Graphene Adsorption Research Articles

Enhanced post-combustion CO2 capture and direct air capture by plasma surface functionalization of graphene adsorbent

Graphene has enormous potential to capture CO2 due to its unique properties and cost-effectiveness. However, graphene-based adsorbents have drawbacks of lower CO2 adsorption capacity and poor selectivity. This work demonstrates a one-step rapid and sustainable N2/H2 plasma treatment process to prepare graphene-based sorbent material with enhanced CO2 adsorption performance. Plasma treatment directly enriches amine species, increases surface area, and improves textural properties. The CO2 adsorption capacity increases from 1.6 to 3.3 mmol/g for capturing flue gas, and from 0.14 to 1.3 mmol/g for direct air capture (DAC). Importantly, the electrothermal property of the plasma-modified aerogels has been significantly improved, resulting in faster heating rates and significantly reducing energy consumption compared to conventional external heating for regeneration of sorbents. Modified aerogels display improved selectivity of 42 and 87 after plasma modification for 5 and 10 min, respectively. The plasma-treated aerogels display minimal loss between 17% and 19% in capacity after 40 adsorption/desorption cycles, rendering excellent stability. The N2/H2 plasma treatment of adsorbent materials would lower energy expenses and prevent negative effects on the global economy caused by climate change.

DFT assessment of the alizarin dye pollutant adsorption by a customized graphene adsorbent

The alizarin (ALZ) dye pollutant adsorption by a customized zinc-atom decorated graphene (ZGR) adsorbent was assessed by density functional theory (DFT) computations. The interactions between ALZ and ZGR were explored to approach an adsorption process, in which different configurations of ALZ@ZGR complexes; A1, A2, and A3, were found. A dominant O…Zn interaction was found for all complexes in addition to the complementary C…C interaction between two substances. Accordingly, different strengths of adsorptions were determined to be meaningful for the removal purpose of ALZ by the ZGR adsorbent. The electronic molecular orbital features were also extracted to approach a sensing function of r ALZ@ZGR complexes formations, in which the variations of such features were mainly monitored by the changes of energy gap and work function. As a consequence, a platform for sensing and removal of the ALZ dye pollutant was proposed in the water and octanol solvents.

A microphysiological system for handling graphene related materials under flow conditions.

The field of nanotechnology has developed rapidly in recent decades due to its broad applications in many industrial and biomedical fields. Notably, 2D materials such as graphene-related materials (GRMs) have been extensively explored and, as such, their safety needs to be assessed. However, GRMs tend to deposit quickly, present low stability in aqueous solutions, and adsorb to plastic materials. Consequently, traditional approaches based on static assays facilitate their deposition and adsorption and fail to recreate human physiological conditions. Organ-on-a-chip (OOC) technology could, however, solve these drawbacks and lead to the development of microphysiological systems (MPSs) that mimic the microenvironment present in human tissues. In light of the above, in the present study a microfluidic system under flow conditions has been optimised to minimise graphene oxide (GO) and few-layer graphene (FLG) adsorption and deposition. For that purpose, a kidney-on-a-chip was developed and optimised to evaluate the effects of exposure to GO and FLG flakes at a sublethal dose under fluid flow conditions. In summary, MPSs are an innovative and precise tool for evaluating the effects of exposure to GRMs and other type of nanomaterials.

GRAPHENE OXIDE DERIVED FROM CASSAVA PEEL AS A POTENTIAL ADSORBENT FOR TETRACYCLINE REMOVAL FROM AQUEOUS ENVIRONMENT

Due to the increase in bacterial resistance, the presence of antibiotic residues in ambient water is becoming a serious problem. In order to stop antibiotic-related water contamination, graphene oxide has been extensively employed as an advanced adsorbent. In this study, cassava peel was utilized to create graphene oxide, which was then applied as an adsorbent to remove tetracycline. The modified Hummers technique was used to produce graphene oxide, along with an oxidizing agent. Studies have been done on graphene oxide characterization and adsorption process optimization. According to the study, tetracycline removal was best accomplished under settings that included an adsorbent mass of 20 mg, an antibiotic concentration of 10 ppm, a pH of 5, and a contact period of 10 minutes. The adsorbent substance has shown promise in removing tetracycline from aqueous environments.

