Efficient tetracycline adsorptive removal using tricaprylmethylammonium chloride conjugated chitosan hydrogel beads: Mechanism, kinetic, isotherms and thermodynamic study

Adsorption of emerging pollutants utilizing chitosan derivatives: Recent advances and future perspective

Globalization resulted in technological advancement, and urban population growth. Consequently, pollution emerged as an imminent risk to the survival of all species on Earth. Consequently, on a worldwide basis, sustainability become a major issue for legislators. Inconsistent impacts on both human and animal growth and wellness triggered health issues associated with water contamination through the chronic toxicants. Micropollutants' pollution prompted severe concerns due to their malignant, indestructible, and accumulative properties. The elimination of these toxins from industrial processes has become one of the most significant ecological challenges. A variety of both organic and simulated sorbents are available, and each of these have unique benefits. In the recent years, chitosan and its composite materials have been attempted and have been proven to be applicable for the resolution of many challenging issues related to water pollution. Among various notable benefits of adsorption processes, economic viability, ease of access, and adherence to environmental regulations are notable. Considering the above-mentioned issues, the article targets the assessment of chitosan and its composite materials for relevant environmental applications. Accordingly, the article aims to examine the performance, advantages, and disadvantages of chitosan as an adsorbent.

Detection of tetracycline by molecularly imprinted electrochemical sensor based on the modification of poly(3,4-propylene dioxythiophene)/chitosan/au

In this study, a molecularly imprinted polymer (MIP) electrochemical sensor based on poly(3,4-propylenedioxythiophene)/chitosan/Au (PProDOT/CS/Au) composite modification was designed for highly sensitive and selective detection of TC. Green synthesis of CS/Au without the use of reducing agents, followed by in-situ oxidation polymerization of PProDOT. The high electrochemical activity and high stability of PProDOT, the numerous functional groups (-OH, -NH2) of CS, and the excellent electron transport capacity of AuNPs, which provided a suitable incubation chamber for the production of imprinted cavities. Meanwhile, combined with the specific recognition ability of MIP, it showed superior performance over bare glassy carbon electrodes. Under the optimal experimental conditions, this sensor showed good linearity for TC in the concentration ranges of 0.0001-100 μM, with a low limit of detection (LOD) of 0.19 nM. At the same time, the sensor exhibited satisfactory selectivity, repeatability, reproducibility and stability. It was evident from the results of the study that the sensor designed in this paper showed considerable potential for application in the detection of TC in pharmaceuticals, the environment, and food samples.

Versatile and durable polyvinyl alcohol/alginate/gelatin/quaternary ammonium chitosan/Fe3O4 particles hybrid hydrogel beads: adsorption capabilities for cleaning pollutants

A novel hybrid hydrogel bead (HHBFe) composed of polyvinyl alcohol/sodium alginate/gelatin/quaternary ammonium chitosan (PVA/GA/SA/QCS) and Fe3O4 magnetic nanoparticles was developed through green cross-linking of Ca2+ and tannic acid (TA) combined freeze-thaw method. HHBFe exhibited a good spherical shape, porosity, magnetic properties, and excellent mechanical properties and durability. The adsorption capacity of HHB and HHBFe towards methyl orange (MO), tetracycline (Tc), and Cr (VI) was systematically studied and compared. Results revealed similar adsorption capacities for MO and Cr (VI) between HHB and HHBFe, while the presence of Fe3O4 significantly enhanced Tc adsorption, indicating the versatile adsorption functions of HHBFe. Adsorption kinetic followed the pseudo-second-order model, with external diffusion and intra-particle diffusion controlling process. The adsorption data were consistent with the Langmuir isothermal adsorption model, indicating predominantly monolayer adsorption of pollutants by beads. Notably, the beads exhibited easily regenerated, maintaining 60 % of initial adsorption capacity after 5 cycles, particularly for Tc and Cr (VI). The good adsorption performance of HHBFe can be attributed to the strong interaction between their multi-functional groups including phenolic hydroxyl groups, carboxyl groups, amino groups, etc., and pollutant molecules. The multifunctional HHBFe beads prepared in this study and the results obtained with three completely different types of pollutants provide reliability support for their use in different wastewater treatment fields and even in the field of drug carriers.

Revolutionizing wastewater treatment: A review on the role of advanced functional bio-based hydrogels

Water contamination poses a significant challenge to environmental and public health, necessitating sustainable wastewater treatment solutions. Adsorption is one of the most widely used techniques for purifying water, as it effectively removes contaminants by transferring them from the liquid phase to a solid surface. Bio-based hydrogel adsorbents are gaining popularity in wastewater treatment due to their versatility in fabrication and modification methods, which include blending, grafting, and crosslinking. Owning to their unique structure and large surface area, modified hydrogels containing reactive groups like amino, hydroxyl, and carboxyl, or functionalized hydrogels with inorganic nanoparticles particularly graphene nanomaterials, have demonstrated promising adsorption capabilities for both inorganic and organic contaminants. Bio-based hydrogels have excellent physicochemical properties and are non-toxic, environmentally friendly, and biodegradable, making them extremely effective at removing contaminants like heavy metal ions, dyes, pharmaceutical pollutants, and organic micropollutants. The versatility of hydrogels allows for various forms to be used, such as films, beads, and nanocomposites, providing flexibility in handling different contaminants like dyes, radionuclides, and heavy metals. Additionally, researchers also have shown the potential for recycling and regenerating post-treatment hydrogels. This approach not only addresses the challenges of wastewater treatment but also offers sustainable and effective solutions for mitigating water pollution.

