Agarose/micrometer anatase (TiO2) beads were essayed to test the photocatalytic capacity of two of the worldwide most prescribed drugs: paracetamol and ibuprofen. Although the first tests showed good degradation rates for both drugs, the presence of turbidity, due to TiO2 leakage, during the photocatalytic essays induced to improve the stability of the photocatalytic composites. Among the different strategies adopted to strengthen such materials, crosslinking with citric acid and the use of alternative gelling agents: gellan, agargel™ and agar were chosen. Composites obtained merging both strategies were characterized and employed to degrade both drugs under a simulated light that mimics the solar spectrum (indoor). Considering the superior degradation rates obtained when agar and agarose were used to shape the titanium oxide particles, such composites were subjected to a more realistic experiment (outdoor): solar illumination, tap water and higher volumes, that should facilitate its ulterior scale up as a real wastewater depollution procedure.
Research Article
Optimization of Tio2-natural Hydrogels for Paracetamol and Ibuprofen Degradation in Wastewaters.
https://doi.org/10.21203/rs.3.rs-3574890/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 31 Jul, 2024
Read the published version in Environmental Science and Pollution Research →
You are reading this latest preprint version
Polysaccharides
Anatase
photocatalysis
water-purification
Ecofriendly
Pharmaceutical and personal care products have become in a worldwide environmental concern due to their presence and potential harmful effects in many types of aquatic milieus such as wastewaters, surface and ground water or drinking water (Adeyemi et al. 2021, Deb et al. 2019, Meijide et al. 2022, Sanusi et al. 2023, Shaheen et al. 2022, Yang et al. 2017). These substances treatment, whose source may come from inadequate discharges from pharmaceutical industries or hospital and houses sewages, in purification plants is, nowadays, insufficient due to the lack of technology to retain and/or degrade such compounds and their possible intermediates (Ahammad et al. 2022, Alzola-Andrés et al. 2023, Candido et al. 2017, Kumar et al. 2023, Patel et al. 2019, Reis et al. 2022, Rivera-Utrilla et al. 2013, Wu et al. 2023). Ibuprofen (Brillas 2022, Miranda et al. 2021, Tanveer et al. 2019) and paracetamol (Moctezuma et al. 2012, Peralta-Hernández &Brillas 2023, Phong Vo et al. 2019, Shah &Rather 2023, Yang et al. 2008, Zhang et al. 2008), the two drugs subjected to degradation in this study, are among the most synthetized and consumed painkillers globally and have been determined to have deleterious consequences on the aquatic wildlife thus affecting the trophic chain and, ultimately, human health.
Among the different treatments employed to process these pollutants: membranes based techniques, sedimentation, coagulation/flocculation, activated sludge, biodegradation, chemical precipitation and solar photolysis, advanced oxidation technologies or processes (AOTs, AOPs) have consolidated as a powerful and feasible alternative (Gupta &Chauhan 2021, Kaur et al. 2016, Kulišťáková 2023, Kumar et al. 2020, Marinho et al. 2022, Meijide et al. 2022, Reis et al. 2022, Rodriguez-Narvaez et al. 2017, Salimi et al. 2017, Thakur et al. 2023). The anatase polymorph of titanium dioxide, crystallized in the nanometer scale, has been largely utilized for this task (Ajmal et al. 2014, Bosio et al. 2019, Fujishima &Zhang 2006, Hashimoto et al. 2005, He et al. 2016, Kanakaraju et al. 2014, Mahmoud et al. 2017, Nakata &Fujishima 2012, Sarkar et al. 2014, Tong et al. 2012). Different strategies have been adopted to increase the photocatalytic performance by tailoring the textural and microstructural properties: dopants inclusion, controlled synthesis, designable pore architecture, hybrid assemblies or avant-garde support substrates (Chen et al. 2015, Lee &Park 2013, Murgolo et al. 2021, Nakata &Fujishima 2012, Reddy et al. 2015, Santacruz et al. 2012, Sharma et al. 2023). Unfortunately, despite the exceptional results obtained, many of these materials are unviable to be used due to the substantial amounts employed in actual depollution procedures. Above and beyond the complex synthetic routes or technologies required, which rises the expenses and difficult the industrial scale-up, the widespread utilization of nano-sized materials has converted in a argumentative concern due to their latent threat for human health (Baranowska-Wójcik et al. 2020, Bianchi et al. 2014, Sungur 2021).
Likewise, a serious topic to be elucidated is the way the depolluting material is added within the contaminated mass to be processed. The usually-employed addition in the pulverized form preserves the conservation of the tailored properties, mostly the surface area, but compromises its total recovery, particularly when nanoparticles are used. Different strategies have been implemented to overwhelm this problem: pieces shaping, encapsulation, substrate coating…(Rao et al. 2004, Reveendran &Ong 2018, Shan et al. 2010). Among them, the use of natural (Balakrishnan et al. 2022, Bhatnagar &Sillanpää 2009, De Filpo et al. 2015, Gjipalaj &Alessandri 2017, Mohd Adnan et al. 2020, Sarkar et al. 2015) and artificial polymers (Du et al. 2020, Jiang et al. 2016, Katzenberg et al. 2020, Pereira et al. 2021, Reddy et al. 2015) to aggregate the photocatalytic particles under mild conditions results a encouraging shaping alternative. Indeed, these polymeric matrixes have demonstrated a remarkable capacity to immobilize/sequester diverse pollutants such as pesticides, dyes, pharmaceuticals or heavy metals even when no photocatalytic component is included (Baigorria et al. 2021, De Gisi et al. 2016, Karimi-Maleh et al. 2021, Mai et al. 2017, Mai et al. 2018, Rafatullah et al. 2010, Rathi &Kumar 2021, Seow &Hauser 2016).
