost-effective and environmental friendly strategy for the removal of metals from contaminated water. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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16 pages, 2199 KiB

Open AccessArticle

Biochar from A Freshwater Macroalga as A Potential Biosorbent for Wastewater Treatment

by Izabela Michalak, Sylwia Baśladyńska, Jakub Mokrzycki and Piotr Rutkowski

Water 2019, 11(7), 1390; https://doi.org/10.3390/w11071390 - 06 Jul 2019

Cited by 65 | Viewed by 5537

Abstract

The multi-elemental composition, surface texture and morphology of biochar, produced by pyrolysis at 300, 350, 400 and 450 °C from freshwater macroalga Cladophora glomerata, as a biosorbent of toxic metals was examined with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Scanning Electron [...] Read more.

The multi-elemental composition, surface texture and morphology of biochar, produced by pyrolysis at 300, 350, 400 and 450 °C from freshwater macroalga Cladophora glomerata, as a biosorbent of toxic metals was examined with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. It was found that the yield of pyrolysis was inversely proportional to temperature: for 300 °C it was 63%, whereas for 450 °C—47%. The proximate analysis revealed that also biochar’s moisture and volatile matter was inversely proportional to temperature. The content of ash increased with temperature. All biochars were characterized by a similar total pore area of about 20 m² g⁻¹. FT-IR analysis showed that all biochars peaked at 3500–3100 cm⁻¹ which was attributed to O–H stretching of the hydroxyl groups, at 2850–2970 cm⁻¹, stretching vibrations of C–H bonds in aliphatic CH₂ and CH groups, at 1605 cm⁻¹, stretching vibrations from C=C of aromatics, at 1420 cm⁻¹, bending oscillations from CH₂, at about 1111 cm⁻¹, stretching vibrations of Si–O, at 618 cm⁻¹, vibrations from Fe–O bonds, and at 475 cm⁻¹—Si–O–Si deformation vibrations. The biosorption properties of biochar towards Cr(III) ions were examined in kinetic studies. The biosorption capacity of biochar increased with an increase of pyrolysis temperature: the highest was for biochar obtained at 450 °C—87.1 mg Cr(III) g⁻¹ and the lowest at 300 °C—45.9 mg g⁻¹. Cladophora biochar also demonstrated a good ability to simultaneously remove metal ions from a multi-metal system, e.g., wastewater. The removal efficiency for Cr(III) was 89.9%, for Cu(II) 97.1% and for Zn(II) 93.7%. The biochar derived from waste-freshwater macroalgae can be a potent and eco-friendly alternative adsorptive material. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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11 pages, 752 KiB

Open AccessArticle

Effect of Dissolved Silicon on the Removal of Heavy Metals from Aqueous Solution by Aquatic Macrophyte Eleocharis acicularis

by Ha T.H. Nguyen, Masayuki Sakakibara, Minh N. Nguyen, Nhuan T. Mai and Vinh T. Nguyen

Water 2019, 11(5), 940; https://doi.org/10.3390/w11050940 - 04 May 2019

Cited by 2 | Viewed by 2909

Abstract

Silicon (Si) has been recently reconsidered as a beneficial element due to its direct roles in stimulating the growth of many plant species and alleviating metal toxicity. This study aimed at validating the potential of an aquatic macrophyte Eleocharis acicularis for simultaneous removal [...] Read more.

Silicon (Si) has been recently reconsidered as a beneficial element due to its direct roles in stimulating the growth of many plant species and alleviating metal toxicity. This study aimed at validating the potential of an aquatic macrophyte Eleocharis acicularis for simultaneous removal of heavy metals from aqueous solutions under different dissolved Si. The laboratory experiments designed for determining the removal efficiencies of heavy metals were conducted in the absence or presence of Si on a time scale up to 21 days. Eleocharis acicularis was transplanted into the solutions containing 0.5 mg L⁻¹ of indium (In), gallium (Ga), silver (Ag), thallium (Tl), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) with various Si concentrations from 0 to 4.0 mg L⁻¹. The results revealed that the increase of dissolved Si concentrations enhanced removal efficiencies of E. acicularis for Ga, Cu, Zn, Cd, and Pb, while this increase did not show a clear effect for In, Tl, and Ag. Our study presented a notable example of combining E. acicularis with dissolved Si for more efficient removals of Cu, Zn, Cd, Pb, and Ga from aqueous solutions. The findings are applicable to develop phytoremediation or phytomining strategy for contaminated environment. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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15 pages, 4313 KiB