Theoretical calculation study on enhancing the sensitivity and optical properties of graphene adsorption of nitrogen dioxide via doping

In order to study the adsorption of NO<sub>2</sub> on pristine graphene and doped graphene (N-doped, Zn-doped, and N-Zn co-doped), we simulate the adsorption process by applying the first-principles plane-wave ultrasoft pseudopotentials of the density-functional theory in this work. The adsorption energy, Mulliken distribution, differential charge density, density of states, and optical properties of NO<sub>2</sub> molecules adsorbed on the graphene surface are calculated. The results show that the doped graphene surface exhibits higher sensitivity to the adsorption of NO<sub>2</sub> compared with the pristine graphene surface, and the order of adsorption energy is as follows: N-Zn co-doped surface > Zn-doped surface > N-doped surface > pristine surface. Pristine graphene surface and N-doped graphene surface have weak interactions with and physical adsorption of NO<sub>2</sub>. Zn-doped graphene surfac and N-Zn co-doped graphene surface form chemical bonds with NO<sub>2</sub> and are chemisorbed. In the visible range, among the three doping modes, the N-Zn co-doped surface is the most effective for improving the optical properties of graphene, with the peak absorption and reflection coefficients improved by about 1.12 and 3.42 times, respectively, compared with pristine graphene. The N-Zn co-doped graphene not only enhances the interaction between the surface and NO<sub>2</sub>, but also improves the optical properties of the material, which provides theoretical support and experimental guidance for NO<sub>2</sub> gas detection and sensing based on graphene substrate.

Fabrication of Fe3O4@GO@ZIF-8 nanohybrids via in-situ self-assembly with magnetic collectability for efficient adsorption of As(III) and As(V)

Fe3O4@GO@ZIF-8 nanohybrids were successfully fabricated as a novel magnetic graphene adsorbent via in-situ self-assembly of ZIF-8 and graphene oxide (GO) onto magnetic ferroferric oxide nanoparticles. The adsorbent was thoroughly characterized using various techniques. The results showed that Fe3O4@GO@ZIF-8 exhibits strong magnetic properties, abundant functional groups and a large specific surface area of 779.48 m2 g−1. Additionally, the effects of time, pH, initial concentration and temperature on the adsorption performances of Fe3O4@GO@ZIF-8 for trivalent arsenite (As(III)) and pentavalent arsenate (As(V)) were explored. The results revealed that Fe3O4@GO@ZIF-8 possesses fast reaction kinetics (reaching saturation in approximately 180 min for As(III) and 120 min for As(V)), as well as excellent adsorption capabilities (achieving adsorption capacities of 87.621 mg g−1 for As(III) and 113.37 mg g−1 for As(V)). Furthermore, recycling experiments demonstrated that Fe3O4@GO@ZIF-8 exhibits favorable adsorption ability, enabling easy recovery under an applied magnetic field. These results highlight the magnetic properties, good reusability, and adsorption capacity of Fe3O4@GO@ZIF-8, rendering it highly practical for extracting arsenic wastes in harsh environments.

High-efficiency loading and controlled release of cyclophosphamide on graphene oxide and adsorption isotherm studies

In this research, Graphene oxide (GO) used as a platform, is synthesized for the purpose of nanoparticles for loading of cyclophosphamide (CYP) and the identification of the structure of this new nano drug (CYP/GO) is made using several analytical devices such as XRD, FTIR, SEM, and UV. The morphology, functionalization, stability, loading and controlled release behaviors of cyclophosphamide on GO at different pH, temperatures, contact time and concentrations were investigated. The loading and controlled release of CYP indicated strong pH dependence which is implied hydrogen-bonding interaction between GO and CYP. The equilibrium adsorption data were analyzed by Langmuir and Freundlich models. The results showed that the adsorption behavior could be fitted better to the Freundlich model. Nearly 80 % of CYP was released in simulated gastric fluid, pH 1.2, in 4 h and 68 % in simulated intestinal fluid, pH 7.4, in 30 h.

High efficiency removal of methyl blue using phytic acid modified graphene oxide and adsorption mechanism

Phytic acid modified graphene oxide (PGO) has encouraging prospect in environmental application. Herein, PGO was fabricated with a simple hydrothermal method and used as adsorbent to remove methyl blue (MB). Elaborate inspection based on the hard-soft acid-base (HSAB) principle, spectroscopic characterization, as well as batch adsorption and fitting were conducted to unravel the adsorption mechanism. Results show, PGO efficiently adsorbs 89.08 mg·g−1 of MB in 22 min. HSAB principle proposes, high electron transfer (ΔN) and energy lowering (ΔE) induce covalent bond (chemical interaction), while low ΔN and ΔE induce electrostatic effect (physical interaction). Accordingly, both the first and second strongest interaction occurs between PA moiety and MB: π electrons of MB flows towards O atom in OH and O(–O–) of PA, respectively. Yet the third strongest interaction happens between GO moiety and MB: electron of O atom in OH group of GO flows towards N atom of MB. Above top three interactions are characterized by prominent ΔN and ΔE implying the formation of covalent bond. However, other interactions yield low ΔN and ΔE, suggesting the presence of electrostatic effect. HSAB principle conclusion was substantiated by FTIR and UV–Vis analyses. These findings confirm that PA modification enhances the adsorption affinity of graphene oxide. Thereby, chemical adsorption induced by physical interaction is proposed. This work may inspire the design of efficient adsorbent based on PGO framework for environmental restoration.