In a previous work (Ponce et al. 2022) a material, constituted by agarose as a support/vehicle to shape the photocatalytic micrometer-particles (anatase), was optimized to degrade two textile dyes: Methylene Blue and Rhodamine. The present work focusses on the adaptation of this material to the degradation of two drugs, always having in mind the design of a low-cost and eco-friendly product thank to the use of renewable polysaccharides, the minimization of the fabrication and processing technology and the possibility of reutilization for several depolluting cycles.
2.1 Pieces preparation
Table 1 depicts the compositions prepared containing two amounts of TiO2 (60 and 90% w/w denoted to the solid content) and a fixed percentage (5% w/v) of the hydrogel content. The so obtained materials were termed as a function of the polysaccharide used and the quantity of anatase.
Regardless of the type of hydrogel employed, these composites were prepared following this synthetic procedure: 5 g of the polysaccharide were suspended in 100 mL of deionized water, stirred and heated to 85ºC. Subsequently, the ceramic amount was poured into the translucent sol and the so obtained suspension was energetically stirred before being added into molds.
The composites were shaped as spheres/ellipsoids of approximately 5 mm in diameter since our previous work (Ponce et al. 2022), devoted to the degradation of methylene blue and rhodamine, showed the best compromise between degradation capacity, easiness of fabrication, manipulation and recovery after a decontamination process.
The agarose-based pieces, showing a rubbery consistency, were directly used, as prepared, in the previous degradation tests that allowed to detect the generation of a turbidity due to the leakage of the photocatalytic ceramic. These same pieces were employed in the coating and crosslinking strategies (Fig. 1). In the COATING route the beads were immersed for two hours in 2.5% (w/v) aqueous solutions of alginate, gelatin (the solution was heated to 50oC) and chitosan (in this case the required amount, 2.5 g, was previously added in 100 mL of an acetic acid solution in water (1% w/v) and left overnight to guarantee its total dissolution). Similar solutions were employed to prepare the materials by BLENDING them with equivalent volumes of agarose solutions containing the corresponding amount of TiO2. The CROSSLINKING route consist on submerging the beads into a 0.1M citric acid solution and left overnight at 40oC; subsequently the pieces were rinsed in a NaOH 0,01M solution and deionized water until a pH = 7 is reached. In the case of the strategy based on increasing the percentage of the GELLING CONTENT the beads were prepared by duplicating the amount of agarose (10% w/v) and maintaining the ceramic quantities.
The different types of spheres/ellipsoids were freezed at -86oC before being freeze driying in a (Lia-bor) lyophilizer reaching freezing and sublimation temperatures and a sublimation pressure into a chamber of -45 ºC, from − 45 to 25ºC and 4.54 x 10− 4 atm., respectively. Alternatively, beads were maintained in the fresh (hydrated) state by immersing them, once prepared, in deionized water.
2.2 Drug degradation experiments
Two different pigments: paracetamol (PRT, acetaminophen) and ibuprofen (IBU) were exposed to an indoor degradation essay illuminating by means of an Osram Vitalux (daylight) lamp, fixed one meter over the solutions to guarantee 10 W/m2, as measured with a DSE-100 X/L Spectroline Photometer. The materials to be tested were submerged into 250 mL of a 20 ppm PRT or a 20 ppm IBU solution; each essay implied three Erlenmeyer containing the pieces to be tested and a fourth with no material that acted as a blank test. One of these sets was exposed to artificial illumination and a second one was maintained in a dark area. A Jasco V-650 UV-VIS Spectrophotometer was used for monitoring the dyes degradation. The concentration of the PCT and IBU dyes was determined from the absorption values at 245 and 222 nm, respectively; calibration curves with R2 > 0.99 were acquired for each dye.
2.3 Pieces characterization
The samples were characterized by X-ray Diffraction (XRD) in a Philips X-Pert MPD diffractometer with Bragg-Brentano geometry, working with CuKα radiation (λ = 1.5406 Å) at 45 kV and 40 mA. The X-ray diffraction patterns were collected over the range between 4o and 40o 2θ with a step size of 0.02ο 2θ and a counting time of 5 s per step. Surface morphology was studied by Scanning Electron Microscopy (SEM) in a JEOL 6400 Electron microscope equipped with an Energy Dispersive X-Ray (EDX) analyzer. An Hg intrusion porosimetry characterization was performed employing a Micromeritics AutoPore III 9410 porosimeter between 0.1 and 30,000 psi. Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) were carried out in a TA instruments TG/DTA analyser, with 10oC/min heating ramps. The textural properties were determined by nitrogen adsorption/desorption analyses at 77 K on a Micromeritics ASAP 2020 instrument (Micromeritics Co, Norcross, USA). The surface area (SBET) was calculed using the Brunauer-Emmett-Teller (BET) method.
2.4 Reagents
Acetaminophen (Paracetamol) (Sigma-Aldrich, A5000), Acetic Acid (Sigma-Aldrich, 695092), Agar extra pure, EMPROVE® ESSENTIAL, Ph. Eur., BP (Sigma-Aldrich, 1.01615), Agargel™ (Sigma-Aldrich, A3301), Agarose, BioReagent, for molecular biology, low EEO (Sigma-Aldrich, A9539), Chitosan (Guinama, QC-00170161), Gelatine from porcine skin (Sigma-Aldrich, G2500), Ibuprofen (Sigma-Aldrich, I4883), Phytagel™ (Gellan) (Sigma-Aldrich, P8169), Sodium alginate (Sigma-Aldrich, W201502), Sodium Hydroxide (Sigma-Aldrich, S5881), Titanium oxide (anatase, Panreac 2021010914).