A waste-to-wealth conversion of plastic bottles into effective carbon-based adsorbents for removal of tetracycline antibiotic from water

Currently, plastic waste and antibiotic wastewater are two of the most critical environmental problems, calling for urgent measures to take. A waste-to-wealth strategy for the conversion of polyethylene terephthalate (PET) plastic bottles into value-added materials such as carbon composite is highly recommended to clean wastewater contaminated by antibiotics. Inspired by this idea, we develop a novel PET-AC-ZFO composite by incorporating PET plastic-derived KOH-activated carbon (AC) with ZnFe2O4 (ZFO) particles for adsorptive removal of tetracycline (TTC). PET-derived carbon (PET-C), KOH-activated PET-derived carbon (PET-AC), and PET-AC-ZFO were characterized using physicochemical analyses. Central composite design (CCD) was used to obtain a quadratic model by TTC concentration (K), adsorbent dosage (L), and pH (M). PET-AC-ZFO possessed micropores (d ≈ 2 nm) and exceptionally high surface area of 1110 m2 g-1. Nearly 90% TTC could be removed by PET-AC-ZFO composite. Bangham kinetic and Langmuir isotherm were two most fitted models. Theoretical maximum TTC adsorption capacity was 45.1 mg g-1. This study suggested the role of hydrogen bonds, pore-filling interactions, and π-π interactions as the main interactions of the adsorption process. Thus, a strategy for conversion of PET bottles into PET-AC-ZFO can contribute to both plastic recycling and antibiotic wastewater mitigation.

Bacterial cellulose microfilament biochar-architectured chitosan/polyethyleneimine beads for enhanced tetracycline and metronidazole adsorption

This study investigates the potential applications of incorporating 2D bacterial cellulose microfibers (BCM) biochar into chitosan/polyethyleneimine beads as a semi-natural sorbent for the efficient removal of tetracycline (TET) and metronidazole (MET) antibiotics. Batch adsorption experiments and characterization techniques evaluate removal performance and synthesized adsorbent properties. The adsorbent eliminated 99.13 % and 90 % of TET and MET at a 10 mg.L-1 concentration with optimal pH values of 8 and 6, respectively, for 90 min. Under optimum conditions and a 400 mg.L-1 concentration, MET and TET have possessed the maximum adsorption capacities of 691.325 and 960.778 mg.g-1, respectively. According to the isothermal analysis, the adsorption of TET fundamentally follows the Temkin (R2 = 0.997), Redlich-Peterson (R2 = 0.996), and Langmuir (R2 = 0.996) models. In contrast, the MET adsorption can be described by the Langmuir (R2 = 0.997), and Toth (R2 = 0.991) models. The pseudo-second-order (R2 = 0.998, 0.992) and Avrami (R2 = 0.999, 0.999) kinetic models were well-fitted with the kinetic results for MET and TET respectively. Diffusion models recommend that pore, liquid-film, and intraparticle diffusion govern the rate of the adsorption process. The developed semi-natural sorbent demonstrated exceptional adsorption capacity over eleven cycles due to its porous bead structure, making it a potential candidate for wastewater remediation.

Preparation of novel and recyclable chitosan-alumina nanocomposite as superabsorbent to remove diazinon and tetracycline contaminants from aqueous solution

This work presents a novel, strong and efficient adsorbent (CS@TDI@EDTA@γ-AlO(OH)) prepared through the green process using three components, chitosan, BNPs and EDTA using amide and ester bridges. An eco-friendly and easy approach was used for the preparation of this novel adsorbent, the low cost, easy access to the used materials, and the simplicity of the preparation method are some of the interesting advantages of this work. Also, this prepared adsorbent was used as an adsorbent to remove diazinon organophosphate poison and tetracycline antibiotic from aqueous solutions. In order to confirm the prepared adsorbent structure, the CS@TDI@EDTA@γ-AlO(OH) composite was investigated by various analyses including FT-IR, EDX, XRD, FESEM and TGA. The adsorption behavior of the adsorbent prepared for the removal of tetracycline and diazinon was investigated under different conditions by varying the concentration, temperature, the adsorbent dose, pH and contact time. Based on various tests, the highest diazinon adsorption capacity was obtained for 0.12 g/L adsorbent at pH 7 and 60 °C with 40 mg/L initial concentration. Also, the maximum adsorption capacity of the tetracycline was obtained for 0.12 g/L adsorbent at pH 9 and 60 °C with 30 mg/L initial concentration. The equilibrium results for diazinon and for tetracycline were in good accordance with the Langmuir and Freundlich isotherm models, respectively. Also, the highest adsorption capacities for diazinon at pH 7 and tetracycline at pH 9 were 1428.5 and 555.5 mg/g, respectively. Also the kinetic investigations revealed that the correlation factor (R2) of pseudo-second-order model obtained for the adsorption of diazinon and tetracycline was 0.9986 and 0.9988, while the coefficient k (g/mg.min) was 0.000084 and 0.0033, respectively. These results indicate that the adsorption of diazinon and tetracycline is pseudo-second-order kinetics model. Formation of hydrogen bonds between adsorbate and adsorbent as well as the high specific surface area and porosity of the adsorbent are the main mechanisms that contribute to the adsorption process. In addition, thermodynamic studies indicated that the adsorption of diazinon and tetracycline is a spontaneous endothermic process. The adsorbent prepared in this work was expected to have wide range of applications in wastewater treatment thanks to its good reusability in water and strong removal of diazinon and tetracycline compared to other adsorbents.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.

Hydrothermal Pretreatment of KOH for the Preparation of PAC and Its Adsorption on TC

The environment has been heavily contaminated with tetracycline (TC) due to its excessive use; however, activated carbon possessing well-developed pores can effectively adsorb TC. This study synthesized pinecone-derived activated carbon (PAC) with high specific surface area (1744.659 cm²/g, 1688.427 cm²/g) and high adsorption properties (840.62 mg/g, 827.33 mg/g) via hydrothermal pretreatment methods utilizing pinecones as precursors. The results showed that PAC treated with 6% KOH solution had excellent adsorption properties. It is found that the adsorption process accords with the PSO model, and a large amount of C=C in PAC provides the carrier for π-πEDA interaction. The results of characterization and the isothermal model show that TC plays a key role in the adsorption process of PAC. It is concluded that the adsorption process of TC on PAC prepared by hydrothermal pretreatment is mainly pore filling and π-πEDA interaction, which makes it a promising adsorbent for TC adsorption.

