Optimization and characterization of silver nanoparticle-modified luffa for the adsorption of ketoprofen and reactive yellow 15 from aqueous solutions

In the current work, luffa was modified with silver nanoparticles to prepare LF/AgNPs adsorbent for the elimination of ketoprofen and reactive yellow 15 (RY15) from aqueous media. Various characterization techniques, including FT-IR, XRD, BET, and SEM–EDS analysis, were employed to confirm the successful modification of LF/AgNPs. Several key parameters such as contact time, adsorbent dosage, concentration, pH, and agitation technique were fine-tuned to optimize the adsorption process. Ketoprofen removal was found to be most effective in weakly acidic conditions (pH = 5), while reactive yellow 15 adsorption was enhanced in an acidic environment (pH = 2). At 298 K, the highest adsorption capacities reached 56.88 mg/g for ketoprofen and 97.76 mg/g for reactive yellow 15. In both scenarios involving the elimination of ketoprofen and RY15, the Temkin isotherm exhibits higher R2 values, specifically 0.997 for ketoprofen and 0.963 for RY15, demonstrating a strong correlation with the observed adsorption data. Additionally, the kinetics of ketoprofen adsorption were best described by the Pseudo-first order model (R2 = 0.989), whereas the Pseudo-second order model provided the most accurate fit for reactive yellow 15 adsorption (R2 = 0.997). Importantly, the LF/AgNPs adsorbent displayed consistent performance over five consecutive reuse cycles, affirming its stability and efficacy in removing both contaminants. These findings underscore the exceptional potential of LF/AgNPs as a reliable adsorbent for the removal of reactive yellow 15 and ketoprofen from aqueous solutions.


Synthesis of luffa powders
The luffa was purchase from a store located in Isfahan.The luffa was reduced in size by being fragmented and purified with distilled water to eliminate any foreign matters that could dissolve into the water.Subsequently, it was dehydrated in an oven set at 40 °C for 4 h.After that, the reduced fragments of luffa were ground for 25 min using a ball mill operating at 20 Hz, resulting in white luffa powder.

Applying silver nanoparticles to the surface of luffa for modifying
APTES and 2-hydroxybenzaldehyde were utilized as connectors to surge the quantity of Ag on the surface of luffa through silver nanoparticle modification 54 .The first step involved refluxing 1 g of luffa powder with 70 mmol APTES and 25 ml of EtOH for 48 h, resulting in a precipitate labeled A. The solid substance obtained was subjected to filtration and multiple washing procedures with DI water and EtOH and dried at 40 °C for 4 h.Next, substance A in solid form was refluxed with 10 mmol 2-hydroxybenzaldehyde and 25 ml EtOH for 24 h, resulting in another precipitate named B.This collected solid was subjected to filtration and multiple rounds of washing with DI water and ethanol, and dried at 40 °C.
The chemical reduction approach was employed to synthesize silver nanoparticles in the third step 55 .AgNO 3 was utilized as a precursor, and polyvinylpyrrolidone (PVP) and ethylene glycol (EG) were utilized as stabilizer and reducing agent, respectively.To dissolve PVP in EG, a flask was loaded with 40 ml of Ethylene glycol and 4 g of PVP and placed in an ultrasonic bath.The potential interaction that may occur between PVP and silver nitrate in the process of AgNPs formation is illustrated in Fig. 1.
A reddish-brown solution, called Solution C, was produced by gradually adding a solution to 2 mmol of silver nitrate in a container that was protected by aluminum foil.The container was then put in an ultrasonic bath at 25 °C for duration of 30 min until the reaction was completed.
To modify the surface of the luffa by AgNPs, the magnetic stirrer was used to stir precipitate B and solution C for a duration of 48 h in a dark area.Once the reaction was complete, the brown collected solid was subjected

Experimental method
The adsorption experiments were carried out in a 10 mL falcon tube under consistent agitation using digital vortex mixers at ambient temperature.Investigations were carried out under optimum contact time, contaminant concentration, pH, and adsorbent dosage by one-at-a-time method.A solution of HCl/NaOH with a concentration of 0.1 M was utilized to adjust the pH.To perform the adsorption of ketoprofen and RY15 onto LF/AgNPs, a 10 mL solution of the contaminant was blended with the adsorbent.Following the conclusion of the adsorption process, the solution underwent centrifugation at 5000 rpm for 10 min to separate the LF/AgNPs.The residual  www.nature.com/scientificreports/concentration of contaminants was then determined spectrophotometrically.The following equations show the calculation methods for ketoprofen and RY15 adsorbed at equilibrium q e (mg/g), and the removal rate: C 0 (mg/L) is the starting concentration, C e (mg/L) is the equilibrium concentration of contaminant, m (mg) is the adsorbent dosage added to the solution, and V (ml) is the volume of the solution 56,57 .