Calculation of Graphene Work Function Variations Due to Alkali Metal + Oxygen Adsorption

Graphene has a high work function of 4.6 eV, and it can't be directly used as thermionic emission material. The graphene work function shows a decreasing trend in alkali metal/oxygen (AM/O) coadsorption experiments. Anderson–Newns (AN) model is a classical theoretical model for calculating the work function of adsorption surface. The present study, aiming at AM/O adsorption system, modifies and optimizes the AN model by redefining the calculation method of adsorption bond length λ and establishes the relationship between material work function, thermionic emission performance, and surface coverage. Based on the modified model, the influence of work function decline and thermionic emission performance of cesium/oxygen, potassium/oxygen, and sodium/oxygen graphene adsorption systems is studied. The results show that the work function of graphene affected by the three AM/O adsorbents is basically the same with the increase of coverage, and all of them quickly decrease to the lowest value and then increase slightly. The maximum work function declines are 3.51, 3.30, and 2.83 eV, respectively. At 1000 K, the maximum output current densities are 340, 36, and 0.15 A cm−2, respectively.

Theoretical verification on adsorptive removal of caffeine by carbon and nitrogen-based surfaces: Role of charge transfer, π electron occupancy, and temperature

Eliminating an emerging water pollutant, caffeine molecules, from an aqueous solution using carbon and nitrogen-based adsorbents is of significant interest to public health. These adsorbents have been shown to have decent adsorption capacity toward caffeine due to their surface functionality. Therefore, screening various carbon and nitrogen-based surfaces can be a better option for high-performance adsorbents to remove caffeine efficiently from wastewater. Herein, we present combined first principles and molecular dynamics quantification of the adsorption enthalpies of caffeine molecules on the possible active sites of carbon and nitrogen-based adsorbents (graphene, phagraphene, graphdiyne, single-wall carbon nanotube, fullerene, and graphitic carbon nitride) with the incorporation of Van der Waals interactions. From the DFT calculations, N-doped carbon surfaces show the highest adsorption energies of single and dimer CAF compared to pristine carbon-based adsorbents. A charge density difference and Bader charge analysis display that high charge transfer occurs between the caffeine's oxygen and the surface's nitrogen atoms. An abundance of π-electrons from the nitrogen atoms, composed of large electron clouds of aromatic rings on the graphitic carbon surface, tends to favor extensive π-π interactions with the caffeine molecule. The high value of pz electron occupancy (1.445) of N in the hexagonal ring of the graphitic surface transfers additional charge transfer, which leads to strong adsorption energy of CAF than pristine surfaces. Also, the g-C3N4 surface adsorbs the CAF molecule with higher adsorption than other N-doped carbon surfaces due to the high pz_eo (1.5448) of N atoms on the surface. At 310 K, the water molecules' kinetics aids the single and dimer caffeine molecules to adsorb with the highest adsorption energies on the active sites of g-C3N4 surfaces than graphene adsorbent.

Remediation of Amitriptyline Pharmaceutical Wastewater by Heteroatom-Doped Graphene Oxide: Process Optimization and Packed-Bed Studies

Amitriptyline residue released into the aquatic ecosystem can have detrimental consequences on marine organisms and human wellbeing via consumption of polluted water. With a uniquely large surface area and abundant functionalities, graphene oxide adsorption offers a remediation solution for such water pollution. This study focused on synthesizing a novel graphene-based adsorbent via ice-templating of boron-doped graphene substrate. The batch adsorption performance of the as-synthesized adsorbent was explored by central composite design (CCD), while its potential large-scale application was evaluated with a packed-bed column study. The CCD optimized conditions of 12.5 mg dosage, 32 min adsorption time, 30 °C operating temperature and 70 ppm concentration produced the highest removal efficiency of 87.72%. The results of the packed-bed study indicated that continuous adsorption of amitriptyline was best performed at a graphene bed of 3.5 cm in height, with 100 ppm of the pharmaceutical solution flowing at 2 mL/min. Furthermore, the breakthrough curve was effectively portrayed by the Log Bohart–Adams model. The as-synthesized adsorbent showed a high regeneration potential using ethanol eluent via multiple adsorption–desorption cycles. The results suggest the boron-doped graphene adsorbent in packed-bed as a highly effective system to remediate amitriptyline in an aqueous environment.

