A practical silver nanoparticle-based adsorbent for the removal of Hg2+ from water

Recent Progress in Nanoparticles Based Sensors for the Detection of Mercury (II) Ions in Environmental and Biological Samples

To maintain a green and sustainable environment for human beings, rapid detection of potentially toxic heavy metals like mercury (Hg(II)) has attracted great attention. Recently, sensors have been designed which can selectively detect Hg(II) over other common available cations and give a naked eye or fluorometric response. In the last two decades, the trend is shifting from bulky organic chemosensors toward nanoparticles due to their rapid response, low cost, eco-friendly and easy synthesis. In this review, promising nanoparticles-based sensors for Hg(II) detection are discussed. The nano-sensors are functionalized with nucleotide or other suitable materials which coordinate with Hg(II) ions and give clear color or fluorescence change. The operational mechanisms are discussed focusing on its four basic types. The nanoparticles-based sensors are even able to detect Hg in three different oxidation states (Hg(II), Hg(I) and Hg(0)). Recently, the trend has been shifted from ordinary nanoparticles to magnetic nanoparticles to simultaneously detect and remove Hg(II) ions from environmental samples. Furthermore, the nano-sensors for Hg(II) are compared with each other and with the reported organic chemosensors.

Metal nanostructures in polymeric matrices for optical detection and removal of heavy metal ions, pesticides and dyes from water

Water pollutants such as heavy metal ions, pesticides, and dyes pose a worldwide issue. Their presence in water resources interferes with the normal growth mechanisms of living beings and causes long or short-term diseases. For this reason, research continuously tends to develop innovative, selective, and efficient processes or technologies to detect and remove pollutants from water. This review provides an up-to-date overview on metal nanoparticles loaded in polymeric matrices, such as hydrogels and membranes, and employed as optical sensors and as removing materials for water pollutants. The synthetic pathways of nanomaterials loading into polymeric matrices have been analyzed, particularly focusing on noble metal nanoparticles, noble metal nanoclusters, and metal oxide nanoparticles. Moreover, the sensing properties of modified matrices towards water pollutants have been discussed in addition to the interaction mechanisms between the sensors and the toxic compounds. The last part of the review has been devoted to illustrating the separation mechanism and removal performance of membranes loaded with nanomaterials in the treatment and purification of water streams from different contaminants (heavy metals, dyes and pesticides).

Ionic and nanoparticulate silver alleviate the toxicity of inorganic mercury in marine microalga Chaetoceros muelleri

Toxicological effects of silver nanoparticles (SNPs) in different organisms have been studied; however, interactions of SNPs with other environmental pollutants such as mercury are poorly understood. Herein, bioassay tests were performed according to ΟECD 201 guideline to assess the toxic effects induced by mercury ions (mercury chloride, MCl) on the marine microalga Chaetoceros muelleri in the presence of SNPs or silver ions (silver nitrate, SN). Acute toxicity tests displayed that the presence of SNPs or SN (0.01 mg L-1) significantly reduced the toxicity of MCl (0.001, 0.01, 0.1, 1, 10, and 100 mg L-1) and increased the IC50 of MCl from 0.072 ± 0.014 to 0.381 ± 0.029 and 0.676 ± 0.034 mg L-1, respectively. In the presence of SN or SNPs, the mercury-reducing effect on algal population growth significantly decreased. Considering the increase of IC50, the mercury toxicity decreased approximately 5.44 and 9.66 times in the presence of SNPs or SN, respectively. The chlorophyll a and c contents decreased at all exposures; however, the decrease by MCl-SNPs and MCl-SN was significantly less than MCl except at 1 mg L-1. The lowering effect of MCl-SN on chlorophyll contents was less than MCl and MCl-SNPs. MCl exposure induced significant raises in total protein content (TPC) at concentrations < 0.01mg  L-1, with a maximum of ~ 70.83% attained at 100 mg L-1. The effects of MCl-SNPs and MCl-SN on TPC were significantly less than MCl. Total lipid content (TLC) at all MCl concentrations was higher than the control, while at coexposure to MCl-SN, TLC did not change until 0.01 mg L-1 compared with the control. The effects of MCl-SN and MCL-SNPs on TPC and TLC were in line with toxicity results, and were significantly less than those of MCl individually, confirming their antagonistic effects on MCl. The morphological changes of algal cells and mercury content of the cell wall at MCl-SN and MCl-SNPs were mitigated compared with MCl exposure. These findings highlight the mitigatory impacts of silver species on mercury toxicity, emphasizing the need for better realizing the mixture toxicity effects of pollutants in the water ecosystem.

An efficient wastewater treatment through reduction of organic dyes using Ag nanoparticles supported on cellulose gum beads

This work reports silver nanoparticles (AgNPs) supported on biopolymer carboxymethyl cellulose beads (Ag-CMC) serves as an efficient catalyst in the reduction process of p-nitrophenol (p-NP) and methyl orange (MO). For Ag-CMC synthesis, first CMC beads were prepared by crosslinking the CMC solution in aluminium nitrate solution and then the CMC beads were introduced into AgNO3 solution to adsorb Ag ions. Field emission scanning electron microscopy (FE-SEM) analysis suggests the uniform distribution of Ag nanoparticles on the CMC beads. The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis revealed the metallic and fcc planes of AgNPs, respectively, in the Ag-CMC catalyst. The Ag-CMC catalyst exhibits remarkable reduction activity for the p-NP and MO dyes with the highest rate constant (kapp) of a chemical reaction is 0.519 and 0.697 min-1, respectively. Comparative reduction studies of Ag-CMC with CMC, Fe-CMC and Co-CMC disclosed that Ag-CMC containing AgNPs is an important factore in reducing the organic pollutants like p-NP and MO dyes. During the recyclability tests, the Ag-CMC also maintained high reduction activity, which suggests that CMC protects the AgNPs from leaching during dye reduction reactions.

