Sorption Behavior of Bisphenol A and Triclosan by Graphene: Comparison with Activated Carbon

Effects of reduced graphene oxide nanomaterials on transformation of 14C-triclosan in soils

Increasing use and release of graphene nanomaterials and pharmaceutical and personal care products (PPCPs) in soil environment have polluted the environment and posed high ecological risks. However, little is understood about the interactive effects and mechanism of graphene on the behaviors of PPCPs in soil. In the present study, the effects of reduced graphene oxide nanomaterials (RGO) on the fate of triclosan in two typical soils (S1: silty loam; S2: silty clay loam) were investigated with 14C-triclosan, high-resolution mass spectrometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, and microbial community structure analysis. The results showed that RGO prolonged the half-life of triclosan by 23.6-51.3 %, but delayed the formation of transformed products such as methyl triclosan and dechlorinated dimer of triclosan in the two typical soils. Mineralization of triclosan to 14CO2 was inhibited by 48.2-79.3 % in 500 mg kg-1 RGO in comparison with that in the control, whereas the bound residue was 54.2-56.4 % greater than the control. RGO also reduced the relative abundances of triclosan-degrading bacteria (Pseudomonas and Sphingomonas) in soils. Compared to silty loam, RGO more effectively inhibited triclosan degradation in silty clay loam. Furthermore, the DFT calculations suggested a strong association of the adsorption of triclosan on RGO with the van der Waals forces and π-π interactions. These results revealed that RGO inhibited the transformation of 14C-triclosan in soil through strong adsorption and triclosan-degrading bacteria inhibition in soils. Therefore, the presence of RGO may potentially enhance persistence of triclosan in soil. Overall, our study provides valuable insights into the risk assessment of triclosan in the presence of GNs in soil environment.

Critical review on the environmental behaviors and toxicity of triclosan and its removal technologies

As a highly effective broad-spectrum antibacterial agent, triclosan (TCS) is widely used in personal care and medical disinfection products, resulting in its widespread occurrence in aquatic and terrestrial environments, and even in the human body. Notably, the use of TCS surged during the COVID-19 outbreak, leading to increasing environmental TCS pollution pressure. From the perspective of environmental health, it is essential to systematically understand the environmental occurrence and behavior of TCS, its toxicological effects on biota and humans, and technologies to remove TCS from the environment. This review comprehensively summarizes the current knowledge regarding the sources and behavior of TCS in surface water, groundwater, and soil systems, focusing on its toxicological effects on aquatic and terrestrial organisms. Effluent from wastewater treatment plants is the primary source of TCS in aquatic systems, whereas sewage application and/or wastewater irrigation are the major sources of TCS in soil. Human exposure pathways to TCS and associated adverse outcomes were also analyzed. Skin and oral mucosal absorption, and dietary intake are important TCS exposure pathways. Reducing or completely degrading TCS in the environment is important for alleviating environmental pollution and protecting public health. Therefore, this paper reviews the removal mechanisms, including adsorption, biotic and abiotic redox reactions, and the influencing factors. In addition, the advantages and disadvantages of the different techniques are compared, and development prospects are proposed. These findings provide a basis for the management and risk assessment of TCS and are beneficial for the application of treatment technology in TCS removal.

Tungsten-based nanocatalysts with different structures for visible light responsive photocatalytic degradation of bisphenol A

