Cysteine-metal affinity chromatography: determination of heavy metal adsorption properties

Removal of hazardous ions from aqueous solutions: Current methods, with a focus on green ion flotation

Hazardous ions, like those of heavy metals, cause significant health and environmental problems when they are discharged into water resources naturally or through various industrial processes. Removing these ions from water is of significant importance in the provision of high-quality water for drinking and agricultural usage. This work discusses current techniques that are frequently used for the removal of heavy-metal ions from aqueous solutions by absorption, particularly the use of biodegradable surfactants in ion flotation. Certain new surfactants promise high efficiency in their use in the ion-flotation process and in their application in industrial-water treatment to remove heavy metals. As an example, this work demonstrates the high efficiency of surfactants based on an amino-acid (L-cysteine) in removing a range of heavy-metal ions in a simple, single-stage ion-flotation process. High foaming ability, the ability to operate in various temperatures and pHs, decomposing into natural products and high binding affinity for heavy-metal ions make the cysteine-based surfactants a highly suitable compound to replace current commercial surfactants in ion- and froth-flotation processes. Removal of particular ions can also be achieved in ion flotation; a suitable choice of parameters, such as pH and surfactant concentration, favours the surfactant binding to those ions. Further intensive work is required to develop an optimal process to recover valuable elements from waste solutions.

Trends and potential human health risk of trace elements accumulated in transplanted blue mussels during restoration activities of Flekkefjord fjord (Southern Norway)

The monitoring of contaminants represents a priority to preserve the integrity of marine ecosystems, as well as to plan and to manage restoration activities in order to protect environmental and human health. In the present study, a 6-months active biomonitoring was performed to explore the levels of eighteen trace and toxic elements, including heavy metals (TEs; i.e. Al, As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, Sr, Ti, and Zn), accumulated in soft tissues of blue mussel (Mytilus edulis Linnaeus, 1758) individuals transplanted at different depths (5- and 15-m depth) in five locations within the Flekkefjord fjord (Southern Norway). As this area suffered a long-lasting contamination due to both organic and inorganic contaminants, a series of restoration activities were activated to tackle and to prevent potential risks for ecosystem and local population. Our results demonstrated that the levels of TEs accumulated in edible tissues of transplanted mussels in the Flekkefjord fjord were generally low before the beginning of the restoration activities. However, location- and time-specific differences in the accumulation of TEs were noted after the implementation of such activities. Interestingly, the levels of Fe and Mn significantly increased after the beginning of the restoration activities, likely because the release of these TEs from the slag used in such operations and/or resuspension of contaminated sediments. However, assuming that native mussels can accumulate the same TEs at levels measured in transplanted individuals, our results suggest a substantial safety for human consumption of native mussels from the Flekkefjord fjord, regardless of restoration activities.

Synthesis and application of a green surfactant for the treatment of water containing PFAS/ hazardous metal ions

In this work, the effectiveness of a biodegradable and natural surfactant synthesized through a novel method has been studied through the ion flotation process to treat waters containing Per/Poly Fluoroalkyl Substances (PFAS) and heavy-metal ions. This cysteine-based surfactant, which is environmentally acceptable, showed considerable solubility and foaming ability over a wide range of pH. It also could remove 97-99(%) of 5 mg/L of cadmium, chromium, copper, nickel, zinc, and manganese ions in a single batch physicochemical process. Moreover, for the first time, a foam fractionation method in association with using this cysteine-based surfactant was applied for perfluorooctanoic acid (PFOA) removal from water. This surfactant was used as a co-surfactant and could readily remove 72% of PFOA (40 mg/L) from water. The characterization of the surfactant was undertaken using ¹H NMR, FT-IR, elemental analysis, melting point, and determination of its critical micelle concentration (CMC). This environmentally friendly surfactant has high potential applications in green chemistry especially in the treatment of waters contaminated with PFAS/heavy-metal ions.

