Adsorption mechanisms of emerging micro-pollutants with a clay mineral: Case of tramadol and doxepine pharmaceutical products

Selected emerging contaminants in water: Global occurrence, existing treatment technologies, regulations and associated risk

Emerging contaminants (ECs) in aquatic environments have recently attracted the attention of researchers due to their ubiquitous occurrence and the potential risk they may pose to life. While advance analytical methods have improved global reporting in water matrices, additional information is needed to compile data on their occurrence, existing legislation, treatment technologies and associated human health risks. Therefore, the present study provides an overview of the occurrence of selected ECs, including personal care product, antibiotics, NSAIDs, EDCs and psychiatric drugs, the existing regulatory framework and their toxicological effects on human health. The water matrices under review are the treated wastewater, surface water, groundwater and, in a few cases, drinking water. The study also highlights different treatment technologies available, and evaluates their performance based on the removal efficiency for different classes of ECs. For removal of almost all ECs considered, ozonation integrated with gamma radiation was reported highly efficient. Risk analysis was also performed for selected ECs including diclofenac, ibuprofen, naproxen, carbamazepine, estrone, 17 β-estradiol, bisphenol A, sulfamethoxazole, erythromycin and triclosan. The human health risk analysis indicated the highest number of locations with potential risk due to the EDCs, with South America, Europe and Asia having multiple risks due to estrone and Bisphenol A. The results of this study will give a better insight into the current situation of ECs in the global water matrices, the performance assessment of treatment technologies and the risk analysis will describe the need for more robust regulatory structures around the world to prevent the occurrence of such contaminants in the aquatic environment.

Competitive sorption experiments reveal new regression models to predict PhACs sorption on carbonaceous materials

Sorption of hydrophobic organic contaminants onto thermally altered carbonaceous materials (TACM) constitutes a widely used technology for remediation of polluted waters. This process is typically described by sorption isotherms, with one of the most used models, the Polanyi-Dubinin-Manes (PDM) equation, including water solubility (Sw) as a normalizing factor. In case of pharmaceutical active compounds (PhACs), Sw depends on the pH of the environment due to the ionic/ionizable behavior of these chemicals, a fact frequently ignored in sorption studies of PhACs. In this work, we set the theoretical framework to include the variation of Sw with pH in the definition of the PDM model, and we applied this approach to describe the effect of ambient pH in the competitive sorption of three commonly detected PhACs (carbamazepine, ibuprofen, and sulfamethoxazole) onto three carbonaceous sorbents (biochar, powder activated carbon, and colloidal activated carbon). Changes in the ambient pH and hence in the hydrophobicity of the compounds could explain the strong variations observed in single-solute sorption and also in competitive sorption. Furthermore, Sw was used as a parameter for the linear regression model of sorption coefficients of our experiments, suggesting the incorporation of this variable as an improvement to existing approaches for prediction of PhACs sorption onto TACM.

Integrated study of antiretroviral drug adsorption onto calcined layered double hydroxide clay: experimental and computational analysis

This study focused on the efficacy of a calcined layered double hydroxide (CLDH) clay in adsorbing two antiretroviral drugs (ARVDs), namely efavirenz (EFV) and nevirapine (NVP), from wastewater. The clay was synthesized using the co-precipitation method, followed by subsequent calcination in a muffle furnace at 500 °C for 4 h. The neat and calcined clay samples were subjected to various characterization techniques to elucidate their physical and chemical properties. Response surface modelling (RSM) was used to evaluate the interactions between the solution's initial pH, adsorbent loading, reaction temperature, and initial pollutant concentration. Additionally, the adsorption kinetics, thermodynamics, and reusability of the adsorbent were evaluated. The results demonstrated that NVP exhibited a faster adsorption rate than EFV, with both reaching equilibrium within 20-24 h. The pseudo-second order (PSO) model provided a good fit for the kinetics data. Thermodynamics analysis revealed that the adsorption process was spontaneous and exothermic, predominantly governed by physisorption interactions. The adsorption isotherms followed the Freundlich model, and the maximum adsorption capacities for EFV and NVP were established to be 2.73 mg/g and 2.93 mg/g, respectively. Evaluation of the adsorption mechanism through computational analysis demonstrated that both NVP and EFV formed stable complexes with CLDH, with NVP exhibiting a higher affinity. The associated adsorption energies were established to be -731.78 kcal/mol for NVP and -512.6 kcal/mol for EFV. Visualized non-covalent interaction (NCI) graphs indicated that hydrogen bonding played a significant role in ARVDs-CLDH interactions, further emphasizing physisorption as the dominant adsorption mechanism.

Experimental data and modeling of sulfadiazine adsorption onto raw and modified clays from Tunisia

In recent years, the increasing detection of emerging pollutants (particularly antibiotics, such as sulfonamides) in agricultural soils and water bodies has raised growing concern about related environmental and health problems. In the current research, sulfadiazine (SDZ) adsorption was studied for three raw and chemically modified clays. The experiments were carried out for increasing doses of the antibiotic (0, 1, 5, 10, 20, and 40 μmol L-1) at ambient temperature and natural pH with a contact time of 24 h. The eventual fitting to Freundlich, Langmuir and Linear adsorption models, as well as residual concentrations of antibiotics after adsorption, was assessed. The results obtained showed that one of the clays (HJ1) adsorbed more SDZ (reaching 99.9 % when 40 μmol L-1 of SDZ were added) than the other clay materials, followed by the acid-activated AM clay (which reached 99.4 % for the same SDZ concentration added). The adsorption of SDZ followed a linear adsorption isotherm, suggesting that hydrophobic interactions, rather than cation exchange, played a significant role in SDZ retention. Concerning the adsorption data, the best adjustment corresponded to the Freundlich model. The highest Freundlich KF scores were obtained for the AM acid-treated and raw HJ1 clays (606.051 and 312.969 Ln μmol1-n kg-1, respectively). The Freundlich n parameter ranged between 0.047 and 1.506. Regarding desorption, the highest value corresponded to the AM clay, being generally <10 % for raw clays, <8 % for base-activated clays, and <6 % for acid-activated clays. Chemical modifications contributed to improve the adsorption capacity of the AM clay, especially when the highest concentrations of the antibiotic were added. The results of this research can be considered relevant as regard environmental and public health assessment since they estimate the feasibility of three Tunisian clays in SDZ removal from aqueous solutions.