Open AccessArticle

Removal Efficiency and Mechanism of Cr(VI) from Aqueous Solution by Maize Straw Biochars Derived at Different Pyrolysis Temperatures

by Haixia Wang, Mingliang Zhang and Qi Lv

Water 2019, 11(4), 781; https://doi.org/10.3390/w11040781 - 15 Apr 2019

Cited by 51 | Viewed by 4233

Abstract

The removal efficiency and mechanism of Cr(VI) removal from aqueous solution on semi-decomposed maize straw biochars pyrolyzed at 300 to 600 °C were investigated. The removal of Cr(VI) by the biochars decreased with pyrolysis temperature increasing from 300 to 600 °C, and the [...] Read more.

The removal efficiency and mechanism of Cr(VI) removal from aqueous solution on semi-decomposed maize straw biochars pyrolyzed at 300 to 600 °C were investigated. The removal of Cr(VI) by the biochars decreased with pyrolysis temperature increasing from 300 to 600 °C, and the maximum removal capacity of Cr(VI) for maize straw biochar pyrolyzed at 300 °C was 91 mg/g at pH 2.0. The percentage removal of Cr(VI) rapidly decreased with pH increasing from 2.0 to 8.0, with the maximum (>99.9%) at pH 2.0. The variation of Cr(VI) and Cr(III) concentrations in the solution after reaction showed that Cr(VI) concentration decreased while Cr(III) increased and the equilibrium was reached after 48 h, while the redox potential after reaction decreased due to Cr(VI) reduction. X-ray photoelectron spectroscopy (XPS) semi-quantitative analysis showed that Cr(III) accounted for 75.7% of the total Cr bound to maize straw biochar, which indicated reductive adsorption was responsible for Cr(VI) removal by the biochars. Cr(VI) was firstly adsorbed onto the positively charged biochar surface and reduced to Cr(III) by electrons provided by oxygen-containing functional groups (e.g., C=O), and subsequently part of the converted Cr(III) remained on the biochar surface and the rest released into solution. Fourier transform infrared (FTIR) data indicated the participation of C=O, Si–O, –CH₂ and –CH₃ groups in Cr(VI) removal by the biochars. This study showed that maize straw biochar pyrolyzed at 300 °C for 2 h was one low-cost and efficient adsorbent for Cr(VI) removal from aqueous solution. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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17 pages, 2264 KiB

Open AccessArticle

Adsorption of Aqueous As (III) in Presence of Coexisting Ions by a Green Fe-Modified W Zeolite

by Adriana Medina-Ramirez, Procoro Gamero-Melo, Beatriz Ruiz-Camacho, Jesus Isaac Minchaca-Mojica, Rafael Romero-Toledo and Karen Yazmin Gamero-Vega

Water 2019, 11(2), 281; https://doi.org/10.3390/w11020281 - 06 Feb 2019

Cited by 20 | Viewed by 4745

Abstract

The high toxicity of arsenite and the difficulty to remove it is one of the main challenges for water treatment. In the present work the surface of a low cost zeolite was modified by chemical treatment with a ferrous chloride to enhance its [...] Read more.

The high toxicity of arsenite and the difficulty to remove it is one of the main challenges for water treatment. In the present work the surface of a low cost zeolite was modified by chemical treatment with a ferrous chloride to enhance its arsenite adsorption capacity. The effect of pH, ions coexistence, concentration, temperature and dosage was studied on the adsorption process. Additionally, the Fe-modified W zeolite was aged by an accelerated procedure and the regeneration of the exhausted zeolite was demonstrated. The Fe-modified W zeolite was stable in the pH range of 3 to 8 and no detriment to its arsenite removal capacity was observed in the presence of coexisting ions commonly found in underground water. The studies showed that the adsorption of As (III) on Fe-modified W zeolite is a feasible, spontaneous and endothermic process and it takes place by chemical bonding. The exhausting process proved the adsorption of 0.20 mg g⁻¹ of As (III) by the Fe-modified W zeolite and this withstand at least five aging cycles without significant changes of its arsenite adsorption capacity. Fe-modified W zeolite prepared from fly ash might be a green and low-cost alternative for removal of As (III) from groundwater. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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11 pages, 2322 KiB