Functionally-designed floatable amino-modified ZnLa layered double hydroxides/cellulose acetate beads for tetracycline removal: Performance and mechanism

The over-reliance on tetracycline antibiotics (TC) in the animal husbandry and medical field has seriously affected the safety of the ecological environment. Therefore, how to effectively treat tetracycline wastewater has always been a long-term global challenge. Here, we developed a novel polyethyleneimine (PEI)/Zn-La layered double hydroxides (LDH)/cellulose acetate (CA) beads with cellular interconnected channels to strengthen the TC removal. The results of the exploration on its adsorption properties illustrated that the adsorption process exhibited a favorable correlation with the Langmuir model and the pseudo-second-order kinetic model, namely monolayer chemisorption. Among the many candidates, the maximum adsorption capacity of TC by 10 %PEI-0.8LDH/CA beads was 316.76 mg/g. Apart from that, the effects of pH, interfering species, actual water matrix and recycling on the adsorption of TC by PEI-LDH/CA beads were also analyzed to verify their superior removal capability. The potential for industrial-scale applications was expanded through fixed-bed column experiments. The proven adsorption mechanisms mainly included electrostatic interaction, complexation, hydrogen bonding, n-π EDA effect and cation-π interaction. The self-floating high-performance PEI-LDH/CA beads exploited in this work provided fundamental support for the practical application of antibiotic-based wastewater treatment.

Design of separable magnetic chitosan grafted-benzaldehyde for azo dye removal via a response surface methodology: Characterization and adsorption mechanism

In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe₃O₄) was hydrothermally prepared using benzaldehyde as a grafting agent to produce a promising adsorbent for the removal of acid red 88 (AR88) dye. The CS-BD/Fe₃O₄ was characterized by infrared spectroscopy, surface area analysis, scanning electron microscopy-energy dispersive X-ray, vibrating sample magnetometry, powder X-ray diffraction, CHN elemental analysis, and point of zero charge (pH_PZC). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe₃O₄ dose (0.02-0.1 g), B: pH (4-10), and time C: (10-90 min)). The ANOVA results of the BBD model indicated that the F-value for the AR88 removal was 22.19 %, with the corresponding p-value of 0.0002. The adsorption profiles at equilibrium and dynamic conditions reveal that the Temkin model and the pseudo-first-order kinetics model provide an adequate description of the isotherm results, where the maximum adsorption capacity (qmax) with the AR88 dye was 154.1 mg/g. Several mechanisms, including electrostatic attraction, n-π interaction, π-π interaction, and hydrogen bonding, regulate the adsorption of AR88 dyes onto CS-BD/Fe₃O₄ surface. As a result, this research indicates that the CS-BD/Fe₃O₄ can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater.

Insight into the adsorptive removal of ibuprofen using porous carbonaceous materials: A review

Over the last decade, the removal of pharmaceuticals from aquatic bodies has garnered substantial attention from the scientific community. Ibuprofen (IBP), a non-steroidal anti-inflammatory drug, is released into the environment in pharmaceutical waste as well as medical, hospital, and household effluents. Adsorption technology is a highly efficient approach to reduce the IBP in the aquatic environment, particularly at low IBP concentrations. Due to the exceptional surface properties of carbonaceous materials, they are considered ideal adsorbents for the IBP removal of, with high binding capacity. Given the importance of the topic, the adsorptive removal of IBP from effluent using various carbonaceous adsorbents, including activated carbon, biochar, graphene-based materials, and carbon nanostructures, has been compiled and critically reviewed. Furthermore, the adsorption behavior, binding mechanisms, the most effective parameters, thermodynamics, and regeneration methods as well as the cost analysis were comprehensively reviewed for modified and unmodified carbonaceous adsorbents. The compiled studies on the IBP adsorption shows that the IBP uptake of some carbon-based adsorbents is significantly than that of commercial activated carbons. In the future, much attention is needed for practical utilization and upscaling of the research findings to aid the management and sustainability of water resource.

Research Progress of Polysaccharide-Based Natural Polymer Hydrogels in Water Purification

The pollution and scarcity of freshwater resources are global problems that have a significant influence on human life. It is very important to remove harmful substances in the water to realize the recycling of water resources. Hydrogels have recently attracted attention due to their special three-dimensional network structure, large surface area, and pores, which show great potential for the removal of pollutants in water. In their preparation, natural polymers are one of the preferred materials because of their wide availability, low cost, and easy thermal degradation. However, when it is directly used for adsorption, its performance is unsatisfactory, so it usually needs to be modified in the preparation process. This paper reviews the modification and adsorption properties of polysaccharide-based natural polymer hydrogels, such as cellulose, chitosan, starch, and sodium alginate, and discusses the effects of their types and structures on performance and recent technological advances.