Environmental pollution, such as water contamination, is a critical issue that must be absolutely addressed. Here, three different morphologies of tungsten-based photocatalysts (WO3 nanorods, WO3/WS2 nanobricks, WO3/WS2 nanorods) are made using a simple hydrothermal method by changing the solvents (H2O, DMF, aqueous HCl solution). The as-prepared nanocatalysts have excellent thermal stability, large porosity, and high hydrophilicity. The results show all materials have good photocatalytic activity in aqueous media, with WO3/WS2 nanorods (NRs) having the best activity in the photodegradation of bisphenol A (BPA) under visible-light irradiation. This may originate from increased migration of charge carriers and effective prevention of electron‒hole recombination in WO3/WS2 NRs, whereby this photocatalyst is able to generate more reactive •OH and •O2- species, leading to greater photocatalytic activity. About 99.6% of BPA is photodegraded within 60 min when using 1.5 g/L WO3/WS2 NRs and 5.0 mg/L BPA at pH 7.0. Additionally, the optimal conditions (pH, catalyst dosage, initial BPA concentration) for WO3/WS2 NRs are also elaborately investigated. These rod-like heterostructures are expressed as potential catalysts with excellent photostability, efficient reusability, and highly active effectivity in different types of water. In particular, the removal efficiency of BPA by WO3/WS2 NRs reduces by only 1.5% after five recycling runs and even reaches 89.1% in contaminated lake water. This study provides promising insights for the nearly complete removal of BPA from wastewater or different water resources, which is advantageous to various applications in environmental remediation.

Unveiling combined ecotoxicity: Interactions and impacts of engineered nanoparticles and PPCPs

Emerging contaminants such as engineered nanoparticles (ENPs), pharmaceuticals and personal care products (PPCPs) are of great concern because of their wide distribution and incomplete removal in conventional wastewater and soil treatment processes. The production and usage of ENPs and PPCPs inevitably result in their coexistence in different environmental media, thus posing various risks to organisms in aquatic and terrestrial ecosystems. However, the existing literature on the physicochemical interactions between ENPs and PPCPs and their effects on organisms is rather limited. Therefore, this paper summarized the ecotoxicity of combined ENPs and PPCPs by discussing: (1) the interactions between ENPs and PPCPs, including processes such as aggregation, adsorption, transformation, and desorption, considering the influence of environmental factors like pH, ionic strength, dissolved organic matter, and temperature; (2) the effects of these interactions on bioaccumulation, bioavailability and biotoxicity in organisms at different trophic levels; (3) the impacted of ENPs and PPCPs on cellular-level biological process. This review elucidated the potential ecological hazards associated with the interaction of ENPs and PPCPs, and serves as a foundation for future investigations into the ecotoxicity and mode of action of ENPs, PPCPs, and their co-occurring metabolites.

Efficient removal of triclosan from water through activated carbon adsorption and photodegradation processes

This study investigated the application of adsorption with activated carbons (ACs) and photodegradation to reduce the concentration of triclosan (TCS) in aqueous solutions. Concerning adsorption, ACs (Darco, Norit, and F400) were characterised and batch experiments were performed to elucidate the effect of pH on equilibrium. The results showed that at pH = 7, the maximum adsorption capacity of TCS onto the ACs was 18.5 mg g-1 for Darco, 16.0 mg g-1 for Norit, and 15.5 mg g-1 for F400. The diffusional kinetic model allowed an adequate interpretation of the experimental data. The effective diffusivity varied and increased with the amount of TCS adsorbed, from 1.06 to 1.68 × 10-8 cm2 s-1. In the case of photodegradation, it was possible to ensure that the triclosan molecule was sensitive to UV light of 254 nm because the removal was over 80 % using UV light. The removal of TCS increased in the presence of sulfate radicals. It was possible to identify 2,4-dichlorophenol as one of the photolytic degradation products of triclosan, which does not represent an environmental hazard at low concentrations of triclosan in water. These results confirm that the use of AC Darco, Norit, and F400 and that photodegradation processes with UV light and persulfate radicals are effective in removing TCS from water, reaching concentration levels that do not constitute a risk to human health or environmental hazard. Both methods effectively eliminate pollutants with relatively easy techniques to implement.