Characterization
To study the morphological characteristics and perform elemental analysis of the adsorbent, scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDAX) analysis was employed.The analysis was carried out using the Te-scan, MIRA III equipment from the Czech Republic.To determine the functional group present in the adsorbents, Fourier Transform Infrared spectrometry (FT-IR) was conducted using a Thermo AVATAR IR spectrophotometer, with a spectral range of 4000-400 cm −1 .Brunauer-Emmett-Teller (BET) technique was used to obtain the porous structural data for luffa sponge, powdered luffa, and LF/AgNPs.The concentration variations in the solutions were determined using a UV-Visible spectrophotometer (T80 + , PG, UK).Additionally, X-ray diffraction (XRD) patterns were obtained using a diffractometer (Bourevestnik, DRON-8) equipped with Cu K α radiation and operated at 40 kV and 40 mA, over a range (2θ) of 10°-80°.

Characterization
As shown in Fig. 3, EDAX analysis is employed to exhibit the elements present in the LF/AgNPs structure.In addition, the luffa contains the 2-hydroxybenzaldehyde linker, which plays a more significant role compared to other components.The detection of silicon and nitrogen peaks in the analysis can be indicative of the presence of the 3-aminopropyl triethoxysilane linker.To summarize, the appearance of a silver peak in the analysis may show the presence of silver particles on the surface of the LF/AgNPs adsorbent.Moreover, it is evident that the element with the highest distribution is carbon.This can be attributed to the presence of carbon in both the luffa structure and the salicylic aldehyde linker structure.
Figure 4a depicts the structure of a luffa sponge.The SEM image displays that unmodified luffa has a fibrous structure with varying fiber diameters.However, as seen in Figs.4b, the fibrous structure is lost in the luffa powders.Figures 4c exhibit pictures of the LF/AgNPs structure, in which the luffa surface is covered with silver nanoparticles having a spherical shape, and their arrangement can be clearly observed.On the LF/AgNPs substrate, Fig. 4d illustrates the size distribution of silver nanoparticles, indicating an average size ranging from 20 to 25 nm.
The TEM image of LF/AgNPs offers a detailed glimpse into the structure of silver nanoparticles, as depicted in Fig. 5.The image distinctly illustrates the uniform dispersion of silver nanoparticles within the luffa framework, devoid of any agglomeration.Moreover, the image reveals that the silver nanoparticles assume a spherical form.
Table 1 presents the porous structural data obtained from BET analysis for luffa sponge, powdered luffa, and LF/AgNPs.The luffa sponge exhibits a limited surface area, but after ball-milling, both surface area and pore volume increase.Ball-milling disrupts the fibrous structures of luffa, exposing more surfaces and opening its pores.The surface area of LF/AgNPs is comparable to powdered luffa, but the pore volume is reduced, possibly (1)   www.nature.com/scientificreports/due to the dispersion of nanoparticles within the pores.While the presence of silver nanoparticles decreases porosity, it enhances active adsorbent sites for the elimination of contaminants.FT-IR analysis was conducted to confirm the process of modifying the surface of luffa by using AgNPs.Figure 6a depicts the raw luffa spectrum, and the peak observed around 3400 cm −1 is the stretching vibrations of OH-groups on the surface of luffa.Additionally, the peak observed at approximately 2900 cm −1 is associated with both symmetric and asymmetric stretching vibrations of C-H bonds.The peak observed around 1650 cm −1 is the vibrations of C=C and C=O bonds.The stretching vibration peaks observed at approximately 1055 cm −1 and 1115 cm −1 suggest the presence of C-OR and anhydroglucose in cellulose, as reported in previous studies 4,42,58 .Figure 6b presents the spectrum of LF/AgNPs which demonstrates the investigation of the binding of 4-aminopropyl triethoxysilane molecules on the surface of luffa.The bending and stretching vibration peaks of the N-H bond were not visible in the spectrum due to the overlapping of the peaks at 1650 cm −1 and 3400 cm −1 .However, it can be observed that the intensity of these peaks has increased 59 .The presence of a Si-O-C peak observed at approximately 1240 cm −1 , along with the aforementioned peaks, provides evidence of the attachment of an amino linker to the luffa structure, as reported in previous studies 60 .Moreover, the C=N peak observed at 1634 cm −1 provides evidence of the binding of salicylic aldehyde to 4-aminopropyl triethoxysilane, which forms an imine group 61 .The vibrational peaks associated with the stretching of C=C bonds in the aromatic ring of salicylic aldehyde are visible at approximately 1634 cm −1 and 756 cm −1 .It is worth noting that the peak observed at 1634 cm −1 has overlapped with the previous peaks, and its intensity has increased 62 .Peaks observed in the range of 1400-1500 cm −1 are associated with the vibration of the -N-C-group.It should be noted that the stretching peak at 1650 cm −1 , which belongs to the C=O group of polyvinyl pyrrolidone, is observed to overlap with the previous peaks.Additionally, it is observed that the peak at 502 cm −1 corresponds to the vibration of the Ag-O bond 42,63,64 .
The X-ray diffraction (XRD) pattern of LF/AgNPs is depicted in Fig. 7.The XRD pattern of LF/AgNPs displays peaks at 2θ of 35.84, 45.68, 64.76, and 77.64, which are the lattice planes (111), ( 200), (220), and (311), respectively, indicating the face-centered cubic (FCC) silver nanoparticle structure.Therefore, the XRD pattern clearly indicates that the synthesized silver nanoparticles are crystalline in nature 42 .Furthermore, the obtained diffraction patterns were compared with JCPDS card numbers, and it was found that they closely matched with the card number 04-0783.
The potential zeta test was conducted to measure the surface charge of luffa and LF/AgNPs at pH 3-7. Figure 8 displays the outcomes, revealing that LF/AgNPs had a PZC value of 5.39.The original luffa material carried a negative charge, but the alteration of its surface with silver nanoparticles led to a modification of its charge.When the pH value is below 5.39, the LF/AgNPs material acquires a positive charge that is notably cationic when the pH is at 3. If the pH value exceeds 5.39, the surface of the adsorbent becomes negatively charged.It is worth noting  www.nature.com/scientificreports/ that each particle demonstrates distinct characteristics at varying pH levels.By selecting the suitable pH level, this arrangement can govern the behavior and reaction of the adsorbents in different environments.

