Activated Carbon, Carbon Nanotubes and Graphene: Materials and Composites for Advanced Water Purification

Cutting edge technology for wastewater treatment using smart nanomaterials: recent trends and futuristic advancements

Water is a vital component of our existence. Many human activities, such as improper waste disposal from households, industries, hospitals, and synthetic processes, are major contributors to the contamination of water streams. It is the responsibility of every individual to safeguard water resources and reduce pollution. Among the various available wastewater treatment (WWT) methods, smart nanomaterials stand out for their effectiveness in pollutant removal through absorption and adsorption. This paper examines the application of valuable smart nanomaterials in treating wastewater. Various nanomaterials, including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), nanoadsorbents, nanometals, nanofilters, nanocatalysts, carbon nanotubes (CNTs), nanosilver, nanotitanium dioxide, magnetic nanoparticles, nanozero-valent metallic nanoparticles, nanocomposites, nanofibers, and quantum dots, are identified as promising candidates for WWT. These smart nanomaterials efficiently eliminate toxic substances, microplastics, nanoplastics, and polythene particulates from wastewater. Additionally, the paper discusses comparative studies on the purification efficiency of nanoscience technology versus conventional methods.

Kinetics and Mechanism of Cyanobacteria Cell Removal Using Biowaste-Derived Activated Carbons with Assessment of Potential Human Health Impacts

Harmful cyanobacteria blooms and the escalating impact of cyanotoxins necessitates the effective removal of cyanobacteria from water ecosystems before they release cyanotoxins. In this study, cyanobacteria removal from water samples taken from the eutrophic Aleksandrovac Lake (southern Serbia) was investigated. For that purpose, novel activated carbons derived from waste biomass-date palm leaf stalk (P_AC), black alder cone-like flowers (A_AC), and commercial activated carbon from coconut shell (C_AC) as a reference were used. To define the best adsorption conditions and explain the adsorption mechanism, the influence of contact time, reaction volume, and adsorbent mass, as well as FTIR analysis of the adsorbents before and after cyanobacteria removal, were studied. The removal efficiency of P_AC and A_AC achieved for the applied concentration of 10 mg/mL after 15 min was ~99%, while for C_AC after 24 h was only ~92% for the same concentration. To check the safety of the applied materials for human health and the environment, the concentrations of potentially toxic elements (PTEs), the health impact (HI) after water purification, and the toxicity (MTT and Comet assay) of the materials were evaluated. Although the P_AC and A_AC achieved much better removal properties in comparison with the C_AC, considering the demonstrated genotoxicity and cytotoxicity of the P_AC and the higher HI value for the C_AC, only the A_AC was further investigated. Results of the kinetics, FTIR analysis, and examination of the A_AC mass influence on removal efficiency indicated dominance of the physisorption mechanism. Initially, the findings highlighted the superior performance of A_AC, with great potential to be globally commercialized as an effective cyanobacteria cell adsorbent.

An Evolutionary Review of Hemoperfusion Adsorbents: Materials, Preparation, Functionalization, and Outlook

Accumulation of pathogenic factors in the blood may cause irreversible damage and may even be life-threatening. Hemoperfusion is an effective technique for eliminating pathogenic factors, which is widely used in the treatment of various diseases including liver failure, renal failure, sepsis, and others. Hemoperfusion adsorbents are crucial in this process as they specifically bind and remove the target pathogenic factors. This review describes the development of hemoperfusion adsorbents, detailing the different properties exhibited by inorganic materials, organic polymers, and new materials. Advances in natural and synthetic polymers and novel materials manufacturing techniques have driven the expansion of hemoperfusion adsorbents in clinical applications. Stimuli-responsive (smart responsive) adsorbents with controllable molecular binding properties have many promising and environmentally friendly biomedical applications. Knowledge gaps, future research directions, and prospects for hemoperfusion adsorbents are discussed.

Advances in selenium from materials to applications

Over the past few decades, single-element semiconductors have received a great deal of attention due to their unique light-sensitive and heat-sensitive properties, which are of great application and research significance. As one promising material, selenium, being a typical semiconductor, has attracted significant attention from researchers due to its unique properties including high optical conductivity, anisotropic, thermal conductivity, and so on. To promote the application of selenium nanomaterials in various fields, numerous studies over the past few decades have successfully synthesized selenium nanomaterials in various morphologies using a wide range of physical and chemical methods. In this paper, we review and summarise the different methods of synthesis of various morphologies of selenium nanomaterials and discuss the applications of different nanostructures of selenium nanomaterials in optoelectronic devices, chemical sensors, and biomedical applications. Finally, we discuss possible challenges for selenium nanodevices and provide an outlook on the future applications of selenium nanomaterials.

