Microwave

Scientific Reports volume 13, Article number: 11306 (2023) Cite this article

558 Accesses

2 Altmetric

Metrics details

The chromium adsorption behavior from aqueous solution by the amphoteric Janus nitrogen-doped carbon quantum dots (AJ–N–CQDs) was investigated. The pseudo-first-order and the second-order adsorption kinetics models were employed to analyze the experimental data; the second-order adsorption kinetics model presented a better correlation to the experimental data, suggesting a chemisorptions process. The values obtained in the pseudo-first-order are still suitable for describing the Kinetics of Cr(VI) sorption. These values elucidate the surface processes involving chemisorption and physisorption in the adsorption of Cr(VI) by AJ–N–CQDs. The R2 of the Boyd model gave a better fit to the adsorption data of AJ–N–CQDs (i.e., external diffusion), which means the surface processes involving external Cr(VI) adsorption by AJ–N–CQDs. The higher value of α may be due to the greater surface area of the AJ–N–CQDs for the immediate adsorption of Cr(VI) from the aqueous solution. AJ–N–CQDs have fluorescence spectra before and after Cr(VI) adsorption, indicating they are promising for chemical sensor applications.

Accumulation of agricultural waste is harmful to the environment. As a result, recycling is in demand. The primary component of sugarcane bagasse is cellulose, which comprises β-1,4-glycosidic linkages of the D-glucose unit1,2,3,4. Utilizing agricultural waste has recently undergone a more significant effort. One was employing bagasse as a feedstock to produce carbon-based materials. It is the most dependable source for producing valuable products by eco-friendly techniques to remove metal ions from wastewater1,5.

Carbon quantum dots (CQDs) and graphene (G) are two valuable products that can be produced from agricultural wastes. CQDs are 10 nm diameters with colossal surface area ball nanomaterials, while graphene quantum dots (GQDs) are a mixture of G with CQDs. The most marked functional groups are O–H, –C = O, and C–O–C. Several methods, such as hydrothermal and solvothermal heating of organic molecules, laser ablation of graphite, and pyrolytic carbonization, have been used to create GQDs. However, studies have revealed that microwave heating is suitable for developing more rapid and reasonably priced CQD synthesis procedures5.

Amphoteric Janus nitrogen-doped CQDs (AJ–N–CQDs) containing –O– and –N– functional groups are amphoteric Janus materials (AJMs) due to the presence of hydrophobic carbon cores shielded by the layer of hydrophilic –O– and –N–2,6,7. Polymeric compounds with hydrophobic and hydrophilic moieties are called AJMs7.

Furthermore, N–CQDs are fluorescent and eco-friendly nanomaterials successfully used in wastewater treatment1,5. Despite its toxic character, Cr(VI) is widely used in various industries, and its recovery from the corresponding liquid effluents is a primary target before its discharge to natural waters. Therefore, monitoring the environmental content of Cr(VI) is essential for public health. Several materials have found applications to remove and/or recover Cr(VI) from wastes, such as activated carbon, natural zeolites, carbon nanotubes, etc.8. Among them, the adsorption onto AJ–N–CQDs could be competitive due to their high adsorption efficiency due to the presence of N and O functional groups and their fluorescence properties, which make them a suitable detector for Cr(VI)1,5. Several conventional approaches, including electrochemical technology, chromatography, etc., have been used to detect Cr(VI). Sample preparation is arduous, complicated, and time-consuming in most of these approaches. The fluorescence detection method is considered the more powerful than other conventional techniques because of its high sensitivity and low cost.

Consequently, the present work used microwave energy to prepare different carbon nanomaterials (GQDs and AJ–N–CQDs) from bagasse. The produced N–GQDs have no fluorescence properties due to the large amount of G. AJ–N–CQDs have fluorescence properties, making them promising adsorbents and sensors for metal ions such as Cr(VI). The Kinetics of the adsorption process at different times and the fluorescence of AJ–N–CQDs with/ without Cr(VI) were studied. The results are promising for chemical sensor applications.

Sugarcane bagasse (SB) obtained from the paper industry, Quena company, Egypt, was grounded to a mesh size of 450 microns. Dimethyl formamide (DMF) and citric acid (CA) are of analytical grades and used without further purification. Potassium chromate (99%) was purchased from Sigma Aldrich as a model material for Cr(VI) ions.

Adsorption tests were carried out with potassium chromate (15 mg/L; Sigma Aldrich 99%) as a model material for Cr(VI) ions in wastewater.

