Introduction

Over the past decade, the rapid growth of industrialization and human activities has led to pharmaceutical and personal care products emerging as significant pollutants in aquatic environments, posing a serious global concern. These compounds, along with their metabolites, enter water bodies through various sources such as households, hospitals, factories, and sewage treatment plants, resulting in detrimental effects on water quality and causing substantial harm to aquatic ecosystems (Davarnejad et al. 2018; Sophia and Lima 2018). Antibiotics and anti-inflammatory agents, among the various pharmaceutical contaminants, are particularly noteworthy due to their increasing global consumption (Akhil et al. 2021; Anand et al. 2022; Muñiz-González 2021; Nguyen et al. 2022b; Rameshwar et al. 2023).

Ibuprofen, scientifically known as 2-[4-(2-Methylpropyl) phenyl] propanoic acid, holds the distinction of being the third most commonly used drug worldwide, with an annual consumption of approximately 200 tons (Chopra and Kumar 2020). This non-steroidal anti-inflammatory drug is highly sought after in the market and is primarily produced by Shasun Chemicals and Drugs Ltd., with the lot number IBU0307598 (Mestre et al. 2007). It is commonly prescribed for rheumatoid arthritis, osteoarthritis, pain relief, inflammation, and fever management (Shaheen et al. 2022). Ibuprofen has been detected in wastewater and rivers across multiple countries (Brun. et al. 2006; Mestre et al. 2007; Nakada et al. 2006; Vieno et al. 2005), with increasing concentrations observed in wastewater treatment plants and water bodies. Given its bioactive nature, it poses a potential environmental hazard, as shown in Fig. 1.

Fig. 1
figure 1

Fate of ibuprofen in the environment. The daily usage of ibuprofen is steadily rising, leading to a corresponding increase in waste containing ibuprofen. This waste is generated by pharmaceutical industries, hospitals, and households and is often disposed of in sewage systems, landfills, or municipal treatment plants. Unfortunately, this disposal method allows ibuprofen to enter water bodies, where living organisms can absorb it and subsequently enter the food chain. Improper disposal of ibuprofen poses a significant risk of bioaccumulation and ecological harm

Various methods have been explored for the removal of pharmaceutical compounds from different matrices (Caban and Stepnowski 2021; Taoufik et al. 2020), including filtration (Femina Carolin et al. 2021; Gu et al. 2018; Taheran et al. 2016), advanced oxidation processes (Akbari Beni et al. 2020; Bastami et al. 2017; Brillas 2022; Kanakaraju et al. 2014; Sruthi et al. 2021), ion exchange (Jiang et al. 2015), biological treatment (Tiwari et al. 2017), and adsorption (Bello and Raman 2019; Duarte et al. 2022; Osman et al. 2023a; Ranjbari et al. 2020). However, among these methods, adsorption has gained significant attention due to its cost-effectiveness, simplicity, high efficiency, regenerability, and scalability (Ayati et al. 2019; Karimi-Maleh et al. 2021b; Shahinpour et al. 2022). Adsorption has emerged as a superior approach for pharmaceutical compound removal from aqueous solutions (Ahmed 2017; Huang et al. 2021; Igwegbe et al. 2021; Prasetya et al. 2023).

Extensive research has been conducted on removing ibuprofen from aquatic media through adsorption, leading to the exploration of a wide range of adsorbents with diverse origins. These adsorbents include activated carbons (Labuto et al. 2022; Matějová et al. 2022), polymers (Karimi-Maleh et al. 2021a; Yu et al. 2022; Van Tran et al. 2019b). Pyrolysis has enhanced their surface areas and porosities and broadened their applications (Yu et al. 2021). Among them, porous activated carbon derived from the pyrolysis of metal–organic framework-6 and activated with potassium hydroxide has demonstrated a high sorption capacity for pharmaceutical compounds, including ibuprofen (An et al. 2018). Moreover, highly porous nitrogen-/oxygen-doped porous carbons obtained from the zeolitic-imidazolate framework-8, namely ZIF-8, have shown effective performance in the adsorptive removal of antibiotics, such as ciprofloxacin (Li et al. 2017), diclofenac (Bhadra et al. 2017), and ibuprofen (Bhadra et al. 2017). Bhadra et al. (2017) found that H-bonding interactions, mainly through the phenolic group, are responsible for ibuprofen adsorption using zeolitic imidazolate framework-8-derived carbon, with carbon acting as the hydrogen-bond donor and ibuprofen as the H-bond acceptor.