Preparation and characterization of chitosan-curdlan composite magnetized by zinc ferrite for efficient adsorption of tetracycline antibiotics in water

Tetracycline (TC) antibiotic-related water pollution directly threatens human health and ecosystems. Here, a zinc ferrite/chitosan-curdlan (ZNF/CHT-CRD) magnetic composite was prepared via a co-precipitation method to be used as a novel, green adsorbent for TC removal from water. Benefiting from a multitude of functional groups, CRD was first crosslinked with CHT and then magnetized with ZNF to provide an easy separation from the solution with an external magnetic force. The successful synthesis and magnetization of the composite were verified with different characterization techniques. The effect of solution pH and composite dosage was carefully evaluated. The optimum solution pH and composite dosage were 6 and 0.65 g/L, respectively, with complete TC removal. The adsorption process by the magnetic composite followed the pseudo-first-order kinetics and Langmuir isotherm models. The maximum adsorption capacity determined from the Langmuir model was 371.42 mg/g at 328 K. Thermodynamic parameters indicated endothermic and spontaneous adsorption. Meanwhile, the composite could be readily separated from the aqueous solution thanks to its magnetic property. Then, it was regenerated with acetone and ethanol to be reused for five more successive cycles. Interestingly, the prepared adsorbent was highly stable and performant in removing TC, maintaining approximately 90 % of its first-cycle adsorption capacity. The adsorption mechanism was primarily attributed to electrostatic and hydrogen bonding attractions. Overall, the currently developed adsorbent could be a more favorable, efficient, and cost-effective candidate than other magnetic chitosan-based composites. These features make it applicable for treating water contaminated with various pharmaceutical pollutants with high separation efficiency and easy recovery under successive adsorption-desorption cycles.

Chitosan Nanoparticles as Potential Nano-Sorbent for Removal of Toxic Environmental Pollutants

Adsorption is the most widely used technique for advanced wastewater treatment. The preparation and application of natural renewable and environmentally friendly materials makes this process easier and more profitable. Chitosan is often used as an effective biomaterial in the adsorption world because of its numerous functional applications. Chitosan is one of the most suitable and functionally flexible adsorbents because it contains hydroxyl (-OH) and amine (-NH₂) groups. The adsorption capacity and selectivity of chitosan can be further improved by introducing additional functions into its basic structure. Owing to its unique surface properties and adsorption ability of chitosan, the development and application of chitosan nanomaterials has gained significant attention. Here, recent research on chitosan nanoparticles is critically reviewed by comparing various methods for their synthesis with particular emphasis on the role of experimental conditions, limitations, and applications in water and wastewater treatment. The recovery of pollutants using magnetic nanoparticles is an important treatment process that has contributed to additional development and sustainable growth. The application of such nanoparticles in the recovery metals, which demonstrates a "close loop technology" in the current scenarios, is also presented in this review.

Highly Efficient Adsorption of Tetracycline Using Chitosan-Based Magnetic Adsorbent

Herein, tetracycline adsorption employing magnetic chitosan (CS·Fe₃O₄) as the adsorbent is reported. The magnetic adsorbent was synthesized by the co-precipitation method and characterized through FTIR, XRD, SEM, and VSM analyses. The experimental data showed that the highest maximum adsorption capacity was reached at pH 7.0 (211.21 mg g^-1). The efficiency of the magnetic adsorbent in tetracycline removal was dependent on the pH, initial concentration of adsorbate, and the adsorbent dosage. Additionally, the ionic strength showed a significant effect on the process. The equilibrium and kinetics studies demonstrate that Sips and Elovich models showed the best adjustment for experimental data, suggesting that the adsorption occurs in a heterogeneous surface and predominantly by chemical mechanisms. The experimental results suggest that tetracycline adsorption is mainly governed by the hydrogen bonds and cation-π interactions due to its pH dependence as well as the enhancement in the removal efficiency with the magnetite incorporation on the chitosan surface, respectively. Thermodynamic parameters indicate a spontaneous and exothermic process. Finally, magnetic chitosan proves to be efficient in TC removal even after several adsorption/desorption cycles.

TiO2/activated carbon synthesized by microwave-assisted heating for tetracycline photodegradation

A furfural residue-derived activated carbon (AC) supported black-TiO₂ photocatalyst was successfully prepared by ultrasonic-assisted sol-gel treatment (USG) and solvothermal treatment (ST) combined with microwave-assisted heating (MH). The prepared composites were characterized and evaluated based on the degradation of tetracycline hydrochloride (TC) under ultraviolet (UV) illumination. The average TiO₂ nanoparticle size of the as-synthesized catalysts was between 9 and 11 nm. The bandgap of TiO₂-USGM was 1.6 eV, much lower than that of other reference catalysts. Organic carbon and AC in the catalyst play positive roles in reducing the band gap (e.g. 1.6∼2.6 eV) and improving visible-light absorption. The oxygen vacancies are responsible for UV-visible absorption. Adding AC into black TiO₂ resulted in a lower degree of recombination of photogenerated electrons. Mott-Schottky plots showed that AC-containing TiO₂@AC-STM reduced the value of conduction band value from -0.59 eV to -0.24 eV, which is beneficial to photogenerated electrons. Compared with TiO₂, the Ti-O-C and Ti-C- in TiO₂@AC remarkably improved the adsorption and catalytic efficiency of TC. In a near-neutral pH environment, TiO₂@AC-STM and TiO₂@AC-USGM exhibited high removal efficiencies (88.0% and 75.7%, respectively) and degradation rates (0.0418 and 0.0302 μmol/g/s, respectively) at a catalyst load of 0.25 g/L. Notably, the catalyst can be effectively used over a wide range of pH (6-9). The solution pH after treatment was close to neutral, which is advantageous for wastewater treatment. The activation energies were found to be approximately 3.47 kJ/mol. The thermodynamic parameters showed that the photodegradation process was non-spontaneous and endothermic. Based on the trapping experiments, O₂⋅^- was mainly responsible for TC photodegradation over TiO₂@AC-STM, followed by h⁺. The TC degradation pathways and catalyst stability were also investigated. Biomass-derived carbon-supported catalysts have great potential for waste biomass utilization as green, and low-cost catalysts.