Natural Nano-Minerals (NNMs): Conception, Classification and Their Biomedical Composites

Natural nano-minerals (NNMs) are minerals that are derived from nature with a size of less than 100 nm in at least one dimension in size. NNMs have a number of excellent properties due to their unique nanostructure and have been applied in various fields in recent years. They are rising stars in various disciplines, such as materials, biomedicine, and chemistry, taking advantage of their huge surface area, multiple active sites, excellent adsorption capacity, large quantity, low cost, and nontoxicity, etc. To provide a more comprehensive overview of NNMs and the biomedical applications of NNMs-based nanocomposites, this review classifies NNMs into three types by dimension, lists the structure and properties of typical NNMs, and illustrates their biomedical applications. Furthermore, a novel concept of natural nanomineral medical materials (NNMMs) is proposed, focusing on the medical value of NNMs. In addition, this review attempts to address the current challenges and delineate future directions for the advancement of NNMs. With the deepening of biomedical applications, it is believed that NNMMMs will inevitably play an important role in the field of human health and contribute to its promotion.

SU-101 for the removal of pharmaceutical active compounds by the combination of adsorption/photocatalytic processes

Pharmaceutical active compounds (PhACs) are some of the most recalcitrant water pollutants causing undesired environmental and human effects. In absence of adapted decontamination technologies, there is an urgent need to develop efficient and sustainable alternatives for water remediation. Metal-organic frameworks (MOFs) have recently emerged as promising candidates for adsorbing contaminants as well as providing photoactive sites, as they possess exceptional porosity and chemical versatility. To date, the reported studies using MOFs in water remediation have been mainly focused on the removal of a single type of PhACs and rarely on the combined elimination of PhACs mixtures. Herein, the eco-friendly bismuth-based MOF, SU-101, has been originally proposed as an efficient adsorbent-photocatalyst for the elimination of a mixture of three challenging persistent PhACs, frequently detected in wastewater and surface water in ng L-1 to mg·L-1 concentrations: the antibiotic sulfamethazine (SMT), the anti-inflammatory diclofenac (DCF), and the antihypertensive atenolol (At). Adsorption experiments of the mixture revealed that SU-101 exhibited a great adsorption capacity towards At, resulting in an almost complete removal (94.1 ± 0.8% for combined adsorption) in only 5 h. Also, SU-101 demonstrated a remarkable photocatalytic activity under visible light to simultaneously degrade DCF and SMT (99.6 ± 0.4% and 89.2 ± 1.4%, respectively). In addition, MOF-contaminant interactions, the photocatalytic mechanism and degradation pathways were investigated, also assessing the toxicity of the resulting degradation products. Even further, recycling and regeneration studies were performed, demonstrating its efficient reuse for 4 consecutive cycles without further treatment, and its subsequent successful regeneration by simply washing the material with a NaCl solution.

Tetracycline adsorption/desorption by raw and activated Tunisian clays

Clay-based adsorbents have applications in environmental remediation, particularly in the removal of emerging pollutants such as antibiotics. Taking that into account, we studied the adsorption/desorption process of tetracycline (TC) using three raw and acid- or base-activated clays (AM, HJ1 and HJ2) collected, respectively, from Aleg (Mazzouna), El Haria (Jebess, Maknessy), and Chouabine (Jebess, Maknessy) formations, located in the Maknessy-Mazzouna basin, center-western of Tunisia. The main physicochemical properties of the clays were determined using standard procedures, where the studied clays presented a basic pH (8.39-9.08) and a high electrical conductivity (446-495 dS m-1). Their organic matter contents were also high (14-20%), as well as the values of the effective cation exchange capacity (80.65-97.45 cmolckg-1). In the exchange complex, the predominant cations were Na and Ca, in the case of clays HJ1 and AM, while Mg and Ca were dominant in the HJ2 clay. The sorption experimental setup consisted in performing batch tests, using 0.5 g of each clay sample, adding the selected TC concentrations, then carrying out quantification of the antibiotic by means of HPL-UV equipment. Raw clays showed high adsorption potential for TC (close to 100%) and very low desorption (generally less than 5%). This high adsorption capacity was also present in the clays after being activated with acid or base, allowing them to adsorb TC in a rather irreversible way for a wide range of pH (3.3-10) and electrical conductivity values (3.03-495 dS m-1). Adsorption experimental data were studied as regards their fitting to the Freundlich, Langmuir, Linear and Sips isotherms, being the Sips model the most appropriate to explain the adsorption of TC in these clays (natural or activated). These results could help to improve the overall knowledge on the application of new low-cost methods, using clay based adsorbents, to reduce risks due to emerging pollutants (and specifically TC) affecting the environment.

Evaluation of acyclovir adsorption on granular activated carbon from aqueous solutions: batch and fixed-bed parametric studies

The present study is aimed to assess the adsorptive potential of carbonaceous material for the acyclovir (ACVR) removal from the aquatic environment using batch and fixed-bed processes. In batch mode, the impact of various process conditions (contact time, pH, adsorbent dose, initial ACVR concentration, and temperature) on ACVR adsorption was investigated. Experimental results revealed that Langmuir isotherm and the pseudo-second-order kinetic model adequately represent the ACVR adsorption mechanism, indicating homogeneous adsorption. The process was found exothermic and spontaneous. Thermodynamic studies concluded that adsorption is a result of both physisorption and chemisorption. To understand the dynamic regime for the design of large-scale column studies, experimental data obtained from breakthrough curve were fitted to various analytical kinetic models. Yan model followed by Thomas model demonstrated a greater correlation of breakthrough data, confirming that the results are significant and are in line with Langmuir isotherm and pseudo-second-order kinetic. G-AC exhibits sufficient adsorption capacity for ACVR. Hence, it is concluded that it can be used in a fixed-bed column in continuous mode for the treatment of ACVR-contaminated wastewater.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-023-02810-7.