In our previous work (Ponce et al. 2022) a re-utilizable low-cost eco-friendly material based on TiO2 and agarose was optimized for the degradation of Methylene Blue and Rhodamine B pigments. Taking the obtained conclusions into account, the photocatalytic agent was shaped as Spheres/ellipsoids using 5% wt. agarose solutions aiming to degrade the two drugs objective of this study.
The first results indicated good degradation rates for both drugs, better for A90 (PRM C/Co: 0.29 and IBU C/Co: 0.24) than for A60 pieces (PRM C/Co: 0.39 and IBU C/Co: 0.32) after a one-week lasting experiment. However, a white turbidity was progressively generated during the experiment, more intensively when ibuprofen solutions were degraded in the presence of the highly loaded composites (A90). The precipitate deposited was identified by X-ray diffraction (data not shown) as anatase, the photocatalytic agent introduced in the beads. Thermogravimetry analysis was employed to try to quantify the amount lost, the examination of the beads used in degradation experiments showed that less than a 5% of the ceramic component had been lost. Despite this scarce percentage, different strategies were proposed to minimize the TiO2 leakage by reinforcing the gelling matrix (Fig. 1). The first idea consisted on increasing the agarose CONTENT to try to entrap more efficiently the ceramic particles. However, the leakage did not completely disappear and the fabrication of the pieces was hindered due to the higher viscosity of the agarose gels. The COATING or BLENDING with chitosan, alginate or gelatin did not eliminate completely the turbidity generation and complicated the beads manufacture. Fortunately, the use of citric acid to CROSSLINK the agarose resulted in less permeable matrixes that did not allow the TiO2 particles migration as deduced from the absence of turbidity. Figure 2 shows the degradation results obtained for crosslinked vs. non treated materials; in addition, freshly prepared samples, treated with citric ac., were, as well, included in this preliminary photocatalytic characterization. These results confirmed a superior photocatalytic efficiency for those samples containing the higher ceramic percentage (A90), and shoed very similar degradation rates for the different series considered: non-treated lyophilized, and crosslinked lyophilized and non-lyophilized. The employment of beads without a drying preservation method had not been included among the strategies depicted in Fig. 1 but it was considered taking into account the possible alteration of the matrix integrity during the freeze-drying and rehydration process.
The use of hydrated beads, i.e. without being preserved through a drying procedure, was considered as a plausible and practical alternative once that it was observed that they could be easily stored in water during years. These materials did not evidence any shape alterations, morphology modifications or ceramic particles leakage and maintained the photocatalytic efficiency. This work focuses on the use of this type of “hydrated or fresh” spheres thus avoiding the requirement of a drying step by means of a freeze-drying infrastructure, not always available. Indeed, following the objective of this research of minimizing the complexity of the synthetic and fabrication routes, aiming to facilitate the scale-up of this technology, the citric acid treatment was productively replicated under sunlight in a summer day in a greenhouse. In this sense, the alternative gelling agents: gellan, agargel™ and agar were chosen, besides their aggregation capacity, as a function of their renewal origin as well as, in the last case, lower cost and higher availability.
Manipulable and stable beads containing the two already studied percentages (60, 90) were successfully prepared by employing the four gelling agents. All these materials show the same macroscopic aspect exposed in the inset of Fig. 2. Once crosslinked, the FTIR characterization allows to confirm the formation of an ester bond as evidenced, more easily in the absence of the ceramic component, by the band observed at 1720 cm− 1 (Fig. 3) (Awadhiya et al. 2016, Mali et al. 2017, Ponnusamy et al. 2022, Simões et al. 2020). Despite the simplicity of this procedure: low temperatures and the absence of activators, it ensures a sufficient crosslinking to support the aggressive media generated during the drug degradation experiments. In addition, it can be, even, applied out of a laboratory contrastingly to other more effective and controlled routes. Moreover, citric acid has been termed as a “green” cross-linker due to its non-toxic nature, readily availability and inexpensively that has been successfully employed in the biomaterials field (Moon et al. 2019, Salihu et al. 2021). A scheme of the agarose crosslinking due to the presence of the citric acid has been depicted in Fig. 1.
A potential concern may arise about how this treatment may affect to the morphology and microstructure of these composites. The characterization techniques employed (SEM, TG-DTA and MIP) allows to conclude that these materials, independently on the gelling agent used, can still be described as a hydrogel matrix in which the TiO2 particles are completely embedded, even for the higher ceramic loads. The polysaccharide chains, whose mobility has been restricted due to the crosslinking, do not only entrap the anatase particles but also generates a pore architecture that allow a fluids migration throughout the materials that ensure the intimate contact between the dissolved drugs and the photocatalytic agent. This structure can be envisaged by means of the Mercury Intrusion Porosimetry (MIP), depicted in Fig. 4, that shows two different assemblies depending on the amount of ceramic included. Independently on the gelling agent, the highly loaded spheres (90%) showed an almost monodispersal pore distribution centered between 0,1 − 0,05 µm that can be attributed to the space left among the ceramic particles. On the contrary, in those samples with less amount of TiO2, the role of the hydrogel component increases leading to the generation of a porosity, around 100–200 µm when freeze-drying is applied, which otherwise would be occupied by water. This much opened structure resulted more effective to degrade the dyes studied in our previous work (Ponce et al. 2022) but, taking into account the degradation results already mentioned and those described hereinafter, the amount of photocatalytic agent is more critical in this case. Figure 5, that depicts the SEM micrographs, show scarce differences between the different gelling agents (a-d), all showing the characteristic honeycomb structure based on the 100–200 µm pore distribution already detected by MIP. This figure demonstrates, as well, the perfect integration of the ceramic particles within the agarose and agar polysaccharides as can be observed, even, within the thin walls that compose the cells of the honeycomb (e,f). In order to discern whether this embedding may affect to the catalytic surface exposed, N2 adsorption measurements were carried out. As shown in Fig. 6, very similar isotherms and specific surface area values (7 m2/g) can be observed for the TiO2 powder and the A60 and A90 composites.