Highly efficient decontamination of tetracycline and pathogen by a natural product-derived Emodin/HAp photocatalyst

To address the water pollution induced by pharmaceuticals, especially antibiotics, and pathogens, natural product emodin, a traditional Chinese medicine with the characteristic large π-conjugation anthraquinone structure, was used to rationally develop a novel Emodin/HAp photocatalyst by integrating with a thermally stable and recyclable support material hydroxyapatite (HAp) through a simple preparation method. It was found that its photocatalytic activity to generate reactive oxygen species (ROS) was greatly improved due to the migration of photogenerated electrons and holes between emodin and HAp upon visible light irradiation. Thus, this Emodin/HAp photocatalyst not only quickly photodegraded tetracycline with 99.0% removal efficiency but also exhibited complete photodisinfection of pathogenic bacteria Staphylococcus aureus upon visible light irradiation. Therefore, this study offers a new route for the design and preparation of multifunctional photocatalysts using widely available natural products for environmental remediation.

Ionic liquid based composites: A versatile materials for remediation of aqueous environmental contaminants

Water pollution is one of the most aggravated problems threatening the sustainability of human race and other life forms due to the rapid pace of civilization and industrialization. A long history exists of release of hazardous pollutants into the water bodies due to selfish human activities since the Industrial Revolution, but no effort has been completely successful in curbing the activities that result in the degradation of our environment. These pollutants are harmful, carcinogenic and have adverse health effects to all forms of life. Thus, remarkable efforts have been geared up to obtain clean water by exploiting science and technology. The application of Ionic liquids (ILs) as sustainable materials have received widespread attention since the last decade. Their interesting properties, simplicity in operation and satisfactory binding capacities in elimination of the contaminants makes them a valuable prospect to be utilized in wastewater treatment. Immobilizing and grafting the solid supports with ILs have fetched efficient results to exploit their potential in the adsorptive removal processes. This review provides an understanding of the recent developments and outlines the possible utility of IL based nano adsorbents in the removal of organic compounds, dyes and heavy metal ions from aqueous medium. Effect of several parameters such as sorbent dosage, pH and temperature on the removal efficiency has also been discussed. Moreover, the adsorption isotherms, thermodynamics and mechanism are comprehensively studied. It is envisioned that the literature gathered in this article will guide the budding scientists to put their interest in this area of research in the days to come.

Utilization of a double-cross-linked amino-functionalized three-dimensional graphene networks as a monolithic adsorbent for methyl orange removal: Equilibrium, kinetics, thermodynamics and artificial neural network modeling

Herein, it is aimed to develop a high-performance monolithic adsorbent to be utilized in methyl orange (MO) adsorption. Therefore, amino-functionalized three-dimensional graphene networks (3D-GN_f) fulfilling the requirements of reusability and high capacity have been fabricated via hydrothermal self-assembly approach followed by a double-crosslinking strategy. The potential utilization of 3D-GN_f as an adsorbent for removal MO has been assessed using both batch-adsorption studies and an artificial neural network (ANN) approach. Graphene oxide sheets have been amino-functionalized and cross-linked, by ethylenediamine (EDA) during hydrothermal treatment, following the glutaraldehyde has used as a double-crosslinking agent to facilitate the crosslinking of architecture. The successful fabrication of 3D-GN_f has been confirmed by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopy (XPS). Moreover, N₂ adsorption/desorption isotherms have revealed the high specific surface area (1015 m² g^-1) with high pore volume (1.054 cm³ g^-1) and hierarchical porous structure of 3D-GN_f. The effect of initial concentration, contact time, and temperature on adsorption capacity have been thoroughly studied, and the kinetics, isotherms, and thermodynamics of MO adsorption have been modelled. The MO adsorption has been well defined by the pseudo-second-order kinetic model and Langmuir isotherm model with a monolayer adsorption capacity of 270.27 mg g^-1 at 25 °C. The thermodynamic findings have revealed MO adsorption has occurred spontaneously with an endothermic process. The Levenberg-Marquardt backpropagation algorithm has been implemented to train the ANN model, which has used the activation functions of tansig and purelin functions at the hidden and output layers, respectively. An optimum ANN model with high-performance metrics (coefficient of determination, R² = 0.9995; mean squared error, MSE = 0.0008) composed of three hidden layers with 5 neurons in each layer was constructed to forecast MO adsorption. The findings have shown that experimental results are consistent with ANN-based data, implying that the suggested ANN model may be used to forecast cationic dye adsorption.

Sustainable adsorptive removal of antibiotic residues by chitosan composites: An insight into current developments and future recommendations

During COVID-19 crisis, water pollution caused by pharmaceutical residuals have enormously aggravated since millions of patients worldwide are consuming tons of drugs daily. Antibiotics are the preponderance pharmaceutical pollutants in water bodies that surely cause a real threat to human life and ecosystems. The excellent characteristics of chitosan such as nontoxicity, easy functionality, biodegradability, availability in nature and the abundant hydroxyl and amine groups onto its backbone make it a promising adsorbent. Herein, we aimed to provide a comprehensive overview of recent published research papers regarding the removal of antibiotics by chitosan composite-based adsorbents. The structure, ionic form, optimum removal pH and λmax of the most common antibiotics including Tetracycline, Ciprofloxacin, Amoxicillin, Levofloxacin, Ceftriaxone, Erythromycin, Norfloxacin, Ofloxacin, Doxycycline, Cefotaxime and Sulfamethoxazole were summarized. The development of chitosan composite-based adsorbents in order to enhance their adsorption capacity, reusability and validity were presented. Moreover, the adsorption mechanisms of these antibiotics were explored to provide more information about adsorbate-adsorbent interactions. Besides the dominant factors on the adsorption process including pH, dosage, coexisting ions, etc. were discussed. Moreover, conclusions and future recommendations are provided to inspire for further researches.