Efficient and selective use of functionalized material in the decontamination of water: removal of emerging micro-pollutants from aqueous wastes

The contamination of the aquatic environment with emerging micro-pollutants is a serious global concern. The aim of this investigation was to synthesize novel functionalized material (BNAPTES) precursor to natural bentonite in a single pot facile synthetic route. The material was utilized for efficient and selective removal of tetracycline (TC) and triclosan (TCS) in aqueous wastes. The grafting of silane was confirmed with the FT-IR (Fourier Transform Infra-Red) analysis and the EDX (Energy Dispersive X-ray) analysis showed the incorporation of amino group with the bentonite. The structural changes of clay due to silane grafting were studied with the help of XRD (X-ray Diffraction) and BET (Brunner-Emmett-Teller) surface area analyses. Batch adsorption studies showed that functionalized clay significantly increased the selectivity and adsorption capacity of bentonite for TC and TCS. The Langmuir monolayer adsorption capacity was found to be 15.36 and 17.15 mg/g for TC and TCS, respectively. The rapid uptake of TC and TCS by functionalized material followed pseudo-second-rate kinetics. Further, a total of 78% of TC and 73% of TCS were removed within 5 min of contact and the adsorption equilibrium was achieved within 120  min. The influence of background electrolytes and co-existing ions indicated that TC and TCS were selective towards BNAPTES. The loading capacities of the column packed with BNAPTES were found to be 56.00 and 44.42 mg/g for TC and TCS, respectively. Further, BNAPTES was found efficient even in real water treatment since the attenuation of TC and TCS was not affected significantly in the real water matrix.

The increased oxygen vacancy by morphology regulation of MnO2 for efficient removal of PAHs in aqueous solution

Manganese dioxide (MnO₂) is considered to have a promising future in degrading polycyclic aromatic hydrocarbons (PAHs) in aqueous phase because of its low cost and environmental friendliness. In this study, various MnO₂ morphologies were prepared, and their removal performance and mechanism were evaluated using benzo(a)pyrene (B[a]P) as model molecule. Results showed that nanoflower MnO₂ with higher concentration of oxygen vacancies exhibited better oxidative and easier oxygen migration properties, and thus enhanced PAHs removal by 14.28%-43.21% compared with other MnO₂ samples. Additionally, the transformation rate of PAHs is correlated with their ionization potential (IP) values. Further mechanism studies showed that the degradation of B[a]P by MnO₂ process was first to form a combination and then oxidized by non-radical Mn species and superoxide radical (O₂^-•) to produce degradation product (B[a]P-6-one and B[a]P-6,12-quinone). The specific surface area was not the main factor affecting the removal of B[a]P by MnO₂ and oxidation was the main removal mechanism of degrading B[a]P by MnO₂. Mn³⁺ and absorbed oxygen (O_abs) played an important role in the process of removing PAHs by MnO₂. Additionally, synergistic effects of oxygen vacancy and Mn³⁺could be benefit for transforming O_abs to O₂^-•, leading to the efficient degradation of PAHs.

High utilization efficiencies of alkylbenzokynones hybridized inside the pores of activated carbon for electrochemical capacitor electrodes

Benzoquinone derivatives (BQDs) are hybridized inside activated carbon (AC) pores via gas-phase adsorption to prepare electrochemical capacitor materials. In this study, 2 mmol of BQDs are hybridized with 1 g of AC. The hybridization of alkylbenzoquinones (ABQs) with AC enhances the volumetric capacitances of the hybrids from 117 to 201 F cm^-3 at 0.05 A g^-1 and the capacitances are retained up to 73% at 10 A g^-1. Meanwhile, the volumetric capacitances are increased to 163 F cm^-3 at 0.05 A g^-1 by the hybridization of halobenzoquinones (HBQs) and the capacitance retentions at 0.05 A g^-1 are ∼62%, which are higher than that of AC (46%). The results of electrochemical measurements suggest that HBQs exist as agglomerates while ABQs are finely dispersed inside the pores. The ABQs have good contact with the conductive carbon pore surface compared to the HBQs. Consequently, most of the ABQ molecules undergo reversible redox reactions (i.e., high utilization efficiencies), and a large contact area facilitates charge transfer at the large contact interface, thereby endowing the hybrids of ABQs with fast charging and discharging characteristics. HBQ molecules can be finely dispersed by liquid-phase adsorption, but the finely dispersed HBQ molecules are mobile inside the pores at room temperature and gradually form agglomerates. The difference in the existing form of BQDs is explained by the dominant interaction affecting the BQD molecules. ABQs have a strong interaction with the carbon pore surface while the intermolecular interaction is dominant for HBQs.