QDs were prepared using domestic and lab microwaves; a mixture of the SB (1 g), DMF (20 ml), and CA (0.1 g) was placed in a domestic microwave at 750 W for 3 min. The final brownish-black powder was washed with water, filtered, and dried under a vacuum to produce GQDs1,5.

The same mixture was placed in the lab microwave at 100 °C, 750 W, for 135 min. The final solution was left to cool down at room temperature, followed by centrifugation, filtration, and drying under vacuum, after which AJ–N–CQDs-based fluorescence nanoparticles were obtained.

Fourier-transform infrared spectra were collected employing Mattson 5000 spectrometer (Unicam, United Kingdom) using the KBr disk method.

TEM images were taken with a JEOL JEM-2100 electron microscopy at an acceleration voltage of 120 kV.

The elemental distribution of GQDs and AJ–N–CQDs was investigated using the non-destructive energy dispersive X-ray (EDX) unit attached to scanning electron microscopy (JSM 6360LV, JEOL/Noran). For surface morphology, imaging was recorded using an accelerating voltage of 10–15 kV.

The crystallinity was studied by X-ray powder diffraction. The diffraction patterns were measured by Bruker D-8 Advance X-ray diffractometer (Germany), applying a 40 kV voltage and a 40 mA current employing copper (Kα) radiation (1.5406 Å).

where A1 = area of the crystalline domain, At = area of the total domain9.

The BET was evaluated by Brunauer–Emmett–Teller (BET) technique using St 2 on NOVA touch 4LX, Quantachrome Instruments. The samples were pre-heated at a high temperature (120 °C). These samples were measured at liquid nitrogen after existence gassed at 200 °C under the flow of N2 for 3 h. The Barrett-Joyner-Halenda (BJH) method was used to measure the pore size.

TGA analysis was performed on the prepared polymer powder employing Perkin Elmer thermogravimetric analyzer by heating the sample to 1000 °C of 10 °C/min under a nitrogen atmosphere. Thermal decomposition kinetics was explored for both N–CQDs and AJ–N–CQDs samples. The thermal analysis data were recorded to determine the thermal degradation's activation energy (Ea). Equations (3) and (4) were applied under the Coats-Redfern approach.

Plotting the relationship between {log10 [1-(1-α)1-n] / T2 (1-n)} and 1/T using various suitable n values should show a straight-line correlation following Eq. (3). For n = 1, the relationship between log {–log(1-α)] / T2} and 1/T was plotted following Eq. (4). As a result, the least square method was used by selecting several n values (ranging from 0 to 3), calculating the correlation coefficient (r) for each value of n, and estimating the standard error (SE). The frequency factor A was determined from the intercept (log AR/ßE) of the Coats-Redfern equation by the most suitable value of n, while the activation energy (E) was calculated from the slope (E/2.303R). Equation (5) was used to estimate the other kinetic parameters, such as enthalpy (∆H), entropy (∆S), and free energy change (∆G)10.

where (h) and (k) are Planck and Boltzmann constants, respectively.

The Spectrofluorometer model Jasco FP – 6500, Japan, evaluated fluorescence spectra with a light source: a Xenon arc lamp 150 Watt.

Comparative removal efficiency (R %) and adsorption capacity (qe) of AJ–N–CQDs were studied using 20 mg of absorbent in 20 ml of Cr(VI) aqueous solution at a concentration (15 mg/L), pH ≈ 5, and at different contact times (15, 30, 45, 60, 120, 240, and 360 min). Equations 6 and 7 were used to evaluate the AJ–N–CQDs sorption efficiencies.

where Co and Ct are the Cr(VI) concentrations (mg/L) in the solution before and after adsorption, respectively. V is the volume of solution (L), m is the amount (g) of the sorbent employed in the adsorption experiment10.

Zero order, Pseudo-first-order, and Pseudo-second-order can be determined from the Eqs. (8), (9) and ((10).

where qe and qt are the amounts of Cr (VI) adsorbed (mg/g) at equilibrium sorption capacity and time t, respectively. Ce is the final concentration of the AJ–N–CQDs with t (contact time). K1 (min−1) is the Pseudo-first-order rate constant of adsorption. K2 is the rate constant of Pseudo second-order adsorption. Values of qe2 and K2 were calculated from the slope and intercept plot of t/qt against t, respectively6.