New fabrication of CuFe2O4/PAMAM nanocomposites by an efficient removal performance for organic dyes: Kinetic study

Today, removing pollutants from water sources is essential because of the population increase and the growing need for safe drinking water. Dyes are one of the most critical pollutants from industrial effluents such as paper and textile industries that profoundly affect the environment. There are several ways to remove environmental contaminants. Magnetic nanoparticles have a high ability to adsorb dyes. Of course, increasing the interaction between magnetic nanomaterials and pollutants is also essential, which can be done using porous materials such as dendrimers. In this work, the synthesis of CuFe₂O₄ magnetite nanoparticles within the polyamidoamine dendrimers structure was used as an efficient sorbent to remove both alizarin reds (ARS) and brilliant green (BG) dyes. Moreover, various parameters for dyes removal were studied. The optimum removal conditions were obtained for ARS within 30 min at a sorbent dose of 2 mg per 5 mL for the initial dye concentration of 7.0 ppm in pH 6 at 25 °C, and for BG within 45 min at a sorbent dose of 5 mg per 5 mL for the initial dye concentration of 17.0 ppm in pH 8 at 25 °C. At the optimum values of the above parameters, both dyes' removal efficiency was more than 97%. Also, the obtained results showed that the adsorption isotherm follows the Langmuir model and Temkin model for ARS and BG, respectively. This method was successfully used for the removal of both dyes in water samples.

Substantial improvement in the adsorption behavior of montmorillonite toward Tartrazine through hexadecylamine impregnation

In the present work, the surface of montmorillonite K10 was successfully modified by hexadecylamine surfactant (Mt-HDA) and its intercalation and characteristics were assessed by XRD, FTIR, SEM, EDX and BET methods. Also, its adsorption performance was systematically examined in the removal of Tartrazine (TZ), as a sulfonated azo dye model, from aqueous phase. Our results showed that the HDA modification remarkably improved the adsorption ability of montmorillonite toward TZ molecules. The highest adsorption efficiency was achieved >98% at the pH range of 4-6 within a fast process (less than 30 min). The maximum adsorption capacity Mt-HDA toward TZ molecules was found to be ~59 mg/g at 45 °C. The kinetic study indicated that the adsorption kinetic follows pseudo-second-order model, which shows the chemisorption process between Mt-HDA and TZ molecules. Besides, the adsorption isotherm showed the monolayer coverage of Mt-HDA surface adsorption sites, which was fitted with the Langmuir isotherm model in an exothermic process. The adsorption mechanism was studied.

The surfactant-ionic liquid bi-functionalization of chitosan beads for their adsorption performance improvement toward Tartrazine

In this study, the ionic liquid (Aliquat-336) and anionic surfactant (cetyltrimethylammonium bromide, CTAB) bi-functionalized chitosan beads were prepared and characterised using different techniques, including FTIR, XRD, SEM, EDS and BET surface area analysis. The characteristic analysis confirmed the successful conjugation of chitosan beads with both surfactant and ionic liquid. The novel fabricated beads (CS-CTAB-AL) were efficiently employed, as a high-performance adsorbent, for the removal of Tartrazine (TZ), an anionic food dye, from polluted water. The optimum adsorption of TZ onto the CS-CTAB-AL was found at 2 g L^-1 of adsorbent in the wide pH range of 4-11, whereas just 45 min was required to reach more than 90% adsorption efficiency in the studied conditions. Also, the adsorption and kinetic studies showed that the experimental data well fitted the pseudo-first-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of prepared beads was found to be 45.95 mg g^-1 at 45 °C. The adsorption properties of enabling CS-CTAB-AL conjugation introduced a new type of adsorbents, exploited the combination of ionic liquid and surfactant capabilities for wastewater treatment.

Magnetic alginate/glycodendrimer beads for efficient removal of tetracycline and amoxicillin from aqueous solutions

The release of antibiotic drugs into aquatic environments is a serious environmental and health problem in recent years. Therefore, the development of potential adsorbents for the effective removal of tetracycline (TC) and amoxicillin (AMX) of aqueous media is of great importance. In this study, new alginate beads were successfully prepared by encapsulation of Fe₃O₄@maltose-functionalized triazine dendrimer in alginate (Alg/Fe₃O₄@C@TD) for the first time. The obtained beads were utilized as a well adsorbent for the removal of TC and AMX antibiotics from aqueous solutions by batch adsorption procedure. The characteristics of the synthesized beads were investigated using FT-IR, Zeta potential, SEM, XRD, EDX, VSM, and BET. The effects of various operation factors such as adsorbent dose, pH of the solution, contact time, antibiotic initial concentration, temperature, and ionic strength on the removal of antibiotics were studied. Moreover, Langmuir and Freundlich adsorption isotherm results showed that the Langmuir model fitted well for the adsorption of both antibiotics onto Alg/Fe₃O₄@C@TD beads. Based on the Langmuir model, the maximum adsorption capacity of TC and AMX onto Alg/Fe₃O₄@C@TD beads at 25 °C was 454.54 and 400 mg/g, respectively. Kinetic and thermodynamic studies also indicated that the TC and AMX adsorption were found to be well fitted with a pseudo-second-order kinetic model, feasible, endothermic, and spontaneous in nature. In addition, the Alg/Fe₃O₄@C@TD beads showed excellent reusability for removal from both antibiotics after six adsorption cycles. Overall, the obtained results suggest that Alg/Fe₃O₄@C@TD beads could be considered as a low-cost and eco-friendly adsorbent for antibiotic contaminants removal from aquatic media.

Removal of metal ions using a new magnetic chitosan nano-bio-adsorbent; A powerful approach in water treatment

In this study, a magnetic chitosan/Al₂O₃/Fe₃O₄ (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.