Simultaneous removal of triclosan and Cd(Ⅱ) by bio-reduced graphene oxide and its mechanism

The co-existence of contaminants such as triclosan (TCS) and Cadmium in wastewater is a major public health problem because of their persistence and toxicity. In this study, bio-reduced graphene oxide (B-rGO) synthesized by Lysinibacillus sp. Simultaneously remove TCS and Cd(II), with adsorption capacities of 81.91 and 23.32 mg g^-1, for TCS and Cd (Ⅱ), respectively. This was significantly higher than that previously reported for commercially available reduced graphene oxide (C-rGO), which was only 31.94 and 2.01 mg g^-1, for TCS and Cd (Ⅱ), respectively. Fourier transform infrared spectroscopy (FTIR) showed that rGO surface-bound extracellular polymeric substances (EPS) played a key role in the observed enhanced contaminant removal, which was verified by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). In addition, the absorption of both Cd(II) and TCS on B-rGO was confirmed by XPS and high-performance liquid chromatography (HPLC-UV). The adsorption kinetics of both TCS and Cd(II) fitted well to the pseudo-second-order model, while the adsorption isotherms of Cd(II) followed the Langmuir model, and triclosan the Freundlich model. A mechanism of simultaneous removal of TCS was proposed based on π-π interactions and hydrogen bonding, while Cd(II) was removed by a combination of electrostatic and chelation/complexation. Finally, the adsorption of TCS and Cd(II) by B-rGO in real wastewater was shown to be 76.67 and 16.53 mg g^-1, respectively, demonstrating that B-rGO has the potential for practical simultaneous removal of TCS and Cd(II) from wastewater.

Bisphenol A in the environment and recent advances in biodegradation by fungi

Bisphenol A (BPA) is a compound used in the manufacture of a wide variety of everyday materials that, when released into the environment, causes multiple detrimental effects on humans and other organisms. The reason for this review is to provide an overview of the presence, distribution, and concentration of BPA in water, soil, sediment, and air, as well as the process of release and migration, biomagnification, and exposure mechanisms that cause various toxic effects in humans. Therefore, it is important to seek efficient and economic strategies that allow its removal from the environment and prevent it from reaching humans through food chains. Likewise, the main removal techniques are analyzed, focusing on biological treatments, particularly the most recent advances in the degradation of BPA in different environmental matrices through the use of ligninolytic fungi, non-ligninolytic fungi and yeasts, as well as the possible routes of metabolic processes that allow their biotransformation or biodegradation due to their efficient extracellular enzyme systems. This review supports the importance of the application of new biotechnological tools for the degradation of BPA.

Facile Synthesis of ZnO-CeO2 Heterojunction by Mixture Design and Its Application in Triclosan Degradation: Effect of Urea

In this study, simplex centroid mixture design was employed to determine the effect of urea on ZnO-CeO. The heterojunction materials were synthesized using a solid-state combustion method, and the physicochemical properties were evaluated using X-ray diffraction, nitrogen adsorption/desorption, and UV–Vis spectroscopy. Photocatalytic activity was determined by a triclosan degradation reaction under UV irradiation. According to the results, the crystal size of zinc oxide decreases in the presence of urea, whereas a reverse effect was observed for cerium oxide. A similar trend was observed for ternary samples, i.e., the higher the proportion of urea, the larger the crystallite cerium size. In brief, urea facilitated the co-existence of crystallites of CeO and ZnO. On the other hand, UV spectra indicate that urea shifts the absorption edge to a longer wavelength. Studies of the photocatalytic activity of TCS degradation show that the increase in the proportion of urea favorably influenced the percentage of mineralization.