The thermogravimetric characterization allows, by examining the amount of the ceramic residue that remains after calcining at 600oC, to confirm the scarce differences of the prepared materials, in terms of composition, when compared to the theoretical values shown in table 1. Moreover, Fig. 7a depicts the thermal decomposition of lyophilized samples as well as those hydrated; the last ones experiment a significant weight loss around 100oC, and a second one more extended, in terms of temperature, that can be ascribed to water and agarose elimination, respectively. The hydrogel calcination can be more precisely outlined in dried samples; the agarose is completely removed at 450oC thus allowing to calculate the organic (polysaccharide) and inorganic (TiO2) percentages. In addition, the detection, by means of the Differential Thermal analysis, of endo and exothermic transitions during the polysaccharide’s elimination allows to deduce modifications attributable to chemical changes after the crosslinking, interaction with the titanium oxide or spatial distribution of the organic component among the ceramic particles. The curves observed after the crosslinking treatment are characterized by a unique endothermic peak around 400-450oC that supposes a slight temperature displacement (agarose, gellan) or a simplification on the decomposition pattern (agar, agargel™). However, much considerable changes are detected due to the interaction with the ceramic: decomposition patterns with less intense peaks located at 300 and 400oC. Finally, Fig. 7b includes, as well, the curves of samples employed in a degradation experiment under light (A90 L) or dark (A90 D) conditions; the null changes observed when compared with the as prepared sample (A90) reveals that the interaction with the drugs do not alter the photocatalytic composites.
In order to test the degradation capacity, as well as the possibility of reutilizing several times the photocatalytic beads, an experiment, consisting on exposing these materials to three cycles in which the ibuprofen or paracetamol solution was renewed, was carried out. The already used spheres were rinsed in deionized water before initiating a new cycle. Figure 8, which depicts the UV spectra at the different times considered in each cycle, demonstrates a progressive diminution on the intensity of the most characteristic bands, including those employed to quantify the degradation of paracetamol (245 nm) and ibuprofen (222 nm) The degradation results depicted in Figs. 9 (paracetamol) and 10 (ibuprofen) permit to draw the following tendencies: 1) Agar and agarose manifest the best results when compared with gellan or agargel 2) Higher ceramic contents ensure better catalyzation 3) Similar degradation rates are observed for both drugs only differentiating in the faster initial catalysis followed by a much-sustained step of ibuprofen while paracetamol is destroyed more progressively in a linear way 4) Degradation rates slightly increase with the recycling cycles.
The observed degradation percentages reach, in the most efficient experiments (agarose and agar with the highest ceramic amount), up to 70–75% of drug destruction in the first series of essays. This degradation increases in a 5% after a new experiment reusing the photocatalytic beads thus demonstrating a stability and regenerating capacity that has been scarcely described for photocatalytic materials used in drug treatment (Choina et al. 2014, Jallouli et al. 2017, Khedr et al. 2019). Lower destruction rates were obtained when gellan alone or blended with agar (Agargel™) were employed. Despite these slightly lower results these gelling agents have demonstrated the capacity to obtain durable and stable materials with similar microstructure to those containing agar or agarose. In fact, gellan containing TiO2 particles has been proposed to be applied as wound dressing as well as for diverse cleaning and disinfecting purposes (De Filpo et al. 2015, Ismail et al. 2019, Razali et al. 2020). The excellent results obtained with agar supposes a cheaper and even more ecofriendly (no extraction process of agarose is required) alternative to the use of this polysaccharide as a gelling agent.
Concerning the role of the ceramic content, it can be clearly observed that any of drugs degradation improves with the amount of anatase, around a 10% when comparing samples containing a 60% in the solid content to the equivalent inclosing a 90%. Conversely, in the previously studied dye degradation, lower ceramic percentages, which ensures a higher porosity and a faster and more facile interaction with the surrounding media, yield higher degradation rates. This difference can be attributed to the slower degradation rate observed for the drugs essayed when compared to the pigments studied (methylene blue and rhodamine). As it has been demonstrated by means of the texture and porosity characterization (Figs. 4, 5), the drug-polluted media reaches in no time the photocatalytic particles whose exposed surface is not altered by the shaping action of the gelling agent. At this point the higher amount of titanium dioxide interacting with the drugs to be degraded explains these higher depletion percentages.
The degradation rates, very comparable for both drugs but slightly higher for ibuprofen, can be explained considering the analogous structure based on an aromatic ring that undergoes an initial hydroxylization of the side chain groups followed by the ring opening which finally gives out CO2 and H2O. Both degradation mechanisms, initiated by the HO• radicals formed by the photogenerated e− and h+ pairs when the anatase is illuminated by solar light, have been extensively discussed in the literature: the different intermediates formed during the paracetamol (Moctezuma et al. 2012, Phong Vo et al. 2019, Yang et al. 2008, Zhang et al. 2008) and ibuprofen (Brillas 2022, Choina et al. 2014, Ferrando-Climent et al. 2012, Jiménez-Salcedo et al. 2019, Miranda et al. 2021) destruction explain the dissimilar degradation kinetics by which the initially ibuprofen fast catalyzation is followed by a much steady step that equals the results obtained for paracetamol.