Effect of agitation technique
The stirring method is a crucial factor to consider as it enhances the contact area between the sample solution and the adsorbent.To this end, three stirring techniques, namely mechanical stirring, vortex, and ultrasonication, were assessed.As shown in Fig. 9, the elimination efficiency is greater for vortex and magnetic stirring.
The reason for the lower removal rate in the ultrasonication method can be the expulsion of particles from the surface of the adsorbent due to the intensity of the ultrasonic waves.

Effect of solution pH
Another parameter that affects the adsorption process is pH.The initial pH value can be adjusted to determine the features of the adsorbent, such as the surface charge and ionization degree.In this study, the influence of pH was investigated over a range of 2-11.As previously mentioned, the LF/AgNPs had a PZC of 5.39.This implies that the surface charge is positive when the pH is less than 5.39, and negative when the pH is greater than 5.39.On the one hand, since ketoprofen is in the weak acidic range (ketoprofen pK a = 4.45), it can exhibit different behaviors at different pH levels.For instance, at pH levels below pK a , ketoprofen exist as a neutral species, whereas at pH levels higher than pK a , it is present in anionic form.The pH-dependent adsorption of Ketoprofen onto LF/ AgNPs is illustrated in Fig. 10.The peak adsorption rate was observed at pH = 5 for Ketoprofen, where the anionic form of ketoprofen can be electrostatically adsorbed onto the positively charged adsorbent.For pH values below pK a , the neutral form of Ketoprofen can adhere to the surface through Van der Waals interactions or hydrogen bonding.On the other hand, the removal efficiency of RY15 is also shown in Fig. 10.RY15 removal efficiency dropped from 98 to 6% by increasing the pH from 2 to 11.The higher rate of RY15 elimination by LF/AgNPs at  www.nature.com/scientificreports/acidic pH is assigned to the electrostatic attraction among the charged molecular substances of adsorbent and RY15 molecules.By reducing the pH to 2, these positively charged groups become more available.Electrostatic exchanges between these opposing groups with negative and positive charges could be the primary system concerning ketoprofen and RY15 removal.Through an electrostatic interaction, the negative −SO − 3 group of the anionic dye interacts with a positive composite group, as reported in previous studies 65 .