Investigation of Thermodynamic, Kinetic, and Isothermal Parameters for the Selective Adsorption of Bisphenol A

Herein, a novel imprinted solid-phase extraction cartridge was fabricated to investigate the kinetic, thermodynamic, and isothermal parameters for the selective adsorption of Bisphenol A (BPA). The imprinted polymeric cartridges (BMC) for the BPA adsorption were fabricated in the presence of a template and functional monomer using the in situ polymerization technique. To prove the efficiency and selectivity of BMC, the nonimprinted polymeric cartridges (BNC) and the empty polymeric cartridges (EC) were also fabricated with and without functional monomer using the same manner for the preparation of BMC. The characterization of cartridges was performed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, and swelling tests. BPA removal studies were performed by analyzing some parameters such as temperature, BPA concentration, flow rate, salt type, and concentration. The highest capacity was determined as 103.2 mg BPA/g polymer for a 0.75 mL/min flow rate of 0.75 M (NH₄)₂SO₄ containing 200 mg/L BPA solution at 50 °C. NaOH (1.0 M) was used as a desorption agent. The reusability performance was examined by performing 10 consecutive cycles. The solid-phase extraction (SPE) performance was also checked to determine the enrichment and extraction recovery factors for tap water and synthetic wastewater samples. Temkin, Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were applied to BPA adsorption data examining the adsorption mechanism, surface properties, and adsorption degree. The most suitable isotherm model for BPA adsorption was determined as the Langmuir isotherm model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were investigated to reveal the thermodynamics of adsorption. Adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated using the thermodynamic equilibrium constant (thermodynamic equilibrium constant, K°) values that change with temperature. It was determined that BPA adsorption was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) and entropy increased (ΔS° > 0) at the temperatures studied in the BPA adsorption process. The rate control step in the adsorption process was examined by applying pseudo-first-order and pseudo-second-order kinetic models to the adsorption data for the investigations of BPA adsorption kinetics, and the pseudo-second-order kinetic model was found to be more suitable for describing BPA adsorption kinetics. In examining the selectivity of cartridges, structural analogues of hydroquinone, phenol, β-estradiol, and 8-hydroxyquinoline were tested.

Interactions between microplastics, pharmaceuticals and personal care products: Implications for vector transport

Microplastics are well known for vector transport of hydrophobic organic contaminants, and there are growing concerns regarding their potential adverse effects on ecosystems and human health. However, recent studies focussing on hydrophilic compounds, such as pharmaceuticals and personal care products (PPCPs), have shown that the compounds ability to be adsorbed onto plastic surfaces. The extensive use of PPCPs has led to their ubiquitous presence in the environment resulting in their cooccurrence with microplastics. The partitioning between plastics and PPCPs and their fate through vector transport are determined by various physicochemical characteristics and environmental conditions of specific matrices. Although the sorption capacities of microplastics for different PPCP compounds have been investigated extensively, these findings have not yet been synthesized and analyzed critically. The specific objectives of this review were to synthesize and critically assess the various factors that affect the adsorption of hydrophilic compounds such as PPCPs on microplastic surfaces and their fate and transport in the environment. The review also focuses on environmental factors such as pH, salinity, and dissolved organics, and properties of polymers and PPCP compounds, and the relationships with sorption dynamics and mechanisms. Furthermore, the ecotoxicological effects of PPCP-sorbed microplastics on biota and human health are also discussed.

Removal of pharmaceutical and personal care products (PPCPs) from waterbody using a revolving algal biofilm (RAB) reactor

The occurrence of Pharmaceutical and Personal Care Products (PPCPs) in the aquatic environment has raised concerns due to their accumulation in the ecosystem. This study aims to explore the feasibility of using a Revolving Algal Biofilm (RAB) reactor for PPCPs removal from waterbody. Five model PPCP compounds including ibuprofen, oxybenzone, triclosan, bisphenol A and N, N-diethyl-3-methylbenzamide (DEET) were mixed and added to the culture medium. It shows that PPCP removal efficiencies of the RAB reactor ranged from 70% to 100%. The degradation of PPCPs by the RAB reactor contributed > 90% PPCP removal while < 10% PPCPs removal was due to accumulation in the algal biomass. The nutrients removal performance of the RAB reactor was not affected by exposing to the PPCPs. The extracellular polysaccharides content of the biomass increased when exposing to PPCPs, while the extracellular proteins content remained constant. The Chl a content maintained constant in the PPCPs-treated biomass, but decreased in the biomass without PPCP treatment. It was also found that the microbial consortium of the RAB reactor was enriched with PPCPs degradation microorganisms with the progressing of feeding PPCPs. Collectively, this work demonstrates that the RAB system is a promising technology for removing PPCPs from wastewater.