The adsorption capacity of activated carbon was also improved by other parameters, including activation time (Ulfa et al. 2020b) and activator concentration (Ulfa et al. 2020a). One study demonstrated that increasing the activator concentration improved adsorption capacity by precipitating impurities, increasing the surface area, and increasing the functional groups (Ulfa et al. 2020a). Other advanced treatments, such as ozonation (Guillossou et al. 2019) and sonication, have been found to effectively enhance the ibuprofen adsorption capacity of activated carbons (Fröhlich et al. 2018a; Ondarts et al. 2018). These treatments form new binding sites on the activated carbon surface (Yazidi et al. 2019). For example, Fröhlich et al. (2018b) demonstrated that ultrasound-modified activated carbon exhibited a 25% higher adsorption capacity than unmodified activated carbon.

In the adsorption of ibuprofen onto activated carbon, hydrophobic and π-π interactions between the carbon surface and micro-pollutants play a significant role in the adsorption mechanism. While hydrophobic interactions may not be directly responsible for the adsorption of ibuprofen onto activated carbon, their influence cannot be ignored (Kaur et al. 2018; Zhao et al. 2016). In acidic media, dispersive π–π and donor–acceptor interactions occur between the carbonyl groups in activated carbon and the aromatic ring of ibuprofen (Fröhlich et al. 2018b). As expected, ibuprofen adsorption is higher in monopollutant systems than in wastewater effluent due to particle pore blocking and competition for adsorption sites (Guillossou et al. 2020). While the small size of ibuprofen molecules allows for its fast and high sorption, its molecular configuration and adsorbent size will affect adsorption efficiency (Turk Sekulic et al. 2019).

The surface functionalization or crosslinking of activated carbon presented a promising solution for removing pharmaceuticals (Ali et al. 2019; Tian et al. 2022). These modifications can affect both the adsorption kinetics and adsorption capacity. Recent studies have demonstrated the effectiveness of ethylamine- and ethylenediamine-functionalized activated carbon, which possesses basic and hydrophobic surfaces, respectively, in the Langmuir monolayer adsorption of ibuprofen through endothermic and spontaneous processes (Ali et al. 2019). Following the pseudo-second-order model, the equilibrium adsorptions were faster on the functionalized activated carbons than on unmodified activated carbon. However, the maximum sorption capacity was observed to be in the order of activated carbon more than ethylenediamine-functionalized activated carbon more than ethylamine-functionalized activated carbon (An et al. 2018; Fröhlich et al. 2019). In one study, a magnetic nickel ferrite (NiFe2O4)/activated carbon composite with a high surface area of 564 m2/g showed great potential for ibuprofen removal with a maximum adsorption capacity of 261 mg/g (Fröhlich et al. 2019). In such cases, activated carbon serves not only as a support but also actively participates in ibuprofen uptake through physisorption, attributed to its high surface area, or chemisorption, which is facilitated by the presence of heteroatoms on the surface (Pakade et al. 2019). Wasilewska and Deryło-Marczewska (2022) successfully enhanced the adsorption capacity of activated carbon by immobilizing it in calcium alginate. They achieved maximum sorption capacities of 0.873 mmol/g for diclofenac and 0.381 mmol/g for ibuprofen drugs. The samples with higher activated carbon content exhibited increased hygroscopicity, polarity, and superior adsorption rate and capacity. The higher sorption capacity for diclofenac can be attributed to the disparities in adsorbate solubilities. In contrast, the faster removal rate of ibuprofen is attributed to the variance in the molecular sizes of the drugs.