The Weber–Morris intra-particle diffusion can be determined from Eq. (11).

where K3 is the intra-particle diffusion rate constant and C is the slope which represents the thickness of the boundary layer5.

The Boyd, and Elovich models can be determined from Eqs. (12) and (13), respectively11.

where Bt is a mathematical function of F, equivalent to qt/qe, representing the fraction of adsorbate adsorbed at different times. Also, α is the initial rate of adsorption (mg/g/min), and b is related to the extent of surface coverage and activation energy for chemisorption (g/mg). A plot of qt against ln t yields a straight line with α and b determined using the slope (1/b) and intercept (ln αb/b), respectively12. The Elovich kinetic model can study the adsorption rate based on absorption capacity on heterogeneous surfaces13. This model is used further to describe the pseudo-second-order kinetic (i.e., chemisorptions), assuming that the sorbent surface is energetically heterogeneous14.

Fluorescent carbon quantum dots (CDs) are synthesized and employed as adsorbent and fluorescent chemosensors for the selective detection of Cr(VI) ions. FT-IR, TEM, SEM/EDX, XRD, and TGA/DTG investigated the structure, size, and morphology.

The FTIR spectra of the prepared GQDs, as shown in Fig. 1, revealed a broad peak at absorption band 3426.06 cm-1 attributed to the vibration contributions of O–H groups. The AJ–N–CQDs and AJ–N–CQDs/Cr(VI) showed separated peaks for O–H and –N–H at 3721.96, 3422.61 and 3344.41, 3286.30 cm-1, respectively. For GQDs, AJ–N–CQDs, and AJ–N–CQDs/Cr(VI), the peaks between 2919.87–2935.25, 2858.78–2878.5, 1654.70–1743.43, 1496.47–1656.65, 1438.25–1596.86, 1381.80–1387.08, 1238.15–1254.67, and 1033.72–1094.95 cm-1 were attributed to–CH–, –CH2, C = O, amide I, amide II bands, C = C, O–C = O, and C–O–C, respectively. There is an additional C–N group for AJ–N–CQDs and AJ–N–CQDs/Cr(VI) between 659.71 and 661.49 cm-1. The presence of amine groups (N–H and C–N) for AJ–N–CQDs and AJ–N–CQDs/Cr(VI) confirmed the formation of aminated CQDs1,2,5. At the same time, the O–H of N–GQDs at 3426.06 cm−1 was shifted to 3422.61 cm−1 for AJ–N–CQDs. This shift is attributed to the stronger intermolecular H-bonding. The calculated mean hydrogen bond strengths (MHBS) were 0.90 and 0.98 for N–GQDs and AJ–N–CQDs, respectively, confirming the formation of this intermolecular H-bonding10.

FTIR spectra of GQDs, AJ–N–CQDs, and AJ–N–CQDs/Cr(VI).

The relative absorbance (RA) of the characteristic –N–H are 1.09 and 0.95, and for C–N group are 3.62 and 0.97 for AJ–N–CQDs and AJ–N–CQDs/Cr(VI), respectively, confirmed the high content of nitrogenized groups in the prepared AJ–N–CQDs than AJ–N–CQDs/Cr(VI), which due to the bonding of Cr(VI) with the aminated groups. The Cr(VI) reduction in the presence of amide I and amide II in AJ–N–CQDs is apparent for AJ–N–CQDs/Cr(VI)) by a decreased intensity of the C = O peak (1743.43 cm-1) than AJ–N–CQDs (1654.70 cm-1(. The RA of the O–H group was 0.87 and 0.96 for AJ–N–CQDs and AJ–N–CQDs/Cr(VI), respectively. The fluorescence inner filter effect further supports this in the fluorescence spectra. The FTIR for AJ–N–CQDs/Cr(VI) showed an additional peak at 599.78 cm-1 assigned to Cr–O bonds due to the adsorbed Cr(VI).

From TEM analysis (Fig. 2), graphene (G) sheets were observed for GQDs with small amounts of dots, while AJ–N–CQDs depicted pure nanoparticles with spherical regularity without graphene sheets. The average diameters of nanoparticles were 13.34 and 8.42 nm for GQDs and AJ–N–CQDs, respectively. In addition, the particle size distribution is wide and narrow for GQDs (8–15 nm) and AJ–N–CQDs (between 8 and 9 nm), respectively. Using a domestic microwave, TEM images revealed the presence of GQDs5. While by using a lab microwave with changing the conditions produced pure CQDs. Figure 2 shows that the number of dots in AJ–N–CQDs is higher than in GQDs, confirming the lab's efficiency over the domestic microwave for preparing pure AJ–N–CQDs.