Treatment of produced water using Mn oxide nanoparticales loaded on walnut shells

Sorption of ²²⁶Ra from produced water with oil production on manganese oxide nanoparticles loaded on walnut shell media was investigated using batch-type technique. The results showed that ²²⁶Ra is effectively adsorbed onto the adsorbent with equilibrium time of approximately 30 min. Removal efficiency of ²²⁶Ra from produced water depends mainly on the adsorbent dose and concentration of associated ions; removal efficiency decreased when their concentrations increase. The maximum adsorption capacity is reached 58 Bq g^-1. The adsorbent is effective and suitable for removing ²²⁶Ra ions from the produced water under the studied conditions in this work.

Lignin nanoparticle-decorated nanocellulose cryogels as adsorbents for pharmaceutical pollutants

Adsorption is a relatively simple wastewater treatment method that has the potential to mitigate the impacts of pharmaceutical pollution. This requires the development of reusable adsorbents that can simultaneously remove pharmaceuticals of varying chemical structure and properties. Here, the adsorption potential of nanostructured wood-based adsorbents towards different pharmaceuticals in a multi-component system was investigated. The adsorbents in the form of macroporous cryogels were prepared by anchoring lignin nanoparticles (LNPs) to the nanocellulose network via electrostatic attraction. The naturally anionic LNPs were anchored to cationic cellulose nanofibrils (cCNF) and the cationic LNPs (cLNPs) were combined with anionic TEMPO-oxidized CNF (TCNF), producing two sets of nanocellulose-based cryogels that also differed in their overall surface charge density. The cryogels, prepared by freeze-drying, showed layered cellulosic sheets randomly decorated with spherical lignin on the surface. They exhibited varying selectivity and efficiency in removing pharmaceuticals with differing aromaticity, polarity and ionic characters. Their adsorption potential was also affected by the type (unmodified or cationic), amount and morphology of the lignin nanomaterials, as well as the pH of the pharmaceutical solution. Overall, the findings revealed that LNPs or cLNPs can act as functionalizing and crosslinking agents to nanocellulose-based cryogels. Despite the decrease in the overall positive surface charge, the addition of LNPs to the cCNF-based cryogels showed enhanced adsorption, not only towards the anionic aromatic pharmaceutical diclofenac but also towards the aromatic cationic metoprolol (MPL) and tramadol (TRA) and neutral aromatic carbamazepine. The addition of cLNPs to TCNF-based cryogels improved the adsorption of MPL and TRA despite the decrease in the net negative surface charge. The improved adsorption was attributed to modes of removal other than electrostatic attraction, and they could be π-π aromatic ring or hydrophobic interactions brought by the addition of LNPs or cLNPs. However, significant improvement was only found if the ratio of LNPs or cLNPs to nanocellulose was 0.6:1 or higher and with spherical lignin nanomaterials. As crosslinking agents, the LNPs or cLNPs affected the rheological behavior of the gels, and increased the firmness and decreased the water holding capacity of the corresponding cryogels. The resistance of the cryogels towards disintegration with exposure to water also improved with crosslinking, which eventually enabled the cryogels, especially the TCNF-based one, to be regenerated and reused for five cycles of adsorption-desorption experiment for the model pharmaceutical MPL. Thus, this study opened new opportunities to utilize LNPs in providing nanocellulose-based adsorbents with additional functional groups, which were otherwise often achieved by rigorous chemical modifications, at the same time, crosslinking the nanocellulose network.

Study of the effect of current intensity on the structural performance of electrogenerated mesoporous aluminum phosphate: application for adsorption

To keep up with the development of contaminants in the water supply, it is required to create new adsorbents or improve current ones. The adsorption capacity of AlPO₄ electrocoagulated with varying current intensities was examined. AlPO₄ was produced by electrolysis in a NaCl solution using aluminum electrodes and a 0.1 M phosphate buffer at varying current intensities. Current efficiency was enhanced. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy were used to analyze the adsorbents (FTIR). The specific surface area was estimated by the quantity of methylene blue adsorbed by particles in an aqueous solution. Numerous operating factors must be addressed, including pH, starting concentration, adsorbent dose, and contact duration. The electrostatic interaction between positively charged MB molecules and negatively charged adsorbents drives adsorption at alkaline pH. When describing equilibrium adsorption, the Langmuir model is more accurate. Modeling using an adsorption isotherm may further improve the predicted specific surface area. At 0.2 amperes, the observed specific surface area was 2.86 m²/g.

Translating wastewater reuse for irrigation from OECD Guidelines: Tramadol sorption and desorption in soil-water matrices

Treated and untreated wastewater is often used for agricultural irrigation and, despite the many benefits of this practice, it poses the risk of biologically active chemical pollutants (such as pharmaceuticals, like tramadol) entering the environment. The partitioning of tramadol between soil/water at environmentally relevant concentrations is important to understand its environmental toxicity. Kinetics and isotherm sorption studies based on the Organisation for Economic Cooperation and Development (OECD) 106 Guideline were undertaken, ensuring comparability to previous studies. Studies were undertaken in three soils of different characteristics using aqueous concentrations of tramadol from 500 ng L^-1 (environmentally relevant) to 100 μg L^-1 (comparable to previous studies). Two of the soils presented a significantly (p < 0.05) higher sorption at a lower initial tramadol concentration (5000 ng L^-1), compared to 20,000 ng L^-1. Hysteresis was observed in all studied soils, indicating the accumulation of tramadol. Higher sorption to soils correlated with higher clay content, with soil/water partitioning coefficients (K_d) of 5.5 ± 13.3, 2.5 ± 3.8 and 0.9 ± 3.0 L kg¹ for soils with clay contents of 41.9%, 24.5% and 7.4%, respectively. Cation exchange was proposed as the main sorption mechanism for tramadol to soils when the pH was below tramadol's pK_a values (9.41 and 13.08). A comparative kinetics study between tramadol in soil/calcium chloride buffer and soil/wastewater effluent demonstrated significantly higher (p < 0.05) tramadol sorption to soil from wastewater effluent. This has the environmental implication that clay soils will be able to retain tramadol from irrigation water, despite the organic content of the irrigation water. Therefore, our studies show that tramadol soil sorption is likely to be higher in agricultural environments reusing wastewater than that predicted from experiments using the OECD 106 Guideline calcium chloride buffer.