As presented in Table 1, several studies have shown that maximum ibuprofen adsorption occurs under acidic conditions, particularly between pH 2 and 4. This may be due to the repulsion between the negatively charged activated carbon surface in alkaline media and the negatively charged ibuprofen molecules, which hinders adsorption (Dubey et al. 2010). In acidic solutions, excess hydrogen ions neutralize the negative charges on the adsorbent surface, facilitating the diffusion of ibuprofen molecules. Combining activated carbon adsorption systems and biological treatment or hybrid membrane systems was also proposed to remove ibuprofen (Ferrer-Polonio et al. 2020; Kim et al. 2019; Zhang et al. 2019). For example, granular activated carbon has been efficiently used in the pilot- and full-scale hybrid adsorption columns and membrane systems to remove ibuprofen from aquatic media (Jamil et al. 2020; Zhang et al. 2019). Numerous research studies have been conducted to analyze the thermodynamics of ibuprofen adsorption on activated carbons. As shown in Table 1, the presence of negative ΔG° values confirms the viability and spontaneous nature of ibuprofen sorption onto activated carbons. Moreover, highly negative ΔG° values indicate a significant level of favorability in terms of adsorption (Ahmed 2017).

Apart from activated carbon, other carbon-based materials, such as biochar and hydrochar obtained through the pyrolysis and hydrothermal carbonization of biomass wastes, including agricultural waste, have also been investigated for their potential in ibuprofen adsorption (Delgado-Moreno et al. 2021; Osman et al. 2023c; Patel et al. 2022). Table 2 provides an overview of some specific examples of these adsorbents. Several natural waste sources, such as date palm leaflets (Ali et al. 2019), wood waste (Van Limbergen et al. 2022), Cocos nucifera shell (Chakraborty et al. 2019), date palm fiber wood (Van Limbergen et al. 2022), date seeds (Chakraborty et al. 2020), bamboo waste (Reza et al. 2014), waste coffee residue (Shin et al. 2022), almond shells (Show et al. 2021), Quercus brantii (oak), coffee bean husk (Van Limbergen et al. 2022), sugarcane bagasse (Chakraborty et al. 2018b), tamarind seeds (Show et al. 2022a), Albizialebbeck seeds (Sivarajasekar et al. 2018), and kola nut husk (Bello et al. 2020a), have been used as ibuprofen-adsorbent biochars. The main adsorption mechanism involves a combination of acid/base sorbate equilibria and the interaction of carboxylic acid and phenolic hydroxyl sites with varying pH levels (Essandoh et al. 2015).

Table 2 Biochar and hydrochar as adsorbents for removing ibuprofen

To enhance the sorption capacity of biochars in the removal of ibuprofen, various pre- and post-treatment methods have been explored (Shin et al. 2021). These methods include physical modifications like ball milling (Chakraborty et al. 2020; Luo et al. 2020), composite formation (Moreno-Pérez et al. 2021), chemical oxidation (Ali et al. 2019), and acid/base modification (Shin et al. 2020). For example, Shin et al. (2021) demonstrated that the reinforced aromatic structure of sodium hydroxide-activated biochar obtained from spent coffee waste facilitated π–π interaction, significantly improving its adsorption capacity. In another study, Chakraborty et al. (2019) presented a study highlighting the effective performance of activated biochar derived from Cocos nucifera shells, which underwent physical and chemical modifications, in the adsorption of ibuprofen. The modified activated biochar demonstrated maximum sorption capacities of 9.7 mg/g and 12.2 mg/g, respectively. Recently, Moreno-Pérez et al. (2021) explored the adsorption potential of a zinc aluminium alloy (ZnAl)/biochar composite for pharmaceutical compounds. Following the Henry isotherm model, they achieved a remarkable adsorption capacity of 1032 mg/g for ibuprofen. The primary mechanism of transport was identified as surface flux within the particles. Activated carbons also exhibited promise as adsorbents due to their numerous surface functional groups, large surface area, and well-developed pore structures, making them suitable for removing ibuprofen molecules from aqueous environments. Notably, commercial activated carbon (Zhao et al. 2018) and activated carbon derived from primary pulp mill sludge (Coimbra et al. 2019) exhibited remarkable behavior in the adsorptive removal of ibuprofen.