Efficient self-cleaning and antibacterial ceramics with ultra-low doping and high exposure of silver

The secondary bacterial infection of COVID-19 is known to contribute significantly to mortality rates. Silver (Ag)-based antibacterial ceramics have emerged as a prominent solution for daily antibacterial applications, aiming to minimize the reliance on disinfectants while safeguarding human health. However, the fabrication of Ag-based antibacterial ceramics with low Ag content, high dispersion, and high exposure still faces challenges. In this work, an innovative method was proposed to doping Ag nanoparticles (Ag NPs) into glass ceramics (GC) via a "melt-freeze" method, then efficient and stable Ag-doped antibacterial ceramics (GC-xAg@BiOCl) were fabricated through facile in-situ HCl etching GC. Results indicate that the low Ag content (0.03 mol%) and high dispersion of Ag NPs are fully exposed and anchored on the surface, and constructed Schottky junction Ag/BiOCl contributed to antibacterial and photocatalytic activity. The degradation rates of norfloxacin and methylene blue by GC-0.25Ag@BiOCl can reach 71.0% and 55.3% under visible light irradiation, respectively. Moreover, The GC-0.25Ag@BiOCl exhibited significant antibacterial activity against Escherichia coli (E.coli) and Staphylococcus aureus (S. aureus), with E.coli at 7.3 log10 cfu/mL and S. aureus at 7.0 log10 cfu/mL completely inactivated under visible light irradiation. Additionally, the antibacterial mechanism and charge transfer mechanism were explored.

Multivariate modeling and process optimization of Hg(II) remediation using solvothermal synthesized 2D MX/Fe3O4 by response surface methodology: characteristics and mechanism study

Two-dimensional MXene with layered structure has recently emerged as a nanomaterial with fascinating characteristics and applicability. Herein, we prepared the newly modified magnetic MXene (MX/Fe₃O₄) nanocomposite using solvothermal approach and investigated its adsorption behavior to study the removal efficiency of Hg(II) ions from aqueous solution. The effect of adsorption parameters such as adsorbent dose, time, concentration, and pH were optimized using response surface methodology (RSM). The experimental data fitted well with quadratic model to predict the optimum conditions for maximum Hg(II) ion removal efficiency which were found to be at adsorbent dose 0.871 g/L, time 103.6 min, concentration 40.17 mg/L, and 6.5 pH respectively. To determine the adequacy of the developed model, a statistical analysis of variance (ANOVA) was used, which demonstrated high agreement between the experimental data and the suggested model. According to isotherm result, the experimental data were following the best agreement with the Redlich-Peterson isotherm model. The results of the experiments revealed that the maximum Langmuir adsorption capacity of 699.3 mg/g was obtained at optimum conditions, which was closed to the experimental adsorption capacity of 703.57 mg/g. The adsorption phenomena was well represented by the pseudo-second-order model (R² = 0.9983). On the whole, it was clear that MX/Fe₃O₄ has lot of potential as a Hg(II) ion impurity removal agent in aqueous solutions.

Catalytic activity and mechanism of selective catalytic oxidation of ammonia by Ag-CeO2 under different preparation conditions

Given the problem of the high-temperature window of CeO₂ catalyst activity, this study evaluated the catalytic properties of Ag/CeO₂ prepared by changing the preparation methods and loadings. Our experiments showed that Ag/CeO₂-IM catalysts prepared by the equal volume impregnation method could have better activity at lower temperatures. The Ag/CeO₂-IM catalyst achieves 90% NH₃ conversion at 200 °C, and the main reason is that the Ag/CeO₂-IM catalyst has more vital redox properties, and the NH₃ catalytic oxidation temperature is lower. However, its high-temperature N₂ selectivity still needs to be improved and may be related to the less acidic sites on the catalyst surface. On both catalyst surfaces, the i-SCR mechanism governs the NH₃-SCO reaction.

Application of Cotton Swab-Ag Composite as Flexible Surface-Enhanced Raman Scattering Substrate for DMMP Detection

It is both important and required to quickly and accurately detect chemical warfare agents, such as the highly toxic nerve agent sarin. Surface-enhanced Raman scattering (SERS) has received considerable attention due to its rapid results, high sensitivity, non-destructive data acquisition, and unique spectroscopic fingerprint. In this work, we successfully prepared SERS cotton swabs (CSs) for the detection of the sarin simulant agent dimethyl methyl phosphonate (DMMP) by anchoring N1-(3-trimethoxysilylpropyl) diethylenetriamine (ATS)/silver nanoparticle (AgNP) nanocomposites on CSs using ATS as the stabilizer and coupling agent. Simultaneously, the binding mode and reaction mechanics between the AgNP, ATS, and CS were confirmed by XPS. The modified CSs exhibited good uniformity, stability, and adsorption capability for SERS measurements, enabling the adsorption and detection of DMMP residue from an irregular surface via a simple swabbing process, with a detection limit of 1 g/L. The relative standard deviations (RSDs) of RSD₇₁₀ = 5.6% had high reproducibility. In this research, the fabrication method could easily be extended to other cellulose compounds, such as natural fibers and paper. Furthermore, the versatile SERS CSs can be used for the on-site detection of DMMP, particularly in civil and defense applications, to guarantee food security and the health of the population.

Developing Antibiofilm Fibrillar Scaffold with Intrinsic Capacity to Produce Silver Nanoparticles

The development of biomedical systems with antimicrobial and antibiofilm properties is a difficult medical task for preventing bacterial adhesion and growth on implanted devices. In this work, a fibrillar scaffold was produced by electrospinning a polymeric organic dispersion of polylactic acid (PLA) and poly(α,β-(N-(3,4-dihydroxyphenethyl)-L-aspartamide-co-α,β-N-(2-hydroxyethyl)-L-aspartamide) (PDAEA). The pendant catechol groups of PDAEA were used to reduce silver ions in situ and produce silver nanoparticles onto the surface of the electrospun fibers through a simple and reproducible procedure. The morphological and physicochemical characterization of the obtained scaffolds were studied and compared with virgin PLA electrospun sample. Antibiofilm properties against Pseudomonas aeruginosa, used as a biofilm-forming pathogen model, were also studied on planar and tubular scaffolds. These last were fabricated as a proof of concept to demonstrate the possibility to obtain antimicrobial devices with different shape and dimension potentially useful for different biomedical applications. The results suggest a promising approach for the development of antimicrobial and antibiofilm scaffolds.