Organobeidellites for Removal of Anti-Inflammatory Drugs from Aqueous Solutions

Diclofenac (DC) and ibuprofen (IBU) are widely prescribed non-steroidal anti-inflammatory drugs, the consumption of which has rapidly increased in recent years. The biodegradability of pharmaceuticals is negligible and their removal efficiency by wastewater treatment is very low. Therefore, the beidelitte (BEI) as unique nanomaterial was modified by the following different surfactants: cetylpyridinium (CP), benzalkonium (BA) and tetradecyltrimethylammonium (TD) bromides. Organobeidellites were tested as potential nanosorbents for analgesics. The organobeidellites were characterized using X-ray powder diffraction (XRD), Infrared spectroscopy (IR), Thermogravimetry and differential thermal analysis (TG/DTA) and scanning microscopy (SEM). The equilibrium concentrations of analgesics in solution were determined using UV-VIS spectroscopy. The intercalation of surfactants into BEI structure was confirmed both using XRD analysis due to an increase in basal spacing from 1.53 to 2.01 nm for BEI_BA and IR by decreasing in the intensities of bands related to the adsorbed water. SEM proved successful in the uploading of surfactants by a rougher and eroded organobeidellite surface. TG/DTA evaluated the decrease in dehydration/dehydroxylation temperatures due to higher hydrophobicity. The Sorption experiments demonstrated a sufficient sorption ability for IBU (55–86%) and an excellent ability for DC (over 90%). The maximum adsorption capacity was found for BEI_BA-DC (49.02 mg·g⁻¹). The adsorption according to surfactant type follows the order BEI_BA > BEI_TD > BEI_CP.

Adsorption of five emerging contaminants on activated carbon from aqueous medium: kinetic characteristics and computational modeling for plausible mechanism

Pharmaceuticals and personal care products (PPCPs) do not have standard regulations for discharge in the environment and are categorized as contaminants of emerging concern as they pose potential threats to ecology as well as humans even at low concentrations. Conventional treatment processes generally employed in the wastewater treatment plants are not adequately engineered for effective removal of PPCPs. Identifying cost-effective tertiary treatment is therefore, important for complete removal of PPCPs from wastewater prior to discharge or reuse. Present study demonstrates adsorption using granular-activated carbon (GAC) as a possible tertiary treatment for simultaneous removal of five PPCPs from aqueous media. Adsorbent was characterized in terms of morphology, surface area, surface charge distribution, and presence of functional groups. Performance of GAC was investigated for sorption of three hydrophilic (ciprofloxacin, acetaminophen, and caffeine) and two hydrophobic (benzophenone and irgasan) PPCPs from aqueous solution varying the process parameters (initial concentration, adsorbent dose, pH, agitation time). Langmuir isotherm model (correlation coefficients (R2): 0.993 to 0.998) appeared to fit the isotherm data better than Temkin isotherm model for these adsorbates. Adsorption efficiencies of these compounds (8.26 to 20.40 mg g-1) were in accordance with their log Kow values. While the adsorption kinetics was best explained in terms of a pseudo-second-order kinetic model, the data suggested that adsorption mechanism was mainly governed by the intraparticle diffusion. The role of physical factors like molecular volume, molecular size, and area of targeted PPCPs were investigated through computational studies which in turn can help predicting their uptake onto GAC.

Adsorption of two β-blocker pollutants on modified montmorillonite with environment-friendly cationic surfactant containing amide group: Batch adsorption experiments and Multiwfn wave function analysis

The novel environment-friendly hexadecanoamide propyltrimethy lammonium chloride (NQAS16-3) surfactant with different amounts (0.2, 0.4, 0.6, 0.8, 1.0, 1.2 CEC) was firstly used to modify montmorillonite, and the obtained organomontmorillonite (N-Mt) with the amount of surfactant equal to 1.0 CEC was utilized to adsorb two β-blocker pollutants- Atenolol (ATE) and acebutolol (ACE). The experimental results indicated that the equilibrium adsorption capacity of N-Mt(the organo-montmorillonite that the amount of modifier was 1.0 CEC) for ATE and ACE was 93.47 mg/g and 84.55 mg/g, respectively, which was more than twice that of raw montmorillonite for two pollutants, the adsorption was better fitted with the pseudo-second-order model and Langmuir isotherms model, and the adsorption was the spontaneous and exothermic process. Moreover, combining with the Zeta potential values of N-Mt, and with the help of Multiwfn wave function program based on density functional theory (DFT), the electrostatic interaction and the hydrophobic partitioning between N-Mt and two pollutant molecules were verified, p-π/π interaction between NQAS16-3 and ATE (or ACE) may be contributed to the increasing adsorption capacity of N-Mt for two β-blocker pollutants. The work provided novel organomontmorillonite for the removal of non-degradable β-blocker pollutants and the insight of the adsorption mechanism from the atomic level.