TEM, SEM images and EDX analysis of GQDs and AJ–N–CQDs.

SEM images showed fluffy sheets of GO for GQDs. The dots didn’t appear here due to their low number. In addition, AJ–N–CQDs showed crumpled precipitated structures, which didn’t show any dots due to the small particle size of the AJ–N–CQDs and the agglomeration existing because of the storage of the sample. EDX results showed that the AJ–N–CQDs are nitrogenized with nitrogen content of ~ 2.90% while, GQDs are non-nitrogenized (Fig. 2).

The XRD pattern of GQDs, as shown in Fig. 3, revealed peaks at 10.84 and 22.80° related to the (001) and (002) planes, respectively, due to the presence of GO with the d \(\approx \) 0.18 nm5. The AJ–N–CQDs showed a broad peak at 22.02 related to the (002) plane (JCPDS card no. 26–1076)15. The d value of AJ–N–CQDs (0.20 nm) is higher than GQDs (0.18 nm). This may be due to the presence of N–and O–groups, which enlarge the spacing of AJ–N–CQDs16. The calculated Cr.I. % of GQDs and AJ–N–CQDs were 72.04 and 94.68%, respectively.

XRD pattern of GQDs and AJ–N–CQDs.

The nitrogen (N2) adsorption isotherm was analyzed using the Brunauer- Emmett- Teller (BET) method to calculate the specific area. Figure 4 illustrates the N2 adsorption isotherms and pore size distribution. The pore size and distribution provide the necessary information about the chemical and physical interaction of the adsorbed metal with the adsorbent surface. The N2 adsorption isotherm was used to measure the BET surface and volume of the pores.

Nitrogen adsorption/desorption isotherms (the inset shows the pore size distribution).

The surface area of GQDs and AJ–N–CQDs are 208.48 and 675.75 m2/g, while the average pore radii are 1.63 X 104 and 1.60 X 107 nm, respectively. The results showed that the surface area of AJ–N–CQDs is higher than that of GQDs. In general, a high surface area can provide sufficient adsorption sites. At the same time, increasing the number of pores and volume of the sample adequately makes it contact with the Cr(VI), which can promote the improvement of the adsorption performance. This may be one reason for the difference in fluorescence properties.

The TGA/DTG of GQDs, as shown in Fig. 5, revealed three decomposition steps, while AJ–N–CQDs revealed one decomposition step with a mass loss (ML) of 72.92 and 69.79%, respectively, at 1000 °C, due to the non-volatile contents. The first ML for GQDs was 34.46–143.38 °C with a maximum temperature of 76.79 °C and an average ML of 3.14% due to the moisture content. The second ML stage is between 176.80 and 394.98 °C, with a maximum temperature of 323.99 °C and an average ML of 13.68%, due to the pyrolytic degradation. Finally, the third ML stage is between 709.13 and 1000 °C, with a maximum temperature of 734.55 °C and an average ML of 26.10%, due to the decomposition of the residual carbon9,16.

TGA/DTG of GQDs and AJ–N–CQDs, and their kinetics.

At the same time, the first ML of AJ–N–CQDs was in the range of 68.38–189.32 °C with a maximum temperature of 163.90 °C and an average ML of 61.79% due to the moisture content. As it is seen, the AJ–N–CQDs need more temperature above 1000 °C to complete their degradation due to their high thermal stability6.

According to Table 1, all samples under investigation have values for ΔH for the GQDs decrease from about 9.40 kJ mol-1 at the first stage of the reaction to about 3.94 kJ mol-1 at the second stage, indicating a shallow energy requirement as the reaction progresses (Ea decreased from 12.31 to 8.90 kJ mol-1). With lowering n (from 1.5 to 0.5) values, the ΔH was reduced (3.94 kJ mol-1). After that, with an increasing n value (2.5), the ΔH was increased (16.89 kJ mol-1), indicating a high energy requirement for the final stage (Ea \(\approx \) 25.26 kJ mol-1)1,6. According to the ΔG observations, the AJ–N–CQDs are more non-spontaneous and require external heat input than the GQDs, which improves their high thermal stability4.