Graphene-based materials, such as pristine graphene and graphene oxide, represent a fascinating category of carbonaceous adsorbents with significant promise for removing ibuprofen. Recent studies have revealed the exceptional characteristics of these materials, including their remarkable hydrophobicity, high adsorption capacity, extensive surface area, low toxicity, and recyclability. The nanostructured porous nature of graphene lends itself well to effective ibuprofen adsorption, making it an ideal choice for this application (Amiri et al. 2019; Khalil et al. 2021, 2020; Lou et al. 2010; Lestari et al. 2018; Tabatabaeian et al. 2020). As a result, certain metal–organic frameworks have demonstrated higher removal capacities than commercial activated carbon (Jun et al. 2019; Lin et al. 2018). In addition to their adsorption capabilities, metal–organic frameworks have attracted attention in drug delivery applications, serving as hosts for controlled release (Chávez et al. 2021). This discussion highlights the significant findings and recent contributions in metal–organic framework-based adsorbents, and some noteworthy examples are presented in Table 4.

Table 4 Metal–organic framework-based adsorbent for ibuprofen

The adsorption of ibuprofen onto metal–organic frameworks can be attributed to several potential interaction mechanisms. These mechanisms include the formation of Lewis acid/base complexes between the coordinatively unsaturated sites of the metal ions in metal–organic frameworks and the dissociated ibuprofen molecules. Another mechanism involves hydrogen bonding between the carboxyl group of ibuprofen and oxygen atoms within the structure of the metal–organic framework. Additionally, π–π electron donor–acceptor interactions between the metal–organic frameworks and ibuprofen molecules have been considered (Álvarez-Torrellas et al. 2016; Sun et al. 2019). Furthermore, anion-π interactions between the benzene ring of the metal–organic frameworks and the dissociated carboxyl group of ibuprofen are also possible (Ghasemi et al. 2022; Scheytt et al. 2005; Sun et al. 2019; Wei et al. 2018). Sun et al. (2019) conducted density functional theory calculations to analyze the binding energies and typical structures of ibuprofen adsorbed onto zirconium-based metal–organic framework, namely UiO-66, and amino zirconium-based metal–organic framework, namely UiO-66-NH2, metal–organic frameworks. They comprehensively considered all possible interaction mechanisms involved in pharmaceutical adsorption. They found that the binding energies followed the order of π–π interactions more than hydrogen bonding more than Lewis acid/base more than anion-π interactions. Specifically, hydrogen bonding was identified as the primary pharmaceutical adsorption mechanism, including ibuprofen and oxybenzone, onto the iron-based metal framework, namely MIL-101 (Seo et al. 2016).

Most studies on the adsorption of ibuprofen onto metal–organic frameworks focused on MILs types (Cao et al. 2020; Horcajada et al. 2008; Rajab Asadi et al. 2018). For example, a chemically stable metal–organic framework of iron-based metal–framework, namely MIL-53(Fe), efficiently adsorbed ibuprofen molecules with a removal efficiency above 80% under optimal conditions (Nguyen et al. 2019). In another study, Jun et al. (2019) investigated the effectiveness of aluminium terephthalate, namely MIL-53(Al), as an adsorbent for removing ibuprofen. They observed that the aluminum metal in aluminium terephthalate likely formed coordination bonds with the anionic ibuprofen molecules, contributing to hydrophobic and electrostatic interactions. Additionally, they found that the positive surface charge of aluminium terephthalate decreased gradually as the solution pH increased from 3.5 to 9.5. This reduction in surface charge resulted in enhanced hydrophobic interactions between aluminium terephthalate and ibuprofen molecules.

Furthermore, divalent cations, which act as counter-ions for ibuprofen, have been found to enhance the electrostatic interaction between ibuprofen and metal–organic frameworks by bridging the two entities. On the other hand, divalent anions that coexist with ibuprofen can suppress this electrostatic interaction. The proposed adsorption mechanisms for ibuprofen and carbamazepine are depicted in Fig. 4. Remarkably, the copper-doped iron-based metal–organic framework demonstrated a high adsorption capacity for ibuprofen across a wide pH range, with a maximum sorption capacity of 497 mg/g (** countries. Sci Total Environ 660:57–68. https://doi.org/10.1016/j.scitotenv.2018.12.386 " href="/article/10.1007/s10311-023-01647-6#ref-CR31" id="ref-link-section-d87766045e9916">2019; Martín et al. 2019; Obradović et al. 2022).