Laponites® for the Recovery of 133Cs, 59Co, and 88Sr from Aqueous Solutions and Subsequent Storage: Impact of Grafted Silane Loads

In this study, silylated Laponites^® (LAP) were synthetized with various loads of 3-aminopropyltriethoxysilane (APTES) to evaluate their adsorption properties of ¹³³Cs, ⁵⁹Co, and ⁸⁸Sr during single-solute and competitive experiments. The increase in the initial load of APTES increased the adsorbed amount of APTES in the resulted grafted clay. The characterization of LAP-APTES exhibited a covalent binding between APTES and LAP and emphasized the adsorption sites of APTES for each tested load. In comparison with raw LAP, LAP-APTES displayed significantly higher adsorption properties of Co²⁺, Cs⁺, and Sr²⁺. The competitive adsorption of these three contaminants provides a deeper understanding of the affinity between adsorbate and adsorbent. Therefore, Co²⁺ displayed a strong and specific adsorption onto LAP-APTES. Except for Cs⁺, the adsorption capacity was improved with increasing the load of APTES. Finally, the desorption behavior of the three contaminants was tested in saline solutions. Cs⁺ and Sr²⁺ were significantly released especially by inorganic cations displaying the same valence. Conversely, desorption of Co²⁺ was very low whatever the saline solution. LAP-APTES, therefore, presented suitable adsorption properties for the removal of radionuclides especially for Co²⁺, making this material suitable to improve the decontamination of radioactive wastewaters.

Tuning down the environmental interests of organoclays for emerging pollutants: Pharmaceuticals in presence of electrolytes

The impact of electrolytes on the adsorption of emerging pollutants: pharmaceuticals onto layered materials: a raw clay mineral and its nonionic and cationic organoclay derivatives was studied. The selected pharmaceuticals: amoxicillin, norfloxacin, sulfamethoxazole, metoprolol, carbamazepine, and trimethoprim show different electric charges: zwitterionic, anionic, cationic and neutral and hydrophobic character (different LogP). Without any salts, the set of complementary data obtained by UV and infrared spectroscopies, X-ray diffraction points out the importance of the electric charge which represents a key parameter in both the spontaneity and feasibility of the adsorption. In contrast, the hydrophobicity of the analytes plays a minor role but determines the magnitude of the adsorbed amount of pharmaceuticals onto organoclays. With a dual hydrophilic and hydrophobic behavior, nonionic organoclay appears to be the most polyvalent material for the removal of the pharmaceuticals. In the presence of electrolytes (NaCl at a concentration of 1 × 10^-2 mol L^-1), both nonionic and cationic organoclays show a decrease of their efficiencies, whereas the adsorption is particularly enhanced for Na-Mt except for the cationic species (trimethoprim and metoprolol). Thus, in realistic experimental conditions close to those of natural effluents, raw clay mineral appears as the most appropriate sorbent for the studied pharmaceuticals while it raises the question of the usefulness of organoclays in water remediation strategy.

Leaching behavior of pharmaceuticals and their metabolites in the soil environment

Pharmaceuticals constitute a significant group of emerging pollutants (EPs). The use of pharmaceuticals in animal breeding causes them to reach the soil environment in excrement and fertilizers. Depending on their chemical properties, pharmaceuticals can be sorbed to the soil or be washed out with rainfall and eventually be entered into groundwater. This paper evaluates the mobility of tramadol (TRA) and carbamazepine (CBZ), and two transformation products, O-desmethyltramadol (O-DMTRA) and 10,11-dihydro-10-hydroxycarbamazepine (10-OH-CBZ) in soils. Both pharmaceuticals are applied in human and animal treatment, which makes them enter the environment in native and metabolized form in high doses. Experiments were carried out in accordance with the OECD 106 procedure (batch tests) and DIN 19528:2009-01 procedure (percolation column test). The adsorption coefficients (K_d) for TRA, CBZ, O-DMTRA and 10-OH-CBZ were, respectively, 1.41 ± 0.10, 1.87 ± 0.06, 0.90 ± 0.03 and 0.37 ± 0.07 for sandy soil RS04, and 18.09 ± 0.78, 2.56 ± 0.05, 10.89 ± 0.17 and 0.56 ± 0.38  L kg^-1 for loamy soil RS06. The percolation column test was carried out for sandy soil RS04. The results obtained for TRA and O-DMTRA under static conditions indicated a high mobility of these compounds in soil, whereas the column leaching experiment showed that these compounds bind strongly to soil particles. A correlation between static and dynamic tests was observed in the case of CBZ and 10-OH-CBZ. These compounds will probably be characterized by a high or moderate mobility in soil.

Cation-group interaction as the predominant force for adsorption of substituted dinitrobenzenes by smectite clays

Elucidation of the interaction between NACs and smectites is important to the understanding of the potential for transport of nitroaromatic compounds (NACs) in soils and to implementation of NAC-contaminated soil remediation. The adsorption of dinitrotoluene isomers (DNTs) and substituted dinitrobenzenes (SDNBs) by smectite was determined by batch equilibration and characterized by FTIR and XPS, along with molecular dynamics simulations. The adsorption of DNTs differed substantially among the isomers, attributed to the overall degree of nitro deflection relative to the aromatic ring plane. The substituents in SDNBs strengthened the electrostatic interaction between smectite K⁺ and nitro groups, facilitating SDNB adsorption to smectite. The competition between 2,4-DNT and 1,3-DNB, as well as the inclusion complexation of K⁺ by crown ether 18c6e, both reduced 2,4-DNT adsorption to smectite by weakening the K⁺-nitro interaction. All the results demonstrated that the electrostatic interaction between smectite K⁺ and nitro of NACs was the predominant force in mediating their adsorption. This was supported by FTIR spectra that the N-O bands shifted due to the weakening of N-O bonds and strengthening of C-N bonds via the electron transfer to cations. The XPS of smectite further manifested the cation-nitro interactions that the binding energies of K 2p 1/2, K 2p 3/2, and Si 2p shifted higher with 1,3-DNB adsorbed. Molecular dynamics simulations indicated the aromatic planes of 2,4-DNP and 2,4-DNAs were parallel to the basal plane of smectite and the oxygens of nitro groups in the molecules were directly coordinated with smectite K⁺.

