Nanoscale materials and their use in water contaminants removal-a review

Cellulose Nanocrystals (CNCs) and Cellulose Nanofibers (CNFs) as Adsorbents of Heavy Metal Ions

The isolation of nanocellulose has been extensively investigated due to the growing demand for sustainable green materials. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs), which have the same chemical composition but have different morphology, particle size, crystallinity, and other properties depending on the precursor and the synthesis method used. In comparison, CNC particles have a short rod-like shape and have smaller particle dimensions when compared to CNF particles in the form of fibers. CNC synthesis was carried out chemically (hydrolysis method), and CNF synthesis was carried out mechanically (homogenization, ball milling, and grinding), and both can be modified because they have a large surface area and are rich in hydroxyl groups. Modifications were made to increase the adsorption ability of heavy metal ions. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG), and dynamic light scattering (DLS) can reveal the characteristics and morphology of CNCs and CNFs. The success and effectiveness of the heavy metal adsorption process are influenced by a few factors. These factors include adsorbent chemical structure changes, adsorbent surface area, the availability of active sites on the adsorbent’s surface, adsorption constants, heavy metal ionic size differences, pH, temperature, adsorbent dosage, and contact time during the adsorption process. In this review, we will discuss the characteristics of CNCs and CNFs synthesized from various precursors and methods, the modification methods, and the application of CNCs and CNFs as heavy metal ion adsorbents, which includes suitable isotherm and kinetics models and the effect of pH on the selectivity of various types of heavy metal ions.

Porous nanocomposites for sorptive elimination of ibuprofen from synthetic wastewater and its molecular docking studies

Pharmaceuticals are a new developing pollutant that is threatening aquatic ecosystems and impacting numerous species in the ecosystem. The aim of this study is the green synthesis of TiO₂-Fe₂O₃-Chitosan nanocomposites in conjunction with Moringa olifera leaves extract and its applicability for ibuprofen removal. Various characterization studies were performed for the synthesized nanocomposites. Box-Behnken design (BBD) is employed to optimize pH, agitation speed, and composite dosage. Equilibrium results show that adsorption process matches with Langmuir isotherm, demonstrating adsorption on the nanocomposite's homogenous surface and follows pseudo-first-order kinetics. Using the BBD, pH, adsorbent dose, and agitation speed were examined as adsorption parameters. Ibuprofen elimination was demonstrated to be most successful at a pH of 7.3, using 0.05 g of nanocomposites at a rotational speed of 200 rpm. Thermodynamic parameters for ibuprofen sorption were carried out and the ΔH and ΔS was found to be 76.23 & 0.233. Molecular Docking was performed to find the interaction between the pollutant and the nanocomposite. UV-vis spectra confirm the 243 nm absorption band corresponding to the nanocomposite's surface plasmon resonances. Fourier transform infrared spectroscopy spectra relate this band to a group of nanocomposites. The findings of this work emphasize the importance of TiO₂-Fe₂O₃-Chitosan nanocomposites for removing ibuprofen from wastewater.

Analytical Review on Membrane Water Filter using Different Materials to Prevent Microbial Activities

Drinking water quality monitoring technologies have made significant progress in monitoring water resources and water treatment plants. This paper discusses the adverse effect of microbial contamination and also gives a brief description of the important parameters for drinking water and the technologies currently available used in this field. This paper is focused on studying the requirement for the development of low-cost filter materials that can be suitable as well as economical to be produced on a large-scale for real applications. There are several parameters such as porosity, contact angle, water flux, thickness, microbial activity needed to be focused on in the future to study the transformation of the hydrophilic property on the surface of the water.

Polymer Membranes as Innovative Means of Quality Restoring for Wastewater Bearing Heavy Metals

The problem that has aroused the interest of this review refers to the harmful effect of heavy metals on water sources due to industrial development. In this respect, the review is aimed at achieving a literature survey on the outstanding results and advancements in membranes and membrane technologies for the advanced treatment of heavy metal-loaded wastewaters. Particular attention is given to synthetic polymer membranes, for which the proper choice of precursor material can provide cost benefits while ensuring good decontamination activity. Furthermore, it was also found that better removal efficiencies of heavy metals are achieved by combining the membrane properties with the adsorption properties of inorganic powders. The membrane processes of interest from the perspective of industrial applications are also discussed. A noteworthy conclusion is the fact that the main differences between membranes, which refer mainly to the definition and density of the pore structure, are the prime factors that affect the separation process of heavy metals. Literature studies reveal that applying UF/MF approaches prior to RO leads to a better purification performance.

Adsorption of Mn(ii) ions from wastewater using an AgNPs/GO/chitosan nanocomposite material

Water contaminated with heavy metal ions is extremely poisonous and threatens living organisms. Therefore, scientists place a premium on removing heavy metal ions from water that has already been contaminated. Removing metal ions from water typically involves the use of nanomaterials. Chitosan was made by extracting it from shrimp shells and combining it with a 3 : 1 ratio of synthetically produced AgNPs/GO. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with transmission electron microscopy (TEM), and X-ray diffraction were used to investigate an AgNPs/GO/chitosan nanocomposite (XRD). A number of studies must be run to determine the optimal pH, adsorbent quantity, retention period, stirring speed, temperature, and initial concentration. The studies were conducted in a variety of ways. The isotherms of Langmuir, Freundlich, and Dubinin-Radushkevich were utilized. The industrial wastewater was used in the column adsorption experiment, and the flow rates and column bed heights were varied. An optimum contact time, pH, and adsorbent dosage for Mn(ii) were determined. At 30 minutes, pH 6, and 0.05 grams of Mn(ii) adsorbent per 100 ml, with agitation at 250 rpm, room temperature of 30 °C, and an initial concentration of 40 ppm, the best conditions were discovered. A positive correlation coefficient finding (R ² = 0.925) indicates a good fit for Mn, according to equilibrium studies (II). The pseudo-second-order active model was connected to data that suited the pseudo-first and pseudo-second-order models. In the intra-particle diffusion model, the mechanism must proceed through four phases before equilibrium is reached. In an industrial adsorbent column, the adsorbent was put to the test. The periodicity test demonstrates that the nanocomposite's adsorption capability can be recovered by washing it with 0.1 M HCl. Mn(ii) adsorbed on AgNPs/GO/Chitosan after four cycles was only 20%, insufficient for additional adsorption tests. The repeated cycles that led to the partial loss of the adsorbate may have reduced the adsorbent material's efficacy.