A comprehensive review on monitoring and purification of water through tunable 2D nanomaterials

Instead of typical household trash, the heavy metal complexes, organic chemicals, and other poisons produced by huge enterprises threaten water systems across the world. In order to protect our drinking water from pollution, we must keep a close eye on the situation. Nanotechnology, specifically two-dimensional (2D) nanomaterials, is used in certain wastewater treatment systems. Graphene, g-C3N4, MoS2, and MXene are just a few examples of emerging 2D nanomaterials that exhibit an extraordinary ratio of surface (m3), providing material consumption, time consumption, and treatment technique for cleaning and observing water. In this post, we'll talk about the ways in which 2D nanomaterials may be tuned to perform certain functions, namely how they can be used for water management. The following is a quick overview of nanostructured materials and its possible use in water management: Also discussed in length are the applications of 2D nanomaterials in water purification, including pollutant adsorption, filtration, disinfection, and photocatalysis. Fluorescence sensors, colorimetric, electrochemical, and field-effect transistors are only some of the devices being studied for their potential use in monitoring water quality using 2D nanomaterials. Utilizing 2D content has its benefits and pitfalls when used to water management. New developments in this fast-expanding business will boost water treatment quality and accessibility in response to rising awareness of the need of clean, fresh water among future generations.

Green Synthesis of Advanced Carbon Materials Used as Precursors for Adsorbents Applied in Wastewater Treatment

Huge amounts of vegetable waste, mainly resulting from the food industry, need large areas for storage, as they could cause hazardous environmental impact, leading to soil and water pollution or to CO₂ emissions during accidental incineration. This work was aimed at recycling certain lignocellulosic waste (walnut shells, kernels of peach, apricot, and olive) to design advanced carbon material precursors (ACMP) to be used for obtaining nano-powders with high applicative potential in pollution abatement. Both waste and ACMP were characterized using proximate and elemental analysis, and by optical microscopy. Complex characterization of raw materials by FTIR, TGA-DTG, and SEM analysis were carried out. The ACMP were synthetized at 600-700 °C by innovative microwave heating technology which offers the advantages of lower energy consumption using 3.3 kW equipment at laboratory level. The ACMP ash < 3% and increased carbon content of 87% enabled the development of an extended pore network depending on degassing conditions during heating. TEM analysis revealed a well-developed porous structure of the synthesized ACMP carbonaceous materials. Due to the presence of oxygen functional groups, ACMPs exhibit adsorption properties highlighted by an iodine index of max. 500 mg/g and surface area BET of 300 m²/g, which make them attractive for removal of environmental pollutants such as dyes having molecule sizes below 2 nm and ions with pore dimensions below 1 nm, widely used industrially and found in underground waters (NO₃^-) or waste waters (SO₄^2-).

Graphene Oxide (GO) Materials-Applications and Toxicity on Living Organisms and Environment

Graphene-based materials have attracted much attention due to their fascinating properties such as hydrophilicity, high dispersion in aqueous media, robust size, high biocompatibility, and surface functionalization ability due to the presence of functional groups and interactions with biomolecules such as proteins and nucleic acid. Modified methods were developed for safe, direct, inexpensive, and eco-friendly synthesis. However, toxicity to the environment and animal health has been reported, raising concerns about their utilization. This review focuses primarily on the synthesis methods of graphene-based materials already developed and the unique properties that make them so interesting for different applications. Different applications are presented and discussed with particular emphasis on biological fields. Furthermore, antimicrobial potential and the factors that affect this activity are reviewed. Finally, questions related to toxicity to the environment and living organisms are revised by highlighting factors that may interfere with it.

Ibuprofen Removal by Graphene Oxide and Reduced Graphene Oxide Coated Polysulfone Nanofiltration Membranes

The presence of pharmaceutical products, and their metabolites, in wastewater has become a focus of growing environmental concern. Among these pharmaceutical products, ibuprofen (IBU) is one of the most consumed non-steroidal anti-inflammatory drugs and it can enter the environment though both human and animal consumption, because it is not entirely absorbed by the body, and the pharmaceutical industry wastewater. Nanofiltration has been described as an attractive process for the treatment of wastewater containing pharmaceutical products. In this paper, the modification of a polysulfone nanofiltration membrane by coating with graphene oxide (GO) and reduced graphene oxide (RGO) has been carried out. The morphology and elemental composition of the active layer of unmodified and modified membranes were analyzed by scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. Initial characterization membranes was carried out, studying their water permeability coefficient and their permeate flux and rejection coefficients, at different applied pressures, using magnesium chloride solutions. The behavior of both pristine and coated membranes against ibuprofen solutions were analyzed by studying the permeate fluxes and the rejection coefficients at different pressures and at different contaminant concentrations. The results have shown that both GO and RGO coated membranes lead to higher values of ibuprofene rejection than that of uncoated membrane, the latter being the one that presents better results in the studies of permeability, selectivity, and fouling.

Activated Carbon and Coconut Coir with the Incorporation of ABR System as Greywater Filter: The Implications for Wastewater Treatment

Greywater refers to wastewater generated from domestic activities, which do not contain fecal contamination. Therefore, this study aims to treat greywater in Makassar city to speed up the water cycle and enable reuse, as an environmental conservation strategy. The water parameters measured were pH, Turbidity, Total Suspended Solid (TSS), Biological Oxygen Demand (BOD), and Chemical Oxygen Demand (COD). According to the results, the greywater’s BOD, COD, and TTS contents were 49.98 to 54.88 mg/L, 509 to 655 mg/L, and 404.40 to 464.65 mg/L, respectively, all of which exceed WHO wastewater quality standards. The use of a wastewater treatment installation comprising a combination of Activated Carbon (AC) and Coconut Coir (CC) with the incorporation of the Anaerobic Baffle Reactor (ABR) system as a greywater filter successfully reduced the city’s greywater pollution. In addition, the new BOD content fulfills the environmentally safe wastewater standards, while the new COD and TSS contents were 152 mg/L to 184 mg/L and 59.68 mg/L to 77.42 mg/L, respectively, which are close to the WHO domestic wastewater quality standards.