Adsorption of micropollutants present in surface waters onto polymeric resins: Impact of resin type and water matrix on performance

The occurrence of micropollutants in water resources is raising substantial concerns, worldwide. These pollutants may have adverse impacts on the aquatic ecosystem and human health. Even though activated carbon is commonly used as an adsorbent to remove micropollutants from water, its low removal of hydrophilic components, energy-intensive regeneration procedure and slow adsorption can impair its applicability. Polymeric resins have been suggested as an effective alternative adsorbent due to their high porosity and accessible adsorption sites, significant adsorption concentration and stable chemical properties. In this work, we evaluated the performance of five commercially available polymeric resins (including two ion exchange resins) for the removal of nine selected micropollutants in water. More specifically, we investigated the effect of polymeric resin type and concentration, contact time and water matrix on the removal efficiency of five pharmaceuticals, two pesticides and two endocrine disruptors of high current concern (diclofenac, sulfamethoxazole, fluoxetine, caffeine, carbamazepine, 17-β estradiol, norethindrone, atrazine and desesthylatrazine). Results presented herein indicated that two hydrophobic polymeric resins can effectively adsorb over 80% of the targeted micropollutants within 30 min when the resin concentration was higher than 2.5 mL L^-1. The adsorption data were well described with the Freundlich isotherm and the pseudo-second order kinetic model very well described the kinetic process of the selected micropollutants onto the polymeric resins. Moreover, we observed that increasing the synthetic water temperature from 4 to 22 °C led to a marginally higher micropollutant uptake and the presence of natural organic matter had no noted impact on the efficiency of the resins in removing the tested micropollutants when the resin dosage was 5.4 mL L^-1. On the basis of these promising results, we conclude that polymeric resins are a promising alternative to activated carbon for micropollutants sorption in drinking water treatment.

Environmentally-related contaminants of high concern: Potential sources and analytical modalities for detection, quantification, and treatment

In recent years, emerging contaminants (ECs) of high concern are broadly distributed throughout the environmental matrices because of various industrial practices and anthropogenic inputs, i.e., human-made activities. With ever increasing scientific knowledge, technological advancement, socio-economic awareness, people are now more concern about the widespread distribution of environmentally related ECs of high concern. As, ECs possess serious ecological threats and potential risks to human health and aquatic life, even at minor concentrations. The controlled or uncontrolled discharge and long-term persistence of ECs that includes micro-pollutants, endocrine disruptors (EDs), pesticides, pharmaceuticals, hormones, toxins, and industrially-related synthetic dyes and dyes-containing hazardous pollutants, etc. pose a significant challenge to policy regulators, engineers, and scientific community. The conventional treatment technologies are proved ineffective for the complete elimination and removal of an array of contaminants of emerging environmental concern in various biological and environmental samples. In order to overcome the aforementioned ecological threats, tremendous research efforts have been made to boost the efficiency of remediation techniques or develop new modalities to detect, quantify and treat the samples efficiently. The boom in biotechnology and environmental engineering offers potential opportunities to develop advanced and innovative remediation techniques in the field of water treatment. This review discusses the environmental and health hazards associated with a widespread distribution of micro-pollutants, pesticides, pharmaceuticals, hormones, and industrially-related synthetic dyes and dyes-containing hazardous pollutants, etc. in the water bodies, i.e., surface water, groundwater, and industrial wastewater streams. Life-cycle distribution of emerging (micro)-pollutants with suitable examples from various industrial sources viewpoints is also discussed. The later part of the review focuses on innovative and cost-effective remediation (removal) approaches from phase-changing treatment technologies for these ECs of high concern.

Adsorption Analyses of Phenol from Aqueous Solutions Using Magadiite Modified with Organo-Functional Groups: Kinetic and Equilibrium Studies

Organically-modified magadiite (MAG–CTAB–KH550) was synthesized via ion-exchange method and condensation reaction in the presence of pure magadiite (MAG), cetyltrimethylammonium bromide (CTAB) and γ-aminopropyltriethoxysilane (KH550) in aqueous solution in this research. This new adsorbent material was studied using scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and N₂ adsorption/desorption isotherms process. It was found that the MAG–CTAB–KH550 has high Brunaur-Emmet-Teller (BET) specific surface area and mesoporous pore size distribution which enhanced its ability to remove phenol in aqueous solution; and, the value of pH has a relatively large impact on the adsorption behavior of the sorbent. Finally, the adsorptive behavior of the mesoporous material on phenol was followed pseudo-second-order kinetic adsorption model. In contrast, the adsorption equilibrium isotherm was better performed Langmuir isotherm model than the Freundlich isotherm model; in addition, the results also showed that the MAG–CTAB–KH550 had a better adsorption capacity and removal efficiency than MAG.

Competitive Association of Antibiotics with a Clay Mineral and Organoclay Derivatives as a Control of Their Lifetimes in the Environment

A Na-smectite clay mineral (Na-Mt) was exchanged with two concentrations of benzyldimethyltetradecyl ammonium chloride cationic surfactant up to one time the cation exchange capacity. Nonionic organoclay was prepared with polyoxyethylene (20) oleyl ether (Brij-O20) nonionic surfactant at one concentration. The resulting organoclays displayed lateral layer organization of the surfactants within their interlayer space.. The adsorption properties of these organoclays and the starting raw clay mineral were evaluated for three extensively used antibiotic pharmaceutical products: the amoxicillin (AMX), the sulfamethoxazole (SMX), and the trimethoprim (TRI), recognized as recalcitrant compounds to conventional water treatments and to display a complex behavior for different pH and temperature experimental conditions. Besides showing short half-life time with possible degradation by UV radiation, these antibiotics associated with mineral phases cause serious environmental issues of which the toxic effect can be exacerbated in the presence of other chemical compounds. From the set of data obtained by complementary techniques: UV and Fourier transform infrared spectroscopy, high-performance liquid chromatography coupled with mass spectrometry, and X-ray diffraction, it appears that the nonionic organoclay shows its versatility for the adsorption of individual molecules as well as a pool of antibiotics. The mixing of the three antibiotics showing different electric charged species (cations, anions, and zwitterions) mimics the natural context drives to a deep modification of the adsorption behavior onto the different materials that can act as possible carrier mineral phases in aquatic environment. These competition effects can be measured through the significant decrease of the K _F Freundlich constants for AMX in the presence of other molecules (or electrolytes), whereas TRI and SMX, by their possible association, create a synergistic effect that favors their adsorption on the whole layered materials.