TiO2-NPs and cadmium co-exposure: in vitro assessment of genetic and genomic DNA damage on Dicentrarchus labrax embryonic cells

The increased titanium dioxide nanoparticles (TiO₂-NPs) spread and their interaction with organic and inorganic pollutants arouses concern for the potential hazards for organisms and environment. This study tested in vitro the genotoxic effects of TiO₂-NPs (1 μg/mL) and cadmium (Cd) (0.1 μg/mL) co-exposure using Dicentrarchus labrax embryonic cells (DLEC) as experimental model. The genotoxicity tests (Comet assay, Diffusion Assay and Random Amplification of Polymorphic DNA (RAPD-PCR) were conducted after 3, 24 and 48 hours of exposure to TiO₂-NPs and Cd alone and in combination. The results showed that the percentage of DNA damage and apoptotic cells increases following 48 hours TiO₂-NPs exposure, while DNA instability was detected for all the times tested. Cd induced genotoxic effects starting from 3 hour-exposure and for all the treatment times. Cd + TiO₂-NPs co-exposure did not cause any genomic damage or apoptosis for all the exposure times. The possibility that Cd and TiO₂-NPs form aggregates no longer able of penetrating the nucleus and damaging the genetic material is discussed.

Comparative Analysis of Microbial Consortiums and Nanoparticles for Rehabilitating Petroleum Waste Contaminated Soils

Nano-bioremediation application is an ecologically and environmentally friendly technique to overcome the catastrophic situation in soil because of petroleum waste contamination. We evaluated the efficiency of oil-degrading bacterial consortium and silver nanoparticles (AgNPs) with or without fertilizer to remediate soils collected from petroleum waste contaminated oil fields. Physicochemical characteristics of control soil and petroleum contaminated soils were assessed. Four oil-degrading strains, namely Bacillus pumilus (KY010576), Exiguobacteriaum aurantiacum (KY010578), Lysinibacillus fusiformis (KY010586), and Pseudomonas putida (KX580766), were selected based on their in vitrohydrocarbon-degrading efficiency. In a lab experiment, contaminated soils were treated alone and with combined amendments of the bacterial consortium, AgNPs, and fertilizers (ammonium nitrate and diammonium phosphate). We detected the degradation rate of total petroleum hydrocarbons (TPHs) of the soil samples with GC-FID at different intervals of the incubation period (0, 5, 20, 60, 240 days). The bacterial population (CFU/g) was also monitored during the entire period of incubation. The results showed that 70% more TPH was degraded with a consortium with their sole application in 20 days of incubation. There was a positive correlation between TPH degradation and the 100-fold increase in bacterial population in contaminated soils. This study revealed that bacterial consortiums alone showed the maximum increase in the degradation of TPHs at 20 days. The application of nanoparticles and fertilizer has non-significant effects on the consortium degradation potential. Moreover, fertilizer alone or in combination with AgNPs and consortium slows the rate of degradation of TPHs over a short period. Still, it subsequently accelerates the rate of degradation of TPHs, and a negligible amount remains at the end of the incubation period.

Iron nanoparticles to recover a co-contaminated soil with Cr and PCBs

Little attention has been given to the development of remediation strategies for soils polluted with mixture of pollution (metal(loid)s and organic compounds). The present study evaluates the effectiveness of different types of commercial iron nanoparticles (nanoscale zero valent iron (nZVI), bimetallic nZVI-Pd, and nano-magnetite (nFe₃O₄)), for the remediation of an industrial soil co-contaminated with Cr and PCBs. Soil samples were mixed with nZVI, nZVI-Pd, or nFe₃O₄ at doses selected according to their reactivity with PCBs, homogenized, saturated with water and incubated at controlled conditions for 15, 45 and 70 days. For each sampling time, PCBs and chromium were analyzed in aqueous and soil fractions. Cr(VI) and Cr leachability (TCLP test) were determined in the soil samples. The treatment with the three types of iron nanoparticles showed significant reduction in Cr concentration in aqueous extracts at the three sampling times (> 98%), compared to the control samples. The leachability of Cr in treated soil samples also decreased and was stable throughout the experiment. Results suggested that nZVI and nZVI-Pd immobilized Cr through adsorption of Cr(VI) on the shell and reduction to Cr(III). The mechanism of interaction of nFe₃O₄ and Cr(VI) included adsorption and reduction although its reducing character was lower than those of ZVI nanoparticles. PCBs significantly decreased in soil samples (up to 68%), after 15 days of treatment with the three types of nanoparticles. However, nFe₃O₄ evidenced reversible adsorption of PCBs after 45 days. In general, nZVI-Pd reduced PCB concentration in soil faster than nZVI. Control soils showed a similar reduction in PCBs concentration as those obtained with nZVI and nZVI-Pd after a longer time (45 days). This is likely due to natural bioremediation, although it was not effective for Cr remediation. Results suggest that the addition of nZVI or nZVI-Pd and pseudo-anaerobic conditions could be used for the recovery of soil co-contaminated with Cr and PCBs.