Taking these results into account, only agar and agarose-based beads were employed in the experiment designed (higher volumes of tap water and exposition to sunlight) to approach more closely to the conditions employed in actual decontamination processes. The so obtained results, depicted in Fig. 11, show analogous tendencies to those observed in the indoor essays: similar degradation rates for both drugs and gelling agents as well as greater for beads containing the highest amount of ceramic. The only difference lies in the faintly better destruction percentages that almost reach a 90% under these conditions.
Two renewable polysaccharides, agar and agarose, have been optimized to prepare TiO2-containing beads for drug degradation purposes. A simple treatment: immersion in a citric acid solution, that can even be carried out without any laboratory equipment, reinforces their mechanical and chemical stability. This crosslinking reaction avoids the ceramic leakage detected in the degradation of ibuprofen and paracetamol.
These materials have been designed to be: 1) ready to use after being stored in water, 2) Ecofriendly in terms of the natural origin of the gelling agents and the absence of aggressive chemical reaction or synthetic procedures 3) Re-utilizable as demonstrated by the maintenance of the degradation efficiency after three cycles indoor 4) Economical due to the simplification of the synthetic and processing technology, no lyophilization is needed, together with the use of the cheaper and more available agar.
The application of such materials in an experiment designed to mimic, as far as possible, the conditions employed in a real depollution procedure, yields destruction percentages close to a 90% for the most efficient beads.
Moreover, the crosslinked polysaccharides can be used as a vehicle for any other type of photocatalytic agent with enhanced degradation properties whose tailored microstructural and textural properties would not be significantly modified due to the mild conditions employed in this shaping technology.
Acklowledgements
The XRD measurements were performed at C.A.I Difracción de Rayos X (UCM). The Scanning Electronic Microscopy characterization was carried out at C.A.I. Centro Nacional de Microscopía Electronica (UCM).
Ethical Approval
Not applicable
Consent to Participate
All the authors declare their consent to participate in this research work.
Consent to Publish
All the authors declare their consent to publish this research work.
Competing Interests
The authors have no relevant financial or non-financial interests to disclose.
Funding
The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Author Contributions
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by J. Peña, J. Ponce, D. Sanz and J.M. Pastor. The first draft of the manuscript was written by J. Peña and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
- Adeyemi JO, Ajiboye T, Onwudiwe DC (2021) Mineralization of Antibiotics in Wastewater Via Photocatalysis. Water Air Soil Pollut 232:219
- Ahammad NA, Ahmad MA, Hameed BH, Mohd Din AT (2022) : A mini review of recent progress in the removal of emerging contaminants from pharmaceutical waste using various adsorbents. Environ Sci Pollut Res.
- Ajmal A, Majeed I, Malik RN, Idriss H, Nadeem MA (2014) Principles and mechanisms of photocatalytic dye degradation on TiO2 based photocatalysts: a comparative overview. RSC Adv 4:37003–37026
- Alzola-Andrés M, Domingo-Echaburu S, Segura Y, Valcárcel Y, Orive G, Lertxundi U (2023) Pharmaceuticals in hospital wastewaters: an analysis of the UBA’s pharmaceutical database. Environ Sci Pollut Res 30:99345–99361
- Awadhiya A, Kumar D, Verma V (2016) Crosslinking of agarose bioplastic using citric acid. Carbohydr Polym 151:60–67
- Baigorria E, Galhardi JA, Fraceto LF (2021) Trends in polymers networks applied to the removal of aqueous pollutants: A review. J Clean Prod 295:126451
- Balakrishnan A, Appunni S, Chinthala M, Vo D-VN (2022) Biopolymer-supported TiO2 as a sustainable photocatalyst for wastewater treatment: a review. Environ Chem Lett 20:3071–3098
- Baranowska-Wójcik E, Szwajgier D, Oleszczuk P, Winiarska-Mieczan A (2020) Effects of Titanium Dioxide Nanoparticles Exposure on Human Health—a Review. Biol Trace Elem Res 193:118–129
- Bhatnagar A, Sillanpää M (2009) Applications of chitin- and chitosan-derivatives for the detoxification of water and wastewater — A short review. Adv Colloid Interface Sci 152:26–38
- Bianchi CL, Colombo E, Gatto S, Stucchi M, Cerrato G, Morandi S, Capucci V (2014) Photocatalytic degradation of dyes in water with micro-sized TiO 2 as powder or coated on porcelain-grès tiles. J Photochem Photobiol A 280:27–31
- Bosio M, Satyro S, Bassin JP, Saggioro E, Dezotti M (2019) Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes. Environ Sci Pollut Res 26:4288–4299
- Brillas E (2022) A critical review on ibuprofen removal from synthetic waters, natural waters, and real wastewaters by advanced oxidation processes. Chemosphere 286:131849