Effect of contact time
Typically, the elimination efficiency is dependent on the duration of contact between the adsorbate and sorbent.In general, the removal of pharmaceuticals tends to increase with the contact time until equilibrium is attained.After the equilibrium point, there is typically no significant further uptake of the adsorbate.The effect of contact time on the adsorption process of ketoprofen and RY15 were investigated in the range of 0-100 min for ketoprofen, and 0-80 min for RY15.As depicted in Fig. 11, the elimination rate of Ketoprofen and RY15 increased with an increase in time until a maximum time of 60 min and 40 min is reached respectively.The equilibrium state was achieved at 60 min for ketoprofen and 40 min for RY15.This suggests that the adsorbent becomes saturated with the adsorbate after the equilibrium point.Accordingly, at these points, the optimum contact times were established for the following investigations.

Impact of initial concentration
The initial concentration is one of the most crucial factors that have an impact on the adsorption rate.It is necessary to confine the influence of the primary concentrations of ketoprofen and RY15.The effect of initial concentration on the removal efficiency is illustrated in Fig. 12a,b.The maximum removal efficiency of 98% was seen at both ketoprofen and RY15 in concentrations of 100 mg/L and 25 mg/L, respectively.The lowest removal of 49%    for ketoprofen and 47% for RY15 was observed at 300 mg/L and 200 mg/L, respectively.At lower concentrations, the total available active zones remain constant, allowing effective removal of contaminants.As concentrations increase, the number of contaminant molecules rises, potentially exceeding the capacity of the available active zones.Consequently, higher concentrations result in lower removal efficiency, indicating that all active zones are not utilized efficiently.Just about all ketoprofen and RY15 were removed.Furthermore, the adsorption capacity is higher at lower concentrations because a greater proportion of available active sites can accommodate adsorbate molecules.At higher concentrations, the saturation of active sites may occur, leading to a plateau or decrease in adsorption capacity despite the overall increase in the number of adsorbate molecules in the system.To address this paradox and optimize factors, a concentration of 100 mg/L for ketoprofen and 25 mg/L for RY15 was selected for further investigations.This concentration optimization ensures effective utilization of available active zones while maintaining high removal efficiency for both ketoprofen and RY15.

Effect of adsorbent dosage
The significance of adsorbent dosage is primarily linked to the removal efficiency and overall cost of the process.The adsorption rate of Ketoprofen and RY15 were assessed by varying the dosage of LF/AgNPs at the optimal contact time.As depicted in Fig. 13, the highest removal rate of 97% and 99% was achieved for ketoprofen and RY15 respectively with a dosage of 25 mg of LF/AgNPs.As the amount of adsorbent increased, the removal percentage also increased, which is likely due to the increase in active sites resulting from the higher adsorbent dosage.A 25 mg sorbent dosage was chosen in the following investigations to optimize the remaining factors.

