Molecules

Research

16 pages, 3626 KiB

Open AccessArticle

The Bioreduction of Selenite under Anaerobic and Alkaline Conditions Analogous to Those Expected for a Deep Geological Repository System

by Miguel Angel Ruiz-Fresneda, Jaime Gomez-Bolivar, Josemaria Delgado-Martin, Maria del Mar Abad-Ortega, Isabel Guerra-Tschuschke and Mohamed Larbi Merroun

Molecules 2019, 24(21), 3868; https://doi.org/10.3390/molecules24213868 - 27 Oct 2019

Cited by 18 | Viewed by 3698

Abstract

The environmental conditions for the planned geological disposal of radioactive waste —including hyper-alkaline pH, radiation or anoxia—are expected to be extremely harsh for microbial activity. However, it is thought that microbial communities will develop in these repositories, and this would have implications for [...] Read more.

The environmental conditions for the planned geological disposal of radioactive waste —including hyper-alkaline pH, radiation or anoxia—are expected to be extremely harsh for microbial activity. However, it is thought that microbial communities will develop in these repositories, and this would have implications for geodisposal integrity and the control of radionuclide migration through the surrounding environment. Nuclear waste contains radioactive isotopes of selenium (Se) such as ⁷⁹Se, which has been identified as one of the main radionuclides in a geodisposal system. Here, we use the bacterial species Stenotrophomonas bentonitica, isolated from bentonites serving as an artificial barrier reference material in repositories, to study the reduction of selenite (Se^IV) under simulated geodisposal conditions. This bacterium is able to reduce toxic Se^IV anaerobically from a neutral to alkaline initial pH (up to pH 10), thereby producing elemental selenium (Se⁰) nanospheres and nanowires. A transformation process from amorphous Se (a-Se) nanospheres to trigonal Se (t-Se) nanowires, through the formation of monoclinic Se (m-Se) aggregates as an intermediate step, is proposed. The lesser solubility of Se⁰ and t-Se makes S. bentonitica a potential candidate to positively influence the security of a geodisposal system, most probably with lower efficiency rates than those obtained aerobically. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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8 pages, 1721 KiB

Open AccessCommunication

Copper Ions Removal from Water using A₂B₃ Type Hyperbranched Poly(amidoamine) Hydrogel Particles

by Hojung Choi, Youngsik Eom, Sanghwa Lee and Sang Youl Kim

Molecules 2019, 24(21), 3866; https://doi.org/10.3390/molecules24213866 - 26 Oct 2019

Cited by 7 | Viewed by 3148

Abstract

Micrometer-sized hyperbranched poly(amidoamine) (hPAMAM) particles are prepared with a simple A₂B₃ type Aza–Michael addition reaction between aminoethylpiperazine (AEP) and methylenebisacrylamide (MBA) in an inverse suspension polymerization condition. The synthesized particles exhibited surprisingly high Cu²⁺ sorption capacity (0.223g/g) for a [...] Read more.

Micrometer-sized hyperbranched poly(amidoamine) (hPAMAM) particles are prepared with a simple A₂B₃ type Aza–Michael addition reaction between aminoethylpiperazine (AEP) and methylenebisacrylamide (MBA) in an inverse suspension polymerization condition. The synthesized particles exhibited surprisingly high Cu²⁺ sorption capacity (0.223g/g) for a solid-type absorbent. In addition to the high sorption ability of the particle, its simple synthetic process and convenience, due to its micrometer-sized spherical shape and recyclability, make it a practical and attractive absorbent for heavy metal ion removal from aqueous solutions. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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16 pages, 3495 KiB

Open AccessArticle

Assessment of By-Product from Botryosphaeria rhodina MAMB-05 as an Effective Biosorbent of Pb(II)

by Antonio J. Muñoz, Francisco Espínola, Encarnación Ruiz, Aneli M. Barbosa-Dekker, Robert F. H. Dekker and Eulogio Castro

Molecules 2019, 24(18), 3306; https://doi.org/10.3390/molecules24183306 - 11 Sep 2019

Cited by 4 | Viewed by 2639

Abstract

In this work, two types of biomass preparations (VMSM and M3) from the filamentous fungus Botryosphaeria rhodina MAMB-05, which were previously used in a process of production of β-glucan, were assessed as biosorbents of lead. The operating conditions, optimized through response surface methodology [...] Read more.