Toxicity of Modified Magnetite-Based Nanocomposites Used for Wastewater Treatment and Evaluated on Zebrafish (Danio rerio) Model

Magnetite-based nanocomposites are used for biomedical, industrial, and environmental applications. In this study, we evaluated their effects on survival, malformation, reproduction, and behavior in a zebrafish animal model. Nanoparticles were synthesized by chemical coprecipitation and were surface-functionalized with (3-aminopropyl) triethoxysilane (APTES), L-cysteine (Cys), and 3-(triethoxysilyl) propylsuccinic anhydride (CAS). All these nanocomposites were designed for the treatment of wastewater. Zebrafish embryos at 8 h post-fertilization (hpf) and larvae at 4 days post-fertilization (dpf) were exposed to the magnetic nanocomposites Fe3O4 MNP (magnetite), MNP+APTES, MNP+Cys, MNP+APTES+Cys, and MNP+CAS, at concentrations of 1, 10, 100, and 1000 µg/mL. Zebrafish were observed until 13 dpf, registering daily hatching, survival, and malformations. Behavior was tested at 10 dpf for larvae, and reproduction was analyzed later in adulthood. The results showed that the toxicity of the nanocomposites used were relatively low. Exploratory behavior tests showed no significant changes. Reproduction in adults treated during development was not affected, even at concentrations above the OECD recommendation. Given the slight effects observed so far, these results suggest that nanocomposites at the concentrations evaluated here could be a viable alternative for water remediation because they do not affect the long-term survival and welfare of the animals.

Amino-Functionalized Magnetic Porous Organic Polymer for Selective Removal of Toxic Cationic Dyes from Textile Wastewater

Porous organic polymers (POPs) with fascinating porous properties are promising candidates for the removal of organic dyes from textile wastewater. In this research work, an amino-functionalized magnetic POP (FC-POP-EDA@Fe3O4) containing...

High-efficiency visible-light photocatalytic H2O2 production using CdSe-based core/shell quantum dots

Quantum dots are demonstrated as photocatalysts for high-efficiency photocatalytic production of H2O2 in a designed oil/water two-phase system.

Sustainable multilayer biomass carbon and polymer hybrid column as potential antibacterial water filter

Stipulation of fresh water for domestic use without any microbial, organic and inorganic contaminants is of high need. Sustainable, efficient, cost-effective and robust water purification technologies is of high need and it can be achieved using nanomaterials and their composite. Nanostructured graphene has unique properties like high surface to volume ratio, higher absorbability, reusability with minimal chemical alterations, and low cytotoxicity. From the validation of these properties, we have developed PLLA-Ag@graphene sandwich structures as an effective adsorbate for water purification application. As the real water bodies have lot of bacterial contaminants, the material is also designed as efficient adsorbate with antibacterial efficacy. In view of achieving these objectives, we have synthesized PLLA fibre mats by electrospinning method, followed by PLLA-Graphene and Ag decorated PLLA-graphene mats. The crystallite size for graphite and Ag@graphene was calculated as 30.82 nm and 43.79 nm, respectively. Furthermore, the UV analysis of Ag@graphene shows two peaks corresponding to graphene and Ag NP at 285 nm and 407 nm respectively. The layers were assembled in the order of polymeric fibre, as-fired biomass graphite, Ag@graphene for methodical filtration process. The filtration efficacy of the filtrate was tested using sewage water and the results shows higher contamination removal percentage of 87 % with TDS values in the drinking water standards after filtration. The antibacterial efficacy results also evidence of the potentialities of the hybrid system towards water purification application.

Facial Eco-Friendly Synthesis of Copper Oxide Nanoparticles Using Chia Seeds Extract and Evaluation of Its Electrochemical Activity

In the current study, copper oxide nanoparticles (CuO NPs) were synthesized using chia seed extract in a simple, rapid, and eco-friendly manner for the first time. The synthesized CuO NPs were characterized using different analytical techniques. The images of field emission scanning electron microscopy revealed that the CuO NPs were triangular and pyramid in structure, with a mean particle size of 61.5 nm. The absorption peak of the synthesized CuO NPs was measured using ultraviolet-visible spectroscopy and was recorded at a wavelength of 291 nm. The results of energy-dispersive X-ray analysis confirmed that the CuO NPs synthesized using chia seed extract yielded high-purity CuO NPs. Moreover, the X-ray diffraction analysis indicated the highly crystalline nature of the CuO NPs, and the X-ray photoelectron spectroscopy results indicated that the CuO NPs were prepared successfully. Additionally, electrochemical impedance spectroscopy measurements revealed excellent electrocatalytic conductivity and fast electron transfer at the electrode/electrolyte interface of the synthesized CuO NP-modified glassy carbon electrode.

Recovery trend to co-exposure of iron oxide nanoparticles (γ-Fe2O3) and glyphosate in liver tissue of the fish Poecilia reticulata

Citrate-coated iron oxide nanoparticles (IONPs) have potential use in environmental remediation, with possibilities in decontaminating aquatic environments exposed to toxic substances. This study analyzed IONPs associated to Roundup Original, a glyphosate-based herbicide (GBH), and pure glyphosate (GLY), through ultrastructural and histopathological biomarkers in liver tissue, from females of Poecilia reticulata exposed to: iron ions (0.3 mg/L) (IFe) and IONPs (0.3 mgFe/L) associated with GLY (0.65 mg/L) and GBH (0.65 mgGLY/L (IONP + GBH1) and 1.30 mgGLY/L (IONP + GBH2)) for a period of 7, 14 and 21 days, followed by an equal post-exposure period only in reconstituted water. For the assays, the synthetized IONPs had crystalline and rounded shape with an average diameter of 2,90 nm, hydrodynamic diameter 66,6 mV, zeta potential -55,4 and diffraction profile of maghemite (γ-Fe2O3). The data obtained by biomarkers indicated a high inflammatory response in all treatments. These same parameters, considered during the post-exposure period indicated recovery in reaction patterns of circulatory disturbances and regressive changes, resulting in average reductions of 37,53 points in IFe, 21 points in IONP + GBH1, 15 points in IONP + GBH2 and 11 points in IONP + GLY in total histopathological index of liver after 21 days post-exposure. However, although the cellular and tissue responses were significant, there was no change in the condition factor and hepatosomatic index, denoting resilience of the experimental model.