An approach to removing COD and BOD based on polycarbonate mixed matrix membranes that contain hydrous manganese oxide and silver nanoparticles: A novel application of artificial neural network based simulation in MATLAB

This study aimed to determine the efficacy of novel ultrafiltration and mixed matrix membrane (MMM) composed of hydrous manganese oxide (HMO) and silver nanoparticles (Ag-NPs) for the removal of biological oxygen demand (BOD) and chemical oxygen demand (COD). In the polycarbonate (PC) MMM, the weight percent of HMO and Ag-NP has been increased from 5% to 10%. A neural network (ANN) was used in this study to compare PC-HMO and Ag-NP. MMM was evaluated in combination with HMO and Ag-NP loadings in order to assess their effects on pure water flux, mean pore size, porosity, and efficacy in removing BOD and COD. HMO and Ag-NPs can decrease membrane porosity in the casting solution while increasing mean pore size. According to the study's findings, the artificial neural network model appears to be highly appropriate for predicting the removal of BOD and COD. To develop a successful model, a suitable input dataset was selected, which consisted of BOD and COD. An ideal model architecture for MMM was proposed based on an optimal number of hidden layers (2 layers) and neurons (5-8 neurons). Experiments and predicted data show a strong correlation between the developed models. BOD was predicted with an excellent R2 and a low root mean square error (RMSE) of 0.99 and 0.05%, respectively, while COD was predicted with an excellent R2 and a low RMSE of 0.99 and 0.09%, respectively. Based on the results, Ag-NP was found to be an excellent candidate for the preparation of MMMs as well as convenient for the removal of BOD and COD from polluted water sources.

Engineering of Near-Infrared-Activated Lignin-Polydopamine-Nanosilver Composites for Highly Efficient Sterilization

Photothermal synergistic antimicrobial therapy is considered a promising strategy to cope with antibiotic-resistant bacterial infections. In this work, lignin-based polydopamine nanosilver composites (LS-PDA-Ag) were engineered by a two-step process including self-assembly and microwave-assisted reduction. First, sodium lignosulfonate (LS) was not only used as a carrier to disperse polydopamine (PDA) and silver nanoparticles (AgNPs), but also used to reduce Ag+ for producing AgNPs. Second, PDA could promote the reduction of Ag+ and enhance the photothermal effect of AgNPs to further improve antibacterial efficiency. Finally, LS, AgNPs, and PDA complement each other, forming a synergistic photothermal antibacterial mechanism, achieving efficient bacterial killing within a short time. The antibacterial test of LS-PDA-Ag confirmed that 7.6 log10 CFU/mL of Escherichia coli were killed in 10 min under near-infrared irradiation. Furthermore, the LS-PDA-Ag can be blended with waterborne polyurethane to synthesize hybrid films, which also results in rapid sterilization and mechanical performance improvement. Considering the highly effective antibacterial activity of the LS-PDA-Ag composite, this work may provide perspectives on the design of green photothermal antibacterial materials.

Novel Carboxylic Acid-Capped Silver Nanoparticles as Antimicrobial and Colorimetric Sensing Agents

The present work reports the synthesis, characterization, and antimicrobial activities of adipic acid-capped silver nanoparticles (AgNPs@AA) and their utilization for selective detection of Hg²⁺ ions in an aqueous solution. The AgNPs were synthesized by the reduction of Ag⁺ ions with NaBH₄ followed by capping with adipic acid. Characterization of as-synthesized AgNPs@AA was carried out by different techniques, including UV–Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Dynamic Light Scattering (DLS), and zeta potential (ZP). In the UV–Vis absorption spectrum, the characteristic absorption band for AgNPs was observed at 404 nm. The hydrodynamic size of as-synthesized AgNPs was found to be 30 ± 5.0 nm. ZP values (−35.5 ± 2.4 mV) showed that NPs possessed a negative charge due to carboxylate ions and were electrostatically stabilized. The AgNPs show potential antimicrobial activity against clinically isolated pathogens. These AgNPs were found to be selectively interacting with Hg²⁺ in an aqueous solution at various concentrations. A calibration curve was constructed by plotting concentration as abscissa and absorbance ratio (A_Control − A_Hg/A_Control) as ordinate. The linear range and limit of detection (LOD) of Hg²⁺ were 0.6–1.6 μM and 0.12 μM, respectively. A rapid response time of 4 min was found for the detection of Hg²⁺ by the nano-probe. The effect of pH and temperature on the detection of Hg²⁺ was also investigated. The nano-probe was successfully applied for the detection of Hg²⁺ from tap and river water

Environmental remediation using metals and inorganic and organic materials: a review

In recent times, environmental pollution has been an alarming concern. This is increasing day-in-and-day-out, especially in the Asia-Pacific region due to the increasing population, urbanization, industrialization and inappropriate waste management measures. Pollution abatement is the need of the hour to sustain the biosphere in general and the human life in particular. A range of physical, chemical and biological strategies are commonly employed to remove pollutants from the contained water, soil and air. Physical, chemical or physicochemical remediation processes are commonly employed owing to their high efficiency, stability, recyclable property and low procurement cost as compared to metals, inorganic and organic materials. Materials of the later type include biocomposites, thin films, modified (bio)polymers, nanoparticles, nanofilters, sorbent like activated charcoal, and carbon nanotubes and nanosensors. Remediation mechanism largely follows sorption, degradation, oxidation, reduction, catalytic conversion, detection and microbial toxicity principles. This review details the mechanisms of action by these various remediating entities, their successful applications in pollution abatement, drawbacks and future prospects.HighlightsEnvironmental remediation using metals, inorganic and organic materials are discussed extensively.Major remediating approaches, viz., physical, physicochemical and chemical are elaborated citing latest references.The significance of biocomposites, biopolymers, polymers, thin films, nanoparticles, nanofilters, nanosensors and sorbents in remediation are highlighted.Pollutant removal from water, air and soil has been precisely discussed.A note on drawbacks, improvement and future prospects of remediating agents is presented.

Role of Nanoparticles in Environmental Remediation: An Insight into Heavy Metal Pollution from Dentistry

Environmental damage is without a doubt one of the most serious issues confronting society today. As dental professionals, we must recognize that some of the procedures and techniques we have been using may pose environmental risks. The usage and discharge of heavy metals from dental set-ups pollute the environment and pose a serious threat to the ecosystem. Due to the exclusive properties of nanosized particles, nanotechnology is a booming field that is being extensively studied for the remediation of pollutants. Given that the nanoparticles have a high surface area to volume ratio and significantly greater reactivity, they have been greatly considered for environmental remediation. This review aims at identifying the heavy metal sources and their environmental impact in dentistry and provides insights into the usage of nanoparticles in environmental remediation. Although the literature on various functions of inorganic nanoparticles in environmental remediation was reviewed, the research is still confined to laboratory set-ups and there is a need for more studies on the usage of nanoparticles in environmental remediation.