In this work, two types of biomass preparations (VMSM and M3) from the filamentous fungus Botryosphaeria rhodina MAMB-05, which were previously used in a process of production of β-glucan, were assessed as biosorbents of lead. The operating conditions, optimized through response surface methodology and experimental design, were shown to be pH 5.29 and a biosorbent dose of 0.23 g/L for the VMSM biomass type; and pH 5.06 and a dose of biosorbent of 0.60 g/L for the M3 biomass type, at a constant temperature of 27 °C. Fourier transform-infrared spectroscopy analyzed the presence of functional groups on the biomass surface. In addition to give an extra value to the by-product biomass, the VMSM-type from B. rhodina MAMB-05 showed an excellent lead biosorption capacity (q_m) with a value of 403.4 mg/g for the Langmuir model, comparing favorably with literature results, while the M3 subtype biomass showed a value of 96.05 mg/g. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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16 pages, 1681 KiB

Open AccessArticle

Production of Biosurfactant Produced from Used Cooking Oil by Bacillus sp. HIP3 for Heavy Metals Removal

by Nurul Hanisah Md Badrul Hisham, Mohamad Faizal Ibrahim, Norhayati Ramli and Suraini Abd-Aziz

Molecules 2019, 24(14), 2617; https://doi.org/10.3390/molecules24142617 - 18 Jul 2019

Cited by 79 | Viewed by 7896

Abstract

Heavy metals from industrial effluents and sewage contribute to serious water pollution in most developing countries. The constant penetration and contamination of heavy metals into natural water sources may substantially raise the chances of human exposure to these metals through ingestion, inhalation, or [...] Read more.

Heavy metals from industrial effluents and sewage contribute to serious water pollution in most developing countries. The constant penetration and contamination of heavy metals into natural water sources may substantially raise the chances of human exposure to these metals through ingestion, inhalation, or skin contact, which could lead to liver damage, cancer, and other severe conditions in the long term. Biosurfactant as an efficient biological surface-active agent may provide an alternative solution for the removal of heavy metals from industrial wastes. Biosurfactants exhibit the properties of reducing surface and interfacial tension, stabilizing emulsions, promoting foaming, high selectivity, and specific activity at extreme temperatures, pH, and salinity, and the ability to be synthesized from renewable resources. This study aimed to produce biosurfactant from renewable feedstock, which is used cooking oil (UCO), by a local isolate, namely Bacillus sp. HIP3 for heavy metals removal. Bacillus sp. HIP3 is a Gram-positive isolate that gave the highest oil displacement area with the lowest surface tension, of 38 mN/m, after 7 days of culturing in mineral salt medium and 2% (v/v) UCO at a temperature of 30 °C and under agitation at 200 rpm. An extraction method, using chloroform:methanol (2:1) as the solvents, gave the highest biosurfactant yield, which was 9.5 g/L. High performance liquid chromatography (HPLC) analysis confirmed that the biosurfactant produced by Bacillus sp. HIP3 consists of a lipopeptide similar to standard surfactin. The biosurfactant was capable of removing 13.57%, 12.71%, 2.91%, 1.68%, and 0.7% of copper, lead, zinc, chromium, and cadmium, respectively, from artificially contaminated water, highlighting its potential for bioremediation. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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10 pages, 1008 KiB

Open AccessArticle

Selective Recovery of Zinc from Metallurgical Waste Materials from Processing Zinc and Lead Ores

by Wojciech Hyk, Konrad Kitka and Dariusz Rudnicki

Molecules 2019, 24(12), 2275; https://doi.org/10.3390/molecules24122275 - 19 Jun 2019

Cited by 10 | Viewed by 4142

Abstract

A method for processing of metallurgical waste materials (chemically defined as sulfur-bearing zinc-ferric materials) produced by plants processing zinc ores and their concentrates is proposed. The method proposed is a combination of pyro- and hydrometallurgical treatments of the waste material. The crucial steps [...] Read more.