Tailored functional materials as robust candidates to mitigate pesticides in aqueous matrices-a review

Pesticides are among the top-priority contaminants, which significantly contribute to environmental deterioration. Conventional techniques are not efficient enough to remove pollutants from environmental matrices. The development of functional materials has emerged as promising candidates to remove and degrade pesticides and related hazardous compounds. Furthermore, the nanohybrid materials with unique structural and functional characteristics, such as better material anchorage, mass transfer, electron-hole separation, and charged interaction make them a versatile option to treat and reduce pollutants from aqueous matrices. Herein, we present the current progress in the development of functional materials for the abatement of toxic pesticides. The physicochemical characteristics and pesticide-removal functionalities of various metallic functional materials (e.g., zirconium, zinc, titanium, tungsten, and iron), polymer, and carbon-based materials are critically discussed with suitable examples. Finally, the industrial-scale applications of the functional materials, concluding remarks, and future directions in this important arena are given.

Extraction of Chlorobenzenes and PCBs from Water by ZnO Nanoparticles

Metal oxide nanoparticles have great potential for selective adsorption and catalytic degradation of contaminants from aqueous solutions. In this study, we employ mass spectrometry and molecular dynamics simulations to better understand the chemical and physical mechanisms determining the affinity of chlorobenzenes and polychlorinated biphenyls (PCBs) for zinc oxide nanoparticles (ZnO NPs). The experiments and simulations both demonstrate that the adsorption coefficients for chlorobenzenes increase steadily with the number of chlorine atoms, while, for PCBs, the relation is more complex. The simulations link this complexity to chlorine atoms at ortho positions hindering coplanar conformations. For a given number of chlorine atoms, the simulations predict decreasing adsorption affinity with increasing numbers of ortho substitutions. Consequently, the simulations predict that some of the highest adsorption affinities for ZnO NPs are exhibited by dioxin-like PCBs, suggesting the possibility of selective sequestration of these most acutely toxic PCBs. Remarkably, the experiments show that the PCB adsorption coefficients of ZnO NPs with diameters ≤ 80 nm exceed those of a soil sample by 5–7 orders of magnitude, meaning that a single gram of ZnO NPs could sequester low levels of PCB contamination from as much as a ton of soil.

Nanoadsorbents in focus for the remediation of environmentally-related contaminants with rising toxicity concerns

Modern lifestyle demands high-end commodities, for instance, cosmetics, detergents, shampoos, household cleaning, sanitary items, medicines, and so forth. In recent years, these products' consumption has increased considerably, being antibiotics and some other pharmaceutical and personal care products (PPCPs). Several antibiotics and PPCPs represent a wide range of emerging contaminants with a straight ingress into aquatic systems, given their high persistence in seawater, effluent treatment plants, and even drinking water. Under these considerations, the necessity of developing new and affordable technologies for the treatment and sustainable mitigation of pollutants is highly requisite for a safer and cleaner environment. One possible mitigation solution is an effective deployment of nanotechnological cues as promising matrices that can contribute by attending issues and improving the current strategies to detect, prevent, and mitigate hazardous pollutants in water. Focused on nanoparticles' distinctive physical and chemical properties, such as high surface area, small size, and shape, metallic nanoparticles (MNPs) have been investigated for water remediation. MNPs gained increasing interest among research groups due to their superior efficiency, stability, and high catalyst activity compared with conventional systems. This review summarizes the occurrence of antibiotics and PPCPs and the application of MNPs as pollutant mitigators in the aquatic environment. The work also focuses on transportation fate, toxicity, and current regulations for environmental safety.

Barium/Cobalt@Polyethylene Glycol Nanocomposites for Dye Removal from Aqueous Solutions

Dyes are known as one of the most dangerous industrial pollutants which can cause skin diseases, allergy, and provoke cancer and mutation in humans. Therefore, one of the important environmental issues is the effective removal of dyes from industrial wastewater. In the current work, BaFe₁₂O₁₉/CoFe₂O₄@polyethylene glycol (abbreviated as BFO/CFO@PEG) nanocomposite was synthesized and evaluated regarding its capacity for adsorptive removal of a model dye Acid Blue 92 (denoted as AB92) from aqueous solutions. The characteristics of the prepared nanocomposite was determined by tests such as X-ray diffraction (XRD), scanning electron microscope (SEM), vibration sample magnetization (VSM), and Fourier transform infrared spectroscopy (FTIR). The effects of conditional parameters including pH (2–12), initial concentration of dye (20–100 mg/L), adsorbent dosage (0.02–0.1 g/L) and contact time (0-180 min) on the adsorption of dye were investigated and then optimized. The results indicated that with the increase of the adsorbent dosage from 0.02 to 0.1 g/L, the removal efficiency increased from 74.1% to 78.6%, and the adsorbed amount decreased from 148.25 to 31.44 mg/g. The maximum removal efficiency (77.54%) and adsorption capacity (31.02 mg/g) were observed at pH 2. Therefore, the general optimization conditions revealed that the maximum adsorption efficiency of dye was obtained in condition of initial concentration of 20 mg/L, contact time of 1 h and pH of solution equal 2. The adsorption isotherm and kinetic data were evaluated using a series of models. The pseudo-second order kinetic model and Freundlich isotherm model show the best fitting with experimental data with R²∼0.999.

Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots

We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 10⁴ and 4 × 10⁵ for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.

Biotechnology and nanotechnology for remediation of chlorinated volatile organic compounds: current perspectives

Chlorinated volatile organic compounds (CVOCs) are persistent organic pollutants which are harmful to public health and the environment. Many CVOCs occur in substantial quantities in groundwater and soil, even though their use has been more carefully managed and restricted in recent years. This review summarizes recent data on several innovative treatment solutions for CVOC-affected media including bioremediation, phytoremediation, nanoscale zero-valent iron (nZVI)-based reductive dehalogenation, and photooxidation. There is no optimally developed single technology; therefore, the possibility of using combined technologies for CVOC remediation, for example bioremediation integrated with reduction by nZVI, is presented. Some methods are still in the development stage. Advantages and disadvantages of each treatment strategy are provided. It is hoped that this paper can provide a basic framework for selection of successful CVOC remediation strategies.