Optimization of ketoprofen adsorption from aqueous solutions and simulated effluents using H2SO4 activated Campomanesia guazumifolia bark

This study used the bark of the forest species Campomanesia guazumifolia modified with H₂SO₄ to absorb the anti-inflammatory ketoprofen from aqueous solutions. FTIR spectra confirmed that the main bands remained after the chemical treatment, with the appearance of two new bands related to the elongation of the carbonyl group present in hemicellulose. Micrographs confirmed that the surface started to contain a new textural shape after acid activation, having new pores and cavities. The drug adsorption's optimum conditions were obtained by response surface methodology (RSM). The adsorption was favored at acidic pH (2). The dosage of 1 g L^-1 was considered ideal, obtaining good indications of removal and capacity. The Elovich model very well represented the kinetic curves. The isotherm studies indicated that the increase in temperature negatively affected the adsorption of ketoprofen. A maximum adsorption capacity of 158.3 mg g^-1 was obtained at the lower temperature of 298 K. Langmuir was the best-fit isotherm. Thermodynamic parameters confirmed the exothermic nature of the system (ΔH⁰ = -8.78 kJ mol^-1). In treating a simulated effluent containing different drugs and salts, the removal values were 35, 50, and 80% at 15, 30, and 180 min, respectively. Therefore, the development of adsorbent from the bark of Campomanesia guazumifolia treated with H₂SO₄ represents a remarkable alternative for use in effluent treatment containing ketoprofen.

Magnetic cross-linked chitosan for efficient removing anionic and cationic dyes from aqueous solution

Herein, a novel magnetic cross-linked chitosan CS-BA@Fe₃O₄ was rationally synthesized by cross-linked with epichlorohydrin and coated with Fe₃O₄ to the acylated chitosan, which was prepared by the reaction of chitosan with benzenetricarboxylic anhydride. The as-obtained absorbent was characterized by FTIR, XRD, VSM, TGA, TEM, BET, SEM and EDS. The results showed that the maximum adsorption capacities of CR and CV were 471.46 ± 16.97 mg/g and 515.91 ± 25.12 mg/g at 318.15 K, respectively. The main adsorption mechanisms were H-bonding and electrostatic interaction. The kinetic data were in good agreement with the pseudo-second-order model and closed to adsorption equilibrium at 30 min. Thermodynamic studies showed that the adsorption on CS-BA@Fe₃O₄ were spontaneous and endothermic. More importantly, the adsorbent exhibited excellent regeneration properties after 6 cycles and remarkable stability under harsh environments including strong acid, strong alkali, multi-salt and mixed dyes conditions. Therefore, abundant efforts revealed a broad application prospect of CS-BA@Fe₃O₄ in water remediation.

Eco-Friendly Biosorbents Based on Microbial Biomass and Natural Polymers: Synthesis, Characterization and Application for the Removal of Drugs and Dyes from Aqueous Solutions

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their application in wastewater treatment. Thus, this study aimed to develop biosorbents by immobilizing Saccharomyces cerevisiae, Saccharomyces pastorianus and Saccharomyces pastorianus residual biomass on natural polymers (alginate and chitosan) and to evaluate the biosorptive potential for removal of pharmaceuticals and dyes from water. Six types of biosorbents were synthesized and characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy techniques and their biosorptive capacities for three drugs (cephalexin, rifampicin, ethacridine lactate) and two dyes (orange II and indigo carmine) were evaluated. The obtained results show that the removal efficiency depends on the polymer type used for the immobilization. In case of alginate the removal efficiency is between 40.05% and 96.41% for drugs and between 27.83% and 58.29% for dyes, while in the case of chitosan it is between 40.83% and 77.92% for drugs and between 17.17% and 44.77% for dyes. In general, the synthesized biosorbents proved to be promising for the removal of drugs and dyes from aqueous solutions.

Development of superabsorbent hydrogel based on Gum Arabic for enhanced removal of anxiolytic drug from water

The growing consumption of anxiolytic drugs like diazepam (DZP) has aggravated the problem of persistent organic pollutants in water. Due to its characteristics, the removal of DZP from water and wastewater is a challenging task. As an effort to deals with this issue, in this study, we report the development of a hydrogel based on Gum Arabic (GA) grafted with poly(acrylic acid) (GA-g-PAAc) to be used in the adsorptive removal of DZP from water. The hydrogel formation was confirmed by Fourier-transform infrared (FTIR) spectroscopy and thermal analysis (TGA/DTG) analyses. Images obtained by scanning electron microscopy (SEM) revealed that GA-g-PAAc hydrogel exhibits a porous morphology while swelling experiments suggest a superabsorbent characteristic (degree of swelling> 600%). From batch experiments, it was found that the removal of DZP reached remarkable percentages (>80%) before 300 min in moderate experimental conditions (pH 7, 25 °C, 150 mg of adsorbent). The adsorption of DZP on GA-g-PAAc followed the pseudo-first order kinetics, and the mechanism was described by the linear Langmuir isotherm. The maximum adsorption capacity (q_max) was calculated to be 15.16 mg g^-1 (at 25 °C), which is comparable or superior to other adsorbent materials used in DZP removal. Reuse experiments showed that GA-g-PAAc keeps appreciable adsorption ability even after five reuse cycles. The results reported here suggest this superabsorbent hydrogel could be a promising adsorbent material to treat water contaminated by anxiolytic drugs, like DZP.

Hydrous manganese dioxide modified poly(sodium acrylate) hydrogel composite as a novel adsorbent for enhanced removal of tetracycline and lead from water

In this study, hydrous manganese dioxide (HMO) modified poly(sodium acrylate) (PSA) hydrogel was produced for the first time to remove tetracycline(TC) and lead(Pb(II)) from water. The as-prepared composite was characterized using various techniques, such as SEM-EDS, FTIR, XRD, BET, and XPS, to elucidate the successful loading of HMO and analyze subsequent sorption mechanisms. Different influencing parameters such as adsorbent dose, initial concentration of adsorbates, reaction time, solution pH, and temperature were also investigated. The adsorption kinetic studies of both TC and Pb(II) removal indicated that equilibrium was achieved within 12 h, with respective removal rates of 91.9 and 99.5%, and the corresponding adsorption data were fitted to the second-order kinetics model. According to the adsorption isotherm studies, the sorption data of TC best fitted to the Langmuir isotherm model while the adsorption data of Pb(II) were explained by the Freundlich isotherm model. The maximum adsorption capacities of both TC and Pb(II) were found to be 475.8 and 288.7 mg/g, respectively, demonstrating excellent performances of the adsorbent. The uptake capacity of PSA-HMO was significantly influenced by the level of solution pH, in which optimum adsorption amount was realized at pH 4.0 in the TC and Pb(II) systems, respectively. Thermodynamic studies showed the process of TC and Pb(II) adsorptions were endothermic and spontaneous. Overall this study elucidated that PSA-HMO composite can be a promising candidate for antibiotics and heavy metal removal in water treatment applications.