Combined Toxicity of Metal Nanoparticles: Comparison of Individual and Mixture Particles Effect

Toxicity of metal nanoparticles (NPs) are closely associated with increasing intracellular reactive oxygen species (ROS) and the levels of pro-inflammatory mediators. However, NP interactions and surface complexation reactions alter the original toxicity of individual NPs. To date, toxicity studies on NPs have mostly been focused on individual NPs instead of the combination of several species. It is expected that the amount of industrial and highway-acquired NPs released into the environment will further increase in the near future. This raises the possibility that various types of NPs could be found in the same medium, thereby, the adverse effects of each NP either could be potentiated, inhibited or remain unaffected by the presence of the other NPs. After uptake of NPs into the human body from various routes, protein kinases pathways mediate their toxicities. In this context, family of mitogen-activated protein kinases (MAPKs) is mostly efficient. Despite each NP activates almost the same metabolic pathways, the toxicity induced by a single type of NP is different than the case of co-exposure to the combined NPs. The scantiness of toxicological data on NPs combinations displays difficulties to determine, if there is any risk associated with exposure to combined nanomaterials. Currently, in addition to mathematical analysis (Response surface methodology; RSM), the quantitative-structure-activity relationship (QSAR) is used to estimate the toxicity of various metal oxide NPs based on their physicochemical properties and levels applied. In this chapter, it is discussed whether the coexistence of multiple metal NPs alter the original toxicity of individual NP. Additionally, in the part of "Toxicity of diesel emission/exhaust particles (DEP)", the known individual toxicity of metal NPs within the DEP is compared with the data regarding toxicity of total DEP mixture.

Cysteine chemical modification for surface regulation of biochar and its application for polymetallic adsorption from aqueous solutions

Biochar (BC) has been widely used to remove heavy metals from wastewater. However, due to the hydrophobicity of BC and the lack of its surface functional groups, the effect of metal ions adsorption onto BC is limited. In order to improve the adsorption efficiency, L-cysteine was used to modify biochar derived from pomelo peel (PP) to regulate surface structure. The characteristics of BC and cysteine/biochar composite (cys/BC) were analyzed by various characterization methods. Results showed that the hydrophilicity of biochar was enhanced, and the number of surface functional groups was increased, resulting to strong adsorption ability of Ag(I) (618.9 mg/g), Pb(II) (274.5 mg/g), and As(V) (34.7 mg/g) for cys/BC, which increased approximately by 15%, 35%, and 29% compared with that of BC, respectively. The adsorption process of Pb(II) onto cys/BC was fitted better by the Freundlich isotherm model and for Ag(I) and As(V) by the Langmuir isotherm model. Moreover, the adsorption kinetics followed pseudo-second-order equation and the adsorption process was controlled by the intraparticle diffusion for Ag(I), Pb(II), and As(V) adsorption onto cys/BC. In addition, the adsorption capacities of cys/BC for Ag(I), Pb(II), and As(V) decreased slightly after five adsorption/desorption cycles. Finally, the multiple adsorption mechanisms including functional groups, pore adsorption, surface complexation, and cations-π were analyzed. The paper demonstrated that the cys/BC composite could be reused as effective adsorbents for removing contaminants in the environment.

Batch and Fixed-Bed Column Studies on Palladium Recovery from Acidic Solution by Modified MgSiO3

Effective recovery of palladium ions from acidic waste solutions is important due to palladium’s intensive usage as a catalyst for different industrial processes and to the high price paid for its production from natural resources. In this paper, we test the ability of a new adsorbent, MgSiO₃ functionalized by impregnation with DL-cysteine (cys), for palladium ion recovery from waste solutions. The Brunauer–Emmett–Teller (BET) surface area analysis, Barrett–Joyner–Halenda (BJH) pore size and volume analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and Fourier-Transformed Infrared (FTIR) spectroscopy have been performed to characterize this material. Firstly, the maximum adsorption capacity of the new obtained material, MgSiO₃-cys, in batch, was studied. To establish the adsorption mechanism, the obtained experimental data were fitted using the Langmuir, Freundlich and Sips adsorption isotherms. Studies on the adsorption of palladium ions on the synthesized material were performed in a dynamic regime, in a fixed-bed column. The Pd(II) recovery mechanism in the dynamic column regime was established based on Bohart–Adams, Yoon–Nelson, Thomas, and Clark models. The obtained equilibrium adsorption capacity was 9.3 (mg g⁻¹) in static regime (batch) and 3 (mg g⁻¹) in dynamic regime (column). The models that best describe the Pd(II) recovery process for batch and column adsorption are Sips and Clark, respectively.

l-Cysteine functionalized bagasse cellulose nanofibers for mercury(II) ions adsorption