Adsorption isotherm
Understanding the adsorption isotherm is important to determine an optimal elimination procedure.This study utilized the non-linear forms of Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) equations to characterize the equilibrium adsorption at a temperature of 25 °C.The constant factors related to the analyzed isotherms are described in Table 2. R 2 (Regression coefficient values) defines the practicality of the model.The closer the R 2 value goes to one, the better the isotherm model could define the elimination procedure.The Langmuir model is the most widely used equation that considers the adsorbed substance to form a monolayer with a thickness of one molecule.In the Langmuir model, the adsorption occurs as a single layer of molecules.The equation for the non-linear form of the Langmuir adsorption isotherm model is expressed as below 66,67 : In the Langmuir adsorption isotherm model, q e (mg/g) represents the equilibrium adsorption capacity, q m (mg/g) is the maximum adsorption capacity, C e (mg/L) is the equilibrium concentration of adsorbate in the solution after adsorption, and K L (L/mg) is the Langmuir constant.R L is an additional factor used to forecast the likelihood of the adsorption process.R L is a unitless separation factor that should always fall between zero and one to indicate favorable adsorption (0 < R L < 1).The isotherm type is determined by the value of R L , where R L = 1 represents a linear isotherm, R L > 1 indicates unfavorable adsorption, and R L = 0 signifies irreversible adsorption.Equation (4) defines the separation factor R L , where C 0 refers to the maximum initial concentration of the adsorbate, measures in parts per million (ppm), and K L denotes the Langmuir constant [66][67][68][69] .
(3) q e = q m K L C e 1 + K L C e www.nature.com/scientificreports/ The Freundlich model operates on the premise that the adsorbent surface is non-uniform or heterogeneous in nature.This theory suggests that the active sites of the adsorbent are unevenly spread across its surface and possess varying energies, allowing for the adsorption of multiple layers.The Freundlich isotherm equation lacks a fundamental basis and is considered an empirical model.Equation ( 5) represents the Freundlich isotherm model 68,69 : Hence, if a graph is plotted with ln e on the horizontal axis and ln q e on the vertical axis using linear regression, the surface adsorption data will adhere to the Freundlich isotherm model.In this situation, the intercept on the origin of the graph is equivalent to ln K F , while the slope is equal to 1/n.When 1/n = 0, it suggests the adsorption is irreversible; when 0 < 1/n < 1, it indicates a favorable adsorption process; and when 1/n > 1, it implies an unfavorable adsorption process.The Temkin isotherm, represented by Eq. 6, is used to determine the adsorption heat between Ketoprofen and RY15 onto the LF/AgNPs adsorbent.This isotherm considers the interaction between the two substances: In the equation, R is the universal gas constant (8.314J/mol K), b T (J/mol) is related to the adsorption heat constant, K T is the equilibrium binding constant (L/g), and T (K) is the temperature 69,70 .The Dubinin-Radush- kevich isotherm model is a mathematical model used to describe the adsorption behavior of porous materials.The non-linear form of the D-R isotherm is particularly employed to analyze the adsorption of gases or solutes onto solid surfaces, often in the context of porous materials.Equation ( 7) represents the non-linear form of the D-R isotherm model: qm (mg/g) is the maximum adsorption capacity, K (mol 2 /kJ 2 ) is the D-R isotherm constant, ε (J/mol) is the Polanyi potential, given by Eq. 8, where R is the gas constant (8.314J/mol K), T (K) is the temperature, and C e (mg/L) is the equilibrium concentration of the adsorbate.Equation ( 9) is related to the calculation of the mean free energy using the Polanyi potential.The model assumes that the adsorption process occurs on a heterogeneous surface, and the Polanyi potential is used to account for the variation in adsorption energy on the surface.The non-linear D-R isotherm is valuable in understanding the adsorption mechanism and energetics in heterogeneous systems 66,67,71 .
Figure 14 illustrates a graphical representation of Langmuir, Freundlich, Temkin, and D-R isotherm models.Table 2 provides the calculated basic parameters for each of the isotherms.Although some regions of the surface exhibit single-layer adsorption, the Langmuir model does not fit the experimental data well, as indicated by its lower R 2 values when compared to the Temkin model.In both scenarios involving the elimination of ketoprofen ( 4) ) and RY15, the Temkin isotherm exhibits higher R 2 values, specifically 0.997 for ketoprofen and 0.963 for RY15, demonstrating a strong correlation with the observed adsorption data.The Temkin isotherm model assumes a uniform spread of binding energies and accounts for the indirect interaction between LF/AgNPs and contaminants.According to the Temkin isotherm hypothesis, the adsorption heat decreases linearly with increasing surface coverage.The results affirm that the adsorption process of ketoprofen and RY15 can be characterized as a chemisorption process.The Temkin isotherm provides a means to quantify the heat of adsorption, where a positive b T indicates an exothermic process.Furthermore, the D-R model was not fitted well to experimental data and has the lowest correlation coefficients for both contaminants.