Highly Mesoporous Hybrid Transition Metal Oxide Nanowires for Enhanced Adsorption of Rare Earth Elements from Wastewater

Removal of rare earth elements (REEs) from industrial wastewater is a continual challenge. To date, several approaches to the synthesis of nanoadsorbants for this application have been reported, although these are characterized by insufficient adsorption capacity and limitations in cycling stability. The present work reports the fabrication and performance of hierarchical hybrid transition metal oxide (TMO) nanowires deposited on carbon fibers. An ordered assembly of hybrid TMO nanowires exhibits an outstanding adsorbance of 1000 mg·g^-1 of REEs with 93% recyclability. This superior performance is attributed to the unique mesoporous architecture of the nanowires, which exhibits a high surface area of 122 cm³·g^-1. Further, rapid adsorption/desorption of the REEs reveals minimal morphological alteration and hence high structural stability of these hybrid TMO nanowires after multiple cycles. The ready accessibility of the adsorption sites at crystallite boundaries and the surfaces as well as rapid adsorption of the REEs on the mesoporous nanostructure facilitate considerable adsorption capacity, improved structural stability, and extended cyclability, all of which suggest the potential for this material in REE extraction.

Ultrasound-Assisted Surface Modification of MWCNT Using Organic Acids

In the present work, multiple-wall carbon nanotubes (MWCNTs) were surface modified in an environmentally friendly way, using low-frequency ultrasonic energy. This type of modification was carried-out using two different types of organic acids, citric acid (CA) and oxalic acid (OA). The modification of the MWCNTs was confirmed by Fourier-transform infrared spectroscopy (FTIR), where functional groups such as OH, C=O, O–C=O and COOH were detected. By means of Raman spectroscopy, an increase in carbon surface defects was found. On the other hand, using X-ray photoelectron spectroscopy (XPS), oxidation was evidenced on the surface of the modified MWCNT. In both Raman spectroscopy and XPS, the results indicate a greater modification when CA is used, possibly due to the fact that CA has a larger number of functional groups. MWCNT-CA showed good dispersion in methanol, while MWCNT-OA showed good stability in methanol and ethanol. Finally, a 20% removal of creatinine efficiency improvement was found with respect to the unmodified MWCNTs, while no improvement was found in the case of urea and uric acid.

Bibliometric approach to the perspectives and challenges of membrane separation processes to remove emerging contaminants from water

The presence of contaminants in water is concerning due to the potential impacts on human health and the environment, and ingested contaminants cause harm in various ways. The conventional water treatment systems are not efficient to remove these contaminants. Therefore, novel techniques and materials for the removal of contaminants are increasingly being developed. The separation process using modified membranes can remove these micropollutants; therefore, they have attracted significant research attention. Among the materials used for manufacturing of these membranes, composites based on graphene oxide and reduced graphene oxide are preferred owing to their promising properties, such as mechanical resistance, thermal and chemical stability, antifouling capacity, water permeability, high thermal and electrical conductivity, high optical transmittance and high surface area. Membrane separation processes (MSP) can be used as secondary or tertiary treatment during the supply of wastewater. However, the efficient and accessible applications of these technologies are challenging. This study aims to demonstrate the main concepts of membrane separation processes and their application in the removal of emerging contaminants. This study reports bibliometric mapping, relevant data on studies using membranes as water treatment processes, and their viability in industrial applications. The main challenges and perspectives of these technologies are discussed in detail as well.

Enhanced Fouling Resistance and Antimicrobial Property of Ultrafiltration Membranes Via Polyelectrolyte-Assisted Silver Phosphate Nanoparticle Immobilization

Ultrafiltration (UF) is a low-pressure membrane that yields higher permeate flux and saves significant operating costs compared to high-pressure membranes; however, studies addressing the combined improvement of anti-organic and biofouling properties of UF membranes are lacking. This study investigated the fouling resistance and antimicrobial property of a UF membrane via silver phosphate nanoparticle (AgPNP) embedded polyelectrolyte (PE) functionalization. Negatively charged polyacrylic acid (PAA) and positively charged polyallylamine hydrochloride (PAH) were deposited on the membrane using a fluidic layer-by-layer assembly technique. AgPNPs were immobilized within the crosslinked "bilayers" (BL) of PAH/PAA. The effectiveness of AgPNP immobilization was confirmed by microprofile measurements on membrane surfaces using a solid contact Ag micro-ion-selective electrode. Upon stable and uniform BL formation on the membrane surface, the permeate flux was governed by a combined effect of PAH/PAA-derived hydrophilicity and surface/pore coverage by the BLs "tightening" of the membrane. When fouled by a model organic foulant (humic acid), the functionalized membrane exhibited a lower flux decline and a greater flux recovery due to the electrostatic repulsion imparted by PAA when compared to the unmodified membrane. The functionalization rendered antimicrobial property, as indicated by fewer attachments of bacteria that initiate the formation of biofilms leading to biofouling.

Kinetic and equilibrium study of (poly amido amine) PAMAM dendrimers for the removal of chromium from tannery wastewater

Water gets polluted by industrial effluents, mainly composed of heavy metals and organic materials. Water soluble heavy metals can be taken up by living organisms. Chromium mainly occurs in the form of chromate and cationic hydroxo complexes in water. Apart from conventional methods of heavy metal removal, there are some novel approaches such as using dendrimers for removal of heavy metal. Dendrimers are extremely branched nano sized polymers with a three-dimensional symmetry around a core that imparts poly functionality. PAMAM (poly amido amine) dendrimers having ethylene diamine as core and methyl acrylate as repeating unit was divergently synthesized. Characterization of PAMAM dendrimers was evaluated by UV–Vis spectroscopy, zeta sizer, scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy. Zero generation dendrimers have amine terminal groups, showed intense amide group peak at 1596.76 cm−1. The λ max value was 278 nm. SEM exhibited spherical shape for full generation while needle like structure for −0.5 generation. Evaluation of chromium removal from wastewater has been done by atomic absorption spectroscopy (AAS). The data revealed that optimal removal of Cr occurs at dendrimer concentration of 5 mL, Cr concentration of 300 ppm, contact time of 2 min and pH 7. The synthesized dendrimers have effectively removed Cr from tannery wastewater.