- Candido JP, Andrade SJ, Fonseca AL, Silva FS, Silva MRA, Kondo MM (2017) Ibuprofen removal by heterogeneous photocatalysis and ecotoxicological evaluation of the treated solutions. Environ Sci Pollut Res 24:6397–6397
- Chen J, Qiu F, Xu W, Cao S, Zhu H (2015) Recent progress in enhancing photocatalytic efficiency of TiO2-based materials. Appl Catal A 495:131–140
- Choina J, Fischer C, Flechsig GU, Kosslick H, Tuan VA, Tuyen ND, Tuyen NA, Schulz A (2014) Photocatalytic properties of Zr-doped titania in the degradation of the pharmaceutical ibuprofen. J Photochem Photobiol A 274:108–116
- De Filpo G, Palermo AM, Munno R, Molinaro L, Formoso P, Nicoletta FP (2015) Gellan gum/titanium dioxide nanoparticle hybrid hydrogels for the cleaning and disinfection of parchment. Int Biodeterior Biodegrad 103:51–58
- De Gisi S, Lofrano G, Grassi M, Notarnicola M (2016) Characteristics and adsorption capacities of low-cost sorbents for wastewater treatment: A review. Sustainable Mater Technol 9:10–40
- Deb C, Thawani B, Menon S, Gore V, Chellappan V, Ranjan S, Ganesapillai M (2019) Design and analysis for the removal of active pharmaceutical residues from synthetic wastewater stream. Environ Sci Pollut Res 26:18739–18751
- Du H, Shi S, Liu W, Teng H, Piao M (2020) Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review. Environ Sci Pollut Res 27:12967–12994
- Ferrando-Climent L, Collado N, Buttiglieri G, Gros M, Rodriguez-Roda I, Rodriguez-Mozaz S, Barceló D (2012) Comprehensive study of ibuprofen and its metabolites in activated sludge batch experiments and aquatic environment. Sci Total Environ 438:404–413
- Fujishima A, Zhang XT (2006) Titanium dioxide photocatalysis: present situation and future approaches. C R Chim 9:750–760
- Gjipalaj J, Alessandri I (2017) Easy recovery, mechanical stability, enhanced adsorption capacity and recyclability of alginate-based TiO2 macrobead photocatalysts for water treatment. J Environ Chem Eng 5:1763–1770
- Gupta T, Chauhan RP (2021) Photocatalytic degradation of water pollutants using II-VI semiconducting catalysts: A comprehensive review. J Environ Chem Eng 9:106734
- Hashimoto K, Irie H, Fujishima A (2005) TiO2 photocatalysis: A historical overview and future prospects. Japanese J Appl Phys Part 1-Regular Papers Brief Commun Rev Papers 44:8269–8285
- He Y, Sutton N, Rijnaarts H, Langenhoff A (2016) Degradation of pharmaceuticals in wastewater using immobilized TiO2 photocatalysis under simulated solar irradiation. Appl Catal B 182:132–141
- Ismail NA, Amin KAM, Majid FAA, Razali MH (2019) Gellan gum incorporating titanium dioxide nanoparticles biofilm as wound dressing: Physicochemical, mechanical, antibacterial properties and wound healing studies. Mater Sci Engineering: C 103:109770
- Jallouli N, Elghniji K, Trabelsi H, Ksibi M (2017) Photocatalytic degradation of paracetamol on TiO2 nanoparticles and TiO2/cellulosic fiber under UV and sunlight irradiation. Arab J Chem 10:S3640–S3645
- Jiang W, Liu Y, Wang J, Zhang M, Luo W, Zhu Y (2016) Separation-Free Polyaniline/TiO2 3D Hydrogel with High Photocatalytic Activity. Adv Mater Interfaces 3:1500502
- Jiménez-Salcedo M, Monge M, Tena MT (2019) Photocatalytic degradation of ibuprofen in water using TiO2/UV and g-C3N4/visible light: Study of intermediate degradation products by liquid chromatography coupled to high-resolution mass spectrometry. Chemosphere 215:605–618
- Kanakaraju D, Glass BD, Oelgemöller M (2014) Titanium dioxide photocatalysis for pharmaceutical wastewater treatment. Environ Chem Lett 12:27–47
- Karimi-Maleh H, Ayati A, Davoodi R, Tanhaei B, Karimi F, Malekmohammadi S, Orooji Y, Fu L, Sillanpää M (2021) Recent advances in using of chitosan-based adsorbents for removal of pharmaceutical contaminants: A review. J Clean Prod 291:125880
- Katzenberg A, Raman A, Schnabel NL, Quispe AL, Silverman AI, Modestino MA (2020) Photocatalytic hydrogels for removal of organic contaminants from aqueous solution in continuous flow reactors. Reaction Chem Eng 5:377–386
- Kaur A, Umar A, Kansal SK (2016) Heterogeneous photocatalytic studies of analgesic and non-steroidal anti-inflammatory drugs. Appl Catal A 510:134–155
- Khedr TM, El-Sheikh SM, Ismail AA, Bahnemann DW (2019) Highly efficient solar light-assisted TiO2 nanocrystalline for photodegradation of ibuprofen drug. Opt Mater 88:117–127
- Kulišťáková A (2023) Removal of pharmaceutical micropollutants from real wastewater matrices by means of photochemical advanced oxidation processes – A review. J Water Process Eng 53:103727
- Kumar A, Sharma G, Naushad M, Al-Muhtaseb AaH, García-Peñas A, Mola GT, Si C, Stadler FJ (2020) Bio-inspired and biomaterials-based hybrid photocatalysts for environmental detoxification: A review. Chem Eng J 382:122937