Metal(loid) nanosorbents in restoration of polluted soils: geochemical, ecotoxicological, and remediation perspectives

Nowadays, the applications of nanomaterials (NMs) are becoming the edge over others and referred as one of the pillars of emerging science and technology. Thereby, a wide array of NMs have been developed along with the products that can be used for the reclamation of contaminated terrestrial ecosystems. The NMs got a great consideration due to their peculiar characteristics and high efficacy. Therefore, this review addresses in depth the ability of metal(loid) NMs as nanosorbents along with their applications in soil remediation. Adsorption is commonly employed for the elimination of innumerable contaminants because of low expenses, reliability, and convenience. The first emphasis of this work will be the use of nanoscale meta(loid) adsorbents for contaminated soil remediation along with their geochemistry. Because NMs mediated soil remediation promises more efficient and cost-effective than conventional methods and can enhance the probability of in situ contaminants remediation. However, the extensive usage of NMs is enhancing their concentrations in the environment and get a route to enter the surrounding flora and fauna that can induce serious concerns due to the lack of absolute understanding regarding NMs interactions with living organisms. Therefore, the second focus of this work will be on the ecotoxicological impacts with special attentions on morpho-physiological alterations in edible plants.

Anaerobic bacterial responses to carbonaceous materials and implications for contaminant transformation: Cellular, metabolic, and community level findings

Carbonaceous materials (CM) enhance the abundance and activity of bacteria capable of persistent organic (micro)pollutant (POP) degradation. This review synthesizes anaerobic bacterial responses to minimally modified CM in non-fuel cell bioremediation applications at three stages: attachment, metabolism, and biofilm genetic composition. Established relationships between biological behavior and CM surface properties are identified, but temporal relationships are not well understood, making it difficult to connect substratum properties and "pioneer" bacteria with mature microorganism-CM systems. Stark differences in laboratory methodology at each temporal stage results in observational, but not causative, linkages as system complexity increases. This review is the first to critically examine relationships between material and cellular properties with respect to time. The work highlights critical knowledge gaps that must be addressed to accurately predict microorganism-CM behavior and to tailor CM properties for optimized microbial activity, critical frontiers in establishing this approach as an effective bioremediation strategy.

Fabrication and characterization of a water purification system using activated carbon and graphene nanoplatelets: Toward the development of a nanofiltration matrix

Researchers are trying to tackle water scarcity in numerous ways. One of those ways is the use of nanotechnology in water processing and purification. The current work involves the fabrication and optimization of activated carbon and graphene-based hybrid water purification system. Five different concentrations of methylene blue and deionized water (DI) dye solutions were used, and they were filtered in three different cycles. For the potential usage on the consumer side, a small-scale, low-cost water filter is developed using activated carbon, commercial filter paper, and graphene nanoplatelets. The filter paper is used to hold mixtures of the activated carbon and graphene nanoplatelets within the water filter. The conductivity, TDS, and pH are measured for the feed water and the processed water using an Oakton EcoTestr and Apera Instruments PH60 Premium Pocket pH meter, respectively. A UV-Vis spectrometer is used to measure the absorption of solutions. The distribution and adsorption of the dye particles were observed by scanning electron microscopy. PRACTITIONER POINTS: These results show the effectiveness of the system in the removal of dye particles above a given particle size. The concentration of the dye solution decreased after every cycle. The GnPs filtration system more effectively dye particles as compared to the filtration system containing only Activated carbon. UV-Vis spectroscopy results showed that the methylene blue dye particles decreased after every cycle. This research can open a broad area of projects toward waste/wastewater practice for particles above a certain particle size.

Water Purification of Classical and Emerging Organic Pollutants: An Extensive Review

The main techniques used for organic pollutant removal from water are adsorption, reductive and oxidative processes, phytoremediation, bioremediation, separation by membranes and liquid–liquid extraction. In this review, strengths and weaknesses of the different purification techniques are discussed, with particular attention to the newest results published in the scientific literature. This study highlighted that adsorption is the most frequently used method for water purification, since it can balance high organic pollutants removal efficiency, it has the possibility to treat a large quantity of water in semi-continuous way and has acceptable costs.

Preparation and Performance of PAN-PAC Nanofibers by Electrospinning Process to Remove NOM from Water

The technology based on electrospun membranes exhibits great potential in water treatment. This study presents experimental data involving the fabrication of nanofiber membranes with powdered activated carbon (PAC) and its application for the removal of natural organic matter. The fabricated membrane materials were characterized using various techniques. These include scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction analysis. The incorporation of PAC nanoparticles influences the structure and physicochemical properties as well as the transport and separation characteristics of the produced membranes. The applicability of the fabricated carbon-based membrane was tested in the filtration experiments. The fabricated membrane is characterized by a high NOM removal efficiency of 79% in the filtration process. Further modification of the membrane composition may result in a further increase in the efficiency of removing contaminants from water.