Facile and Safe Synthesis of Novel Self-Pored Amine-Functionalized Polystyrene with Nanoscale Bicontinuous Morphology

The chloromethyl-functionalized polystyrene is the most commonly used ammonium cation precursor for making anion exchange resins (AER) and membranes (AEM). However, the chloromethylation of polystyrene or styrene involves highly toxic and carcinogenic raw materials (e.g., chloromethyl ether) and the resultant ammonium cation structural motif is not stable enough in alkaline media. Herein, we present a novel self-pored amine-functionalized polystyrene, which may provide a safe, convenient, and green process to make polystyrene-based AER and AEM. It is realized by hydrolysis of the copolymer obtained via random copolymerization of N-vinylformamide (NVF) with styrene (St). The composition and structure of the NVF-St copolymer could be controlled by monomeric ratio, and the copolymers with high NVF content could form bicontinuous morphology at sub-100 nm levels. Such bicontinuous morphology allows the copolymers to be swollen in water and self-pored by freeze-drying, yielding a large specific surface area. Thus, the copolymer exhibits high adsorption capacity (226 mg/g for bisphenol A). Further, the amine-functionalized polystyrene has all-carbon backbone and hydrophilic/hydrophobic microphase separation morphology. It can be quaternized to produce ammonium cations and would be an excellent precursor for making AEM and AER with good alkaline stability and smooth ion transport channels. Therefore, the present strategy may open a new pathway to develop porous alkaline stable AER and AEM without using metal catalysts, organic pore-forming agents, and carcinogenic raw materials.

The synthesis strategy to enhance the performance and cyclic utilization of granulated activated carbon-based sorbent for bisphenol A and triclosan removal

For a potential and efficient solution in the mitigation of aquatic pollution, this study reported a well-designed and developed protected granulated activated carbon (GAC) material which ensures high strength property and adsorption performance to meet the industrial application. The prepared GAC material was shaped into a spherical core using natural binders basically assumed to constitute waste solids materials. Then after, the granulated carbon core (GAC core) was protected by a porous ceramic shell which confined the material with strong protection and high mechanical strength to resist against degeneration and pressure drop as a limiting factor for most sorbents employed in solution. The CSGAC characterization results proved that the ceramic shell has a smaller thickness (0.1 cm), good mechanical strength (2.0 MPa), and additionally, it presents larger porous channels which promote the fast and higher adsorption performance making it the desired material for the application in the real liquid environment. The test results showed that the prepared material had higher removal of triclosan (TCS) (30-40 mg/L) than BPA counterpart from the aqueous solutions. Moreover, it showed higher adsorption performance compared to the unprotected carbon materials. Furthermore, the mechanisms of BPA and TCS adsorption by core-shell granulated activated carbon (CSGAC) were discussed.

Robust Aluminum and Iron Phosphinate Metal-Organic Frameworks for Efficient Removal of Bisphenol A

Porous metal-organic frameworks (MOFs) have excellent characteristics for the adsorptive removal of environmental pollutants. Herein, we introduce a new series of highly stable MOFs constructed using Fe³⁺ and Al³⁺ metal ions and bisphosphinate linkers. The isoreticular design leads to ICR-2, ICR-6, and ICR-7 MOFs with a honeycomb arrangement of linear pores, surface areas up to 1360 m² g^-1, and high solvothermal stabilities. In most cases, their sorption capacity is retained even after 24 h of reflux in water. The choice of the linkers allows for fine-tuning of the pore sizes and the chemical nature of the pores. This feature can be utilized for the optimization of host-guest interactions between molecules and the pore walls. Water pollution by various endocrine disrupting chemicals has been considered a global threat to public health. In this work, we prove that the chemical stability and hydrophobic nature of the synthesized series of MOFs result in the remarkable sorption properties of these materials for endocrine disruptor bisphenol A.

