Synthesis and Characterization of Chitosan/Agar/SiO2 Nano Hydrogels For Removal of Amoxicillin and of Naproxen From Pharmaceutical Contaminants

Today, environmental pollutants pose a threat to human societies and all living organisms, which is why they have attracted the attention of environmental researchers. In this study, in order to remove pharmaceutical contaminants Naproxen and Amoxicillin from aqueous media with SiO 2 nanoparticles based on Agar and Chitosan was investigated. The study of structural properties, physical and chemical characterization of synthesized nanocomposite was investigated by FTIR, XRD, TEM, FE-SEM, DLS and EDX analyzes. In addition, the role of parameters affecting the removal of pharmaceutical contaminants such as solution pH, contact time, contaminant concentration and temperature were studied. Nanocomposites prepared from Agar and Chitosan showed good performance in absorbing naproxen and amoxicillin. According to the studies performed to remove naproxen, the max adsorption eciency was obtained at a concentration of 20 mg/l with an absorbent dose of 0.05 g and a pH of 8 and at an optimum temperature of 25 °C and 99% in 15 min. Also, for amoxicillin with nanocomposite prepared with an initial concentration of 20 mg/l and an adsorbent dose of 0.05 g, a time of 10 min, a temperature of 25 °C and a pH of 8, the max removal eciency of 91.15% was obtained.