Recent advances in nanoremediation: Carving sustainable solution to clean-up polluted agriculture soils

Agriculture is one of the foremost significant human activities, which symbolizes the key source for food, fuel and fibers. This activity results in a lot of ecological harms particularly with the excessive usage of chemical fertilizers and pesticides. Different agricultural practices have remained industrialized to advance food production, due to the growth in the world population and to meet the food demand through the routine use of more effective fertilizers and pesticides. Soil is intensely embellished by environmental contamination and it can be stated as "universal incline." Soil pollution usually occurs from sewage wastes, accidental discharges or as byproducts of chemical residues of unrestrained production of numerous materials. Soil pollution with hazardous materials alters the physical, chemical, and biological properties, causing undesirable changes in soil fertility and ecosystem. Engineered nanomaterials offer various solutions for remediation of contaminated soils. Engineered nanomaterial-enable technologies are able to prevent the uncontrolled release of harmful materials into the environment along with capabilities to combat soil and groundwater borne pollutants. Currently, nanobiotechnology signifies a hopeful attitude to advance agronomic production and remediate polluted soils. Studies have outlined the way of nanomaterial applications to restore the eminence of the environment and assist the detection of polluted sites, along with potential remedies. This review focuses on the latest developments in agricultural nanobiotechnology and the tools developed to combat soil or land and or terrestrial pollution, as well as the benefits of using these tools to increase soil fertility and reduce potential toxicity.

Bioremediation and decontamination potentials of metallic nanoparticles loaded nanohybrid matrices - A review

The current nanotechnological advancements provide an astonishing insight to fabricate nanomaterials for nano-bioremediation purposes. Exciting characteristics possessed by hybrid matrices at the nanoscale knock endless opportunities to nano-remediate environmentally-related pollunanomaterials tants of emerging concern. Nanometals are considered among the oldest generation of the world has ever noticed. These tiny nanometals and nanometal oxides showed enormous potential in almost every extent of industrial and biotechnological domains, including their potential multipurpose approach to deal with water impurities. In this manuscript, we discussed their role in the diversity of water treatment technologies used to remove bacteria, viruses, heavy metals, pesticides, and organic impurities, providing an ample perspective on their recent advances in terms of their characteristics, attachment strategies, performance, and their scale-up challenges. Finally, we tried to explore their futuristic contribution to nano-remediate environmentally-related pollutants of emerging concern aiming to collect treated yet safe water that can be reused for multipurpose.

Activity-based NIR fluorescent probes based on the versatile hemicyanine scaffold: design strategy, biomedical applications, and outlook

The discovery of a near-infrared (NIR, 650-900 nm) fluorescent chromophore hemicyanine dye with high structural tailorability is of great significance in the field of detection, bioimaging, and medical therapeutic applications. It exhibits many outstanding advantages including absorption and emission in the NIR region, tunable spectral properties, high photostability as well as a large Stokes shift. These properties are superior to those of conventional fluorogens, such as coumarin, fluorescein, naphthalimides, rhodamine, and cyanine. Researchers have made remarkable progress in developing activity-based multifunctional fluorescent probes based on hemicyanine skeletons for monitoring vital biomolecules in living systems through the output of fluorescence/photoacoustic signals, and integration of diagnosis and treatment of diseases using chemotherapy or photothermal/photodynamic therapy or combination therapy. These achievements prompted researchers to develop more smart fluorescent probes using a hemicyanine fluorogen as a template. In this review, we begin by describing the brief history of the discovery of hemicyanine dyes, synthetic approaches, and design strategies for activity-based functional fluorescent probes. Then, many selected hemicyanine-based probes that can detect ions, small biomolecules, overexpressed enzymes and diagnostic reagents for diseases are systematically highlighted. Finally, potential drawbacks and the outlook for future investigation and clinical medicine transformation of hemicyanine-based activatable functional probes are also discussed.

Toward a Feasible Solution for Removing Toxic Mercury and Chromium From Water Using Copper Oxide Nanoparticles

Objective: Water contaminated with heavy metals causes serious environmental issues for people. Mercury and chromium are considered to be extremely toxic for public health. Diversified technologies have been introduced to purify contaminated water; however, only a few become successful in reducing mercury and chromium below the permissible limit of drinking water (0.001 and 0.05 ppm, respectively, WHO/BIS Guidelines). Our main aim was to synthesize suitable nanoscale materials to make water potable by removing mercury and chromium from contaminated water while keeping essential elements as per the WHO/BIS guidelines.

Methods: Copper(II) oxide nanomaterials are synthesized following a wet chemical process as per earlier reported procedures. Nanoparticles with average diameter of 10–20 nm are formed. XRD confirms the formation of orthorhombic CuO nanoparticles.

Results: The nanoparticles are efficient in removing mercury from 200 ppb to less than 50 ppb (75%) and chromium from 200 ppb to less than 16 ppb (92%) over a wide range of pH.

Conclusion: The nanomaterials have great potential in removing toxic heavy metals from contaminated water. The materials can be applied to integrated water purification systems to produce potable water.

Advancements in heavy metals removal from effluents employing nano-adsorbents: Way towards cleaner production

Due to the development in science field which gives not only benefit but also introducesundesirable pollution to the environment. This pollution is due to poor discharge activities of industrial effluents into the soil and water bodies, surface run off from fields of agricultural lands, dumping of untreated wastes by municipalities, and mining activites, which deteriorates the cardinal virtue of our environment and causes menace to human health and life. Heavy metal(s), a natural constituent on earth's crust and economic important mineral, due to its recalcitrant effects creates heavy metal pollution which affects food chain and also reduces the quality of water. For this, many researchers have performed studies to find efficient methods for wastewater remediation. One of the most promising methods from economic point of view is adsorption, which is simple in design, but leads to use of a wide range of adsorbents and ease of operations. Due to advances in nanotechnology, many nanomaterials were used as adsorbents for wastewater remediation, because of their efficiency. Many researchers have reported that nanoadsorbents are unmitigatedly a fruitful solution to address this world's problem. This review presents a potent view on various classes of nanoadsorbents and their application to wastewater treatment. It provides a bird's eye view of the suitability of different types of nanomaterials for remediation of wastewater and Backspace gives up-to-date information about polymer based and silica-based nanoadsorbents.