- Kumar V, Lakkaboyana SK, Sharma N, Chakraborty P, Umesh M, Pasrija R, Thomas J, Kalebar VU, Jayaraj I, Awasthi MK, Das T, Oladipo AA, Barcelo D, Dumee LF (2023) A critical assessment of technical advances in pharmaceutical removal from wastewater – A critical review. Case Stud Chem Environ Eng 8:100363
- Lee S-Y, Park S-J (2013) TiO2 photocatalyst for water treatment applications. J Ind Eng Chem 19:1761–1769
- Mahmoud WMM, Rastogi T, Kümmerer K (2017) Application of titanium dioxide nanoparticles as a photocatalyst for the removal of micropollutants such as pharmaceuticals from water. Curr Opin Green Sustainable Chem 6:1–10
- Mai NXD, Bae J, Kim IT, Park SH, Lee G-W, Kim JH, Lee D, Son HB, Lee Y-C, Hur J (2017) A recyclable, recoverable, and reformable hydrogel-based smart photocatalyst. Environ Science: Nano 4:955–966
- Mai NXD, Park D, Yoon J, Hur J (2018) Comparative Study of Hydrogel-Based Recyclable Photocatalysts. J Nanosci Nanotechnol 18:1361–1364
- Mali KK, Dhawale SC, Dias RJ (2017) Synthesis and characterization of hydrogel films of carboxymethyl tamarind gum using citric acid. Int J Biol Macromol 105:463–470
- Marinho BA, Suhadolnik L, Likozar B, Huš M, Marinko Ž, Čeh M (2022) Photocatalytic, electrocatalytic and photoelectrocatalytic degradation of pharmaceuticals in aqueous media: Analytical methods, mechanisms, simulations, catalysts and reactors. J Clean Prod 343:131061
- Meijide J, Lama G, Pazos M, Sanromán MA, Dunlop PSM (2022) Ultraviolet-based heterogeneous advanced oxidation processes as technologies to remove pharmaceuticals from wastewater: An overview. J Environ Chem Eng 10:107630
- Miranda MO, Cabral Cavalcanti WE, Barbosa FF, Antonio de Sousa J, Ivan da Silva F, Pergher SBC, Braga TP (2021) Photocatalytic degradation of ibuprofen using titanium oxide: insights into the mechanism and preferential attack of radicals. RSC Adv 11:27720–27733
- Moctezuma E, Leyva E, Aguilar CA, Luna RA, Montalvo C (2012) Photocatalytic degradation of paracetamol: Intermediates and total reaction mechanism. J Hazard Mater 243:130–138
- Mohd Adnan MA, Phoon BL, Muhd Julkapli N (2020) Mitigation of pollutants by chitosan/metallic oxide photocatalyst: A review. J Clean Prod 261:121190
- Moon JH, Park JH, Jeong JH, Sung NS, Jeong Y-G, Song KC, Ahn J-P, Lee N-S, Han S-Y (2019) Metformin-loaded Citric Acid Cross-linked Agarose Films in the Prevention of Postoperative Abdominal Adhesion. Anatomy & Biological Anthropology
- Murgolo S, De Ceglie C, Di Iaconi C, Mascolo G (2021) Novel TiO2-based catalysts employed in photocatalysis and photoelectrocatalysis for effective degradation of pharmaceuticals (PhACs) in water: A short review. Curr Opin Green Sustainable Chem 30:100473
- Nakata K, Fujishima A (2012) TiO2 photocatalysis: Design and applications. J Photochem Photobiology C-Photochemistry Reviews 13:169–189
- Patel M, Kumar R, Kishor K, Mlsna T, Pittman CU Jr., Mohan D (2019) Pharmaceuticals of Emerging Concern in Aquatic Systems: Chemistry, Occurrence, Effects, and Removal Methods. Chem Rev 119:3510–3673
- Peralta-Hernández JM, Brillas E (2023) A critical review over the removal of paracetamol (acetaminophen) from synthetic waters and real wastewaters by direct, hybrid catalytic, and sequential ozonation processes. Chemosphere 313:137411
- Pereira AGB, Rodrigues FHA, Paulino AT, Martins AF, Fajardo AR (2021) Recent advances on composite hydrogels designed for the remediation of dye-contaminated water and wastewater: A review. J Clean Prod 284:124703
- Phong Vo HN, Le GK, Hong Nguyen TM, Bui X-T, Nguyen KH, Rene ER, Vo TDH, Thanh Cao N-D, Mohan R (2019) Acetaminophen micropollutant: Historical and current occurrences, toxicity, removal strategies and transformation pathways in different environments. Chemosphere 236:124391
- Ponce J, Peña J, Román J, Pastor JM (2022) Recyclable photocatalytic composites based on natural hydrogels for dye degradation in wastewaters. Sep Purif Technol 299:121759
- Ponnusamy PG, Sundaram J, Mani S (2022) Preparation and characterization of citric acid crosslinked chitosan-cellulose nanofibrils composite films for packaging applications. J Appl Polym Sci 139:52017
- Rafatullah M, Sulaiman O, Hashim R, Ahmad A (2010) Adsorption of methylene blue on low-cost adsorbents: A review. J Hazard Mater 177:70–80
- Rao KVS, Subrahmanyam M, Boule P (2004) Immobilized TiO2 photocatalyst during long-term use: decrease of its activity. Appl Catal B 49:239–249
- Rathi BS, Kumar PS (2021) Application of adsorption process for effective removal of emerging contaminants from water and wastewater. Environ Pollut 280:116995
- Razali MH, Ismail NA, Mat Amin KA (2020) Titanium dioxide nanotubes incorporated gellan gum bio-nanocomposite film for wound healing: Effect of TiO2 nanotubes concentration. Int J Biol Macromol 153:1117–1135
- Reddy KR, Hassan M, Gomes VG (2015) Hybrid nanostructures based on titanium dioxide for enhanced photocatalysis. Appl Catal A 489:1–16
- Reis RYN, Goulart LA, Mascaro LH, Alves SA (2022) A critical view of the contributions of photoelectrochemical technology to pharmaceutical degradation. J Environ Chem Eng 10:107859