A comprehensive review on magnetic carbon nanotubes and carbon nanotube-based buckypaper for removal of heavy metals and dyes

Industrial effluents contain several organic and inorganic contaminants. Among others, dyes and heavy metals introduce a serious threat to drinking waterbodies. These pollutants can be noxious or carcinogenic in nature, and harmful to humans and different aquatic species. Therefore, it is of high importance to remove heavy metals and dyes to reduce their environmental toxicity. This has led to an extensive research for the development of novel materials and techniques for the removal of heavy metals and dyes. One route to the removal of these pollutants is the utilization of magnetic carbon nanotubes (CNT) as adsorbents. Magnetic carbon nanotubes hold remarkable properties such as surface-volume ratio, higher surface area, convenient separation methods, etc. The suitable characteristics of magnetic carbon nanotubes have led them to an extensive search for their utilization in water purification. Along with magnetic carbon nanotubes, the buckypaper (BP) membranes are also favorable due to their unique strength, high porosity, and adsorption capability. However, BP membranes are mostly used for salt removal from the aqueous phase and limited literature shows their applications for removal of heavy metals and dyes. This study focuses on the existence of heavy metal ions and dyes in the aquatic environment, and methods for their removal. Various fabrication approaches for the development of magnetic-CNTs and CNT-based BP membranes are also discussed. With the remarkable separation performance and ultra-high-water flux, magnetic-CNTs, and CNT-based BP membranes have a great potential to be the leading technologies for water treatment in future.

DFT computational study of trihalogenated aniline derivative's adsorption onto graphene/fullerene/fullerene-like nanocages, X12Y12 (X = Al, B, and Y = N, P)

Adsorption of 2,4,6-tribromoaniline (BA), 2,4,6-trifluoroaniline (FA) and 2,4,6-trichloroaniline (CA) onto the surface of coronene/fullerene/fullerene-like nanocages was investigated by theoretical calculations. Due to the adsorption of BA/FA/CA, there are significant changes in chemical descriptors and nonlinear optical properties. Energy gap values of all nanoclusters are lowered, giving an increase in conductivity of complexes except for fullerene. All complex's ultraviolet visible wavenumber is blue-shifted and especially for fullerene complex, the values are very high. The enhancement of Raman intensities shows that it is possible to design a nanocage sensor for detecting these compounds by surface-enhanced Raman scattering (SERS).Communicated by Ramaswamy H. Sarma.

DFT computational study towards investigating psychotropic drugs, promazine and trifluoperazine adsorption on graphene, fullerene and carbon cyclic ring nanoclusters

Detection and qualification process related to impurities assume importance in pharmacological drug development programmes and the present article gives the structural and spectral characterisation of phenothiazine derivatives, promazine (PME) and trifluoperazine (TPE) and their self-assembly with graphene/fullerene/carbon ring (CG/CF/CR) systems theoretically. The investigation of adsorption behaviour of these compounds can provide valuable information about its reactivity, electronic and structural properties. Three-dimensional electrostatic potential diagrams were mapped. The frontier orbital energies and energy band gaps of the molecules were computed. Delocalization of charge density between the bonding or lone pair and antibonding orbitals is calculated by NBO analysis. Docking was executed to investigate binding areas of chemical compounds. Bioactivity scores show that the pharmacokinetic and pharmacological properties of the ligands are appropriate leading to be considered potential drug agents. The obtained theoretical wavenumber results of the present study were fully compatible with the experimental results.

Carbon Nanoparticles as Sources for a Cost-Effective Water Purification Method: A Comprehensive Review

As the global population grows, the demand for cost-effective and eco-friendly water purification methods is increasing, which presently is at its peak due to the increase of impurities in water and the increasing awareness of waterborne disease. Carbon-based materials, which includes activated carbon, carbon nanotubes (CNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), fullerene, and carbon dots, are observed as potential candidates for water treatment. In the present review, developments related to water purification methods using carbon nanomaterials over the last decade are critically summarized, with an emphasis on their thermophysical properties. The fabrication techniques for activated carbon, CNTs, graphene, and graphene oxide are presented, with an emphasis on the properties of carbon materials that allow their usage for water purification. Then, an extensive review of 71 patents dedicated to water purification using carbon materials such as activated carbon and cotton fibers is performed. Subsequently, the more important research studies on water purification using carbon nanomaterials are discussed, showing that CNTs, GO, and rGO are widely used in water treatment processes. The present review critically discusses the recent developments and provides important information on water purification using carbon materials.