Effective column adsorption of triclosan from pure water and wastewater treatment plant effluent by using magnetic porous reduced graphene oxide

The ubiquitous presence of triclosan (TCS) in aquatic systems is of great concern. In the present work, magnetic porous reduced graphene oxide (MPrGO) was synthesized via in situ chemical co-precipitation of Fe³⁺and porous graphene oxide and, was used as an adsorbent for the removal of TCS with μg/L level from both pure water and wastewater treatment plant (WWTP) effluent by conducting with continuous flow fixed column. The BET surface area of MPrGO (1070 m²/g) was about tenfold higher than that of commercial powder activated carbon (PAC). Fast adsorption equilibrium can be reached within 20 s, the maximum adsorption capacity of TCS on MPrGO reached 1105.8 mg/g, and the sorbent can be regenerated for reusability about 5 cycles. The breakthrough time was 50 days for the bed depth of 2.3 mm at the inlet TCS concentration of 100 μg/L. MPrGO exhibited a much higher affinity toward TCS than PAC as the breakthrough time for MPrGO was 6.5 times longer than that for PAC. The Thomas and Yoon-Nelson models provide a better fitting curve than that by the Adams-Bohart model. High TCS adsorption capacity of 935.3 mg/g was calculated from WWTP effluent.

Cross-linked chitosan/zeolite as a fixed-bed column for organic micropollutants removal from aqueous solution, optimization with RSM and artificial neural network

Organic micropollutants (MPs) in low concentrations can affect aquatic ecosystems and human health. Adsorption technique is one of the promising methods to remove MPs. Chitosan and zeolites are environmentally friendly and low-cost adsorbents. Thus, removal of organic MPs (such as bisphenol A (BPA), carbamazepine (CBZ), ketoprofen (KTF) and tonalide (TND) from aqueous solution via cross-linked chitosan/zeolite, as a fixed-bed column, was investigated in the current study. Hydraulic retention time was set at 0.8 h pH and concentration of organic MPs ranged from 4 to 8 and 0.50 mg/L to 2.0 mg/L, and they were considered as factors in optimizing the removal of pollutants via response surface methodology (RSM). Approximately 1.4560 mg/L (89.0%) of BPA, 1.4724 mg/L (90.0%) of CBZ, 1.4920 mg/L (91.2%) of KTF and 1.4118 mg/L (86.3%) of TND were removed at 5.1 pH and 1.636 mg/L initial concentration as the optimum removal efficiency on the basis of RSM. Artificial neural network (ANN) was used to optimise removal effectiveness for each MP. The high R² values and reasonable mean squared errors indicated that ANN optimized MP removal in a logical aspect. Adsorption isotherm studies revealed that organic MP removal through chitosan/zeolite could be explained with Freundlich and Langmuir isotherms.

Structured carbon foam derived from waste biomass: application to endocrine disruptor adsorption

In this paper, a novel structured carbon foam has been prepared from argan nut shell (ANS) was developed and applied in bisphenol A (BPA) removal from water. The results showed that the prepared carbon foam remove 93% of BPA (60 mg/L). The BPA equilibrium data obeyed the Liu isotherm, displaying a maximum uptake capacity of 323.0 mg/g at 20 °C. The calculated free enthalpy change (∆H° = - 4.8 kJ/mol) indicated the existence of physical adsorption between BPA and carbon foam. Avrami kinetic model was able to explain the experimental results. From the regeneration tests, we conclude that the prepared carbon foam has a good potential to be used as an economic and efficient adsorbent for BPA removal from contaminated water. Based on these results and the fact that the developed structured carbon foam is very easy to separate from treated water, it can serve as an interesting material for real water treatment applications.