Firstly, GQDs did not produce any fluorescence spectra. This may be due to the presence of a large number of graphene, which blocks the fluorescent dots in the GQDs. So, in this study, we will use AJ–N–CQDs for Cr(VI) adsorption. Figure 6 shows the fluorescence emission spectra of the AJ–N–CQDs and AJ–N–CQDs/Cr(VI). They were excited at 350 nm and showed a maximum emission wavelength of 442.0 and 459.0 nm, respectively. This blue shift emission could theoretically prove using of these materials as sensors. Fluorescence emission is caused by C = O/C = N moieties of the CQDs' surfaces. The emission peaks at 511.0 and 499.5 nm are derived from the oxygen vacancy for AJ–N–CQDs and AJ–N–CQDs/Cr(VI), respectively. The oxygen vacancy defects in the AJ–N–CQDs/Cr(VI) case are almost hidden and may be due to Cr(VI) adsorption. The high RA of OH groups prove this oxygen vacancy from FTIR. The fluorescence quenching efficiency (FQE) was determined using the following formula17:

where F0 and F refer to the F.I. of AJ–N–CQDs and AJ–N–CQDs/Cr(VI) Cr(VI), respectively. The calculated FQE was 49.57%, indicating relatively high sensitivity. The interaction between nitrogenized and oxygenated surface functionalities (–COOH, –OH, and –NH2) of AJ–N–CQDs/Cr(VI) was found to be responsible for the FQE18. The reduction in fluorescence intensity of AJ–N–CQDs/Cr(VI) compared to AJ–N–CQDs is due to IFE. The Cr(VI) ions absorb light radiation in the same range of wavelength of AJ–N–CQDs. As a result, the intensity is reduced, reducing the fluorescence intensity of AJ–N–CQDs/Cr(VI)19. In addition, because of high FQE, these findings validated the efficiency of AJ–N–CQDs synthesized from bagasse as an excellent material for further utilization in chemical sensing applications.

Fluorescent spectra of AJ–N–CQDs and AJ–N–CQDs/Cr(VI).

In this study, we choose AJ–N–CQDs with fluorescent properties to remove Cr(VI). The effect of contact time on the adsorption efficiency of AJ–N–CQDs was studied at different times, namely 15, 30, 45, 60, 120, 240, and 360 min. As shown in Fig. 7, the affinity of AJ–N–CQDs towards Cr(VI) was not the same, and the removal of Cr(VI) by AJ–N–CQDs was found to be fast at first due to the presence of more free functional groups then became slow. There was no remarkable increase in the adsorption rate observed after 45 min. So, the optimum time for Cr(VI) adsorption on AJ–N–CQDs at 25 °C is 45 min. Cr(VI) adsorption to AJ–N–CQDs was 83.85% and stable until 45 min. The adsorption may be due to high nitrogen and oxygen content. After 45 min, the adsorption rate decreased due to the leaching process1,6.

Effect of contact time, Zero order reaction, pseudo-first-order & the pseudo-second-ordere, Boyd model, and Elovich model for Cr(VI) adsorption by AJ–N–CQDs.

The Zero order reaction did not make it suitable for describing the Kinetics of Cr (VI) sorption on AJ–N–CQDs which assumes that increasing the concentration of reactants does not affect the magnitude of the reaction rate20. Therefore, pseudo-first-order and pseudo-second-order equations are utilized to model the Cr (VI) Kinetics on AJ–N–CQDs. Concerning the values of R2 presented in Table 2, it is seen that the pseudo-second-order model gave a better fit to the adsorption data of AJ–N–CQDs (chemical bonds in the adsorption). However, the values obtained in the pseudo-first-order are still suitable for describing the Kinetics of Cr (VI) sorption. These values elucidate the surface processes involving chemisorption and physisorption in the adsorption of Cr (VI) by AJ–N–CQDs5.

The Boyd model shows that the linear adjustment does not cross the axis at the origin, indicating that external diffusion was not only the rate-controlling step. Therefore, the lowest slope for the Boyd model is relatively associated with a strong effect of intra-particle diffusion. At the same time, R2 of the Boyd model gave a better fit to the adsorption data of AJ–N–CQDs (external diffusion). These values elucidate the surface processes involving external and intra-particle diffusion in Cr(VI) adsorption by AJ–N–CQDs. The higher value of α may be due to the greater surface area of the AJ–N–CQDs for the immediate Cr(VI) adsorption from an aqueous solution5,21.