Removal of Zinc Ions Using Hydroxyapatite and Study of Ultrasound Behavior of Aqueous Media

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM, respectively). The effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions was stressed out through ultrasonic measurements. Both Langmuir and Freundlich models properly fitted on a wide range of concentration the equilibrium adsorption isotherms, allowing us to precisely quantify the affinity of zinc to hydroxyapatite nanopowders and to probe the efficacy of hydroxyapatite in removal of zinc ions from aqueous solutions in ultrasonic conditions.

The efficacy of raw and concentrated bentonite clay in reducing the toxic effects of aflatoxin in broiler chicks

The objective of this study was to evaluate the efficacy of two adsorbents, a raw bentonite clay (RC) and a concentrated bentonite clay (CC), in ameliorating the toxic effects of aflatoxin B1 (AFB1). Results of the in vitro study (pH 3.0) indicated the CC adsorbed more AFB1 than RC (93.39 mg/g vs. 79.30 mg/g) suggesting that CC may be more effective than RC in reducing the toxic effects of AFB1. One hundred and eighty day-old straight run broiler chicks were assigned to 6 replicate pens of 5 chicks each and assigned to 6 dietary treatments from hatch to day 21. Dietary treatments included: 1) basal diet (BD) containing no AFB1 or adsorbents; 2) BD plus 0.50% RC; 3) BD plus 0.50% CC; 4) BD plus 2.0 mg AFB1/kg; 5) BD plus 2.0 mg AFB1/kg plus 0.50% RC; and 6) BD plus 2.0 mg AFB1/kg plus 0.50% CC. Dietary AFB1 concentrations were confirmed by analysis and diets were screened for other mycotoxins prior to the start of the experiment. The addition of AFB1 to the feed reduced (P < 0.05) growth performance and increased (P < 0.05) relative liver weight (RLW) and kidney weight (RKW) of chicks fed AFB1 compared to control chicks on day 21. These changes were ameliorated (P < 0.05) by the addition of RC and CC to the AFB1 diet. Mild to moderate lesions of aflatoxicosis (2.25) were observed in chicks fed AFB1 alone on day 21. The addition of both RC and CC to the AFB1 diet decreased (P < 0.05) but did not prevent liver lesions (0.92 and 1.42, respectively). Results indicate that both RC and CC were effective in reducing the toxic effects of AFB1, however the cost of processing of CC would make the RC a more economical product for reducing the effects of AFB1 in young broiler chicks.

Application of vermiculite-derived sustainable adsorbents for removal of venlafaxine

Removal of emerging pollutants, such as pharmaceuticals, from wastewater is a challenge. Adsorption is a simple and efficient process that can be applied. Clays, which are natural and low-cost materials, have been investigated as adsorbent. In this work, raw vermiculite and its three modified forms (expanded, base, and acid/base treated) were tested for removal of a widely used antidepressant, venlafaxine. Adsorption kinetics followed Elovich's model for raw vermiculite while the pseudo-2nd order model was a better fit in the case of other materials. Equilibrium followed Langmuir's model for the raw and the acid/base-treated vermiculite, while Redlich-Peterson's model fitted better the expanded and the base-treated materials. The adsorption capacity of vermiculite was significantly influenced by the changes in the physical and chemical properties of the materials caused by the treatments. The base-treated, raw, and expanded vermiculites showed lower maximum adsorption capacities (i.e., 6.3 ± 0.5, 5.8 ± 0.7, 3.9 ± 0.2 mg g^-1, respectively) than the acid/base-treated material (33 ± 4 mg g^-1). The acid/base-treated vermiculite exhibited good properties as a potential adsorbent for tertiary treatment of wastewater in treatment plants, in particular for cationic species as venlafaxine due to facilitation of diffusion of the species to the interlayer gallery upon such treatment. Graphical abstract ᅟ.

Removal of pharmaceutical pollutants from synthetic wastewater using chemically modified biomass of green alga Scenedesmus obliquus

Pharmaceutical compounds are considered emerging environmental pollutants that have a potential harmful impact on environment and human health. In this study, the biomass of alga (Scenedesmus obliquus) was modified using alkaline solution, and used for the biosorption of tramadol (TRAM) and other pharmaceuticals. The adsorption kinetics and isotherms were investigated. The obtained results reveal high adsorption capacity of tramadol over modified algal biomass (MAB) after 45min with removal percentage of 91%. Pseudo-second order model was well fitted with the experimental data with correlation coefficient (0.999). Biosorption of tramadol on modified algal biomass proceeds with Freundlich isotherm model with correlation coefficient (0.942) that emphasized uptake of TRAM by MAB is driven by chemisorption. FTIR spectra of MAB before and after the adsorption were analyzed; some IR bands were detected with slight shift and low intensity suggesting their involving in adsorption. The tramadol biosorption by MAB is a chemical process as confirmed by Dubinin-Radushkevich. The adsorption of pharmaceutical over MAB is mainly preceded by hydrophilic interactions between amino and carbonyl groups in pharmaceutical molecules and hydroxyl and carbonyl functional groups on surface of biosorbent. It was emphasized by disappearance O-H and C-O from biomass IR spectra after adsorption. In matrix of pharmaceutical, the recorded adsorption capacities for CEFA, PARA, IBU, TRAM and CIP are 68, 58, 42, 42 and 39mg/g over MAB at natural pH and MAB dose of 0.5g/L. Furthermore, oxygen uptake by bacteria was applied for estimate the toxicity of pharmaceutical. The recorded result concluded the efficient reusability of modified algal biomass for biosorption of pharmaceuticals, as well only the adsorption efficiency decreased by 4.5% after three runs. Subsequently, the modified algal biomass is a promising reusable adsorbent for decontamination of wastewater from pharmaceuticals.

