Nanobiohybrids: Synthesis strategies and environmental applications from micropollutants sensing and removal to global warming mitigation

Micropollutants contamination and global warming are critical environmental issues that require urgent attention due to natural and anthropogenic activities posing serious threats to human health and ecosystems. However, traditional technologies (such as adsorption, precipitation, biodegradation, and membrane separation et al.) are facing challenges of low utilization efficiency of oxidants, poor selectivity, and complex in-situ monitoring operations. To address these technical bottlenecks, nanobiohybrids, synthesized by interfacing the nanomaterials and biosystems, have recently emerged as eco-friendly technologies. In this review, we summarize the synthesis approaches of nanobiohybrids and their utilization as emerging environmental technologies for addressing environmental problems. Studies demonstrate that enzymes, cells, and living plants can be integrated with a wide range of nanomaterials including reticular frameworks, semiconductor nanoparticles and single-walled carbon nanotubes. Moreover, nanobiohybrids demonstrate excellent performance for micropollutant removal, carbon dioxide conversion, and sensing of toxic metal ions and organic micropollutants. Therefore, nanobiohybrids are expected to be environmental friendly, efficient, and cost-effective techniques for addressing environmental micropollutants issues and mitigating global warming, benefiting both humans and ecosystems alike.

Effect of dissolved organic matter and heavy metals ions on sorption of phenanthrene at sedimentary particle scale

Human activities significantly increase the input of offshore heavy metals and organic pollutants. Although particle-scale and heterogeneous organic matters are fundamentally important to the fate of hydrophobic organic compounds (HOCs), deep understanding of the adsorption mechanism of HOCs on soil/sediment particles under the influence of heavy metal and organic pollution input is needed. This study investigates the effects of exotic DOM and heavy metals ions on the phenanthrene adsorption on sediment fractions. The adsorption experiments demonstrated that exotic DOM increased phenanthrene adsorption amount of sediment, with the greatest enhancement on clay particles (<2 µm). Nevertheless, the mechanism was differentiated accordingly to particle dimensions in terms of increased binding coefficients and mobility of phenanthrene. Furthermore, the introduction of heavy metals considerably enhanced the nonlinear sorption of phenanthrene. The Freundlich exponent N reduced by 0.01-0.24 when adding Cu²⁺, Zn²⁺ and Pb²⁺, especially for coarse particles (31-63 µm) fraction. In comparison, the enhancement of nonlinearity adsorption by Cu²⁺ and Zn²⁺ is significantly lower than Pb²⁺ ions. To our knowledge, the particle-scale study broadens the horizon of environmental fate and ecological risk of HOCs in intertidal regions, which is significantly affected by tidal action.

Chemometric study on the biochemical marker of the manglicolous fungi to illustrate its potentiality as a bio indicator for heavy metal pollution in Indian Sundarbans

The study represents in vitro chemometric approach for assessing the heavy metal pollution in Indian Sundarbans. Physio-chemical and elemental characterisation of the sediment samples of Indian Sundarbans had shown high enrichments of toxic metal ions. It was characterised by elevated enrichment factors (2.16-10.12), geo-accumulation indices (0.03 -1.21), contamination factors (0.7-3.43) and pollution load indices (1.0-1.25) which showed progressive sediment quality deterioration and ecotoxicological risk due to metal ions contamination. The physio-chemical parameters of the sediments were replicated and computational chemometric modeling was utilized to assess fungal metabolic growth. All the fungi isolates had shown maximum metabolic activity in high temperature, alkaline pH, and high salinity. Further, the fungal metabolic activity was assessed in different gradient of heavy metal concentration. The significant deterioration of biochemical marker with increasing concentration of heavy metal indicates the status of the microbial health due to toxic metal pollution in the mangrove habitat.

A review of polyampholytic ion scavengers for toxic metal ion removal from aqueous systems

Pollution by heavy metal ions in aqueous systems gained researchers attention gradually. Toxic metal ions were always present in the environment and the living organisms could get used to specific concentrations of contaminants with given time, however, sudden concentration rise we are observing can make it impossible for the living organisms to adapt. Many ion removal technologies were developed and optimised over the years to cope with this problem, including chemical precipitation, adsorption, membrane filtration and ion-exchange. Adsorption and ion exchange are processes that employ certain materials, that can be collectively named ion scavengers, to remove ions from aqueous solutions. Some of the scavenger materials are still barely studied, in particular polyampholytes - polymeric zwitterionic materials. This review showcases papers published on toxic metal ion removal by polyampholytes, both commercial and experimental, over last two decades. Many recent publications show promising properties of experimental materials that match or even outperform commercial scavengers. This review was prepared to encourage other researchers to investigate this broad and still not well-studied class of materials especially in context of their ion-scavenging properties. Polyamphytes which may be especially worth the attention and further research have been highlighted as literature studies show that the most unexplored materials in the class of polyamphytes are those containing aminomethylphosphonate, aminomethylsulfonate or hypophosphorous acid group.