In our study we used a Cr(VI) of 15 mg/L to stimulate the pollutant water, so at 100% removal of Cr(VI) the adsorbent capacity will be 15 mg/g. The maximum Cr(VI) removal % of AJ–N–CQDs is 83.85% by AJ–N–CQDs which is higher than the adsorption of other adsorbents stated in the literature (Table 3). For example, R % was 48, 45, and 37% for carbon dots modified mesoporous organosilica as an adsorbent for the removal of Hg(II), Cu(II), and Pb(II), respectively22. In addition, the maximum R % of Cr(VI) by TiO2/CQDs was 43.39%23.

This research reported a simple microwave method for preparing nitrogen-doped CQDs (AJ–N–CQDs) from bagasse, citric acid, and DMF. The AJ–N–CQDs have a high adsorption capacity and high sensing to Cr(VI). It is shown that Cr(VI) adsorption on AJ–N–CQDs is rapid in the first 45 min due to the presence of high nitrogen and oxygen functional group. FTIR-Spectra, XRD, TEM, and SEM/EDX confirmed the formation of AJ–N–CQDs. The morphology and BET studies confirmed that AJ–N–CQDs had a porous structure, significantly affecting their absorption properties. The kinetic absorption studies of as-prepared AJ–N–CQDs for Cr(VI) followed the Pseudo-second-order model. The fluorescence intensity of AJ–N–CQDs was reduced with Cr(VI) adsorption. Therefore, the present work offers a practical strategy toward a simple production method for preparing AJ–N–CQDs and their potential applications for Cr(VI) adsorption and chemosensor of Cr(VI).

Data are available on request from the corresponding author.

Tohamy, H. A. S., El-Sakhawy, M. & Kamel, S. Eco-friendly synthesis of carbon quantum dots as an effective adsorbent. J. Fluoresc. 33, 423 (2022).

Article PubMed PubMed Central Google Scholar

Tohamy, H.-A.S. & Magar, H. S. A flexible, low-cost, disposable non-enzymatic electrochemical sensor based on MnO2/cellulose nanostructure. ECS J. Solid State Sci. Technol. 11(12), 127003 (2022).

Article ADS Google Scholar

Tohamy, H.-A.S. et al. Preparation of hydroxyethyl cellulose/mangiferin edible films and their antimicrobial properties. BMC Chem. 16(1), 1–7 (2022).

Article Google Scholar

Tohamy, H.-A.S., Reinforced modified carboxymethyl cellulose films with graphene oxide/silver nanoparticles as antimicrobial agents. (2022).

Tohamy, H.-A.S. et al. Boosting the adsorption capacity and photocatalytic activity of activated carbon by graphene quantum dots and titanium dioxide. Diam. Relat. Mater. 132, 109640 (2023).

Article ADS CAS Google Scholar

Tohamy, H.-A.S., El-Sakhawy, M. & Kamel, S. Carbon nanotubes from agricultural wastes: Effective environmental adsorbent. Egypt. J. Chem. 65, 437–446 (2022).

Google Scholar

Wurm, F. & Kilbinger, A. F. Polymeric janus particles. Angew. Chem. Int. Ed. 48(45), 8412–8421 (2009).

Article CAS Google Scholar

Alguacil, F. J. & Lopez, F. A. Removal of Cr (VI) from waters by multi-walled carbon nanotubes: Optimization and kinetic investigations. In Water and Wastewater Treatment 55–65 (IntechOpen London, 2019).

Google Scholar

Tohamy, H.-A.S., El-Sakhawy, M. & Kamel, S. Development of graphene oxide-based styrene/acrylic elastomeric disks from sugarcane bagasse as adsorbents of Nickel (II) ions. J. Polym. Res. 29(3), 1–13 (2022).

Article Google Scholar

Tohamy, H.-A.S., El-Sakhawy, M. & Kamel, S. Development of magnetite/graphene oxide hydrogels from agricultural wastes for water treatment. J. Renew. Mater. 10(7), 1889 (2022).

Article CAS Google Scholar

Dahri, M. K., Kooh, M. R. R. & Lim, L. B. Application of Casuarina equisetifolia needle for the removal of methylene blue and malachite green dyes from aqueous solution. Alex. Eng. J. 54(4), 1253–1263 (2015).

Article Google Scholar

Edet, U. A. & Ifelebuegu, A. O. Kinetics, isotherms, and thermodynamic modeling of the adsorption of phosphates from model wastewater using recycled brick waste. Processes 8(6), 665 (2020).