Synergistic effect of Ficus-zero valent iron supported on adsorbents and Plantago major for chlorpyrifos phytoremediation from water

Chlorpyrifos and the metabolite 3, 5, 6-trichloro-2-pyridinol (TCP) are widespread contamination of aquatic environments especially freshwater fish. The objectives of this study were to evaluate the contribution of using Ficus zero-valent iron nanoparticles supported on adsorbents (F-Fe⁰ ad) as green nanotechnology and Plantago major as phytoremediation for removing chlorpyrifos and degradation product TCP polluted water. The shapes of F-Fe⁰ were circular, with sizes from 2.46 nm to 11.49 nm. Wheat bran (WB) showed the highest extent of removal of chlorpyrifos, while Rice straw ash (RSA) showed the lowest extent of removal. F-Fe⁰ supported on adsorbents has demonstrated faster removal toward chlorpyrifos compared with tested adsorbents or F-Fe⁰. Chlorpyrifos was removed more quickly and effectively by P. major L. plus F-Fe⁰ supported on different adsorbents (nearly 100%) than that by P. major (43.76%) or F-Fe⁰ (81.69%). The degradation product TCP was more greatly accumulated in water treated with F-Fe⁰ than that P. major alone or F-Fe⁰ supported with adsorbents and combined with P. major. Furthermore, TCP significantly accumulated in P. major roots and leaves in the water treated with F-Fe⁰ supported with adsorbents plus P. major more than that in the P. major roots and leaves alone, this is attributed to the role of F-Fe⁰ adsorbents for the degradation of chlorpyrifos to TCP, Which strongly accumulated in the P. major roots and leaves. It can be concluded that the contribution of using F-Fe⁰ supported on adsorbents, especially WB as green nanotechnology and P. major as phytoremediation would be a major role for the complete removal of chlorpyrifos from the water with a significant reduction in the toxic degradation product TCP.

Versatile Process for the Preparation of Nanocomposite Sorbents: Phosphorus and Arsenic Removal

Nanomaterials are being increasingly utilized for environmental remediation. The use of these materials, however, is greatly hindered due to challenges in material handling and deployment. Here we present a novel nanocomposite synthesis method based on the direct growth of nanoparticles on and within solid support materials, referred to as Crescoating. In this work, iron and copper nanoparticles have been grown on polyurethane support materials using this process and applied as sorbents for dissolved phosphorus and arsenic in water, respectively. These nanocomposite sorbents exhibit rapid sorption with saturation occurring in less than 5 min. The loading capacity is 104.8 mg PO₄^3- g^-1 and 254.4 mg As(III) g^-1 for the iron and copper nanocomposite sorbents respectively, which is up to four times higher than commercially available alternatives. In addition, phosphorus can be recovered from the iron nanocomposite sorbent. This coating by growth process produces nanocomposites that do not emit particles and has the capability to be scaled and applied to other nanoparticles for diverse pollutant sorption applications.

Green nano-phytoremediation and solubility improving agents for the remediation of chlorfenapyr contaminated soil and water

Chlorfenapyr is a novel class of insecticide-miticide used for crop protection. It poses substantial risks to the reproductive ability of birds as well as environmental stability. This study was focused on the remediation of chlorfenapyr-polluted soil and water through the combined application of green nanotechnology, solubility improving agents and phytoremediation. An analysis using electron microscopy showed that the green synthesis resulted in circular ficus iron nanoparticles (F-Fe⁰) with diameters of 2.46 nm-11.49 nm, while the ipomoea-silver (Ip-Ag⁰) and brassica-silver nanoparticles (Br-Ag⁰) were circular, cubical, hexagonal, triangular and rod -like in shape with sizes ranging from 6.27 to 21.23 nm in IP-Ag⁰ and from 6.05 to 15.02 nm in Br-Ag⁰. After 24 h of treatment with F-Fe⁰, Ip-Ag⁰ and Br-Ag⁰ supported on activated charcoal (Ach), the chlorfenapyr in the aqueous solution was reduced to 86%, 79.70%, and 79.70%, respectively, compared to the 6.16% in aqueous solution. Moreover, after 24 h of treatment with Plantago major plus F-Fe⁰Ach, P. major plus Ip-Ag⁰Ach, and P. major plus Br-Ag⁰Ach, the chlorfenapyr in the aqueous solution was reduced to 93.7%, 91.30%, and 92.92%, respectively, as compared to the 69.27% in P. major. After four days of exposure, the percentage of chlorfenapyr degradation in the soil (i.e. control) only reached 12.40%,while the degradation rates were enhanced by 71.22%, 57.32% and 73.10%, respectively, in the presence of P. major plus nanoparticles (F-Fe0, Ip-Ag0 and Br-Ag0). The integration of green nanotechnology, solubility-improving agents, and phytoremediation by Plantago major has played a major role in the remediation of soil and water contaminated with chlorfenapyr.