Design of an Integrated Microfluidic Paper-Based Chip and Inspection Machine for the Detection of Mercury in Food with Silver Nanoparticles

For most of the fast screening test papers for detecting Hg2+, the obtained results are qualitative. This study developed an operation for the μPAD and combined it with the chemical colorimetric method. Silver nanoparticle (AgNP) colloids were adopted as the reactive color reagent to combine and react with the Hg standards on the paper-based chip. Then, the RGB values for the color change were used to establish the standard curve (R2 > 0.99). Subsequently, this detection system was employed for the detection tests of actual samples, and the detected RGB values of the samples were substituted back to the formula to calculate the Hg2+ contents in the food. In this study, the Hg2+ content and recovery rate in commercially available packaged water and edible salts were measured. The research results indicate that a swift, economical, and simple detection method for Hg2+ content in food has been successfully developed.

High-efficient photocatalytic degradation of commercial drugs for pharmaceutical wastewater treatment prospects: A case study of Ag/g-C3N4/ZnO nanocomposite materials

Pharmaceutical drugs' removal from wastewater by photocatalytic oxidation process is considered as an attractive approach and environmentally friendly solution. This report aims to appraise the practical application potential of Ag/g-C₃N₄/ZnO nanorods toward the wastewater treatment of the pharmaceutical industry. The catalysts are synthesized by straightforward and environmentally-friendly strategies. Specifically, g-C₃N₄/ZnO nanorods heterostructure is constructed by a simple self-assembly method, and then Ag nanoparticles are decorated on g-C₃N₄/ZnO nanorods by a photoreduction route. The results show that three commercial drugs (paracetamol, amoxicillin, and cefalexin) with high concentration (40 mg L^-1) are significantly degraded in the existence of a small dosage of Ag/g-C₃N₄/ZnO nanorods (0.08 g L^-1). The Ag/g-C₃N₄/ZnO nanorods photocatalyst exhibits degradation performance of paracetamol higher 3.8, 1.8, 1.3 times than pristine g-C₃N₄, ZnO nanorods, and g-C₃N₄/ZnO nanorods. Furthermore, Ag/g-C₃N₄/ZnO nanorods have an excellent reusability and a chemical stability that achieved paracetamol degradation efficiency of 78% and remained chemical structure of the photocatalyst after five cycles. In addition, the photocatalytic mechanism explanation and comparison of photocatalytic drugs' degradation ability have also been discussed in this study.

Heavy metal pollution and the role of inorganic nanomaterials in environmental remediation

Contamination of water and soil with toxic heavy metals is a major threat to human health. Although extensive work has been performed on reporting heavy metal pollutions globally, there are limited review articles on addressing this pernicious phenomenon. This paper reviews inorganic nanoparticles and provides a framework for their qualities required as good nanoadsorbents for efficient removal of heavy metals from water. Different inorganic nanoparticles including metals, metal oxides and metal sulfides nanoparticles have been applied as nanoadsorbents to successfully treat water with high contaminations of heavy metals at concentrations greater than 100 mg l^-1, achieving high adsorption capacities up to 3449 mg g^-1. It has been identified that the synthesis method, selectivity, stability, regeneration and reusability, and adsorbent separation from solution are critical parameters in deciding on the quality of inorganic nanoadsorbents. Surface functionalized nanoadsorbents were found to possess high selectivity and capacity for heavy metals removal from water even at a very low adsorbent dosage of less than 2 g l^-1, which makes them better than conventional adsorbents in environmental remediation.

New sensing platform of poly(ester-urethane)urea doped with gold nanoparticles for rapid detection of mercury ions in fish tissue

A new electrochemical sensor has been fabricated based on the in situ synthesis of poly(ester-urethane) urea (PUU) doped with gold nanoparticles (AuNPs), and the obtained composite materials (PUU/AuNPs) were used as a new sensing platform for highly sensitive and selective detection of mercury(II) ions in fish tissue. PUU was synthesized and fully characterized by XRD, TGA, DSC, and FTIR to analyze the chemical structure, thermal stability, and morphological properties. As a polymeric structure, the PUU consists of urethane and urea groups that possess pronounced binding abilities to Hg²⁺ ions. SEM-EDX was carried out to confirm this kind of interaction. Using ferricyanide as the redox probe, PUU alone exhibited weak electrochemical signals due to its low electrical conductivity. Therefore, a new series of nanocomposites of PUU with different nanostructured materials were applied, and their electrochemical performances were evaluated. Among these materials, the PUU/AuNP-modified electrode showed high voltammetric signals towards Hg²⁺. Consequently, the parameters affecting the performance of the assay, such as electrode composition, scan rate, and sensing time, as well as the effect of electrolyte and pH were studied and optimized. The sensor showed a linear range of 5 ng mL^-1 to 155 ng mL^-1 with the regression coefficient R ² = 0.986, while the calculated values of the limit of detection (LOD) and limit of quantification (LOQ) were 0.235 ng mL^-1 and 0.710 ng mL^-1, respectively. In terms of cross reactivity testing, the sensor exhibited a high selectivity against heavy metals which are commonly determined in seafood (Cd²⁺, Pb²⁺, As³⁺, Cr³⁺, Mg²⁺, and Cu²⁺). For real applications, total Hg²⁺ ions in fish tissue were determined with very high recovery and no prior complicated treatments.

Process Optimization of Silver Nanoparticle Synthesis and Its Application in Mercury Detection

Silver nanoparticles (AgNPs) have stable reactivity and excellent optical absorption properties. They can be applied in various industries, such as environmental protection, biochemical engineering, and analyte monitoring. However, synthesizing AgNPs and determining their appropriate dosage as a coloring substance are difficult tasks. In this study, to optimize the process of AgNP synthesis and obtain a simple detection method for trace mercury in the environment, we evaluate several factors-including the reagent addition sequence, reaction temperature, reaction time, the pH of the solution, and reagent concentration-considering the color intensity and purity of AgNPs as the reaction optimization criteria. The optimal process for AgNP synthesis is as follows: Mix 10 mM of silver nitrate with trisodium citrate in a hot water bath for 10 min; then, add 10 mM of sodium borohydride to produce the AgNPs and keep stirring for 2 h; finally, adjust the pH to 12 to obtain the most stable products. For AgNP-based mercury detection, the calibration curve of mercury over the concentration range of 0.1-2 ppb exhibits good linearity (R2 > 0.99). This study provides a stable and excellent AgNP synthesis technique that can improve various applications involving AgNP-mediated reactions and has the potential to be developed as an alternative to using expensive detection equipment and to be applied for the detection of mercury in food.