Adsorption kinetics
The rate of the adsorption procedure onto the LF/AgNPs adsorbent is significant in all interactions.The Pseudo first-order (PFO) kinetic equation is expressed as follows 4,72 : K 1 (1/min) represents the rate constant of the Pseudo first-order kinetic model.Another model used to describe the adsorption kinetics is the Pseudo second-order model (PSO), which can be expressed using the following equation: K 2 (g/mg min) represents the rate constant of the Pseudo second-order kinetic model.(10)   www.nature.com/scientificreports/ The third equation is the Elovich equation and is expressed as below: α is equivalent to the primary adsorption rate (mg/g min), and β is the desorption constant (g/mg).Moreover, β is linked to the surface coverage degree and activation energy for chemisorption.Equation ( 14) represents the non-linear form of the fractional power equation: The antilogarithm of intercept directs to the k p value.q t is the amount of analyte adsorbed at time t.V p is a constant usually below one if adsorption kinetic data suits well into the power function model.Figure 15 illustrates the plots of Pseudo first-order, Pseudo second-order, Elovich, and fractional power adsorption kinetics 73,74 .
According to the data presented in Table 3, the correlation coefficient (R 2 ) and adsorption capacity were evaluated to determine the most appropriate kinetic model.When comparing the correlation coefficients for ketoprofen removal, it was found that the pseudo-first-order model (R 2 = 0.989) outperformed the other models indicating that it is the leading model that manages the adsorption procedure.The R 2 values of pseudo-secondorder, Elovich, and fractional power models were 0.987, 0.948, and 0.912 respectively.Regarding RY15 removal, the pseudo-second-order model demonstrated superior performance compared to other models, with a correlation coefficient (R 2 ) of 0. 997.The R 2 values of pseudo-first-order, Elovich, and fractional power models were 0.967, 0.992, and 0.972 respectively.Furthermore, when using the pseudo-second-order model, the calculated equilibrium capacity value of ketoprofen (q e , cal = 43.914mg/g) and RY15(q e , cal = 28.925mg/g), were found to be closer to the corresponding experimental value (q e , exp) compared to the results obtained from the other models.Figure 15 presents the results obtained from the mentioned models, including the plots generated through non-linear curve fitting.Table 3 presents the parameters associated with each of the adsorption kinetics.

Possible mechanism of Ketoprofen and RY15 adsorption by LF/AgNPs adsorbents
Figure 16 presents the potential mechanism of Ketoprofen and RY15 adsorption by the LF/AgNPs.Through the modification of the surface of luffa with silver nanoparticles, it is hypothesized that various scenarios could occur.The best scenario for the adsorption mechanism of Ketoprofen and RY15 onto the LF/AgNPs involves the interaction of silver nanoparticles with the aromatic ring of Ketoprofen and RY15.The binding of Ag(I) to the conjugate system of the aromatic ring occurs through the π-metal bond 42,75,76 .Furthermore, the modification of the LF/AgNPs surface resulted in a positively charged adsorbent.This positive charge plays a crucial role in the adsorption of anionic Ketoprofen and RY15 in the.During the synthesis of the LF/AgNPs adsorbent, aromatic groups were introduced into the structure by adding salicylic aldehyde.These aromatic groups can form π-π interactions with the aromatic ring of Ketoprofen and RY15.Moreover, the hydrogen groups present on the surface of the luffa structure can result in the adsorption of Ketoprofen and RY15 molecules.Formation of hydrogen-bonding and π-Hydrogen bonding between the LF/AgNPs adsorbent and contaminants.

Reusability of LF/AgNPs
From an economic standpoint, the choice of adsorbent holds paramount importance both in laboratory experiments and industrial applications in the field of adsorption.Researchers are actively exploring the utilization of economical biomaterials derived from natural sources that are abundantly available in the environment.The reusability of an adsorbent is one of the critical factors that affect the overall cost of the removal process 77 .The present study rigorously examined the reusability potential of LF/AgNPs under optimized conditions, as visually represented in Fig. 17.The results show that the removal percentage of Ketoprofen and RY15 decreased after undergoing five cycles of use.Impressively, even after experiencing five cycles of use, the removal efficiency for  ketoprofen and RY15 adsorption consistently exceeded 85%.Washing LF/AgNPs with ethanol enhances the bonding of Ketoprofen and RY15 with the hydroxyl groups of ethanol, which facilitates the separation of the contaminants from the adsorbent surface.The reduced recovery process also suggests that some Ketoprofen and RY15 molecules tend to attach strongly to the adsorbent surface and are not easily separated during the recovery process.Therefore, in terms of reusability, LF/AgNPs adsorbents demonstrated satisfactory results for the adsorption of Ketoprofen and RY15.