High-efficiency loading and controlled release of cyclophosphamide on graphene oxide and adsorption isotherm studies

High-efficiency loading and controlled release of cyclophosphamide on graphene oxide and adsorption isotherm studies

Preconcentration and Removal of Pb(II) Ions from Aqueous Solutions Using Graphene-Based Nanomaterials.

Direct determination of lead trace concentration in the presence of relatively complex matrices is often a problem. Thus, its preconcentration and separation are necessary in the analytical procedures. Graphene-based nanomaterials have attracted significant interest as potential adsorbents for Pb(II) preconcentration and removal due to their high specific surface area, exceptional porosities, numerous adsorption sites and functionalization ease. Particularly, incorporation of magnetic particles with graphene adsorbents offers an effective approach to overcome the separation problems after a lead enrichment step. This paper summarizes the developments in the applications of graphene-based adsorbents in conventional solid-phase extraction column packing and its alternative approaches in the past 5 years.

Investigation of oily wastewater treatment by few-layer graphene adsorbent and UV-Vis spectral analysis

Investigation of oily wastewater treatment by few-layer graphene adsorbent and UV-Vis spectral analysis

Graphene at Liquid Copper Catalysts: Atomic-Scale Agreement of Experimental and First-Principles Adsorption Height.

Liquid metal catalysts have recently attracted attention for synthesizing high-quality 2D materials facilitated via the catalysts' perfectly smooth surface. However, the microscopic catalytic processes occurring at the surface are still largely unclear because liquid metals escape the accessibility of traditional experimental and computational surface science approaches. Hence, numerous controversies are found regarding different applications, with graphene (Gr) growth on liquid copper (Cu) as a prominent prototype. In this work, novel in situ and in silico techniques are employed to achieve an atomic-level characterization of the graphene adsorption height above liquid Cu, reaching quantitative agreement within 0.1 Å between experiment and theory. The results are obtained via in situ synchrotron X-ray reflectivity (XRR) measurements over wide-range q-vectors and large-scale molecular dynamics simulations based on efficient machine-learning (ML) potentials trained to first-principles density functional theory (DFT) data. The computational insight is demonstrated to be robust against inherent DFT errors and reveals the nature of graphene binding to be highly comparable at liquid Cu and solid Cu(111). Transporting the predictive first-principles quality via ML potentials to the scales required for liquid metal catalysis thus provides a powerful approach to reach microscopic understanding, analogous to the established computational approaches for catalysis at solid surfaces.

Space Charge Suppression Method of Insulation Layer of HVDC Cable Based on Semi‐Conductive Shielding Layer Modified by Nitrogen‐Doped Graphene

Space charge accumulation in the cable insulation will cause local electric field distortion, and accelerate the aging of the material. The inner semi‐conductive layer as an important structure of cable will affect the charge injection characteristics in the insulation layer. This work intended to explore the method of modifying the semi‐conductive layer with the Nitrogen‐doped graphene (NG) to suppress the charge accumulation utilizing the super‐smoothness of graphene and electron adsorption of N element. First, the NG is prepared using N‐modified graphene, and the semi‐conductive layer with different NG content is fabricated. Second, the physical and chemical properties of the semi‐conductive composite are carried out, then the charge accumulation characteristics in the insulation layer under the effect of the semi‐conductive layer are characterized. The results showed that an appropriate amount of NG doping can significantly inhibit the charge accumulation in the insulation layer. The surface roughness decreased by about 32.13% when the doped NG content is 0.5 phr. With the increase of NG content from 0 to 1 phr, the accumulation charges inside the insulation layer decreased by about 36.84%. This research provided a new approach for suppressing space charge accumulation in the insulation material of high voltage cable.

Electronic Structure and Adsorption Behavior of Non-Metallic Atoms and Aluminum Atoms on the Surface of Graphene: DFT Theoretical Calculation