Fluorescence resonance energy transfer between carbon quantum dots and silver nanoparticles: Application to mercuric ion sensing

Fluorescence resonance energy transfer (FRET) process as a practical and competitive sensing strategy was utilized between carbon quantum dots (C-dots) and silver nanoparticles (Ag NPs) for the determination of mercuric ions. The novel synthesized C-dots with the quantum yield of 84% acted as the donor and Ag NPs operated as the acceptor in the FRET process leading to the fluorescence quenching of the C-dots. In the presence of Hg(II) ions, the FRET-quenched fluorescence emission of the C-dots-Ag NPs system was recovered owing to oxidation of Ag NPs by Hg(II) ions, so that the turn-on fluorescence intensity was directly proportional to the Hg(II) ion concentration. Accordingly, combination of the FRET system with the redox reaction was firstly utilized to construct an innovative turn-off/on fluorescent sensor for the quantification of Hg(II) ion. The calibration plot was linear in the concentration range 0.5-500.0 nmol L^-1 with a determination coefficient (R²) of 0.9965. The limit of detection and limit of quantification were 0.10 and 0.35 nmol L^-1, respectively, according to the IUPAC definition. The method was applied for the determination of Hg(II) ion in lake water, wastewater and tea samples, and the proper relative recoveries (98.0-104.0%) were obtained for the spiked samples. The method has high potential to diagnose trace values of mercuric ions in real samples with high sensitivity and repeatability.

Silver-Based Nanomaterials as Therapeutic Agents Against Coronaviruses: A Review

Since the identification of the first human coronavirus in the 1960s, a total of six coronaviruses that are known to affect humans have been identified: 229E, OC43, severe acute respiratory syndrome coronavirus (SARS-CoV), NL63, HKU1, and Middle East respiratory syndrome coronavirus (MERS-CoV). Presently, the human world is affected by a novel version of the coronavirus family known as SARS-CoV-2, which has an extremely high contagion rate. Although the infection fatality rate (IFR) of this rapidly spreading virus is not high (ranging from 0.00% to 1.54% across 51 different locations), the increasing number of infections and deaths has created a worldwide pandemic situation. To provide therapy to severely infected patients, instant therapeutic support is urgently needed and the repurposing of already approved drugs is presently in progress. In this regard, the development of nanoparticles as effective transporters for therapeutic drugs or as alternative medicines is highly encouraged and currently needed. The size range of the viruses is within 60-140 nm, which is slightly larger than the diameters of nanoparticles, making nanomaterials efficacious tools with antiviral properties. Silver-based nanomaterials (AgNMs) demonstrate antimicrobial and disinfectant effects mostly by generating reactive oxygen species (ROS) and are presently considered as a versatile tool for the treatment of COVID-19 patients. Other metal-based nanoparticles have been primarily reported as delivery agents or surface modifying agents, vaccine adjuvant against coronavirus. The present review summarizes and discusses the possible effectiveness of various surface-modified AgNMs against animal coronaviruses and presents a concept for AgNM-based therapeutic treatment of SARS-CoV-2 in the near future.

Efficient removal of mercury (II) from water by use of cryogels and comparison to commercial adsorbents under environmentally relevant conditions

Mercury is a toxic element, which can be found in air, water and soil in several inorganic and organic forms. Mercury pollution comes from a variety of industrial sources, including vinyl-chloride, pulp and paper, fertilizers and pharmaceuticals industry, gold mining and cement production. Gels have increasingly attracted the interest over the past decades and one of the investigated applications is the fast removal of organic substances, metals and other cations and anions from water. In this work, two types of cryogels were synthesized at sub-zero temperature by free-radical polymerization technique, characterized by using a set of complimentary methods and used for the removal of mercury from aqueous solutions of different chemistry. Kinetics and equilibrium studies were performed in ultra-pure water solutions in order to study the mechanisms in the presence nitrate and chloride ions. The cryogels exhibited excellent efficiency towards mercury removal from all model solutions. Moreover, the cryogels were tested in different water matrixes (tap, river and sea water) and compared to commercial adsorbents (activated carbon, strong acid resin and zeolite Y). Cryogels were able to remove mercury much faster than commercial adsorbents with the exception of seawater where activated carbon was superior.

Removal of Cd2+ from Water by Use of Super-Macroporous Cryogels and Comparison to Commercial Adsorbents

In this study amphoteric cryogels were synthesized by the use of free-radical co-polymerization of acrylate-based precursors (methacrylic acid and 2-acrylamido-2-methyl-1-propansulfonic acid) with allylamine at different ratios. The physico-chemical characteristics of the cryogels were examined using SEM/EDX, FT-IR, XPS and zeta potential measurements. The cryogels were tested toward Cd²⁺ removal from aqueous solutions at various pH and initial concentrations. Equilibrium studies revealed a maximum sorption capacity in the range of 132-249 mg/g. Leaching experiments indicated the stability of Cd²⁺ in the cryogel structure. Based on kinetics, equilibrium and characterization results, possible removal mechanisms are proposed, indicating a combination of ion exchange and complexation of Cd²⁺ with the cryogels' surface functional groups. The cryogels were compared to commercially available adsorbents (zeolite Y and cation exchange resin) for the removal of Cd²⁺ from various water matrices (ultrapure water, tap water and river water) and the results showed that, under the experimental conditions used, the cryogels can be more effective adsorbents.

Selective Reductive Removal of Silver Ions from Acidic Solutions by Redox-Active Covalent Organic Frameworks

The selective removal and recovery of silver ions from an aqueous solution is necessary, owing to the toxicity, persistency, and recoverable value. Herein, we first reported that silver ions could be selectively removed from an acidic solution by utilizing redox-active covalent organic framework (COF) materials as an adsorbent, resulting in the loading of Ag nanoparticles (NPs) with a narrow size distribution onto the framework simultaneously. The redox-active COF not only showed promising performance in adsorbing silver ions but also had a high selectivity at a low pH value. Subsequently, it was found that the N sites of amine groups within the framework took responsibility for the Ag NP generation after the systematic investigation on the redox adsorption mechanism. Furthermore, the recycled Ag@COF materials could be further used as new adsorbents to remove Hg(II) ions from water via NPs as a "bridge", exhibiting ultrahigh atomic utilization (>100%). Accordingly, this work not only provides a novel insight for the use of redox-active COF in the removal of metal ions but also opens a new field for designing of functionalized COF for their potential application in diverse areas.