Comparison of LF/AgNPs with other adsorbents
Numerous studies have been conducted to eliminate Ketoprofen and RY15, emerging contaminants, from aqueous solutions.Tables 4 and 5 present a comparison of LF/AgNPs adsorbent with other natural-based adsorbents that have been investigated in recent years for their ability to remove Ketoprofen and RY15.Comparing various adsorbents based solely on their adsorption capacity is not sufficient.To make a more accurate comparison, other factors such as the removal percentage and contact time for adsorption should also be taken into consideration.

Conclusion
This study has demonstrated that the LF/AgNPs adsorbent is highly effective in removing Ketoprofen and RY15 from water media.The addition of Ag nanoparticles to the surface of the adsorbent changes its charge from negative to positive, empowering electrostatic attraction with anionic Ketoprofen and RY15 and altogether progressing its adsorption proficiency.According to the results obtained, the maximum removal efficiencies of Ketoprofen and RY15 from aqueous solutions were 94% and 98% respectively, indicating the high performance of the LF/AgNPs adsorbent in removing Ketoprofen and RY15.The most likely mechanism for the adsorption of Ketoprofen and RY15 is the interaction between the π-electrons of the aromatic ring of Ketoprofen and RY15 and the existed metal (Ag) nanoparticles on the surface of the adsorbent.This type of interaction is known as π-π stacking, and it plays a significant role in the adsorption of organic compounds onto metal surfaces.When it comes to eliminating ketoprofen, the similarity in R 2 values between the Freundlich and Temkin models implies that the adsorption process can adhere to both systems.This suggests the existence of multi-layer adsorption on the adsorbent's surface.In the case of RY15 removal, the Freundlich model is more suitable for describing the adsorption mechanism.Furthermore, it was observed that the pseudo-first-order model surpassed the other models in eliminating ketoprofen.This suggests that it is the primary model governing the adsorption process.In the case of RY15 removal, the pseudo-second-order model exhibited better performance in comparison to other models.Regarding reusability, it is noteworthy that the removal efficiency for ketoprofen and RY15 consistently stayed above 85% even after undergoing five usage cycles.Consequently, in the realm of recyclability, LF/AgNPs adsorbent demonstrated encouraging results for the adsorption of both Ketoprofen and RY15.

Figure 1 .
Figure 1.The potential interaction of PVP and AgNO 3 during the formation of AgNPs.

Figure 9 .
Figure 9.The effect of agitation technique within 10 and 30 min under the optimum conditions.

Figure 10 .
Figure 10.The effect of pH on the removal of RY15 and ketoprofen under the optimum conditions (contact times of 60 min and 40 min, adsorbent dosage of 25 mg and 25 mg, and initial concentrations of 100 mg/L for ketoprofen and 25 mg/L for RY15, respectively).

Figure 11 .
Figure 11.The effect of contact time on the (a) ketoprofen and (b) RY15 removal under the optimum conditions (pH levels of 5 and 2, adsorbent dosage of 25 mg and 25 mg, and initial concentrations of 100 mg/L for ketoprofen and 25 mg/L for RY15, respectively).

Figure 12 .
Figure 12.The effect of initial concentration on the (a) ketoprofen and (b) RY15 removal under the optimum conditions (pH levels of 5 and 2, contact times of 60 min and 40 min, and adsorbent dosage of 25 mg for ketoprofen and 25 mg for RY15, respectively).

Figure 13 .
Figure 13.The effect of adsorbent dosage on the ketoprofen and RY15 removal under the optimum conditions (pH levels of 5 and 2, contact times of 60 min and 40 min, and initial concentrations of 100 mg/L for ketoprofen and 25 mg/L for RY15, respectively).

Table 1 .
The porous structural data obtained from BET analysis.

Table 2 .
Basic parameters calculated for isotherms.

Table 3 .
Kinetic parameters for RY15 and Ketoprofen adsorption.

Table 4 .
Comparison with other adsorbents for the removal of Ketoprofen.

Table 5 .
Comparison with other adsorbents for the removal of Reactive yellow 15.LF/AgNPs adsorbent showed an excellent removal efficiency of 94% for ketoprofen, and 98% for RY15.The adsorption capacity for ketoprofen and RY15 were 56.88 and 97.76 mg/g respectively.In comparison to various natural-based adsorbents, the LF/AgNPs adsorbent demonstrates its suitability and practicality for effectively removing Ketoprofen and RY15 from aqueous solutions.