Presence of mercury ions in water, even in trace amounts, is a serious environmental hazard. Hence, there is imperative need to develop innovative and environmentally-friendly materials for their removal from wastewaters. In the present study, cellulose nanofibers (CNFs) extracted from bagasse was esterified with l-cysteine to yield thiol and amine functionalized green material (Cys-CNFs) for removal of Hg²⁺ ions. The Cys-CNFs were well characterized by SEM, TEM, FTIR, EDS and XRD and evaluated for selective removal of Hg²⁺ ions from the simulated wastewater. It was observed that Cys-CNFs adsorb Hg²⁺ ions even at a very low concentration of 1.0mg/L and it exhibited a maximum adsorption capacity of 116.822mgg^-1. Kinetic analysis of the data revealed that pseudo-second order kinetics and Langmuir isotherm were followed for adsorption of Hg²⁺ ions.

Exposure to low environmental concentrations of manganese, lead, and cadmium alters the serotonin system of blue mussels

Serotonin plays a crucial role in mussel survival and reproduction. Although the serotonin system can be affected by metals, the effects of environmental concentrations of metals such as manganese (Mn), lead (Pd), and cadmium (Cd) have never been studied in blue mussels. The present study aimed to determine the effects of exposure to Mn, Pb, or Cd on serotonin levels, monoamine oxidase (MAO) activity, and serotonin transporter (SERT) levels in the blue mussel Mytilus edulis. Mussels were exposed in vivo to increasing and environmentally relevant doses of Mn (10-1000 nM; 0.5-50 μg/L), Pb (0.01-10 nM; 0.002-2 μg/L), or Cd (0.01-10 nM; 0.001-1 μg/L) for 28 d. Serotonin levels, MAO activity, and SERT expression were analyzed in the mussel mantle. Expression of SERT protein was significantly decreased, by up to 81%, following Mn, Pb, or Cd exposure. The activity of MAO in females was almost 2-fold higher, versus males, in nonexposed control mussels. In mussels exposed to 0.1 nM of Pb (0.02 μg/L), MAO activity was increased in males and decreased in females. In Cd-exposed mussels, a sex-dependent, inverted nonmonotonic pattern of MAO activity was observed. These results clearly indicate that low environmental concentrations of Mn, Pb, and Cd affect the serotonin system in blue mussels. Environ Toxicol Chem 2018;37:192-200. © 2017 SETAC.

Peptide self-assembly triggered by metal ions

This review summarizes the recent development of structures, functions, as well as strategies of a peptide self-assembly induced by metal ions.

Orange-red silver emitters for sensing application and bio-imaging

Strongly fluorescent HFL-containing Ag@Au particles are synthesized via a modified hydrothermal technique. This solution is used for sulfide sensing and cell imaging.

Mechanisms behind bacteria induced plant growth promotion and Zn accumulation in Brassica juncea

The growth and metal-extraction efficiency of plants exposed to toxic metals has been reported to be enhanced by inoculating plants with certain bacteria but the mechanisms behind this process remain unclear. We report results from glasshouse experiments on Brassica juncea plants exposed to 400mgZnkg(-1) that investigated the abilities of Pseudomonas brassicacearum and Rhizobium leguminosarum to promote growth, coupled with synchrotron based μXANES analysis to probe Zn speciation in the plant roots. P. brassicacearum exhibited the poorest plant growth promoting ability, while R. leguminosarum alone and in combination with P. brassicacearum enhanced plant growth and Zn phytoextraction. Reduced growth in un-inoculated plants was attributed to accumulation of Zn oxalate and Zn sulfate in roots. In plants inoculated with P. brassicacearum the high concentration of Zn polygalacturonic acid in the root may be responsible for the stunted growth and reduced Zn phytoextraction. The improved growth and increased metal accumulation observed in plants inoculated with R. leguminosarum and in combination with P. brassicacearum was attributed to the storage of Zn in the form of Zn phytate and Zn cysteine in the root. When combined with the observation that both bacteria do not statistically improve B. juncea growth in the absence of Zn, this work suggests that bacteria-induced metal chelation is the key mechanism of plant growth promoting bacteria in toxicity attenuation and microbial-assisted phytoremediation.