Article CAS Google Scholar

Riyanto, C. and E. Prabalaras. The adsorption kinetics and isotherm of activated carbon from Water Hyacinth Leaves (Eichhornia crassipes) on Co (II). in Journal of Physics: Conference Series. (IOP Publishing, 2019).

Rashed, M. N., Arfien, A. & El-Dowy, F. Adsorption of heavy metals on chemically modified muscovite. Aswan Univ. J. Environ. Stud. 1(2), 183–203 (2020).

Article Google Scholar

Shaikh, A. F. et al. Bioinspired carbon quantum dots: An antibiofilm agents. J. Nanosci. Nanotechnol. 19(4), 2339–2345 (2019).

Article CAS PubMed Google Scholar

Tang, L. et al. Deep ultraviolet photoluminescence of water-soluble self-passivated graphene quantum dots. ACS Nano 6(6), 5102–5110 (2012).

Article CAS PubMed Google Scholar

Zhao, S. et al. Carbon dots combined with masking agent for high selectivity detection of Cr (VI) to overcome interference associated challenges. Ecotoxicol. Environ. Saf. 244, 114069 (2022).

Article CAS PubMed Google Scholar

Torres, S., Bogireddy, N. K. R., Kaur, I., Batra, V. & Agarwal, V. Heavy metal ion detection using green precursor derived carbon dots. IScience 2022, 103816 (2022).

Article ADS Google Scholar

Wani, A. A., Khan, A. M., Manea, Y. K., Salem, M. A. & Shahadat, M. Selective adsorption and ultrafast fluorescent detection of Cr (VI) in wastewater using neodymium doped polyaniline supported layered double hydroxide nanocomposite. J. Hazard. Mater. 416, 125754 (2021).

Article CAS PubMed Google Scholar

Eri, I. R., Pramudinta, N. K. & Nurmayanti, D. Adsorption kinetics of edamame soybean peel activated carbon in reducing the level of phosphate. J. Ecol. Eng. 23(2), 97 (2022).

Article Google Scholar

Manjuladevi, M., Anitha, R. & Manonmani, S. Kinetic study on adsorption of Cr (VI), Ni (II), Cd (II) and Pb (II) ions from aqueous solutions using activated carbon prepared from Cucumis melo peel. Appl. Water Sci. 8, 1–8 (2018).

Article CAS Google Scholar

Wang, L. et al. Carbon dots modified mesoporous organosilica as an adsorbent for the removal of 2, 4-dichlorophenol and heavy metal ions. J. Mater. Chem. 3, 13357–13364 (2015).

Article CAS Google Scholar

Falara, P. P. et al. Bi-functional photocatalytic heterostructures combining titania thin films with carbon quantum dots (C-QDs/TiO2) for effective elimination of water pollutants. Environ. Sci. Pollut. Res. 2023, 1–16 (2023).

Google Scholar

Download references

Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). The authors appreciate the National Strategy for Genetic Engineering and Biotechnology, Phase iii: Applications & Products Development, for supporting this work.

Cellulose and Paper Department, National Research Centre, 33 El Bohouth Str., P.O. 12622, Dokki, Giza, Egypt

Hebat-Allah S. Tohamy, Mohamed El-Sakhawy & Samir Kamel

You can also search for this author in PubMed Google Scholar

H.-A.S.T.: Conceptualization, Methodology, Software, Validation, Formal analysis, Data curation, writing—original draft preparation, Visualization, and Project administration. M.E.-S.: Conceptualization, Methodology, Software, Validation, Formal analysis, Data curation, writing—original draft preparation, Visualization, Supervision, and Project administration. S.K.: Conceptualization, Methodology, Software, Validation, Formal analysis, Data curation, writing—original draft preparation, Visualization, Supervision, and Project administration. All authors have read and agreed to the published version of the manuscript.

Correspondence to Mohamed El-Sakhawy.

The authors declare no competing interests.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and Permissions

Tohamy, HA.S., El-Sakhawy, M. & Kamel, S. Microwave-assisted synthesis of amphoteric fluorescence carbon quantum dots and their chromium adsorption from aqueous solution. Sci Rep 13, 11306 (2023). https://doi.org/10.1038/s41598-023-37894-4

Download citation

Received: 02 April 2023

Accepted: 29 June 2023

Published: 12 July 2023

DOI: https://doi.org/10.1038/s41598-023-37894-4

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Blog