A method for processing of metallurgical waste materials (chemically defined as sulfur-bearing zinc-ferric materials) produced by plants processing zinc ores and their concentrates is proposed. The method proposed is a combination of pyro- and hydrometallurgical treatments of the waste material. The crucial steps in the developed method include: roasting the material at 450 °C to generate sulfur dioxide (SO₂), absorption of SO₂ in an aqueous system to form sulfuric acid (IV), carbothermic decomposition of zinc ferrite compounds, and leaching of zinc from the roasted material using sulfuric (IV) acid. The method allows one to extract up to 40% of zinc from the waste material and, consequently, to generate a fraction of material with substantially higher content of iron oxides. The proposed method takes advantage of the presence of sulfur in the processed material which upon roasting is converted to sulfuric acid (IV)—a leaching agent for selective extraction of zinc. The properly adjusted pH of the aqueous medium in which the leaching process is carried out is the key factor determining the quantitative and selective separation of zinc. If the amount of sulfur in the processed material is insufficient, it may be supplemented by adding sulfuric acid (VI) to adjust the pH. The method proposed was tested at a laboratory scale and quarter industrial scale using the real samples taken from stockpiles in the vicinity of the plant processing zinc and lead ores in Poland. It may also work for any zinc-ferric materials from various sources. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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15 pages, 1036 KiB

Open AccessArticle

Application of Response Surface Methodology and Desirability Function in the Optimization of Adsorptive Remediation of Arsenic from Acid Mine Drainage Using Magnetic Nanocomposite: Equilibrium Studies and Application to Real Samples

by Aphiwe Siyasanga Gugushe, Azile Nqombolo and Philiswa N. Nomngongo

Molecules 2019, 24(9), 1792; https://doi.org/10.3390/molecules24091792 - 9 May 2019

Cited by 32 | Viewed by 3938

Abstract

A magnetic multi-walled carbon nanotube/zeolite nanocomposite was applied for the adsorption and removal of arsenic ions in simulated and real acid mine drainage samples. The adsorption mechanism was investigated using two-parameter (Langmuir, Freundlich, Temkin) and three-parameter (Redlich–Peterson, and Sips) isotherm models. This was [...] Read more.

A magnetic multi-walled carbon nanotube/zeolite nanocomposite was applied for the adsorption and removal of arsenic ions in simulated and real acid mine drainage samples. The adsorption mechanism was investigated using two-parameter (Langmuir, Freundlich, Temkin) and three-parameter (Redlich–Peterson, and Sips) isotherm models. This was done in order to determine the characteristic parameters of the adsorptive removal process. The results showed that the removal process was described by both mono- and multilayer adsorptions. Adsorption studies demonstrated that a multi-walled carbon nanotube/zeolite nanocomposite could efficiently remove arsenic in simulated samples within 35 min. Based on the Langmuir isotherm, the adsorption capacity for arsenic was found to be 28 mg g⁻¹. The nanocomposite was easily separated from the sample solution using an external magnet and the regeneration was achieved by washing the adsorbent with 0.05 mol L⁻¹ hydrochloric acid solution. Moreover, the nanoadsorbent was reusable for at least 10 cycles of adsorption-desorption with no significant decrease in the adsorption capacity. The nanoadsorbent was also used for the arsenic removal from acid mine drainage. Overall, the adsorbent displayed excellent reusability and stability; thus, they are promising nanoadsorbents for the removal of arsenic from acid mine drainage. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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25 pages, 7726 KiB

Open AccessArticle

Recovery of Rare Earth Elements from Wastewater Towards a Circular Economy

by Óscar Barros, Lara Costa, Filomena Costa, Ana Lago, Verónica Rocha, Ziva Vipotnik, Bruna Silva and Teresa Tavares

Molecules 2019, 24(6), 1005; https://doi.org/10.3390/molecules24061005 - 13 Mar 2019

Cited by 56 | Viewed by 6459

Abstract

The use of rare earth elements is a growing trend in diverse industrial activities, leading to the need for eco-friendly approaches to their efficient recovery and reuse. The aim of this work is the development of an environmentally friendly and competitive technology for [...] Read more.