In such cases, the adsorbed surfactant's chemical nature strongly affected organoclay materials' adsorption properties (Ghemit et al. 2019). For example, organoclay derivatives of Na+-exchanged montmorillonite, which contained benzyldimethyltetradecylammonium as a cationic surfactant and polyoxyethylene (20)oleyl-ether as a non-ionic surfactant, exhibited a certain versatility in the removal of diverse pharmaceuticals from the effluent of a rural wastewater facility in France (De Oliveira et al. 2020). It was proposed as a filter between the transitions from different settling tanks in wastewater treatment plants to improve the removal efficiency (De Oliveira et al. 2020). Benzyldimethyltetradecylammonium- montmorillonite showed a remarkable affinity for anionic pharmaceutical compounds, while cationic pharmaceutical compounds were better adsorbed onto polyoxyethylene (20)oleyl-ether-montmorillonite and Na+-exchanged montmorillonite, with its dual hydrophobic-hydrophilic nature via compensating Na+ cations and the non-ionic surfactant. The intercalation of surfactants within the interlayer space of organoclays created a hydrophobic environment that adsorbed numerous pharmaceuticals through weak π–π and/or van der Waals interactions. Mainly, electrostatic interactions controlled the adsorption of drugs onto the Na+-exchanged montmorillonite, nonionic polyoxyethylene (20)oleyl-ether-montmorillonite, and cationic benzyldimethyltetradecylammonium- montmorillonite organoclay adsorbents.

The cationic octadecylamine surfactant modification of clays, such as Na+-exchanged mica (Martín et al. 2018) and montmorillonite (Malvar et al. 2020), significantly increased their affinity for ibuprofen molecules. Hydrophobic interactions between the surfactant alkyl chains of modified clay and organic compounds play a major role in adsorption, and the incorporation of ibuprofen occurred on the external surface and in the interlayers (Martín et al. 2018). Martín et al. (2019) compared ibuprofen adsorption to octadecylamine-modified montmorillonite and Na+-exchanged mica. While adsorption was faster onto modified montmorillonite, smaller than 5 min, than modified Na+-exchanged Mica, smaller than 60 min, both adsorption kinetics followed the pseudo-second order, indicating chemisorption. Furthermore, the adsorption isotherm of modified montmorillonite corresponded to the Langmuir model, while that of modified Na+-exchanged mica fitted better to the Freundlich model, indicating a difference in the types of adsorption.

In addition to ibuprofen molecules, the efficient adsorption performance of octadecylamine-modified montmorillonite was also demonstrated in the removal of primary ibuprofen metabolites, including 1-hydroxyibuprofen, 2-hydroxyibuprofen, and carboxyibuprofen, from aqueous solution (Malvar et al. 2020). It was mainly due to electrostatic interaction and partitioning in the adsorption mechanism. The maximum adsorption capacities toward ibuprofen and all its primary metabolites within 20–30 min were 64 mg/g, 20 mg/g, 63 mg/g, and 19 mg/g, respectively (Malvar et al. 2020). It should be noted that the sorption capacities were considerably lower in mixture solutions due to competition for adsorbent active sites.

Hexadecyltrimethylammonium is another surfactant used to modify montmorillonite and zeolite to efficiently absorb ibuprofen and salicylic acid at pH 7 (Choi and Shin 2020). Due to the higher organic carbon content of modified montmorillonite, a higher adsorption capacity compared to that of modified zeolite was observed; furthermore, because of the higher hydrophobicity and molar volume of ibuprofen molecules, it showed higher uptake than salicylic acid. Since the anionic speciation of ibuprofen is more prolific at pH 7, higher than pKa, its adsorption onto modified montmorillonite mainly occurs via two-dimensional surface adsorption onto the pseudo-organic medium in the adsorbent, while bonding to the positively charged “head” of hexadecyltrimethylammonium is responsible for modified zeolite. The adsorption isotherms corresponded well to the Polanyi-Dubinin-Manes model, indicating that pore-filling was the dominant adsorption mechanism.