Multi-ion imprinted polymers (MIIPs) for simultaneous extraction and preconcentration of Sb(III), Te(IV), Pb(II) and Cd(II) ions from drinking water sources

Simultaneous extraction and preconcentration of several potentially toxic metal ions have received great attention because of their toxicological effects on aquatic life and human beings. Multi-ion imprinted polymers (MIIP) have proved to be promising adsorbents with excellent specific recognition performance than single-ion imprinted polymer. Therefore, in this study, the MIIP strategy was employed for simultaneous extraction and enrichment of Sb(III), Cd(II), Pb(II) and Te(IV) ions from drinking water sources. MIIPs was used as a sorbent material in ultrasound-assisted dispersive solid phase extraction combined with inductively coupled plasma optical emission spectrometry (UA-DSPE/ICP-OES). The experimental parameters that affect the extraction efficiency and recovery of Sb(III), Cd(II), Pb(II) and Te(IV) were investigated using response surface methodology. Under optimum conditions, the enhancement factors, linear range, limit of detection (LOD) and limit of quantification (LOQ) were 37.7-51.1, 0.04-100 µg L^-1, 0.011-0.28 µg L^-1, 0.037-093 µg L^-1, respectively. The intra-day (n = 10) and inter-day (n = 5) precision expressed as relative standard deviations (%RSDs,) were 3% and 5%, respectively. The proposed UA-DSPE/ICP-OES method was applied for preconcentration and determination of the trace metal ions in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95% to 99.3%.

Silver enriched silver phosphate microcubes as an efficient recyclable SERS substrate for the detection of heavy metal ions

A rapid, cost-effective and accurate detection of heavy metal ions is crucial for human health monitoring and environmental protection. Surface-enhanced Raman spectroscopy (SERS) has become a reliable method due to its outstanding performance for the identification of contaminants. In this paper, silver phosphate microcubes (Ag₃PO₄) were fabricated using two different precipitation methods for ultrasensitive SERS detection of heavy metal ions. The use of an organic linker (BPy) with Ag₃PO₄ enabled the immobilization of Hg²⁺ and Pb²⁺ ions. The formation of Ag₃PO₄ was confirmed by XRD, UV-DRS, FESEM coupled with EDX and HRTEM. The analytical enhancement factor (AEF) obtained was 10¹⁰ with a detection limit of 10^-15 M indicating high sensitivity. Based on these results, the possible SERS mechanism has been proposed and discussed. Moreover, an excellent reusability of Ag₃PO₄ substrate for at least four cycles was achieved upon the light exposure on heavy metal loaded substrate due to its superior catalytic ability for the degradation of heavy metal ions. The as-prepared substrate demonstrated remarkable stability, selectivity and SERS sensitivity towards real samples. The results conclude that Ag₃PO₄ microcubes offer a great prospect in recyclable SERS applications.

Water soluble porphyrin as optical sensor for the toxic heavy metal ions in an aqueous medium

Here we report the photophysical and sensing properties of the aqueous solution of meso-tetra(N-methyl-4-pyridyl)porphyrin toluene sulfonate (TMPP) for simultaneous detection of toxic metal ions in an aqueous medium by using different physiochemical methods such as UV-vis absorption, steady state and time resolved fluorescence, stopped flow, and cyclic voltammetry. The steady-state absorption and fluorescence spectra in organic solvents (EtOH, DMSO, DMF, MeOH and ACN) showed the formation of monomer form (λ_max^abs = 426 nm and λ_max^flu = 654 and 715 nm). In THF and water, different spectral features were recorded suggested the formation of aggregated forms in both solvents. The formation of aggregated form in water was confirmed by recording the remarkable fluorescence quenching of the singlet excited TMPP with increasing the concentrations of TMPP. In cationic micelles (CTAB), both the absorption and fluorescence spectra were significantly decreased with increasing the concentrations of CTAB with a break at CMC value at 6.0 × 10^-5 M. In an anionic micelle (SDS), the CMC value was found to be 1.0 × 10^-4 M. Upon interacting with different metal ions, the absorption and fluorescence spectra of TMPP showed different features depending on the metal ions. While the optical studies of TMPP showed no significant interaction in the presence of Mn⁺², Co⁺², Ba²⁺, and Ni⁺², TMPP showed that it can function as a single optical chemical sensor for the toxic metal ions in water, particularly Hg⁺², Pb⁺², Cu⁺², and Cd⁺² ions.