Introduction
Pharmaceutical and personal care products are emerging pollutants in water resources that the presence of these products, even in very small quantities, can have adverse effects on the environment.Due to the growing population, according to the forecasts by 2050, the demand for water, food and energy will increase signi cantly by 50%, 70% and 80%, respectively [1].Today, contaminated of the natural water environment by pharmaceutical compounds and personal care products is widespread, and the substances used to treat and prevent disease in humans and animals are compounds in non-steroidal groups [2].According to research conducted in recent years, the presence of sustainable organic compounds such as pharmaceutical and personal care products in e uents and drinking water sources is about µ-ng/l.pharmaceutical compounds and their derivatives due to biological activity and stability in the environment can cause carcinogenesis and mutagenicity in humans, so it must be puri ed before discharge to the environment.Therefore, the elimination of antibiotics, anti-cancer pharmaceutical, cardiovascular, growth stimulants and anti-parasites are of great importance.[3].Also, according to the reports of the US Food and Pharmaceutical Administration (FDA), the concentration of ingredients in pharmaceutical released into the environment is about 0.1 µg/l [4].Naproxen is a non-steroidal antiin ammatory pharmaceutical that does not contain corticosteroids, which block the production of prostaglandins, which are responsible for causing pain and in ammation in the affected area [5,6].Amoxicillin, a component of the antibiotic β-lactam, binds to the penicillin-binding protein (PBP) to inhibit trans peptidases and inhibit the production of bacterial cell wall peptidoglycans, thereby destroying the bacterial cell wall.Among the uses of these pharmaceutical s are pain relief in the treatment of many infections, such as arthritis, muscle spasms, sinusitis, urinary tract infections, and so on [7,8].The chemical structure of naproxen and amoxicillin is shown in Figure 1.
Recently, extensive research has been conducted on the removal of pharmaceutical contaminants, using photocatalytic and adsorbent materials that are biophilic and without any secondary contamination [9][10][11][12].Adsorption processes can be performed through interactions between molecules of contaminants and adsorbents and mainly include hydrogen bonding, electrostatic bonding interactions and π-π interactions [13][14][15][16][17].The adsorption process is also one of the most common and effective wastewater treatment processes that has been considered by many researchers due to its high e ciency, ease of operation and cost-effectiveness [18].SiO 2 particles are spherical shapes and are of special importance due to their unique properties such as high active surface area, high mechanical and thermal resistance, non-toxicity, high porosity, dispersibility in different solvents and environmental compatibility.It has the ability to be an adsorbent or catalyst base, sensors and pharmaceutical carriers [19][20][21][22].Agar extracted from agrophytic algae has a linear polymer structure in nature that is a combination of agarose polysaccharide and agaropectin and is chemically galactane sulfuric ester.Polymer agar can be a potential material as a compound of adsorbent due to its thermal and biodegradability and water resistance, biodegradability, availability and cost-effectiveness [23][24][25][26].Chitosan is a natural polymer derived from cationic polysaccharides, non-toxic and degradable.It also has OH and NH 2 functional groups, which can show a signi cant interaction effect for organic molecules in pharmaceutical uptake.
So far, various methods have been used to remove pharmaceutical contaminants from wastewater, including membrane processes, chemical oxidation, ionic and biological treatment, photofenton decomposition and adsorption, as well as adsorbents such as activated carbon, ash and zeolite [6,32,33].Therefore, the synthesis of adsorbents based on nanoparticles with high surface area, high porosity and adsorption capacity, as well as the ability to separate quickly and easily is essential.One of these methods is the use of natural polymers and SiO 2 nanoparticles that have high porosity and surface area [34][35][36][37][38][39].The inability of contamination treatment plants to remove highly polar micro-contaminated and antibiotics that have entered surface and groundwater sources exacerbates many concerns about microbial and pharmaceutical resistance.Therefore, researchers seek to optimize the adsorption process and achieve new adsorbents with lower cost and higher adsorption capacity [40].
Nodeh and et al. of a GO-MNPs-SiO 2 nanocomposite as an adsorbent for the removal of naproxen.Doping of magnetic Fe 3 O 4 nanoparticles to GO improves permeability and prevents clotting and rapid recovery.The results showed that naproxen was removed by van der Waals interaction force, electrostatic repulsion force and hydrogen bonding.The adsorption capacity with the above adsorbent at pH = 5 was equal to 31 mg/g and also the maximum removal percentage was 90% [5].Conducted and et al. a study to remove ibuprofen, diclofenac, and naproxen from water using chitosan-modi ed rubber tire residues.
The results showed that the larger size range of the modi ed rubber waste tire depends on the chitosan density.As the absorbent dose increases, the absorption rate increases from 25% to 96%.In acidic conditions, due to the protonation of the amine groups in chitosan with a positive charge of the carboxylic group in anti-in ammatory pharmaceutical s, the absorption process has been unfavorable.Also, due to the balance of electrostatic force between chitosan and pharmaceutical in the pH range of 3-6, diclofenac, ibuprofen and ibuprofen were more absorbed, respectively [2].Rahmani Sani et al.Conducted a study using carbon nanotubes to remove the antibiotic sulfadimethoxine from aqueous solutions, which are dangerous environmental pollutants.The results showed that the maximum removal e ciency at pH = 6 with an adsorbent dose of 0.04 g with an initial concentration of 20 mg/g, which was 94.5%.Studies show that the Langmuir model is more consistent with the data obtained [40].Rakhshaei et al. performed a study using synthesized CS-GeL/nZnO nanocomposite scaffolds to heal wounds and increase the antibacterial effects of naproxen.These scaffolds act as a temporary matrix for the proliferation and growth of damaged tissue cells.The bioactivity of chitosan alone is poor and therefore biologically active substances such as collagen or gelatin have been used to overcome these conditions.The micrographs prepared from the scaffolds have well-connected pores with a pore size in the range of 400-50 nm, and therefore the proper hydrogen bond interaction between CS-GeL/nZnO indicates that a size of about 40 nm is suitable for cell growth [41].Ning et al.With the synthesis of CS/SiO 2 /CNTs nanocomposites to investigate the adsorption properties of Direct Blue and Reactive Blue dyes from aqueous solution.The results showed that the maximum adsorption rate occurred at pH=6 for direct blue dye and at pH=2 for reactive blue dye, and also the Langmuir isotherm is consistent with the experimental data [42].In a study Noori et al. of LDH/Al-Mg was investigated to remove carbamazepine, cephalexin, cipro ucan from aqueous media.The results showed that the highest elimination of antibiotics at the time of contact for 120 minutes, the dose of adsorbent per gram of 8 liters and the initial concentration of 30 mg/l for carbamazepine, cephalexin, cipro oxacin were 94%, 91% and 97%, respectively.Also, isotherm and kinetics studies showed that the adsorption data are consistent with the Freundlich and quasi-quadratic model [43].
In this study, in order to remove pharmaceutical contaminants from aqueous media with SiO 2 nanoparticles based on Agar and Chitosan was investigated.The study of structural properties, physical and chemical characterization of synthesized nanocomposites was investigated by FTIR, XRD, TEM, FE-SEM, DLS and EDX analyzes.In addition, the role of parameters affecting the removal of pharmaceutical contaminants such as solution pH, contact time, contaminant concentration and temperature were studied.Nanocomposites prepared from Agar and Chitosan showed good performance in absorbing naproxen and amoxicillin.Nanocomposites prepared as adsorbents were used to remove naproxen and amoxicillin by physical adsorption from aqueous media to take steps to improve the removal of pharmaceutical contaminants from the environment and water and industrial e uents.