Cetyltrimethylammonium bromide, a cationic surfactant with long alkyl chains, creates a suitable organic–inorganic framework for pharmaceutical compound adsorption. It was found to be suitable for synthesizing organobentonite adsorbents with high ibuprofen and diclofenac molecule adsorption capacities of 194 mg/g and 600 mg/g, respectively (Ghemit et al. 2019). The higher potential for the uptake of pharmaceutical contaminants was attributed to the larger interlayer space within organobentonites. The chemical nature of bentonite changes from hydrophilic to hydrophobic by intercalating cationic surfactants through ion exchange, and consequently, hydrophobic interactions play an essential role during adsorption. Both ibuprofen and diclofenac molecules were divided into the organic phase of the interlayer space made by the surfactant. The amount of ibuprofen and diclofenac adsorbed gradually increased with increasing surfactant concentration. In the competitive adsorption of ibuprofen and diclofenac, their monolayer adsorption decreased to 83 mg/g and 188 mg/g, respectively.

Functionalizing clays with amines was also investigated for ibuprofen adsorptive removal. For example, the amine-functionalized nano-clay Cloisite 15A was successfully used for the adsorptive removal of ibuprofen in both batches (Rafati et al. 2018) and continuous fixed-bed column (Rafati et al. 2019) systems. Rafati et al. (2019) showed that the adsorption capacity of the fixed-bed column depended on ibuprofen concentration and bed depth. The Thomas, bed-depth service time, Yoon-Nelson, and Clark mathematical models accurately predicted the breakthrough curves. The strong hydration of the inorganic counter ions in the interlayer space of expandable clay minerals made them hydrophilic and, therefore, often weak adsorbents toward hydrophobic organic compounds (Gámiz et al. 2015).

In another study, polyamidoamine dendrimer was grafted onto halloysite clay mineral (Kurczewska et al. 2020) with an intermediate 3- aminopropyltrimethoxysilane functionalization step. Electrostatic interactions between protonated amine groups on halloysite surfaces in both 3- aminopropyltrimethoxysilane functionalized and polyamidoamine dendrimer grafted halloysite, and the carboxyl groups in pharmaceutical molecules significantly affect adsorption efficiency. However, Tan et al. (2013) indicated that the holloysite-3-aminopropyltriethoxysilane surface had 25% higher ibuprofen loading than the unmodified halloysite. More reactive functional groups were provided by the polyamidoamine dendrimer for favorable adsorption toward ibuprofen and naproxen than organosilane (Kurczewska et al. 2020). Halloysite surfaces bearing covalently attached organic units demonstrated a higher affinity for pharmaceutical molecules than the unmodified mineral, and the ibuprofen and naproxen loading efficiencies increased to high adsorption capacities of 68 mg/g and 5.9 mg/g, respectively, at pH 6.

In a study conducted by Li et al. (2019), the adsorption mechanism of ibuprofen onto a zeolite/sepiolite nano-heterostructure and an organically modified sepiolite called Tetranyl® B-2MTH, namely stearyl dimethyl benzyl ammonium chloride, sepiolite was investigated. The study utilized isotherm studies to propose a pore-filling mechanism, indicating the formation of one or more adsorbed layers. Notably, the results revealed that the bonding of ibuprofen molecules on both adsorbents occurred in both horizontal and non-horizontal, temperature-dependent orientations. This suggests the presence of multi-docking and multi-molecular adsorption, respectively. At higher temperatures, specifically 60 °C, ibuprofen molecules in solution tended to aggregate primarily through dimer formation, with an approximate capture of two ibuprofen molecules. The organically modified sepiolite exhibited a higher adsorption capacity than the zeolite/sepiolite across all studied temperatures. The primary factors influencing the mechanism of ibuprofen adsorption were identified as the adsorption energies and the density of receptor sites. Recently, Njaramba et al. (2023) introduced a novel three-dimensional mesoporous aerogel by incorporating sepiolite and zirconium 1,4-dicarboxybenzene metal–organic framework UiO-66, a zirconium-based metal–organic framework, into gelatin. This innovative aerogel was proposed as a promising alternative adsorbent for efficiently removing ibuprofen and naproxen. The adsorption process was found to be exothermic, and it followed both the pseudo-second-order kinetics and the Langmuir isotherm models. The maximum sorption capacities for ibuprofen and naproxen were determined to be 10 mg/g and 8.5 mg/g, respectively.