Research on the Development of Technologies for the Production of Granulated Activated Carbons Using Various Binders

Activated carbons (ACs) are processed carbon-rich materials with a highly developed inner surface and significant porosity used for different media treatment in municipal and industrial plants. Activated carbon may be manufactured as powdered activated carbon (PAC), gritty activated carbon (in a form of raw angels grains) or granulated activated carbon (GAC). The production of the GAC is based on carbonaceous raw materials and various types of binders. The carbon mass is mixed with the binder and formed in cylindrical granules. The binder’s recognition is in a scientific literature side-topic and still needs wider examination. For many years GAC production have been concentrated on the possibility of using sodium carboxymethylcellulose (SCMC). Therefore, the aim of the research was to develop a new binder, in the available technology of granulated activated carbon production. Such binders were tested such as: tall oil (TO), sugar beet molasses (SBM), sodium carboxymethylcellulose (SCMC), SCMC using a verified technological process and SCMC with the addition of gas tar (GT). The conducted research shows that all the quality requirements were met by activated carbons with SBM as a binder. Additionally they showed very high adsorption properties. The manufacturing process was shorter in comparison to other tested binders and more efficient.

Recent Advancements in the Removal of Cyanotoxins from Water Using Conventional and Modified Adsorbents—A Contemporary Review

The prevalence of cyanobacteria is increasing in freshwaters due to climate change, eutrophication, and their ability to adapt and thrive in changing environmental conditions. In response to various environmental pressures, they produce toxins known as cyanotoxins, which impair water quality significantly. Prolonged human exposure to cyanotoxins, such as microcystins, cylindrospermopsin, saxitoxins, and anatoxin through drinking water can cause severe health effects. Conventional water treatment processes are not effective in removing these cyanotoxins in water and advanced water treatment processes are often used instead. Among the advanced water treatment methods, adsorption is advantageous compared to other methods because of its affordability and design simplicity for cyanotoxins removal. This article provides a current review of recent developments in cyanotoxin removal using both conventional and modified adsorbents. Given the different cyanotoxins removal capacities and cost of conventional and modified adsorbents, a future outlook, as well as suggestions are provided to achieve optimal cyanotoxin removal through adsorption.

Green preparation of activated carbon from pomegranate peel coated with zero-valent iron nanoparticles (nZVI) and isotherm and kinetic studies of amoxicillin removal in water

In present research, the activated carbon was prepared by a green approach from pomegranate peel coated with zero-valent iron nanoparticles (AC-nZVI) and developed as adsorbent for the removal of amoxicillin from aqueous solution. The physicochemical properties of the AC-nZVI were investigated using XRD, FTIR, and FESEM techniques. The optimal values of the parameters for the best efficiency (97.9%) were amoxicillin concentration of 10 mg/L, adsorbent dose of 1.5 g/L, time of 30 min, and pH of 5, respectively. The adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (qmax 40.282 mg/g, R² 0. 0.999) and pseudo-first order kinetics (R² 0.961). The reusability of the adsorbent also revealed that the adsorption efficiency decreased from 83.54 to 50.79% after five consecutive repetitions. Overall, taking into account the excellent efficiency, availability, environmental friendliness, and good regeneration, AC-nZVI can be introduced as a promising absorbent for amoxicillin from aquatic environments.

Conformational analysis and quantum descriptors of two new imidazole derivatives by experimental, DFT, AIM, molecular docking studies and adsorption activity on graphene

1-[2-(2-hydroxy-3-methoxy-5-(4-methoxyphenylazo)benzaldeneamino)ethyl]-3-methyl-3H-imidazole (HMY) and 1-[2-(2-hydroxy-3-methoxy-5-(4-methylphenylazo)benzaldene amino)ethyl]-3-methyl-3H-imidazole (HMM) were synthesized and characterized using spectral analysis. Conformational analysis has been achieved using potential energy scan for different rotable bonds for obtaining the lowest energy conformer. Conformer with minimum energy is obtained along the dihedral angle N30-C31-C34-N37. QTAIM analysis gives nature and strength of hydrogen bonding interactions. UV-Vis, electrostatic potential and chemical descriptors are analyzed. Interaction of HMY and HMM with graphene is analyzed in terms of SERS activity. Chemical reactivity descriptors were investigated for graphene-drug systems. NLO activity of parent drugs and its graphene complexes show good activity. The wavenumber downshift of different modes is noted. Title molecules exhibit inhibitory activity against cytochrome C peroxidase. Interactions with graphene sheets are theoretically predicted for the title compounds.

Carbon Nanotubes (CNTs): A Potential Nanomaterial for Water Purification

Nanomaterials such as carbon nanotubes (CNTs) have been used as an excellent material for catalysis, separation, adsorption and disinfection processes. CNTs have grabbed the attention of the scientific community and they have the potential to adsorb most of the organic compounds from water. Unlike, reverse osmosis (RO), nanofiltration (NF) and ultrafiltration (UF) membranes aligned CNT membranes can act as high-flow desalination membranes. CNTs provide a relatively safer electrode solution for biosensors. The article is of the utmost importance for the scientists and technologists working in water purification technologies to eliminate the water crisis in the future. This review summarizes about the application of CNTs in water purification.