Removal of emerging contaminants from the environment by adsorption

Emerging contaminants (EC's) are pollutants of growing concern. They are mainly organic compounds such as: pesticides, pharmaceuticals and personal care products, hormones, plasticizers, food additives, wood preservatives, laundry detergents, surfactants, disinfectants, flame retardants, and other organic compounds that were found recently in natural wastewater stream generated by human and industrial activities. A majority of ECs does not have standard regulations and could lead to lethal effects on human and aquatic life even at small concentrations. The conventional primary and secondary water treatment plants do not remove or degrade these toxic pollutants efficiently and hence need cost effective tertiary treatment method. Adsorption is a promising method worldwide for EC removal since it is low initial cost for implementation, highly-efficient and has simple operating design. Research has shown that the application of different adsorbents such as, activated carbons(ACs), modified biochars (BCs), nanoadsorbents (carbon nanotubes and graphene), composite adsorbents, and other are being used for EC's removal from water and wastewater. The current review intends to investigate adsorption process as an efficient method for the treatment of ECs. The mechanism of adsorption has also been discussed.

A simple way for targeted delivery of an antibiotic: In vitro evaluation of a nanoclay-based composite

The sodium-modified form of fluorohectorite nanoclay (NaFh) is introduced as a potential drug carrier, demonstrating its ability for the controlled release of the broad-spectrum antibiotic Ciprofloxacin through in vitro tests. The new clay-drug composite is designed to target the local infections in the large intestine, where it delivers most of the incorporated drug thanks to its pH-sensitive behavior. The composite has been conceived to avoid the use of coating technology and to decrease the side-effects commonly associated to the burst-release of the ciprofloxacin at the stomach level. NaFh was obtained from lithium-fluorohectorite by ion exchange, and its lack of toxicity was demonstrated by in vivo studies. Ciprofloxacin hydrochloride (Cipro) was encapsulated into the clay at different values of the pH, drug initial concentration, temperature and time. Systematic studies by X-ray diffraction (XRD), infrared and visible spectrophotometry (FT-IR and UV-vis), and thermal analysis (TGA) indicated that the NaFh host exhibits a high encapsulation efficiency for Cipro, which reaches a 90% of the initial Cipro in solution at 65 oC, with initial concentration of drug in solution of 1.36 x 10-2 mol L-1 at acid pH. XRD revealed that a true intercalation of Cipro takes place between clay layers. TG showed an increased thermal stability of the drug when intercalated into the clay, as compared to the "free" Cipro. IR suggested a strong clay-Cipro interaction via ketone group, as well as the establishment of hydrogen bonds between the two materials. In vitro drug release tests revealed that NaFh is a potentially efficient carrier to deliver Cipro in the large intestine, where the release process is mediated by more than just one mechanism.

Adsorption of diclofenac onto organoclays: Effects of surfactant and environmental (pH and temperature) conditions

Among pharmaceutical products (PPs) recalcitrant to water treatments, diclofenac shows a high toxicity and remains at high concentration in natural aquatic environments. The aim of this study concerns the understanding of the adsorption mechanism of this anionic PP onto two organoclays prepared with two long-alkyl chains cationic surfactants showing different chemical nature for various experimental pH and temperature conditions. The experimental data obtained by a set of complementary techniques (X-ray diffraction, elemental analyses, gas chromatography coupled with mass spectrometry, and Fourier transform infrared spectroscopy) and the use of Langmuir, Freundlich and Dubinin-Radushkevish equation models, reveal that organoclays show a good affinity to diclofenac which is enhanced as the temperature is under 35°C and for pH above 4.5 (i.e. >pKa of diclofenac) while the chemical nature of surfactant appears to play a minor role. The thermodynamic parameters derived from the fitting procedure point out the strong electrostatic interaction with organic cations adsorbed within the interlayer space in the organoclays for the adsorption of diclofenac. This study stress out the application of organoclays for the adsorption of a recalcitrant PPs in numerous aquatic compartments that can be used as a complement with activated carbon for waste water treatment.

Coupled Organoclay/Micelle Action for the Adsorption of Diclofenac

A Na-smectite clay mineral (Na-Mt) was exchanged with various amounts of benzyldimethyltetradecyl ammonium chloride cationic surfactant (BDTAC) up to four times the cation exchange capacity (CEC). The adsorption properties of these organoclays as well as a coupled micelle/organoclay process were evaluated to remove an anionic pharmaceutical product, the diclofenac (DCF), recognized as a recalcitrant compound for conventional water treatments and to be poorly adsorbed onto untreated clay mineral. The DCF affinity appears to depend on the lipophilic character of organoclays in correlation to the density of intercalated BDTA and is particularly enhanced for sorbent systems with free surfactant or micelle in solution. The combination of both organclay and BDTA in excess or micelle as a one pot adsorption system appears to be the most efficient material for the sequestration of DCF and other pharmaceutical products (PPs) with a KF Freundlich constant of 1.7 L g(-1) and no restriction of the adsorbed DCF amount as the linear adsorption isotherm shows. A BDTA hydrophobic core micelle coupled with a positive electric charge forms an organic complex with DCF that is properly intercalated within the interlayer space of BDTA-Mt organoclays as both Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data supported.

Competitive adsorption of a pool of pharmaceuticals onto a raw clay mineral

The removal of a Pharmaceutically Active Compound (PhAC) pool using a well referenced clay mineral from Wyoming (SWy-2) as a geosorbent was studied for a better understanding of the environmental fate.