The use of rare earth elements is a growing trend in diverse industrial activities, leading to the need for eco-friendly approaches to their efficient recovery and reuse. The aim of this work is the development of an environmentally friendly and competitive technology for the recovery of those elements from wastewater. Kinetic and equilibria batch assays were performed with zeolite, with and without bacterial biofilm, to entrap rare earth ions from aqueous solution. Continuous assays were also performed in column setups. Over 90% removal of lanthanum and cerium was achieved using zeolite as sorbent, with and without biofilm, decreasing to 70% and 80%, respectively, when suspended Bacillus cereus was used. Desorption from the zeolite reached over 60%, regardless of the tested conditions. When in continuous flow in columns, the removal yield was similar for all of the rare earth elements tested. Lanthanum and cerium were the elements most easily removed by all tested sorbents when tested in single- or multi-solute solutions, in batch and column assays. Rare earth removal from wastewater in open setups is possible, as well as their recovery by desorption processes, allowing a continuous mode of operation. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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15 pages, 2411 KiB

Open AccessArticle

The Removal of CuO Nanoparticles from Water by Conventional Treatment C/F/S: The Effect of pH and Natural Organic Matter

by Rizwan Khan, Muhammad Ali Inam, Du Ri Park, Sarfaraz Khan, Muhammad Akram and Ick Tae Yeom

Molecules 2019, 24(5), 914; https://doi.org/10.3390/molecules24050914 - 5 Mar 2019

Cited by 20 | Viewed by 3550

Abstract

The increased use of engineered nanoparticles (ENPs), such as copper oxide nanoparticles (CuO NPs), in commercial products and applications raises concern regarding their possible release into freshwater sources. Therefore, their removal from water is important to eliminate adverse environmental and human health effects. [...] Read more.

The increased use of engineered nanoparticles (ENPs), such as copper oxide nanoparticles (CuO NPs), in commercial products and applications raises concern regarding their possible release into freshwater sources. Therefore, their removal from water is important to eliminate adverse environmental and human health effects. In this study, the effects of pH and natural organic matter (NOM), i.e., humic acid (HA) and salicylic acid (SA) on the removal of CuO NPs by coagulation/flocculation/sedimentation (C/F/S) were evaluated. The results indicated that pH significantly affects the coagulation efficiency, where 10–60% CuO NPs removal was achieved under extreme acidic/alkaline conditions. However, at neutral pH, removal of up to 90% was observed with a lower ferric chloride (FC) dosage (0.2 mM). The coagulation efficiency and mechanism were strongly affected by the type of Fe species present in the aqueous phase, which is mainly controlled by pH. Higher concentrations of both HA and SA decrease the CuO NPs agglomeration rate, and thereby improve the colloidal stability due to the NOM molecules adsorbed onto the NPs surface. The presence of hydrophobic HA needs a higher FC dosage of 0.5–0.8 mM than a dosage of hydrophilic SA of 0.25–0.35 mM, to obtain a similar CuO coagulation efficiency. Moreover, higher removals of dissolved organic carbon (DOC) and UV₂₅₄ were observed more in hydrophobic NOM than in hydrophilic. The results of the Fourier transform infrared (FT-IR) analysis of FC composite flocs confirm that the charge neutralization and enmeshment of coagulant might be a possible removal mechanism. The findings of the current study may provide critical information in the prediction of the fate, mobility, and removal of CuO NPs during C/F/S in water treatment. Full article

(This article belongs to the Special Issue Heavy Metals Removal from Contaminated Soil and Water)

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