Self-Assembled Graphene Composites for Flow-Through Filtration

Spontaneously exfoliated pristine graphene is used as a surfactant to template the formation of electrically conductive filters for the adsorption of an organic dye from water. In contrast to other reported graphene-based adsorption materials, our system provides a continuous approach to water treatment rather than a batch approach, and uses pristine graphene instead of the more costly and environmentally challenging graphene oxide. The use of self-assembled graphene also results in our filters being electrically conductive, providing a convenient route to clean the filters by resistive heating. An investigation of the mechanism of formation and filtration by these filters, templated by self-assembled two-dimensional pristine graphene, is presented. The thermodynamically driven exfoliation of natural flake graphite at a high-energy monomer/water interface produces water-in-oil emulsions stabilized by a thin layer of overlapping graphene sheets. Subsequent polymerization of the continuous monomer phase produces polymer foams with cells lined by graphene. With a combination of acoustic spectroscopy and electron microscopy, the effects of graphite concentration and temperature are studied, as is the correlation between droplet size and the size of the cells in the final polymer foam.

Removal of bacterial growth inhibition of anticancer drugs by using complexation materials

In the context of batch production of cytotoxic drugs in hospital pharmacies with the need of sterility testing, the objective was to validate the use of Rapid Microbiological Method (RMM), and to develop adequate neutralization method in case of inhibition of bacterial growth. The potential microbiological growth inhibitory effect of three anticancer drugs (5 fluorouracil, irinotecan and oxaliplatin) selected for batch production was assessed on BacT/ALERT® system. Among cytotoxic drugs, only 5FU exhibited inhibitory effect on microbiological growth using rapid microbiological method. To counteract this effect our purpose was to use neutralizing agents complexing the drug i. e. activated carbon or ion exchange resins. The microbiological bactericidal concentration of 5FU was very low (1.10–4 mg/mL) indicating the absolute need to neutralize the whole drug before sterility test. The complexation was validated by High Performance Liquid Chromatography control of the residual 5FU concentration in solution after the use of neutralizing agents. Only activated carbon was able to fully capture 5FU when previously diluted at 5 mg/mL. Conversely, the resins, in the condition of the study, were not able to fully capture 5FU whatever the dilution. The microbiological growth on BacT/ALERT® system after active carbon treatment was successfully confirmed with Staphylococcus aureus. Based on this validation results a method was then developed to routinely be able to perform sterility test of the batches produced and was confirmed on five microbiological species (i. e. S. aureus, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans, Aspergillus brasiliensis). Our work gives a new insight for considering sterility testing by rapid microbiological method even for drugs exhibiting inhibitory effect on microbiological growth.

Recent Advances in Applications of Hybrid Graphene Materials for Metals Removal from Wastewater

The presence of traces of heavy metals in wastewater causes adverse health effects on humans and the ecosystem. Adsorption is a low cost and eco-friendly method for the removal of low concentrations of heavy metals from wastewater streams. Over the past several years, graphene-based materials have been researched as exceptional adsorbents. In this review, the applications of graphene oxide (GO), reduce graphene oxide (rGO), and graphene-based nanocomposites (GNCs) for the removal of various metals are analyzed. Firstly, the common synthesis routes for GO, rGO, and GNCs are discussed. Secondly, the available literature on the adsorption of heavy metals including arsenic, lead, cadmium, nickel, mercury, chromium and copper using graphene-based materials are reviewed and analyzed. The adsorption isotherms, kinetics, capacity, and removal efficiency for each metal on different graphene materials, as well as the effects of the synthesis method and the adsorption process conditions on the recyclability of the graphene materials, are discussed. Finally, future perspectives and trends in the field are also highlighted.

Removal and Recovery of Methyl Tertiary Butyl Ether (MTBE) from Water Using Carbon Nanotube and Graphene Oxide Immobilized Membranes

Methyl tert-butyl ether (MTBE) is a widely used gasoline additive that has high water solubility, and is difficult to separate from contaminated ground and surface waters. We present the development in functionalized carbon nanotube-immobilized membranes (CNIM-f) and graphene oxide-immobilized membranes (GOIM) for enhanced separation of MTBE via sweep gas membrane distillation (SGMD). Both types of modified membranes demonstrated high performance in MTBE removal from its aqueous mixture. Among the membranes studied, CNIM-f provided the best performance in terms of flux, removal efficiency, mass transfer coefficients and overall selectivity. The immobilization f-CNTs and GO altered the surface characteristics of the membrane and enhanced partition coefficients, and thus assisted MTBE transport across the membrane. The MTBE flux reached as high as 1.4 kg/m² h with f-CNTs, which was 22% higher than that of the unmodified PTFE membrane. The maximum MTBE removal using CNIM-f reached 56% at 0.5 wt % of the MTBE in water, and at a temperature of 30 °C. With selectivity as high as 60, MTBE recovery from contaminated water is very viable using these nanocarbon-immobilized membranes.