Magnetic Fe3O4-Ag0 Nanocomposites for Effective Mercury Removal from Water

In this study, magnetic Fe3O4 particles and Fe3O4-Ag0 nanocomposites were prepared by a facile and green method, fully characterized and used for the removal of Hg2+ from water. Characterizations showed that the Fe3O4 particles are quasi-spherical with an average diameter of 217 nm and metallic silver nanoparticles formed on the surface with a size of 23–41 nm. The initial Hg2+ removal rate was very fast followed by a slow increase and the maximum solid phase loading was 71.3 mg/g for the Fe3O4-Ag0 and 28 mg/g for the bare Fe3O4. The removal mechanism is complex, involving Hg2+ adsorption and reduction, Fe2+ and Ag0 oxidation accompanied with reactions of Cl− with Hg+ and Ag+. The facile and green synthesis process, the fast kinetics and high removal capacity and the possibility of magnetic separation make Fe3O4-Ag0 nanocomposites attractive materials for the removal of Hg2+ from water.

Utilization of Ag nanoparticles anchored in covalent organic frameworks for mercury removal from acidic waste water

Metal nanoparticles (NPs) have high reaction rate and atom utilization with respect to pollutants in aqueous environments. However, the aggregation and instability in acidic solution limit their practical applications. Mercury removed from acidic solution are still a big problem. In this study, we used a tunable porous covalent organic framework (COF) material as a support for in situ growth of Ag NPs via a one-step solution infiltration method, to enhance the spatial dispersion of NPs and their stability in acidic solution, and for the first time studying the mercury adsorption performance. More importantly, the Ag NPs@COF composite exhibited high removal rate (99 %), ultrahigh Ag atom utilization (150 %), high selectivity and stability, and reusability for Hg(II) removal from acidic aqueous solutions. Meantime, through common characterizations and density functional theory calculations verifying the microscopic adsorption process, we found COF material played an important role in the entire purification process because it provided some electrons to Hg(II) ions via Ag NPs, finally generating an amalgam. Therefore, the present work not only provides a COF-supported Ag NPs material for Hg(II) ions removal from acidic waste water but also opens a new field of design of functionalized COFs material for applications in environmental pollutions control.

Visible light degradation of reactive black-42 by novel Sr/Ag-TiO2@g-C3N4 photocatalyst: RSM optimization, reaction kinetics and pathways

A novel Sr/Ag-TiO₂@g-C₃N₄ (SAT-C) composite catalyst was fabricated through a sol-gel method followed by hydrothermal process. The prepared catalyst was characterized well. The doped Ag and Sr nanoparticles played the crucial role as an electron transfer bridge and the surface plasmon resonance effect of Ag remarkably improved the charge separation efficiency and enhanced visible-light response towards reactive black (RB-42) degradation. The enhanced photogenerated charge separation resulted from the existed integrated electric field of heterojunction and the superposed light response from hybridization of TiO₂ and g-C₃N₄, Sr/Ag-TiO₂@g-C₃N₄ composites exhibited remarkably improved photocatalytic activities for degrading RB-42. Furthermore, the effect of various operational parameters on the photocatalytic process was systematically evaluated by using response surface methodology (RSM). The maximum degradation efficiency (95.6%) was observed under the optimal conditions ([RB-42]₀ = 20 mg/ L, [SAT-C]₀ = 0.2 g/ L, pH = 4.5 and t = 40 min) for RB-42. The RB-42 degradation kinetics was well studied under the optimal conditions. In addition, the main degradation products of RB-42 were identified by the LC/ESI-MS analysis.

Silver/quartz nanocomposite as an adsorbent for removal of mercury (II) ions from aqueous solutions

Silver nanoparticles (AgNPs) and silver/quartz nanocomposite (Ag/Q)NPs)) were synthesized by sol-gel method using table sugar as chelating agent. The synthesized nanosized materials were used for mercury ions adsorption from aqueous solutions. The materials were characterized by X-ray diffraction (XRD), Transmission Electron microscope (TEM), and surface area (BET). Adsorption of Hg²⁺ (10 mg/l) is strongly dependent on time, initial metal concentration, dose of adsorbent and pH value. Silver/quartz nanocomposite ((Ag/Q)NPs)) shows better efficiency than individual silver nanoparticles (AgNPs). This composite removed mercury ions from the aqueous solution with efficiency of 96% at 60 min with 0.5g adsorbent dosage at pH 6. The adsorption process explained well by the pseudo-second-order kinetic model. In conclusion silver/quartz nanocomposite (Ag/Q)NPs)) shows higher removal efficiency for mercury ions from aqueous solutions than individual silver naoparticles (AgNPs) or quartz (Q).

Study of arsenic (III) removal by monolayer protected silver nanoadsorbent and its execution on prokaryotic system

This work deals with the removal of arsenic by nanoadsorbent from aqueous environment that is subsequently applied to the biological system for the evaluation of its efficiency. We started our aspiration by the modification of carboxylate functionalized silver nanoparticle (nanoadsorbent) fabrication process. Batch mode arsenic uptake study by the nanoadsorbent was conducted considering several altering parameters and the reactants in addition to products were evaluated by several analytical techniques for the interpretation of the interaction mechanism. It was found nanoadsorbent, Ag@MSA is an efficient system for the exclusion of arsenic (III) from the aqueous system and due to the alteration in the ratio of silver content and protective agent, the characteristic profile of silver nanoparticles with an average diameter of 15 nm also became changed in respect of reported results. Here the low pH range (4-6) favors the interaction between nanoparticle and arsenic and it was found that the interaction was chemical in nature through adsorption or complex formation with surface carboxylate groups of the protecting agent (MSA). Following the interaction, a successful removal of arsenic (III) was achieved at a percentage of 94.16 with an initial concentration of 45 mg/L and equilibrium time of 60 min. Hence nanoparticles were executed against the toxic effect of arsenic in E. coli, an important gut microbe of higher animals, for the restoration of bacterial growth in arsenic pre-removed media. In this context the validation of this removal efficiency against arsenic induced toxicity was proved through several morphological studies, degree of oxidative damages and other biochemical attributes.

Behavior, remediation effect and toxicity of nanomaterials in water environments

In recent years, nanotechnology has been developing continuously. Due to their advantageous huge specific surface areas, microinterface characteristics, remediation ability and potential environmental risks, nanomaterials have become a hot topic in the field of environmental research. With the mass production and use of nanomaterials, they will inevitably be discharged or leaked into the water environment. In this paper, we will describe some typical nanomaterials, such as nanoscale zero valent iron (nZVI), graphene nanomaterials (GNMs), TiO₂ nanoparticles (NPs), ZnO NPs, Fe₃O₄ NPs, carbon nanotubes (CNTs), Ag NPs, and other nanomaterials in water environments, focusing on the positive and negative effects of some nanomaterials in water environments. The remediation function and the impact of nanomaterials in water environments, including behavior of nanomaterials and their toxicity to aquatic organisms will be discussed. This will be of great significance for our subsequent research on nanomaterials.

