Cross-Linked Carbon Nanotube Adsorbents for Water Treatment: Tuning the Sorption Capacity through Chemical Functionalization (original) (raw)
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Heliyon, 2021
This study investigated the removal of Total Organic Carbon (TOC) from produced water by batch adsorption process using adsorbents developed from Multi-Walled Carbon Nanotubes (MWCNTs). The MWCNTs, synthesized by catalytic chemical vapour deposition method using kaolin-supported tri-metallic (iron-cobalt-nickel) catalyst were purified by H 2 SO 4 /HNO 3 and then functionalized with 1-pyrenebutanoic acid N-hydroxyl succinimidyl ester (PSE). The raw, purified and functionalized MWCNTs were characterized by High Resolution Scanning Electron Microscopy (HRSEM), High Resolution Transmission Electron Microscopy (HRTEM), Brunauer-Emmett-Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR). In the results, HRSEM/HRTEM revealed the structure, purity and also confirmed the attachment of the PSE molecule onto the nano-adsorbent(s). The BET surface areas of MWCNTs, PMWCNTs and FMWCNTs were 970.17, 869.25 and 831.80 m 2 /g, respectively while the FTIR established the existence of surface functional groups. The functionalized MWCNTs (FMWCNTs) nano-adsorbent showed superior performance efficiency (93.6%) than the purified MWCNTs (PMWCNTs) (79.2%) as examined under the same batch adsorption condition: 0.02 g adsorbent dosage, 10-90 min contact time and 30 C solution temperature probably, due the improved wettability resulted from incorporation of PSE. Subsequently, Central Composite Design (CCD) was applied to optimize the process parameters for the sorption of TOC onto FMWCNTs. The CCD in the response surface methodology predicted 260 mg/g adsorption capacity of FMWCNTs in the removal of TOC at the optimum condition of 49.70 min contact time, 34.81 C solution temperature, and 0.02 g adsorbent dosage. The kinetics data were best described by pseudo-second-order model and thermodynamic parameters suggested that the process was feasible, spontaneous and exothermic. It can be inferred from the various analysis conducted that the developed FMWCNTs nano-adsorbent is effective for removal of TOC from oilproduced water and may be explored for removal of organic contaminants from other industrial wastewater.
Recent advances in carbon nanomaterial-based adsorbents for water purification
Coordination Chemistry Reviews, 2020
Deterioration of water quality and the unavailability of drinkable water are pressing challenges worldwide. Removal of toxic organic and inorganic pollutants from water is indispensable for a clean environment, as a response to water scarcity, and for human society. Adsorption-based water technologies are among the most favoured and widely used because of their high efficiency at low-cost, without relying on complicated infrastructure. In recent years, carbon nanomaterials (CNMs), such as graphene and derivatives, carbon nanotubes, carbon nanofibers, nanoporous carbon, fullerenes, graphitic carbon nitride, and nanodiamonds have been extensively exploited as adsorbents due to their extraordinary surface properties, easy modification, large specific surface area, controlled structural varieties, high chemical stability, porosity, low density, ease of regeneration, and reusability. Graphene oxides and other oxidised carbons provide strong acidity and abundant functional groups, and demonstrate excellent adsorption of cationic and basic compounds via electrostatic and hydrogen bonding interactions, while their pristine counterparts exhibit hydrophobic surfaces and offer high adsorption via strong p-p interactions. This review provides a thorough overview of state of the art in CNMs, including significant past and recent advances, as well as future strategies for the use of carbon-based nanoadsorbents in water treatment. This review primarily emphasises the fundamentals of adsorption, its mechanistic aspects, synthesis and properties of CNMs, and adsorption performances of CNMs and their nanocomposites with inorganic and organics materials. Structural engineering and activation processes produce materials with enhanced adsorptive properties and separation efficiencies. Furthermore, the formation of CNMs with 2D and 3D macro-/micro-structures with high porosities is a potential approach to improve adsorption performances and extend CNMs use at the industrial level. This review also addresses some vital issues that persist about these adsorbents, which could shape the future research and industrial application of carbon-based nanoadsorbents in water security.