The effects of potentially toxic metals (copper and zinc) on selected physical and physico-chemical properties of bentonites

The purpose of this study was to determine the effect of copper or zinc ions, absorbed by soil on its physical and physicochemical properties. The change in these properties may reduce the soil usefulness as a mineral protective barrier, for example, on hazardous waste landfills. Parameters such as granulometric composition, effective particle size d₁₀, empirical hydraulic conductivity, Atterberg limits, colloidal activity, specific surface area, sorption moisture content, and montmorillonite content were determined. The tests were carried out on model Na⁺ or Ca²⁺ samples of American bentonites (SWy-3, Stx-1b) and Slovak bentonite from Jelšový potok (BSvk), subjected to ion exchange for Cu²⁺ or Zn²⁺ ion. The content of elements was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Regression analysis showed a significant effect of Zn²⁺ ions on the reduction of sorption moisture content w₉₅ and the increase in the hydraulic conductivity. Nearly complete negative correlation was obtained between the Cu²⁺ ion content and the specific surface area, sorption moisture content w₅₀, and montmorillonite content (R = -0.99). It was observed that the significance of the influence of Cu²⁺ and Zn²⁺ ions on specific clay properties differed, which indicates different behavior of these metals in the clay-water system. The different nature of clays contaminated with Cu²⁺ and Zn²⁺ ions justifies the need to continue research on other potentially toxic metals and to further search for prediction equations of the cohesive soil hydraulic conductivity based on soil parameters that are most frequently modified as a result of their impact.

Identification of Several Toxic Metal Ions Using a Colorimetric Sensor Array

Water pollution by toxic metal ions is a worldwide environmental and health problem, and therefore monitoring of toxic metal ions in water resources is highly desired. In this chapter, we describe a simple colorimetric sensor array for simultaneous detection of multiple toxic heavy metal ions (Hg²⁺, Cd²⁺, Fe³⁺, Pb²⁺, Al³⁺, Cu²⁺, and Cr³⁺) in water. This assay is produced by using 11-mercaptoundecanoic acid (MUA)-capped gold nanoparticles (AuNPs) and five amino acids (lysine, cysteine, histidine, tyrosine, and arginine). The presence of amino acids can enhance or diminish the aggregation MUA-capped AuNPs with metal ions. The color change of the sensor array after aggregation in some of the channels creates unique response patterns for each metal ion.

Source identification, environmental risk assessment and human health risks associated with toxic elements present in a coastal industrial environment, India

This study investigated the source and contamination levels of toxic elements (Cd, Cr, As, Pb, Ni and Hg) present in a coastal environment, Paradip-an industrial hub of the east coast of India. The ecological risk assessment indices and human exposure models were used to evaluate the pollution status. Enrichment factor indicated that all the metal(loid)s found in the sediment are mostly derived from the anthropogenic source. According to the sediment quality quotient, 8.33% of sediments have crossed the ERM limit for Ni that can be fatal to biota. Meanwhile, 66.66, 41.66 and 8.33% of sediments have exceeded PEL range for Cr, Ni and As, respectively, that can register frequent lethal toxicity to benthic biota. As had the highest potential ecological harm coefficient (Er_f > 80), and Hg had moderate ecological harm coefficient (40 < Er_f < 80). Summarily, the sediment quality of this site is moderate to heavily toxic to benthic organisms. The concentration of toxic metals in seawater was below the permissible limit (CCC and CMC) set by USEPA indicating that water is relatively safer for free floating aquatic biota. The health risk index of toxic metal (loid)s present in soils of the residential sites has confirmed that there is a severe non-carcinogenic threat for children (HI child > 1) and a borderline carcinogenic risk for both adult and children. THQ_Cr possesses highest non-carcinogenic threat, which contributed approximately 50% to HI followed by THQ_As. The contribution of carcinogenic risk of chromium (CR_Cr) to TCR is approximately 60%. Cr is the significant contaminant of this site that has highest health effects. Highest exposure risks were associated with ingestion pathway accounting for about 85% of the total for most of the elements.

Colorimetric and fluorimetric detection of Hg2+ and Cr3+ by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells

Colorimetric and fluorimetric detection of toxic metal ions such as Hg²⁺ and Cr³⁺ has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg²⁺ or Cr³⁺ were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg²⁺, Cr³⁺ and Fe³⁺ among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg²⁺ and Cr³⁺ by the change in color of the solution to pink and reddish pink with Fe³⁺. The detailed mechanism involved in the detection of Hg²⁺ was deduced by ¹H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg²⁺ and Cr³⁺ in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg²⁺ and Cr³⁺, which are known for their toxic influence on bacterial cells.