Potential use of ZnO@activated carbon nanocomposites for the adsorptive removal of Cd2+ ions in aqueous solutions

Nowadays, the pollution in water resources has become a major concern, both environmentally and in perspective of human health. The bioaccumulation of pollutants, especially heavy metal ions through the food chain, poses a hazardous risk to humans and other living organisms. Nanomaterials and their composites have been recognized for their potential to resolve such problems. Herein, ZnO nanoparticles were synthesized and characterized via different microscopic/spectroscopic techniques. ZnO nanoparticles (i.e., 20 to 50 nm) were obtained in high yield via a facile chemical approach. The ratio of ZnO nanoparticles and activated carbon was optimized to achieve enhanced electrostatic interactions for the effective adsorption of cadmium ions (Cd²⁺). The adsorptive performance of the nanocomposite was further assessed in relation to several key parameters (e.g., contact time, solution pH, and adsorbent/adsorbate dosage). The nanocomposites (1 mg/ml) offered amaximum adsorption capacity of 96.2 mg/g for Cd²⁺ ions as confirmed through adsorption isotherms for a best interpretation of the adsorption phenomenon. The favourable adsorption capacity of the synthesized ZnO/activated carbon (9:1) nanocomposites supported their use as an efficient sorbent material in practical performance metrics (e.g., partition coefficient of 0.54 mg g^-1μM^-1) for the adsorption of Cd²⁺ ions.

Synthetic sodalite doped with silver nanoparticles: Characterization and mercury (II) removal from aqueous solutions

In this work, a novel silver nanoparticles-doped synthetic sodalitic composite was synthesized and characterized using advanced characterization methods, namely TEM-EDS, XRD, SEM, XRF, BET, zeta potential, and particle size analysis. The synthesized nanocomposite was used for the removal of Hg²⁺ from 10 ppm aqueous solutions of initial pH equal to 2. The results showed that the sodalitic nanocomposites removed up to 98.65% of Hg²⁺, which is ∼16% and 70% higher than the removal achieved by sodalite and parent coal fly ash, respectively. The findings revealed that the Hg²⁺ removal mechanism is a multifaceted mechanism that predominantly involves adsorption, precipitation and Hg-Ag amalgamation. The study of the anions effect (Cl^-, NO₃^-, C₂H₃O₂^-, and SO₄^2-) indicated that the Hg²⁺ uptake is comparatively higher when Cl^- anions co-exist with Hg²⁺ in the solution.

Enhanced detoxification of p-bromophenol by novel Zr/Ag-TiO2@rGO ternary composite: Degradation kinetics and phytotoxicity evolution studies

The toxicity and persistence of the halogenated aromatics, particularly brominated phenolic compounds have drawn serious concerns to the environment, emphasizing the potential effects on human health and ecosystems balance. Advanced oxidation process (AOP) has received much attention as an alternative for the conventional wastewater treatment methods to treat water contaminated with toxic pollutants. This study investigated the degradation and detoxification of p-bromophenol (p-BP) by a novel Zr/Ag-TiO₂@rGO photocatalyst under visible light. Upon 3 h of visible light irradiation over Zr/Ag-TiO₂@rGO, more than 95% of p-BP (15 mg/L) degradation was achieved at a rate of 0.23 min^-1. The degradation products were identified by GC-MS and possible degradation pathway was proposed. The phytotoxicity evolution of the degraded products was assessed on Vigna radiata (V. radiata), in which seeds treated with pure p-BP showed less germination (40%) compared to degradation products (100%). Furthermore, the germination index (GI) of p-BP was found to be 11.1% before degradation while it increased to 80.5% after 3 h of degradation indicated that this photodegradation process achieved detoxification of p-BP. Thus, this study demonstrated that p-BP elimination and detoxification could be simply achieved with Zr/Ag-TiO₂@rGO nanocomposite under visible light irradiation, which provides new solution for wastewater treatment and water reuse in crop irrigation.

Toward the Development of an Innovative Implant: NiTi Alloy Functionalized by Multifunctional β-TCP+Ag/SiO2 Coatings

In recent years, one of the more important and costly problems of modern medicine is the need to replace or supplement organs in order to improve the quality of human life. In this field, promising solutions seem to have been implants which are based on NiTi alloys with shape memory effects. Unfortunately, this material is susceptible to the corrosion and release of toxic nickel to the human organism. Hence, its application as a long-term material is strongly limited. Therefore, this paper presents a new solution which should help to improve the functionality of the NiTi alloy and elongate its medical stability to use. The idea was focused on functionalization of the implant surface by a biocompatible, multifunctional coating without any impact on the features of the substrate, i.e., the martensitic transformation responsible for shape memory effects. For this purpose, we prepared a colloidal suspension, composed of β-TCP (particle size ∼450 nm) and the Ag/SiO₂ nanocomposite which due to the electrophoretic deposition (EPD) led to the formation of structurally atypical calcium phosphosilicate coating. Those biomaterials formed a crack-free coating, adhering well to the NiTi surface when distributed over the entire surface, with low concentration of metallic and oxide silver (<3 at. %). At the same time, the coat-forming materials had resulted in the growth of a Gram-negative bacterial biofilm. Additionally, the additive of the silver-silica composite enhances cell proliferation, effectively a few times higher than commonly used coat-forming materials (e.g., pure β-TCP).

Nanomaterials for the Removal of Heavy Metals from Wastewater

Removal of contaminants in wastewater, such as heavy metals, has become a severe problem in the world. Numerous technologies have been developed to deal with this problem. As an emerging technology, nanotechnology has been gaining increasing interest and many nanomaterials have been developed to remove heavy metals from polluted water, due to their excellent features resulting from the nanometer effect. In this work, novel nanomaterials, including carbon-based nanomaterials, zero-valent metal, metal-oxide based nanomaterials, and nanocomposites, and their applications for the removal of heavy metal ions from wastewater were systematically reviewed. Their efficiency, limitations, and advantages were compared and discussed. Furthermore, the promising perspective of nanomaterials in environmental applications was also discussed and potential directions for future work were suggested.