A monitorable and renewable pollution filter based on graphene nanoplatelets

This paper deals with the fabrication, modeling and experimental characterization of a monitorable and renewable graphene-based pollution filter. The main goal is to demonstrate a method to monitor the status of such a filter in real time during its operating phases: pollutant adsorption, saturation, and regeneration. The filter is realized by a disk of pressed graphene nanoplatelets. This is a low-cost type of graphene which has recently drawn great interest due to its potential use in large scale industrial production. Here the nanomaterial is obtained through the exfoliation method assisted by microwave irradiation, by exploiting the thermal expansion of commercial intercalated graphite, according to a low-cost and ecologically friendly procedure. The filter is used here to adsorb acetonitrile, a toxic water-soluble organic compound that is present in some industrial solvents and paints. The monitoring method is based on the interpretation of the time variation of the electrical impedance measured during filter operation. There are two main results of the paper: Firstly, the graphene filter is shown to be effective in adsorbing the above pollutant, with the additional feature of being fully renewable: all the pollutant can be removed from the filter without the need of costly physical or chemical processes. Secondly, monitoring of the time-evolution of the electrical impedance allows efficient detection of the different phases of the filter life cycle: clean, polluted, saturated and regenerated. This feature is of potential interest since it enables the predictive maintenance of such filters.

Antibiotic Resistance Genes in drinking water of China: Occurrence, distribution and influencing factors

Drinking water samples were collected from 71 cities, including 28 provincial capital cities or municipalities, 20 prefecture cities and 23 counties, of 31 provincial-level administrative regions in China from July to August in 2017. Futhermore, 24 Antibiotic Resistance Genes (ARGs), 16S rRNA and 2 integrase genes were quantified by qPCR to investigate the pollution degree of ARGs. The results revealed that the 16S ranged from 10⁵ - 10⁸ copies/100 mL in the drinking water, and its treatment process could effectively remove bacteria. Moreover, sulfonamides-ARGs were the most prevalent ARGs in the drinking water of China, and the abundance of bla_TEM ranked top five in all cities among the selected ARGs, indicating that the pollution condition of the genes should be aroused more attention. The data of qPCR and correlation analyses indicated that intI1 played a more crucial role than intI2 in the propagation of ARGs in the drinking water. Additionally, the pollution degree of ARGs among different city types showed no significant difference.

Synthesis, Characterization, and Evaluation of Evaporated Casting MWCNT/Chitosan Composite Membranes for Water Desalination

Fresh water scarcity and pollution turn out to be a most serious issue throughout the world due to the rapid population growth. The application of nanomaterials (NMs) for the removal of pollutants from water has attracted significant attention. The nanofiltration membrane was fabricated through the evaporative casting (EC) method using multiwalled carbon nanotubes (MWCNT) and chitosan (CHIT) as the surfactant to enable water purification. The developed EC membrane properties were characterized in mechanical, surface charging (zeta potential), surface morphology, and hydrophobicity properties. Results demonstrated that incorporation of MWCNT and the biopolymers (chitosan) resulted in suitable developments in mechanical properties of the membrane. For example, the membrane has shown values for tensile strength (28 ± 1 MPa), elongation (10.2 ± 1.2%), Young’s modulus (1.2 ± 0.1 GPa), and toughness of (1.9 ± 0.2 J/g). When more significant changes were investigated on the surface morphology of the EC membrane, it was observed that the pores on the surface morphology of the EC membrane decreased as the evaporative casting method was used. Moreover, the permeability of the membrane towards water, inorganic salts, and pH effect on salt rejections was studied using the NF/RO system. These established nanocomposite membranes signify the promising candidates for fresh water desalination and elimination of organic impurities.

Sampling and analyses of surfaces contaminated with chemical warfare agents by using a newly developed triple layered composite wipe

A three-layered composite wipe was fabricated by laminating individual layers of non-woven polypropylene, activated carbon fabric (ACF) and aramid fabric for the sampling and investigation of chemical warfare agents (CWA)-contaminated urban porous and non-porous surfaces. The material of main ACF layer was characterized to ascertain its suitability to act as an efficient adsorbent for the surface wipe sampling. The performance of ACF-based composite wipe was determined by evaluating its extraction efficiency, wiping efficacy and adsorption capacity for the sampling of blister and nerve agent class of CWA-contaminated surfaces using gas chromatography-mass spectrometry (GC-MS). Parameters like amount of wipe required, solvent selection, amount of solvent, time of extraction etc. were optimized to achieve the maximum recovery of contaminating analytes required for the forensic investigations. Overall recoveries of contaminating analytes after sampling and extraction were found to be in the range of 45-85% for all types of surfaces. No breakthrough in wiping process was noticed up to contamination density (CD) 1.6 mg/cm² for non-porous surface and 3.2 mg/cm² for porous surfaces. ACF-based wipe was found capable to significantly reduce the vapour hazards from liquid sulphur mustard (HD) and sarin (GB). Contamination from surfaces could be preserved within the wipe up to 15 days for the extended forensic investigation purposes. Limit of detections (LOD) of contaminants was determined in the range of 0.8-6.8 ng/cm² while limit of quantitation (LOQ) was achieved up to the range of 2.4-14.4 ng/cm² for wipe sampling of different surfaces. Graphical abstract.