- Reveendran Gap, Ong S-T (2018) Application of experimental design for dyes removal in aqueous environment by using sodium alginate-TiO2 thin film. Chem Data Collections 15–16:32–40
- Rivera-Utrilla J, Sánchez-Polo M, Ferro-García MÁ, Prados-Joya G, Ocampo-Pérez R (2013) Pharmaceuticals as emerging contaminants and their removal from water. Rev Chemosphere 93:1268–1287
- Rodriguez-Narvaez OM, Peralta-Hernandez JM, Goonetilleke A, Bandala ER (2017) Treatment technologies for emerging contaminants in water: A review. Chem Eng J 323:361–380
- Salihu R, Abd Razak SI, Ahmad Zawawi N, Rafiq Abdul Kadir M, Izzah Ismail N, Jusoh N, Riduan Mohamad M, Hasraf Mat Nayan N (2021) Citric acid: A green cross-linker of biomaterials for biomedical applications. Eur Polymer J 146:110271
- Salimi M, Esrafili A, Gholami M, Jonidi Jafari A, Rezaei Kalantary R, Farzadkia M, Kermani M, Sobhi HR (2017) Contaminants of emerging concern: a review of new approach in AOP technologies. Environ Monit Assess 189:414
- Santacruz I, Cabeza A, Ibeh P, Losilla ER, De la Torre AG, Aranda MAG (2012) Preparation of photocatalytic TiO2 coatings by gel-dipping with polysaccharides. Ceram Int 38:6531–6540
- Sanusi IO, Olutona GO, Wawata IG, Onohuean H (2023) Occurrence, environmental impact and fate of pharmaceuticals in groundwater and surface water: a critical review. Environ Sci Pollut Res 30:90595–90614
- Sarkar S, Das R, Choi H, Bhattacharjee C (2014) Involvement of process parameters and various modes of application of TiO2 nanoparticles in heterogeneous photocatalysis of pharmaceutical wastes – a short review. RSC Adv 4:57250–57266
- Sarkar S, Chakraborty S, Bhattacharjee C (2015) Photocatalytic degradation of pharmaceutical wastes by alginate supported TiO2 nanoparticles in packed bed photo reactor (PBPR). Ecotoxicol Environ Saf 121:263–270
- Seow WY, Hauser CAE (2016) Freeze–dried agarose gels: A cheap, simple and recyclable adsorbent for the purification of methylene blue from industrial wastewater. J Environ Chem Eng 4:1714–1721
- Shah AH, Rather MA (2023) Ultrasonically assisted hydrothermal synthesis of tungsten(VI) oxide-TiO2 nanocomposites for enhanced photocatalytic degradation of non-narcotic drug paracetamol under natural solar light: insights into degradation pathway, mechanism, and toxicity assessment. Environ Sci Pollut Res 30:93916–93933
- Shaheen JF, Sizirici B, Yildiz I (2022) Fate, transport, and risk assessment of widely prescribed pharmaceuticals in terrestrial and aquatic systems: A review. Emerg Contaminants 8:216–228
- Shan AY, Ghazi TIM, Rashid SA (2010) Immobilisation of titanium dioxide onto supporting materials in heterogeneous photocatalysis: A review. Appl Catal A 389:1–8
- Sharma M, Yadav A, Mandal MK, Dubey KK (2023) TiO2 based photocatalysis: a valuable approach for the removal of pharmaceuticals from aquatic environment. Int J Environ Sci Technol 20:4569–4584
- Simões BM, Cagnin C, Yamashita F, Olivato JB, Garcia PS, de Oliveira SM, Eiras Grossmann MV (2020) Citric acid as crosslinking agent in starch/xanthan gum hydrogels produced by extrusion and thermopressing. LWT 125:108950
- Sungur Ş (2021) Titanium Dioxide Nanoparticles. In: Kharissova OV, Torres-Martínez LM, Kharisov BI (eds) Handbook of Nanomaterials and Nanocomposites for Energy and Environmental Applications. Springer International Publishing, Cham, pp 713–730
- Tanveer M, Guyer GT, Abbas G (2019) Photocatalytic degradation of ibuprofen in water using TiO2 and ZnO under artificial UV and solar irradiation. Water Environ Res 91:822–829
- Thakur AK, Kumar R, Kumar A, Shankar R, Khan NA, Gupta KN, Ram M, Arya RK (2023) Pharmaceutical waste-water treatment via advanced oxidation based integrated processes: An engineering and economic perspective. J Water Process Eng 54:103977
- Tong AYC, Braund R, Warren DS, Peake BM (2012) TiO2-assisted photodegradation of pharmaceuticals — a review. Cent Eur J Chem 10:989–1027
- Wu J-l, Liu Z-h, Ma Q-g, Dai L, Dang Z (2023) Occurrence, removal and risk evaluation of ibuprofen and acetaminophen in municipal wastewater treatment plants: A critical review. Sci Total Environ 891:164600
- Yang L, Yu LE, Ray MB (2008) Degradation of paracetamol in aqueous solutions by TiO2 photocatalysis. Water Res 42:3480–3488
- Yang Y, Ok YS, Kim K-H, Kwon EE, Tsang YF (2017) Occurrences and removal of pharmaceuticals and personal care products (PPCPs) in drinking water and water/sewage treatment plants: A review. Sci Total Environ 596–597:303–320
- Zhang X, Wu F, Wu X, Chen P, Deng N (2008) Photodegradation of acetaminophen in TiO2 suspended solution. J Hazard Mater 157:300–307
- I have not submitted my manuscript to a preprint server before submitting it to Environmental Science and Pollution Research
- I have not submitted my manuscript to a preprint server before submitting it to Environmental Science and Pollution Research.
Table 1: Composition and nomenclature of the prepared materials