Cytotoxicity and ion release of alloy nanoparticles

It is well-known that nanoparticles could cause toxic effects in cells. Alloy nanoparticles with yet unknown health risk may be released from cardiovascular implants made of Nickel-Titanium or Cobalt-Chromium due to abrasion or production failure. We show the bio-response of human primary endothelial and smooth muscle cells exposed to different concentrations of metal and alloy nanoparticles. Nanoparticles having primary particle sizes in the range of 5-250 nm were generated using laser ablation in three different solutions avoiding artificial chemical additives, and giving access to formulations containing nanoparticles only stabilized by biological ligands. Endothelial cells are found to be more sensitive to nanoparticle exposure than smooth muscle cells. Cobalt and Nickel nanoparticles caused the highest cytotoxicity. In contrast, Titanium, Nickel-Iron, and Nickel-Titanium nanoparticles had almost no influence on cells below a nanoparticle concentration of 10 μM. Nanoparticles in cysteine dissolved almost completely, whereas less ions are released when nanoparticles were stabilized in water or citrate solution. Nanoparticles stabilized by cysteine caused less inhibitory effects on cells suggesting cysteine to form metal complexes with bioactive ions in media.

Efficient removal of heavy metal ions from aqueous solution using salicylic acid type chelate adsorbent

In this study, 5-aminosalicylic acid was successfully grafted onto the poly(glycidyl methacrylate) (PGMA) macromolecular chains of PGMA/SiO(2) to obtain a novel adsorbent designated as ASA-PGMA/SiO(2). The adsorption properties of ASA-PGMA/SiO(2) for heavy metal ions were studied through batch and column methods. The experimental results showed that ASA-PGMA/SiO(2) possesses strong chelating adsorption ability for heavy metal ions, and its adsorption capacity for Cu(2+), Cd(2+), Zn(2+), and Pb(2+) reaches 0.42, 0.40, 0.35, and 0.31 mmol g(-1), respectively. In addition, pH has a great influence on the adsorption capacity in the studied pH range. The adsorption isotherm data greatly obey the Langmuir and Freundlich model. The desorption of metal ions from ASA-PGMA/SiO(2) is effective using 0.1 mol l(-1) of hydrochloric acid solution as eluent. Consecutive adsorption-desorption experiments showed that ASA-PGMA/SiO(2) could be reused almost without any loss in the adsorption capacity.

Combining material characterization with single and multi-oxyanion adsorption for mechanistic study of chromate removal by cationic hydrogel

Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from contaminated water was found to be 200 mg/g. Using Fourier transform infrared spectroscopy (FT-IR) study, the mechanism of chromate removal by hydrogel was found to be non-specific adsorption, mainly due to ion exchange, as evidenced by the positively charged functional group, trimethyl ammonium -N+(CH3)3, in the monomer. Verifications were accordingly determined by testing different oxyanion adsorption onto the hydrogel. The results of the chromate adsorption experiments illustrated that the amount of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel, which is part of the evidence for ion exchange. Single and multi-oxyanion adsorption experiments were also performed, and it was demonstrated that ion removal was species independent, but charge dependent, another characteristic of the ion exchange process. It was found that the same Langmuir model can be applied to best fit the findings of single and multi-oxyanion adsorption, which further indicates the mechanism of chromate removal is attributed to ion exchange. In view of the above, the background anions compete for adsorption sites with chromate, evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies, further echoing the ion exchange mechanism.

Interaction of cysteine with Cu2+ and group IIb (Zn2+, Cd2+, Hg2+) metal cations: a theoretical study

The structure and energetics of complexes obtained upon interaction between cysteine and Zn2+, Cd2+, Hg2+ and Cu2+ cations were studied using quantum chemical density functional theory calculations with the 6-311++G** orbital basis set and relativistic pseudopotentials for the cations. Different coordination sites for metal ions on several cysteine conformers were considered. In their lowest energy complexes with the amino acid, the Zn2+ and Cd2+ cations appear to be three-coordinated to carbonyl oxygen, nitrogen and sulfur atoms, whereas the Cu2+ and Hg2+ ions are coordinated to both the carbonyl oxygen and sulfur atoms of one of the zwitterion forms of the amino acid. Bonds of metal cations with the coordination sites are mainly ionic except those established with sulfur, which show a small covalent character that become most significant when Cu2+ and Hg2+ are involved. The order of metal ion affinity proposed is Cu>Zn>Hg>Cd.