The adsorption process onto clay is highly influenced by pH and is susceptible to changes in ionic strength. Behera et al. (2012) observed that the adsorption of ibuprofen onto clays increased as the ionic strength increased. This phenomenon was attributed to the partial neutralization of the positive charge on the surface of the adsorbent, which led to the contraction of the electric double layer due to the presence of chloride ions. Furthermore, chloride ions were found to enhance the adsorption of ibuprofen by effectively pairing their charges. This pairing mechanism reduced repulsion between ibuprofen molecules already adsorbed on the surface, thereby facilitating the adsorption of additional positively charged ibuprofen ions.

Polymer-based adsorbents

Polymeric materials have garnered significant attention as adsorbents for pharmaceutical applications, with chitosan being one of the most extensively studied polymers (Hamidon et al. 2022; Tseng et al. 2022; Yu et al. 2015; Reza et al. 2014; Show et al. 2022a). Methanol desorbed 81% and 74% of ibuprofen from biochar derived from wood apple and its steam-activated analog, respectively (Chakraborty et al. 2018a).

Perspective

The extensive use of ibuprofen and its potential health risks to the aquatic environment necessitate further research on its removal from aqueous solutions. Despite the significant progress made in the study of ibuprofen adsorption, several knowledge gaps still need to be addressed in this field. One crucial concern is the systematic investigation of ibuprofen removal from real or simulated wastewater. While numerous studies have been conducted, only a few have focused explicitly on real wastewater samples. It is crucial to consider variables such as the actual concentration range of ibuprofen, pH levels, presence of competitive pollutants, and temperature conditions that mimic real wastewater scenarios. Furthermore, most studies have been conducted on a laboratory scale, and the efficacy of these sorbents in real-world industrial-scale applications remains uncertain. The applicability of these sorbents in treating real samples, such as industrial and hospital wastewater, as well as groundwater, where higher concentrations of ibuprofen are expected, needs to be better understood.

The inability of some adsorbents to be reused poses a challenge regarding their sustainability and cost-effectiveness. Furthermore, there is a limited focus on dynamic adsorption systems in the existing literature. Therefore, it is essential to assess the capability of adsorbents to remove ibuprofen in dynamic adsorption systems, such as at the point of use, to evaluate their practical applicability. Substantial research is needed to develop low-cost, high-performance adsorbents that remove ibuprofen in wastewater treatment plants. This can open up opportunities for their application in domestic water filters and residential settings.

Additionally, the cost analysis of the adsorption process should be considered, as it is an essential factor that has often been neglected in previous investigations. Future research should also address disposing of spent adsorbents after prolonged use, focusing on environmentally sustainable and friendly techniques. Moreover, combining mechanical or biological treatment methods with adsorption systems should be studied to enhance the overall removal performance of ibuprofen in wastewater treatment processes. By addressing these areas of concern, advancements can be made in develo** and applying effective and sustainable ibuprofen removal technologies.

Conclusion

The presence of ibuprofen in wastewater has recently emerged as a significant environmental and human health concern. Among the various methods employed to remove ibuprofen, adsorption has gained significant attention, particularly in the past five years. The review has demonstrated that functionalized or modified adsorbents perform superior to pristine materials for removing ibuprofen. Various strategies, such as grafting, crosslinking, and material combinations, have been employed to enhance the adsorption capacity of these materials. The review highlighted that activated carbons and biochar are the most widely studied materials for ibuprofen removal, while metal–organic framework structures have also shown promising performance. The adsorption process was found to be influenced by the solution pH, with higher adsorption typically observed under acidic conditions, i.e., pH 3. The dominant mechanisms involved in ibuprofen adsorption were electrostatic and π-π interactions and hydrogen bonding. However, despite the progress made in understanding ibuprofen adsorption, this field is still evolving, and several aspects require continuous investigation and improvement. Essential factors such as cost, safety, and compatibility with industrial conditions must be thoroughly examined to ensure the practical applicability of these adsorbents. Further research is necessary to address these gaps and advance the development of efficient and cost-effective adsorbents for ibuprofen removal.