Graphene has been widely studied in many fields due to its excellent physical and chemical properties. In this paper, we focus on the electronic structure and adsorption behavior of Al atoms and X ([Formula: see text], N, Si, S) atoms co-adsorption on the surface of pure graphene and Al atom adsorption on the surface of X ([Formula: see text], N, Si, S) atoms-doped graphene systematically. The adsorption energy, adsorption distance, bond length, bond angle, and electronic structure were studied using density functional theory (DFT) theoretical calculation. The results show that the adsorption capacity of (Al, X) atoms co-adsorbed on the graphene surface is significantly improved compared to the Al atoms on the pure graphene surface. The adsorption energy of Al and B atoms co-adsorbed on the graphene surface is basically the same as that of Al atoms on the B-doped graphene surface. The calculation results also show that the adsorption capacity of Al atoms and X ([Formula: see text], Si, S) atoms co-adsorbed on the surface of graphene is better than that of Al atoms on the surface of graphene doped with X (X = N, Si, S) atoms. Compared with N atom and S atom-doped systems, the Si-doped graphene surface has a stronger adsorption capacity for Al atoms than pure graphene. However, due to the doping of N and S atoms, the adsorption capacity of Al atoms on the graphene surface is somewhat reduced. Our calculation results provide a theoretical basis for further selection of Al-based graphene composite materials.

Adsorption of Dyes Using Graphene Oxide-Based Nano-Adsorbent: A Review

Graphene Oxide (GO) based adsorbents have attracted much attention from researchers because there have been many reports that they are effective for removing dyes from aqueous environments. That is because GO has good mechanical, electrical, optical and chemical properties, so graphene and its derivatives, such as graphene oxide, have been used in various applications in the field of environmental management. Modifying GO into nano size is an effort to improve its performance in removing dyes. This review uses a database from Science Direct, Google Scholar and Springer, which was screened using graphene oxide, pigments, adsorption and nano adsorbent. The performance of the nano adsorbent showed quite good results in the removal of dyes. The isotherm model suitable for adsorption varies between Langmuir, Freundlich and Redlich-Peterson isotherms. Pseudo-second-order (PSO) is the best model to explain the adsorption process kinetics. Nano-adsorbent modification can be reused at least five times with a reduced adsorption capacity of 4-8%. Studies related to adsorption with GO-based nano adsorbents show promising results in pollutant removal. Still, aspects such as synthesis method, surface functional groups interaction and dye ions and the stability of synthesis products need to be investigated further.

Sugar molasses as a sustainable precursor for the synthesis of graphene sand composite adsorbent for tetracycline and methylene blue removal.

Sugar molasses from agricultural waste could be a sustainable carbon source for the synthesis of graphene adsorbent introduced in this work. The sugar molasses was successfully converted to graphene-like material and subsequently coated on the sand as graphene sand composite (GSC), as proven by XRD, XPS, Raman spectroscopy, and SEM with EDX mapping analyses. The adsorption performance of GSC was evaluated against the removal of Tetracycline (TC) and methylene blue (MB) pollutants from an aqueous solution in a fixed bed column continuous-flow adsorption setup. The effect of different process conditions: bed height (4-12cm), influent flow rate (3-7mL/min), and contaminants' concentration (50-150ppm) was investigated. The results revealed that column performance was improved by increasing the bed depth and lowering the flow rate and concentration of the pollutants. The best removal efficiency was obtained when the bed height was 12cm, the influent flow rate of 3mL/min, and the pollutants' initial concentration was 50mg/L. Thomas, Adams-Bohart, and Yoon-Nelson models were attempted to fit the breakthrough curves. Regeneration of the GSC indicated the decline of breakthrough time from 240-280 to 180min, reflecting the decrease in adsorptive sites due to the incomplete regeneration process. Overall, sugar molasses was shown to be a low-cost precursor for synthesizing valuable graphene material in the form of GSC, which can reduce the problem for industrial waste management of sugar molasses, and the GSC could be used as an adsorbent for environmental application.

Analysis of the adsorption characteristics of gasification pollutants (HCl, COS, H2S, NH3 and HCN) on Ti-anchored graphene substrates

The adsorption characteristics of HCl, COS, H2S, NH3 and HCN (coal gasification pollutants) on the adsorbents (single vacancy, double vacancy, and doped nitrogen atoms) formed by the graphene substrates anchored with titanium atom were analyzed by density functional theory (DFT) calculation. This paper mainly analyzed the geometric configuration of the adsorbent, the adsorption configuration of the gas, and the adsorption energy and the magnetic properties. And through the analysis of the electron density difference and the projected density of states (PDOS), the adsorption mechanism of five coal gasification pollutants on different adsorbents were deeply studied. The calculated results indicate that HCl, COS, H2S, NH3 and HCN can be adsorbed on Ti/SV-N3 graphene adsorbent, and the values of the adsorption energy were −1.07 eV, −1.73 eV, −0.28 eV, −0.41 eV, and -1.23 eV, respectively. Moreover, the introduction of nitrogen atoms significantly enhanced the interaction between single-atom graphene and gas molecules. Based on theoretical results, Ti/SV-N3 was the most suitable for simultaneous removal of these five pollutant gasses, which can guide the development of new materials for pollutant gas removal.