Novel 1-butyl-3-methylimidazolium bromide impregnated chitosan hydrogel beads nanostructure as an efficient nanobio-adsorbent for cationic dye removal: Kinetic study

In the present study, a novel 1-butyl-3-methylimidazolium bromide (BmImBr) impregnated chitosan beads were prepared and characterized using different methods, including XRD, FT-IR, EDX, SEM and BET. The FTIR analysis revealed that the BmImBr was successfully conjugated with the chitosan in the beads structure. The prepared beads were used as an efficient sorbent for the fast removal of methylene blue, as cationic dye model, from aqueous solution, whereas just 25 min was required to reach 86% removal efficiency. The increasing of BmImBr amount improved the adsorption performance of prepared beads. Also, it was found that the dye can be higher adsorbed on the beads surface by increasing the sorbent dosage and pH of solution, while the optimum dosage and pH were obtained 3 mg/L and 11, respectively. The kinetic study showed that the MB adsorption onto the CS-BmImBr beads follows the pseudo-fist order model and the intrinsic penetration controls the adsorption process. The properties of prepared chitosan- BmImBr IL conjugation confirmed that it can be exploited as an efficient adsorbent in the wastewater treatment.

Photocatalytic Degradation of Tetracycline by a Novel (CMC)/MIL-101(Fe)/β-CDP Composite Hydrogel

Herein, we report a novel carboxymethyl cellulose (CMC)/MIL-101 (Fe)/poly(β-cyclodextrin) (β-CDP) hydrogel with high photocatalytic activity. β-CDP can significantly enhance the photoactivity of MIL-101(Fe) in the hydrogel prepared by a simple solvothermal method. The structure and property of this composite hydrogel were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Tetracycline was selected as a model pharmaceutical antibiotic to evaluate the photocatalytic activity of the composite hydrogel under visible light irradiation and darkness, respectively. This composite hydrogel shows excellent activity for degrading pharmaceutical antibiotics under visible light irradiation. The increased photocatalytic activity can be attributed to β-CDP, which acts as a promoter and affords an efficient separation of photogenerated electron-hole pairs of MIL-101(Fe). Moreover, the composite hydrogel is shown to have good water retainability. The hydrogel is inexpensive and shows high photocatalytic activity. Hence, it can be used as an efficient photocatalytic material.

Recyclable magnetic chitosan microspheres with good ability of removing cationic dyes from aqueous solutions

Sr_3.8Fe_25.7O_70.4-chitosan magnetic microparticles (Sr_3.8Fe_25.7O_70.4-CMNs) with a core-shell structure were synthesized, characterized and applied for the removal of two model cationic dyes. The results showed that these magnetic microparticles possess fast adsorption rate and high adsorption efficiency for both crystal violet (CV) and basic red 9 (BR9) at a temperature ranging 30 °C to 40 °C and suitable pH range (pH ≥ 7). The maximum removal efficiency for CV and BR9 attained to 94.5% and 97.5% in 30 min, which was significantly faster and higher than that of chitosan (<50% in 60 min) (P<0.01). And its maximum adsorption capacity for CV and BR9 reached 29.46 mg/g and 32.16 mg/g, respectively. The adsorption process of Sr_3.8Fe_25.7O_70.4-CMNs follows the Langmuir isotherm with a high correlation coefficient (R² > 0.97) and the pseudo-second-order model. Additionally, the synthesized Sr_3.8Fe_25.7O_70.4-CMNs were easy to regeneration and reuse, and the removal rate remained above 90% after 5 recycle times. This study would provide a new more environmental friendly material and method for the treatment of wastewater containing toxic dyes.

Sonication alkaline-assisted preparation of Rhizopus oryzae biomass for facile bio-elimination of tetracycline antibiotic from an aqueous matrix

The present study aimed to remove tetracycline (TET) antibiotic molecule from an aqueous medium using adsorbents prepared from Rhizopus oryzae biomass. The TET adsorption process was discontinuous and the adsorbent biomass was crude and NaOH-sonication-modified Rhizopus oryzae fungi. Specific active surface area for crude and modified Rhizopus oryzae was 10.38 m²/g and 20.32 m²/g, respectively. The results showed that the maximum TET adsorption efficiency was determined at pH 4, temperature 25 °C, initial TET concentration 10 mg/L, contact time 80 min, and biomass quantity 2 g/L. The equilibrium behavior showed that the Langmuir model suitably described the process. The maximum TET adsorption capacity was determined to be 38.02 mg/g and 67.93 mg/g, respectively, indicating that the method of biomass modification promoted the bio-adsorption capacity. A higher correlation coefficient (R²) and lower RMSE for the pseudo-first-order kinetic than other models showed its ability to describe the behavior of TET bio-adsorption. The enthalpy thermodynamic parameter (ΔH°) for the TET adsorption process was determined - 63.847 kJ/mol and - 85.226 kJ/mol for the raw and modified Rhizopus oryzae, respectively. Therefore, it can be suggested that the biomass of Rhizopus oryzae especially the modified version can be effectively used for the TET removal from aqueous environments.