Open AccessArticle

Characterization of the Adsorption of Cu (II) from Aqueous Solutions onto Pyrolytic Sludge-Derived Adsorbents

by Minghui Wang, Tao Chen, Bo Yan, Lili Li, Damao Xu and Xianming Xiao

Water 2018, 10(12), 1816; https://doi.org/10.3390/w10121816 - 10 Dec 2018

Cited by 3 | Viewed by 2466

Abstract

The adsorption of Cu (II) onto two typical types of pyrolytic sludge was investigated in this study. The examined conditions include pH, adsorption time, and temperature, as well as the dosage of adsorbents. Results show that the adsorbents removed the Cu (II) effectively. [...] Read more.

The adsorption of Cu (II) onto two typical types of pyrolytic sludge was investigated in this study. The examined conditions include pH, adsorption time, and temperature, as well as the dosage of adsorbents. Results show that the adsorbents removed the Cu (II) effectively. The adsorbent made from pyrolyzed paper mill sludge (Cu_MS) exhibited exceptional performance, with a removal efficiency of around 100%. Moreover, the adsorption of Cu (II) onto Cu_MS was not affected by pH in the range of 3–9. The kinetic data showed better conformation with the pseudo-second-order kinetic model, and the adsorption processes of the Cu_MS fit well to the Langmuir isotherm model. The adsorption capacity reached 4.90 mg·g⁻¹ under appropriate conditions. Microscopic analysis and FT-IR analysis revealed that the adsorbent with porous structure and high monosilicate content was beneficial to Cu (II) adsorption. Thus, the Cu_MS is a potentially promising candidate for retaining Cu (II) in aqueous environments. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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Review

Jump to: Research

25 pages, 1174 KiB

Open AccessReview

Review of Constructed Wetlands for Acid Mine Drainage Treatment

by Aurora M. Pat-Espadas, Rene Loredo Portales, Leonel E. Amabilis-Sosa, Gloria Gómez and Gladys Vidal

Water 2018, 10(11), 1685; https://doi.org/10.3390/w10111685 - 19 Nov 2018

Cited by 88 | Viewed by 13746

Abstract

The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, [...] Read more.

The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, combines naturally-occurring biogeochemical, geochemical, and physical processes. This technology can be used for the long-term remediation of AMD. The challenge is to overcome some factors, for instance, chemical characteristics of AMD such a high acidity and toxic metals concentrations, to achieve efficient CW systems. Design criteria, conformational arrangements, and careful selection of each component must be considered to achieve the treatment. The main objective of this review is to summarize the current advances, applications, and the prevalent difficulties and opportunities to apply the CW technology for AMD treatment. According to the cited literature, sub-surface CW (SS-CW) systems are suggested for an efficient AMD treatment. The synergistic interactions between CW components determine heavy metal removal from water solution. The microorganism-plant interaction is considered the most important since it implies symbiosis mechanisms for heavy metal removal and tolerance. In addition, formation of litter and biofilm layers contributes to heavy metal removal by adsorption mechanisms. The addition of organic amendments to the substrate material and AMD bacterial consortium inoculation are some of the strategies to improve heavy metal removal. Adequate experimental design from laboratory to full scale systems need to be used to optimize equilibria between CW components selection and construction and operational costs. The principal limitations for CW treating AMD is the toxicity effect that heavy metals produce on CW plants and microorganisms. However, these aspects can be solved partially by choosing carefully constructed wetlands components suitable for the AMD characteristics. From the economic point of view, a variety of factors affects the cost of constructed wetlands, such as: detention time, treatment goals, media type, pretreatment type, number of cells, source, and availability of gravel media, and land requirements, among others. Full article

(This article belongs to the Special Issue Removal of Heavy Metals from Wastewater)

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