Modifying the sorption properties of multi-walled carbon nanotubes via covalent functionalization
Analyst, 2009
We demonstrate that the functionalization of carbon nanotubes dramatically alters their sorption characteristics. The effect of covalent functionalization of multiwalled carbon nanotubes (MWNTs) on the gas phase adsorption and desorption of polar and nonpolar organics is presented. Carboxylation and nitration led to the generation of polar functional groups on the nanotube surface. The derivatized nanotubes showed strong adsorption of polar analytes such as alcohols and relatively weaker adsorption for nonpolar and aromatic compounds. The breakthrough volume of ethanol increased by 300%, where as that of hexane decreased by 75% after functionalization. The functionalized MWNT also showed rapid desorption of the polar as well as nonpolar compounds.
Application of Carbon Nanotubes and Graphene-Based Nanoadsorbents in Water Treatment
BioNanoScience, 2023
In this review, CNT-based adsorbents have been extensively used in the adsorption of inorganic and organic pollutants from water and wastewater. The use of nanoadsorbents is an attractive and promising option in the water treatment process due to its high specific surface area and unique physical and chemical properties. They demonstrate excellent adsorption properties due to their high specific surface area, exceptional porosities, hollow and layered structures, numerous internal and external adsorption sites, π-conjugative structure, and ease of chemical activation and functionalization. A wide range of mechanical, physical, and chemical approaches have been used for the modification or functionalization of CNTs to enhance their adsorptive properties in general or to make them selective toward certain classes of pollutants. Depending on the adsorption conditions and the functionalization involved, CNT-based adsorbents can interact with inorganic contaminants through different mechanisms such as surface complexation, electrostatic interaction, ion exchange, physical adsorption, and precipitation. In the case of organic pollutants, besides physical adsorption, π-π and electrostatic interactions play a major role in adsorption. In some cases, chemical bonding between organics and carbon nanotubes has also been reported as a mechanism of interaction. Properties, functionalization, and mechanisms are involved in CNT-based adsorption of pollutants from aqueous media. An insightful overview of the critical parameters that should be considered while using CNT-based adsorbents for water purification is also provided. In the end, some challenges associated with CNT-based adsorbents are presented, along with the potential solutions.
Functionalized multi-walled carbon nanotubes for oil spill cleanup from water
Clean Technologies and Environmental Policy
The growing global economy resulted in an incessant increase in transportation and exploitation of oil. Hence, the oil spillage has been considered a serious threat to aquatic and terrestrial ecosystems. Therefore, water purification has been considered a major challenge around the world. There are numerous classical methods available for oil removal from water, but owing to multiple defects and disadvantages, research efforts have focused to find such adsorbents which can improve oil adsorption capability. Traditional adsorbent material typically applied in oil removal includes activated carbon, organoclays, wool, zeolites, etc. These materials suffer from several drawbacks such as low absorption capacity, non-selective absorption, and complicated reusability, whereas nano-adsorbents offer multiple advantages such as having multiple sorption sites, large surface area, short intra-particle diffusion distance, tuneable pore size, and ease of low-temperature modification. Multi-walled...
Carbon nanotubes - the promising adsorbent in wastewater treatment
Journal of Physics: Conference Series, 2007
Carbon materials are a class of significant and widely used engineering adsorbent. As a new member of the carbon family, carbon nanotubes have exhibited great potentials in applications as composite reinforcements, field emitters for flat panel display, sensors, energy storage and energy conversion devices, and catalysts support phases, because of their extraordinary mechanical, electrical, thermal and structural properties. In particular, the large specific surface areas, as well as the high chemical and thermal stabilities, make carbon nanotubes an attractive adsorbent in wastewater treatment. The adsorption properties of the carbon nanotubes to a series of toxic agents, such as lead, cadmium and 1,2-dichlorobenzene have been studied and the results show that carbon nanotubes are excellent and effective adsorbent for eliminating these harmful media in water. The effects of the morphologies and the surface status on the carbon nanotube adsorption capacities are also discussed.