Effective exploitation of anionic, nonionic, and nanoparticle-stabilized surfactant foams for petroleum hydrocarbon contaminated soil remediation

Contaminated environments posed serious threats to the ecosystems and their living beings. Suitable preventive approaches should be adopted for effective remediation of contaminated environments to remove or lower their health and environmentally-related hazardous aspects. Petroleum or traces of petroleum contamination from oil fields and refineries to exposed soil in the form of gasoline, petrol, diesel, and used motor oil are a rich source of potential damage to the environment. Conventional ways of treatment and management of hydrocarbon are complicated, insufficient, and expensive. Herein, we reviewed a smart approach for the removal of petroleum source contamination from exposed soil using environment-friendly chemical surfactants and nanoscale surfactant system. The host/guest complexes formation of surfactants with the hydrocarbons (hydrophobic contaminants) of soil and water by the encapsulation mechanism of hydrophobes into the (micelles) a self-assembly aggregation of surfactants. Recently, surfactants stabilized by nanoparticles (NPs) acquired more importance and popularity over surfactant alone. The persistence of diverse hydrocarbon-based contaminants and the mechanisms of removal using pristine surfactants or NP-stabilized surfactant foams are discussed with suitable examples. In summary, herein, an effort has been made to present the notable potentialities of pristine surfactants and NP-stabilized surfactant foams to remediate the petroleum hydrocarbon contaminated soil for a greener and sustainable ecosystem.

Improved metal remediation using a combined bacterial and nanoscience approach

Polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (NPs) were used to explore the potential for improved bioremediation of metals by interaction with the Gram-negative bacterium Halomonas sp. The combined approach improved metal removal and shortened metal remediation times (approx. 100% removal of Pb after 24 h, of Cd after 48 h) compared with bacteria- or NP-only controls. NPs also demonstrated the ability to reduce metal toxicity to bacteria and enhance bacterial growth efficiencies in an additive manner. Cd, Pb, and Fe (from NPs) were analyzed in the following operationally-defined components: EPS, cell-wall, cell membrane, and cytoplasmic fractions; EPS was most important in metal removal. There was a significant promotion of Cd intracellular transportation, but not Pb, by NPs. Reduced Pb internalization may have resulted from EPS acting as an uptake barrier coupled with an effective efflux system of Halomonas sp. as a resistance mechanism. In addition, the majority of Fe was present in bacterial membranes, compared with Cd or Pb, suggesting that bacteria may take up iron oxide NPs as a potential nutrient while recognizing Cd or Pb as toxicants.

Micromixing Efficiency of Particles in Heavy Metal Removal Processes under Various Inlet Conditions

Water quality problems are a persistent global issue since population growth has continually stressed hydrological resources. Heavy metals released into the environment from plating plants, mining, and alloy manufacturing pose a significant threat to the public health. A possible solution for water purification from heavy metals is to capture them by using nanoparticles in micromixers. In this method, conventionally heavy metal capture is achieved by effectively mixing two streams, a particle solution and the contaminated water, under the action of external magnetic fields. In the present study, we investigated the effective mixing of iron oxide nanoparticles and water without the use of external magnetic fields. For this reason, the mixing of particles and the contaminated water was studied for various inlet velocity ratios and inflow angles of the two streams using computational fluid dynamics techniques. The Navier-Stokes equations were solved for the water flow, the discrete motion of particles was evaluated by a Lagrangian method, while the flow of substances of the contaminated water was studied by a scalar transport equation. Results showed that as the velocity ratio between the inlet streams increased, the mixing of particles with the contaminated water was increased. Therefore, nanoparticles were more uniformly distributed in the duct and efficiently absorbed the substances of the contaminated water. On the other hand, the angle between two streams was found to play an insignificant role in the mixing process. Consequently, the results from this study could be used in the design of more compact and cost efficient micromixer devices.

Amine-terminated dendritic polymers as a multifunctional chelating agent for heavy metal ion removals

In this study, amine-terminated hyperbranched PAMAM (polyamidoamine) polymer (AT-HBP) was synthesized as a multifunctional chelating agent to remove two heavy metal ions (Cr(III) and Cu(II)) from the simulated wastewater solutions. The AT-HBP was characterized by Fourier transformed infrared (FTIR), dynamic light scattering (DLS), and proton nuclear magnetic resonance (¹H NMR) analysis. The removal process was carried out in two different methods, centrifuged process and ultrafiltration. The concentration of heavy metal ions before and after removal was measured by inductively coupled plasma (ICP) instrument. The removal processes were evaluated by changing different parameters such as solution pH, AT-HBP dosage, and metal ion concentration. To evaluate the extend of binding of heavy metal ions in the presence of AT-HBP the presence of salt in the solution was also examined on the performance of the removal system. The overall results indicated that removal percentages higher than 98% for Cr(III) and 86% for Cu(II) were achieved for heavy metal concentrations of 100 mg/L for both removal process methods. Furthermore, the function of second generation of polypropylenimine (PPI) was compared to AT-HBP. The results reveal that the removal of Cr(III) and Cu(II) ions by AT-HBP were approximately 20% and 10% higher compared to PPI, respectively. Finally, hyperbranched dendritic polymer with lower expenses to synthesize compared to dendrimer underlined favorable properties as a multifunctional chelating agent and enhancement of ultrafiltration process for wastewater treatment. Graphical abstract.

New micro/mesoporous nanocomposite material from low-cost sources for the efficient removal of aromatic and pathogenic pollutants from water

A new micro/mesoporous hybrid clay nanocomposite prepared from kaolinite clay, Carica papaya seeds, and ZnCl2 via calcination in an inert atmosphere is presented. Regardless of the synthesis temperature, the specific surface area of the nanocomposite material is between ≈150 and 300 m2/g. The material contains both micro- and mesopores in roughly equal amounts. X-ray diffraction, infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy suggest the formation of several new bonds in the materials upon reaction of the precursors, thus confirming the formation of a new hybrid material. Thermogravimetric analysis/differential thermal analysis and elemental analysis confirm the presence of carbonaceous matter. The new composite is stable up to 900 °C and is an efficient adsorbent for the removal of a water micropollutant, 4-nitrophenol, and a pathogen, E. coli, from an aqueous medium, suggesting applications in water remediation are feasible.