Materials
Silicon oxide (SiO 2 ) nanoparticle powder was purchased from US Research Nanomaterials.Agar powder was purchased from Merck, as well as chitosan powder, pharmaceutical amoxicillin and naproxen from Sigma Aldrich.Deionized water was prepared from Neutron Company, cellulose micro lter and 0.22 micrometer syringe lter from Membrane Filter Company.

Synthesis of chitosan/SiO 2 nanocomposites
First, 1 g of chitosan powder was added to 100 ml of 0.1 M acetic acid and placed on a heater-magnet for 60 min at 60 °C to obtain a completely uniform solution.On the other hand, 0.05 g of nanoparticles of SiO 2 was added in 100 ml of deionized water and mixed for 60 min at 50 °C until the solution was completely uniform.The two solutions containing chitosan and SiO 2 were then mixed together and placed in an ultrasonic device for 30 min at 40 °C until completely dispersed.He was then re uxed/ultrasonic for 24 h at a rate of 60 min/15 min.Finally, the resulting mixture was passed through a 0.22 μm cellulose micro lter using a Buchner funnel and an air pump and dried in an oven at 60 °C for 12 h.

Synthesis of Agar/chitosan/SiO 2 nanocomposites
First, 1.05 g of agar powder/ SiO 2 was added to 100 ml of deionized water and placed on a heatermagnet for 1 h at 60 °C to form a uniform solution.On the other hand, add 1.05 g of agar powder to 100 ml of deionized water and mix for 1 h at 60 °C to form a uniform solution.The above solutions were then mixed together and placed in an ultrasonic device for 40 min at 40 °C to disperse.He was then re uxed/ultrasonic for 24 hours at a rate of 60 min/15 min.Finally, the resulting precipitate was centrifuged and passed through a 0.22 μm cellulose micro lter using a Buchner funnel and an air pump.
The material was dried in an oven at 60 °C for 12 h.

Pharmaceutical Adsorption Experiment
Naproxen and amoxicillin at a concentration of 40 mg/l were investigated using synthesized nanocomposite adsorbents.The maximum absorption peak appeared for naproxen 330 nm and amoxicillin 272 nm.The amount of 0.04 g of the mentioned pharmaceutical was selected and reached a volume of 1000 l.Then a certain volume of the above solution was selected and brought to different concentrations.The concentration of the remaining molecules in the solution was isolated by a 0.22 μm syringe micro lter and measured using a UV-Visible spectrophotometer.In this study, the effect of different factors on the adsorption process such as (pH = 8), adsorbent dose of 0.05 g, contact time (5-240 min) and different temperatures were investigated.The removal e ciency, adsorption capacity qt (mg/g) at time t (min) and the adsorption capacity at equilibrium qe (mg/g) were calculated from the following equations: FTIR spectrum was used to characterization the functional groups of synthesized nanocomposite materials.The results of FTIR for the synthesized samples are given in Fig. 2. According to Fig. 2.a, the peaks appearing for chitosan nanoparticles at positions 3434 cm -1 , 1604 cm -1 and 1074 cm -1 correspond to the tensile vibrations of OH, C = C and C-O alkoxy, respectively [44].For SiO 2 nanoparticles, the peaks appearing in positions 3432 cm -1 , 1381 cm -1 and 1074 cm -1 are related to the tensile vibrations of OH, C = C and C-O alkoxy and the peak 572 cm -1 belongs to the SiO 2 group (Fig. 2.b) [45].Also, the peaks observed in 3532 cm -1 , 2898 cm -1 and 1658 cm -1 are related to OH, C = H and C = C tensile strength in agar, respectively (Fig. 2.c) [46].Peaks observed for Agar/Chitosan samples at positions 3740 cm -1 (correspond to the group N-H), 3444 cm -1 (correspond to the group O-H), 1617 cm -1 (correspond to the group C=O), 1058-1368 cm -1 (correspond to the group C-O) and 572 it is related to the presence of Si=O group on the nanocomposite (Fig. 2.d).Observed peaks of Chitosan/SiO 2 nanocomposites in positions 3737 (correspond to the group N-H), 3413 cm -1 (correspond to the group O-H), 16413740 cm -1 (C=C correspond to the group), 1068 cm -1 (C-O correspond to the group) and 687 cm -1 and 646 cm -1 correspond to the belong to the C-C group (Fig. 2.e).For Agar/Chitosan/SiO 2 nanocomposites, the peaks observed in 3435, 1640 cm -1 and 537 cm -1 belong to the tensile group OH, C=C and Si=O, respectively.