The scarcity of water, especially in arid and semi-arid regions of the world is exerting great pressure on resources and establishing more need to provide good quality water for human and other consumptions. Water recovery/recycle/reuse has proven to be effective and successful in creating a new and reliable water supply. Accordingly, attention is being paid to the effective treatment of alternative sources of water (apart from fresh water) such as seawater, storm water, wastewater (e.g. treated sewage water), and industrial wastewater. In this review, the use of carbon nanotubes (CNTs), member of the fullerene structural family, is considered with special focus on the removal of heavy metals from water (lead, chromium , cadmium, arsenic, copper, zinc and nickel). A critical review into the adsorption behavior and use of the CNTs is given with attention being paid to the effects of surface modifications on the adsorption behavior and subsequent heavy metal removal. A review of the effect of a number of key variables including pH, CNTs dosage, time, ionic strength, temperature and surface charge are given. It will be demonstrated that, surface modification enhances positively the adsorption capacity of CNTs towards cadmium, chromium, lead, mercury, copper, zinc, cobalt and nickel as did the solution pH. CNTs have been proven to an excellent adsorbent for the removal of different heavy metals from water. However, most of the applications of CNTs are on lab scale in batch experiments. In spite of high costs, CNTs are expected to be a promising adsorbent in the future due to its high adsorption capacity compared to many traditional adsorbents. Researchers are also in quest of novel environment friendly techniques for the surface modification of CNTs to further improve their properties. Still, the feasibility of CNTs application in large scale treatment needs to be further studied. Effective techniques for regeneration/reuse of CNTs also need to be explored yet. One of the main hurdles that limit the applications of CNTs in large scale operation is the cost of CNTs. Future research works on developing a cost-effective way of CNT production and testing the toxicity of CNTs and CNT-related materials are recommended.
Functionalized carbon nanotubes for hydrocarbon removal from water
This study aims to develop advanced sorbents for the removal of hydrocarbons from surface waters. The mi-croemulsion method was implemented to modify the surface structure of multiwalled carbon nanotube (MWCNTs) by attaching a hydrocarbon tail on its surface. The structural and surface chemistry properties of the prepared adsorbents were studied by different surface analytical techniques such as Brunauer-Emmett-Teller (BET) method, X-Ray diffraction (XRD), Raman-spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). Scanning electron microscopy (SEM) was used to study the microstructure and morphology of the samples. Different model hydrocarbon compounds were used for this investigation. The hydrocarbon removal efficiencies of the unmodified and functionalized sorbents were studied by using total organic carbon analyzer (TOC), gas chromatography (GC), and UV-vis spectroscopy (UV-vis) techniques. Surface chemistry studies over raw and microemulsified multiwalled carbon nanotubes (μEMWCNT) revealed that that microemulsion functionalization resulted in changes in the CH bending vibrations of the functionalized MWCNTs as compared to the raw MWCNTs, demonstrating the existence of intermolecular CH-π interactions between the carbon nanotubes and lauric/miristic acid. The experimental results revealed that microemulsion technique as a type of surface functionalization solved one main issue regarding MWCNTs modification as it proved to have a beneficial effect on MWCNTs' hydrophobic properties without the need for additional func-tionalization and substitution steps to attach hydrocarbon side chains. Using kerosene as a hydrocarbon model mixture, compared with raw MWCNTs, the maximum adsorption capacity of μMWCNTs increased by 63.5 %. Additionally, the outcomes indicated that the n-octane adsorption capacities over μEMWCNTs reached 6.07 g/g. The kinetic studies demonstrated that the adsorption process over μMWCNTs could be well described by the pseudo-second-order model with a high correlation coefficient.
Sustainability
As the world human population and industrialization keep growing, the water availability issue has forced scientists, engineers, and legislators of water supply industries to better manage water resources. Pollutant removals from wastewaters are crucial to ensure qualities of available water resources (including natural water bodies or reclaimed waters). Diverse techniques have been developed to deal with water quality concerns. Carbon based nanomaterials, especially carbon nanotubes (CNTs) with their high specific surface area and associated adsorption sites, have drawn a special focus in environmental applications, especially water and wastewater treatment. This critical review summarizes recent developments and adsorption behaviors of CNTs used to remove organics or heavy metal ions from contaminated waters via adsorption and inactivation of biological species associated with CNTs. Foci include CNTs synthesis, purification, and surface modifications or functionalization, followed...