Centella asiatica phenolic extract-mediated bio-fabrication of silver nanoparticles: characterization, reduction of industrially relevant dyes in water and antimicrobial activities against foodborne pathogens

In this article, we have reported an environmentally benign and cost-effective method for the synthesis of monodispersed silver nanoparticles (AgNPs), based on Centella asiatica phenolic extracts (CAPE). The presence of phenolics was confirmed by ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time of flight mass spectrometry (UHPLC-ESI-qTOF-MS). Colloidal AgNPs synthesized under different concentrations of silver nitrate were monitored with a UV-vis spectrophotometer. Maximum absorption spectra intensity was found to range between 430–440 nm, during a synthesis time of 90 minutes at room temperature. The as-synthesized CAPE-AgNPs, was subjected to various instrumental characterizations such as, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) and zeta potential. At the optimized synthesis conditions, spherical and monodispersed CAPE-AgNPs were obtained, with an absorption maximum at 430 nm. The crystalline CAPE-AgNPs had a face-centered-cubic (fcc) crystallographic structure, possessing average sizes estimated from TEM, to be between 20–25 nm diameter, a hydrodynamic diameter from DLS of about 90 nm and a zeta potential value of −28.7 mV. FTIR results validated the presence of phenolics on the surfaces of CAPE-AgNPs. The anti-microbial capacity of CAPE-AgNPs was further demonstrated on different pathogenic bacterial strains with satisfactory performances. As a result of the high surface area to volume ratio of CAPE-AgNPs, it was investigated as a catalyst towards the reduction of prominent environmental pollutants, 4 nitrophenol (4 NP), Congo red (CR) and methylene blue (MB). Pseudo first order kinetics were obtained with rate constants of 3.9 × 10⁻³ s⁻¹ for 4 NP, 54.7 × 10⁻³ min⁻¹ for MB and 5.6 × 10⁻³ s⁻¹ for CR. The catalytic performance and antimicrobial activities of CAPE-AgNPs suggest its potential application in wastewater treatment and control of pathogenic microbes.

Illustration of biogenic synthesis of AgNPs based on Centella asiatica phenolic extract and applications.

DNA-binding, antioxidant, H2O2 sensing and photocatalytic properties of biogenic silver nanoparticles using Ageratum conyzoides L. leaf extract

Green nanotechnology is gaining widespread interest owing to the elimination of harmful reagents and offers a cost-effective synthesis of expected products.

Adsorption and anion exchange insight of indigo carmine onto CuAl-LDH/SWCNTs nanocomposite: kinetic, thermodynamic and isotherm analysis

Two-dimensional layered materials are gaining much attention in the field of wastewater purification. Herein, we report the synthesis and characterization of an anion selective copper–aluminum-layered double hydroxide/single-walled carbon nanotubes (CuAl-LDH/SWCNTs) composite for the scavenging of organic dye indigo carmine (IC) from aqueous solution. A facile urea hydrolysis method was used for the controlled growth of the metal hydroxides over the SWCNTs. Structural characterization of the prepared materials was investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The obtained results revealed that the CuAl-LDH/SWCNTs composite has a higher potential for the removal of IC in comparison to CuAl-LDH and SWCNTs. The enhanced adsorption capacity of the composite revealed that deposition of CuAl-LDH over SWCNTs increases the active adsorption sites and promotes the interactions between the composite and IC dye via anion exchange, electrostatic, π–π, hydrogen bonding etc. Moreover, adsorption kinetics, isotherms, and thermodynamic studies have been also proposed to illustrate the mechanism of the IC adsorption onto the CuAl-LDH/SWCNTs composite. Thermodynamic parameters showed that the adsorption of IC dye onto the CuAl-LDH/SWCNTs composite was exothermic and spontaneous in nature. Intra-particle diffusion was determined to be the rate-limiting step and adsorption of IC followed the Langmuir isotherm model with the maximum monolayer adsorption capacity 294.117 mg g⁻¹ at 20 °C. The results suggest that the CuAl-LDH/SWCNTs composite is a potential material for IC adsorption in aqueous solution.

Two-dimensional layered materials are gaining much attention in the field of wastewater purification.

Correlated Materials Characterization via Multimodal Chemical and Functional Imaging

Multimodal chemical imaging simultaneously offers high-resolution chemical and physical information with nanoscale and, in select cases, atomic resolution. By coupling modalities that collect physical and chemical information, we can address scientific problems in biological systems, battery and fuel cell research, catalysis, pharmaceuticals, photovoltaics, medicine, and many others. The combined systems enable the local correlation of material properties with chemical makeup, making fundamental questions of how chemistry and structure drive functionality approachable. In this Review, we present recent progress and offer a perspective for chemical imaging used to characterize a variety of samples by a number of platforms. Specifically, we present cases of infrared and Raman spectroscopies combined with scanning probe microscopy; optical microscopy and mass spectrometry; nonlinear optical microscopy; and, finally, ion, electron, and probe microscopies with mass spectrometry. We also discuss the challenges associated with the use of data originated by the combinatorial hardware, analysis, and machine learning as well as processing tools necessary for the interpretation of multidimensional data acquired from multimodal studies.

Design of a Semi-Continuous Selective Layer Based on Deposition of UiO-66 Nanoparticles for Nanofiltration

Deposition of UiO-66 metal⁻organic framework nanoparticles onto a porous polymer support is a promising approach to designing highly-permeable, size-selective, flexible, and stable membranes for water filtration. In this article, a series of UiO-66 nanoparticles having different particle sizes were synthesized and employed to prepare UiO-66-deposited composite membranes. It was found that the size of the UiO-66 nanoparticles had great influences on the performance of the composite membranes for the filtration of a methylene blue aqueous solution. The deposition of smaller nanoparticles afforded a selective layer having a greater external surface area and narrower interparticle voids. These features made the deposition of smaller nanoparticles more advantageous in terms of the flux and rejection, while the deposition of greater nanoparticles afforded a selective layer more tolerant for fouling. Bimodal composite membranes were prepared by depositing mixed UiO-66 nanoparticles of smaller and bigger sizes. These membranes successfully combined the advantages of nanoparticles of a distinct size.