XRD
The crystal structures of Agar/Chitosan, Chitosan/SiO 2 and Agar/Chitosan/SiO 2 nanocomposites were investigated by X-ray diffraction (XRD).The results showed that they were consistent with previous reports (Fig. 3).Sharp peaks at 2 for Chitosan/SiO 2 nanocomposites at 26.41˚ and 11.99˚ and for SiO 2 nanoparticles at 42.29˚, representing amorphous carbon in the structure (Fig .3.c).As shown in Fig. 3.d, the XRD spectrum for Agar/Chitosan nanocomposites is a peak sharpness at 2 at 12˚ and for agar at 28å nd 42˚ representing amorphous carbon.According to Fig .3. e for Agar/Chitosan/SiO 2 nanocomposites Sharp peaks observed at 2 at 8.92˚ for chitosan and peaks at 17˚, 19˚ and 20.74˚ for SiO 2 as well as peaks at 26.47˚And 42.52˚ indicates amorphous carbon in the structure [47][48][49].

TEM and FE-SEM
FE-SEM image was taken from synthesized Agar/Chitosan, Chitosan/SiO 2 and Chitosan/Agar/SiO 2 nanocomposites to investigate morphology and particle size (Fig. 4).According to the FE-SEM image of Fig. 4.a for Agar/Chitosan nanocomposites, the particle size varies from 22.33 -35.73 nm.According to the g.4.bThe morphology of SiO 2 nanoparticles and its presence in the nal product is clearly con rmed and for Chitosan/SiO 2 nanocomposites the size of nanoparticles is between 24.56 -42.43 nm.The image of Chitosan/Agar/SiO 2 nanoparticle nanocomposite is shown in Fig. 4.c which shows the morphology of SiO 2 nanoparticles and its presence in the nal product.According to the image TEM g.5 the morphology of SiO 2 nanocomposites is hexagonal and the particle size varies from 30 to 300 nm.

EDX
EDX analysis was performed to evaluate elemental analysis of synthesized nanocomposite materials (Fig. 6).According to Fig. 6.a for Agar/Chitosan nanocomposites, there is about 51.6% by weight of carbon atoms, 28.9% by weight of oxygen and 19.4% by weight of nitrogen in the synthesized nanocomposite structure.According to the results of EDX analysis, about 52% by weight of carbon atom, 24.2% by weight of oxygen, 16.5% by weight of nitrogen and 7.2% of silicon oxide are present in the Chitosan/SiO 2 nanocomposite, which clearly con rms the presence of silicon oxide (Fig. 6.b).For Agar/Chitosan/SiO 2 oxide nanocomposites, there is about 46.3% by weight of carbon atom, 35.3% by weight of oxygen, 12.7% by weight of nitrogen and 5.9% by weight of silicon oxide in the sample structure (Fig. 6.c).

DLS (Dynamic light scattering)
The light scattering spectrum of Agar/Chitosan/SiO 2 nanocomposites is shown in Fig. 7.As it is known, the synthesized sample was in the size of 100 nm and less and its maximum amount was in the range of 100 nm based on its number.

Pollutant removal 3.2.1. Initial concentration pollutant
Effect of initial concentration on naproxen and amoxicillin pharmaceutical with synthesized adsorbents in different concentrations (10,30,20 and 40 mg/l) in 25 ml of pharmaceutical solution with optimal adsorbent amount (0.05 g) and with optimal pH adjustment (8) was investigated at speci ed intervals (40 min) on a magnetic stirrer at room temperature (25 °C).According to Fig. 8. (a, b), the maximum amount of adsorption for naproxen with Agar/Chitosan and Agar/Chitosan/SiO 2 nanocomposite adsorbents occurred at a concentration of 10 mg/l, which is equal to 99%, which with increasing initial concentration to 40 mg/l, the removal e ciency reached its maximum value and its value remains constant and more active adsorption sites are used and lled, so that after a certain concentration the removal e ciency does not change and remains constant.The maximum adsorption for amoxicillin with Agar/Chitosan and Agar/Chitosan/SiO 2 nanocomposite adsorbents occurred at initial concentrations of 20 mg/l, with removal e ciencies of 97.85% and 87.9%, respectively, and with increasing concentration to 40 mg/l more than The active adsorption sites are used and lled so that the removal e ciency is independent of the concentration and its value remains constant (Fig. 8. (c, d)) [50][51][52][53][54].