Removal of As(V), Cr(III) and Cr(VI) from aqueous environments by poly(acrylonitril-co-acrylamidopropyl-trimethyl ammonium chloride)-based hydrogels

Cationic poly(Acrylonitril-co-Acrylamidopropyl-trimethyl Ammonium Chloride) (p(AN-co-APTMACl)) hydrogels in bulk were synthesized by using acrylonitrile (AN) and 3-acrylamidopropyl-trimethyl ammonium chloride (APTMACl) as monomers. The prepared hydrogels were exposed to amidoximation reaction to replace hydrophobic nitrile groups with hydrophilic amidoxime groups that have metal ion binding ability. Those replacements were increased the hydrogels absorption capacity for As(V) and Cr(VI). Langmuir and Freundlich isotherms equations were utilized to obtain the best-fitted isotherm model for the absorption of the ions at different metal ion concentrations. The absorption data of As(V) ion were fitted well to Freundlich isotherm while those of Cr(VI) and Cr(III) ions were fitted well to Langmuir isotherm. The maximum absorption of poly(3-acrylamidopropyl-trimethyl ammonium chloride (p(APTMACl)) and amid-p(AN-co-APTMACl) macro gels were 22.39 mg and 21.83 mg for As(V), and 30.65 mg and 18.16 mg for Cr(VI) ion per unit gram dried gel, respectively. Kinetically, the absorption behaviors of Cr(III) and Cr(VI) ions were fitted well to a pseudo 2nd-order kinetic model and those of As(V) ions were fitted well to a pseudo 1st order kinetic model.

Architecture of optical sensor for recognition of multiple toxic metal ions from water

Here, we designed novel optical sensor based on the wormhole hexagonal mesoporous core/multi-shell silica nanoparticles that enabled the selective recognition and removal of these extremely toxic metals from drinking water. The surface-coating process of a mesoporous core/double-shell silica platforms by several consequence decorations using a cationic surfactant with double alkyl tails (CS-DAT) and then a synthesized dicarboxylate 1,5-diphenyl-3-thiocarbazone (III) signaling probe enabled us to create a unique hierarchical multi-shell sensor. In this design, the high loading capacity and wrapping of the CS-DAT and III organic moieties could be achieved, leading to the formation of silica core with multi-shells that formed from double-silica, CS-DAT, and III dressing layers. In this sensing system, notable changes in color and reflectance intensity of the multi-shelled sensor for Cu(2+), Co(2+), Cd(2+), and Hg(2+) ions, were observed at pH 2, 8, 9.5 and 11.5, respectively. The multi-shelled sensor is added to enable accessibility for continuous monitoring of several different toxic metal ions and efficient multi-ion sensing and removal capabilities with respect to reversibility, selectivity, and signal stability.

Competition of zinc(II) with cadmium(II) or mercury(II) in binding to a 12-mer peptide

Speciation of the complexes of zinc(II) with a dodecapeptide (Ac-SCPGDQGSDCSI-NH2), inspired by the metal binding domain of MerR metalloregulatory proteins, have been studied by pH-potentiometric titrations, UV, SRCD (synchrotron radiation circular dichroism) and (1)H NMR experiments. (MerR is a family of transcriptional regulators the archetype of which is the Hg(2+)-responsive transcriptional repressor-activator MerR protein.) The aim of the ligand-design was to retain the advantageous metal binding features of MerR proteins in a model peptide for the efficient capture of toxic metal ions. The peptide binds zinc(II) via two deprotonated Cys-thiol groups and one of the Asp-carboxylates in the ZnL parent complex, possessing a remarkably high stability (logK=9.93). In spite of the relatively long peptide loop, bis-complexes are also formed with the metal ion under basic conditions. In a competition with cadmium(II) or mercury(II), zinc(II) cannot prevent the binding of toxic metal ions by the thiolate donor groups of the ligand. Around neutral pH one equivalent of mercury(II) was shown to fully replace zinc(II) from the ZnL species. Partial replacement of zinc(II) from the peptide by one equivalent of cadmium(II), relative to zinc(II) and the ligand, is also presumable, nevertheless, spectroscopic data may suggest the formation of mixed metal ion complexes, as well. Based on the obtained results the investigated dodecapeptide can be a promising candidate for capturing toxic metal ions in practical applications.