Anaerobic digestion of blackwater assisted by granular activated carbon: From digestion inhibition to methanogenesis enhancement

This study investigated the effect of granular activated carbon (GAC) on the digestion of blackwater collected from different collection systems, by monitoring the biochemical methane production (BMP), adsorption of molecules to GAC and their impacts on the microbial community. Without GAC-amendment, BMP reached 35.6, 42.6 and 50.4% in 1L, 5L and 9L water-flushed blackwater, respectively. When 33.3 gL^-1 GAC was added to the cultures, methane potential increased up to 53.1% in 1L water-flushed blackwater, while in 5L and 9L water-flushed conditions the BMP drastically decreased to 16.1 and 9.6%, respectively. The concentration of volatile fatty acids (VFA) in 5L and 9L water-flushed blackwater with GAC-amended cultures was not enhanced, in contrast with 1L water-flushed blackwater. Further tests showed 29.8% (±1.9%) of VFA and 86.0% of soluble chemical oxygen demand were removed by GAC adsorption in 9L water-flushed blackwater. A decrease in biomass density in 5L and 9L GAC-amended cultures was also observed, corroborated by a significant decrease in gene copy numbers of methanogenic archaeal communities. This study gives an insight on the effect of GAC on different strengths of blackwater, which is of relevance for further tests of long-time and full-scale application.

Antifouling Properties of Silver-Zinc Oxide Polyamide Thin Film Composite Membrane and Rejection of 2-Chlorophenol and 2,4-Dichlorophenol

The silver-zinc oxide (Ag-ZnO) polyamide thin film composite (PA-TFC) membrane was prepared by interfacial polymerization. The Ag-ZnO/PA-TFC membrane was characterized by attenuated total reflectance fourier-transform infrared spectroscopy (ATR-FTIR) for polyamide functional groups and contact angle for surface hydrophilicity. The Ag-ZnO/PA-TFC membrane was further characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for morphology and surface roughness, respectively. The performance of the fabricated membrane was investigated using pure water flux, permeability, rejection, flux recovery, and fouling resistance using low molecular weight organic pollutants, 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The results were compared to the neat (PA-TFC) membrane. It was observed that incorporation of Ag-ZnO nanocomposites into the PA-TFC membrane improved hydrophilicity, permeation, rejection, and fouling resistance properties of the membrane. The contact angle decreased from 62.8° to 54° for PA-TFC and the Ag-ZnO/PA-TFC membrane, respectively. The presence of Ag-ZnO enhanced permeability of the membrane from 0.9 (Lm-2h-1bar-1) to 1.9 (Lm-2h-1bar-1). Modification of the membrane with Ag-ZnO further showed an enhanced rejection of 2-CP and 2,4-DCP from 43% to 80% and 58% to 85%, respectively. The 2,4-DCP molecules were rejected more than 2-CP due to enhanced repulsive forces from the extra Cl ion. A high flux recovery of about 95% was achieved for the modified membrane compared to 64% for the neat membrane. The improved flux recovery was an indication of enhanced antifouling propensity.

Graphene Composites for Lead Ions Removal from Aqueous Solutions

The indiscriminate disposal of non-biodegradable, heavy metal ionic pollutants from various sources, such as refineries, pulp industries, lead batteries, dyes, and other industrial effluents, into the aquatic environment is highly dangerous to the human health as well as to the environment. Among other heavy metals, lead (Pb(II)) ions are some of the most toxic pollutants generated from both anthropogenic and natural sources in very large amounts. Adsorption is the simplest, efficient and economic water decontamination technology. Hence, nanoadsorbents are a major focus of current research for the effective and selective removal of Pb(II) metal ions from aqueous solution. Nanoadsorbents based on graphene and its derivatives play a major role in the effective removal of toxic Pb(II) metal ions. This paper summarizes the applicability of graphene and functionalized graphene-based composite materials as Pb(II) ions adsorbent from aqueous solutions. In addition, the synthetic routes, adsorption process, conditions, as well as kinetic studies have been reviewed.

Towards the Extraction of Radioactive Cesium-137 from Water via Graphene/CNT and Nanostructured Prussian Blue Hybrid Nanocomposites: A Review

Cesium is a radioactive fission product generated in nuclear power plants and is disposed of as liquid waste. The recent catastrophe at the Fukushima Daiichi nuclear plant in Japan has increased the 137Cs and 134Cs concentrations in air, soil and water to lethal levels. 137Cs has a half-life of 30.4 years, while the half-life of 134Cs is around two years, therefore the formers' detrimental effects linger for a longer period. In addition, cesium is easily transported through water bodies making water contamination an urgent issue to address. Presently, efficient water remediation methods towards the extraction of 137Cs are being studied. Prussian blue (PB) and its analogs have shown very high efficiencies in the capture of 137Cs+ ions. In addition, combining them with magnetic nanoparticles such as Fe3O4 allows their recovery via magnetic extraction once exhausted. Graphene and carbon nanotubes (CNT) are the new generation carbon allotropes that possess high specific surface areas. Moreover, the possibility to functionalize them with organic or inorganic materials opens new avenues in water treatment. The combination of PB-CNT/Graphene has shown enhanced 137Cs+ extraction and their possible applications as membranes can be envisaged. This review will survey these nanocomposites, their efficiency in 137Cs+ extraction, their possible toxicity, and prospects in large-scale water remediation and succinctly survey other new developments in 137Cs+ extraction.