Effect
The pH of the solution is one of the most important factors in the adsorption process that can change the surface charge of adsorbents as well as the separation of functional groups in the active sites of adsorbent adsorption.Therefore, it is very important and necessary to study the effect of pH on the removal process.Effect of solution pH on naproxen and amoxicillin with Agar/Chitosan and Agar/Chitosan/SiO 2 at different pHs in 25 ml of pharmaceutical solution with optimal concentration (20 mg/l), optimal adsorbent (0.05 g) and was tested for 40 min on a stirrer at room temperature (25 °C).The results of this study are shown in Fig. 9.As shown in Fig. 9. (a, b), the removal e ciency of naproxen with Agar/Chitosan and Agar/Chitosan/SiO 2 adsorbents did not increase signi cantly with increasing the pH of the solution from 6 to 10, and the removal e ciency at pH=6 was at its max 99%.It can be said that slight competition between pharmaceutical ions increases the pH due to decreasing the concentration of H + ions to bind to the adsorbent surface causing a slight change, so pH=6 was considered effective.The removal e ciency of amoxicillin with Agar/Chitosan and Agar/Chitosan/SiO 2 adsorbents reaches its max value of 68% and 84% by increasing the pH of the solution from 4.6 to 8.6, respectively, at pH 7.6, 8.6.From Fig. 9. (c, d) * it can be seen that by increasing the pH of the solution, the removal e ciency increases and increasing the pH of the solution increases the number of hydroxyl groups, which increases the number of active sites with a negative charge between the pharmaceutical and the adsorbent surface [55,56].

Adsorption contact time
Effect of contact time on absorption of naproxen and amoxicillin with synthesized Agar/chitosan and Agar/chitosan/SiO 2 adsorbents in the time range of 5-240 min and by keeping other parameters constant (initial concentration 20 mg/l, the amount of adsorbent was 0.05 g and pH = 8) at room temperature.The results of this study are shown in Fig. 10.As shown in Fig. 10 (a-d), the uptake of these pharmaceutical with Agar/chitosan and Agar/chitosan/SiO 2 adsorbents did not change much over time and reached equilibrium in the early times.Rapid pharmaceutical uptake in the early stages of the uptake process can be attributed to multiple voids and active sites of the adsorbent surface [57,58].The results showed that the optimal values of contact time for removal of naproxen and amoxicillin with Agar/chitosan and Agar/chitosan/SiO 2 adsorbents were 99%, 90%, 80% and 90% in the rst 10 min, respectively.

Impact temperature
The effect of temperature on the adsorption of naproxen and amoxicillin with nanocomposite adsorbents of Agar/chitosan and Agar/chitosan/SiO 2 at speci ed intervals (5-30 min) and by keeping other parameters constant (initial concentration 20 mg/l, the amount of adsorbent (0.05 g and pH = 8) was evaluated at different temperatures (10, 15, 20, 25 and 30 ˚C).The results of this study are presented in Fig. 11.According to Fig. 11.(a, b), with increasing temperature from 10 to 30˚C, the removal e ciency for naproxen for both adsorbents is 99% and is temperature independent.Also, for amoxicillin with increasing temperature from 10 to 30˚C, the removal e ciency for Agar/chitosan adsorbent at 20 °C is 67.35% and for Agar/chitosan/SiO 2 adsorbent at 30 ° C is 87.75%.Because the velocity of pharmaceutical molecules is controlled by temperature, the rate of removal does not change with temperature.In other words, with increasing temperature due to greater resistance of viscous forces, reduces the molecules of the pharmaceutical in the outer boundary layer and the inner pores of the adsorbent particles.On the other hand, the small size of the particle pores causes more resistance to particle emission [59,60].

Conclusion
In this study, in order to removal of pharmaceutical contaminants from aqueous media with nanocomposite Agar/Chitosan/SiO 2 was investigated.The study of structural properties, physical and chemical characterization of synthesized nanocomposites was investigated by FTIR, XRD, TEM, FE-SEM, DLS and EDX analyzes.Nanocomposites prepared from Agar and Chitosan showed good performance in absorbing naproxen and amoxicillin.According to the studies performed to remove naproxen, the max adsorption e ciency was obtained at a concentration of 20 mg/l with an absorbent dose of 0.05 g and a pH of 8 and at an optimum temperature of 25 °C and 99% in 15 min.Also, for amoxicillin with nanocomposite prepared with an initial concentration of 20 mg/l and an adsorbent dose of 0.05 g, a time of 10 min, a temperature of 25 °C and a pH of 8, the max removal e ciency of 91.15% was obtained.