Optimized synthesis of a core-shell structure activated carbon and its adsorption performance for Bisphenol A

The presence of endocrine disrupting chemicals (EDCs) in the environmental water poses a serious threat which requires strong practical solutions. The existing activated carbon-based adsorbents exhibit a number of limitations hindering for their use in adsorption in an aquatic environment. In this work, a controlled technique was used to make a protected Core-Shell structure Activated Carbon (CSAC) material with a smaller size (0.82 cm), thinner shell thickness (0.083 cm) and high mechanical strength (2.41 MPa). The experimental results demonstrated that the sizes of shell precursors used for preparing the ceramic shell had a pronounced influence on the produced material. The shell was prepared by using a mixture of kaolinite (400 mesh) and coal fly ash (100 mesh). The pellet activated carbon core was synthesized by a pelletizing method using powder activated carbon (92%) mixed with the binder (8%) from cassava splinters. The kinetic study evidenced that the performance of the material fitted better for pseudo-second-order kinetic and the intraparticle diffusion. Furthermore, the maximum amount of Bisphenol A (BPA) adsorption by CSAC fitting to Langmuir model was 28.5 mg g^-1. The BPA adsorption by CSAC was an endothermic process. Therefore, this material could be applied in the remediation of various aquatic EDCs.

Eco-friendly rapid removal of triclosan from seawater using biomass of a microalgal species: Kinetic and equilibrium studies

Triclosan is an important emerging pollutant. It has become ubiquitous due to its incomplete elimination in municipal wastewater treatment plants causing serious environmental problems. Biomass from microorganisms as sorbent of pollutants can be an eco-friendly alternative for triclosan removal. In this work, the elimination of triclosan using biomass (dead and living) of the marine microalga Phaeodactylum tricornutum was characterized in cultures exposed to light and in a complex solution (seawater). Maximum removal capacity, isotherms, kinetics, FTIR characterization, pH effect and reuse were evaluated and discussed. Photodegradation of triclosan was also evaluated. Both biomasses showed similar effectiveness; around 100% of pollutant was eliminated when its concentration was 1 mg L^-1 in only 3 h using a biomass concentration of 0.4 g L^-1. A pseudo-second order model guided the biosorption process. Considering the photodegradation as a first-order process, the whole process (photodegradation + biosorption) was suitably modelled with pseudo-third order and Elovich kinetics. Biosorption increased with the decrease in pH. Temkin isotherm showed the best fit for the experimental data. Both biomasses showed good reuse after five cycles, losing only 7% in efficiency. P. tricornutum biomass is an attractive eco-material for triclosan elimination with low-cost and easy handling than other sorbents.

Hierarchically Porous Composite Scaffold Composed of SBA-15 Microrods and Reduced Graphene Oxide Functionalized with Cyclodextrin for Water Purification

Large-scale decontamination of bisphenol A (BPA) from wastewater under field conditions is an urgent need because of the harmful toxic effects of BPA on living organisms. In this study, we report the fabrication of a three-dimensional (3D) hierarchically porous composite scaffold composed of mesoporous SBA-15 silica microrods and reduced graphene oxide (rGO-CD) functionalized with β-cyclodextrin (CD) and its application for BPA separation from contaminated water. The macroporous structure was achieved by sacrificial salt leaching, and the mesoporous structure was derived from the interparticle pores between compressed SBA-15 particles and intrinsic mesopores in SBA-15. The 3D hierarchical macroporous and mesoporous architecture of the scaffold enhances mass transport without any external forces, and the rGO-CD component provides good capture sites for BPA in solution via inclusion complexation between CD and BPA. The inorganic SBA-15 component of the scaffold also allows long-term operation of filters by increasing the mechanical strength of the scaffold. The hierarchically porous SBA-15/rGO-CD composite scaffold could separate BPA from contaminated water significantly better than the scaffold without rGO-CD in both batch and filter systems. Our study indicates that the functional hierarchically porous composite scaffold can be a potential material in wastewater treatment technology.

Co-adsorption of an anionic dye in the presence of a cationic dye and a heavy metal ion by graphene oxide and photoreduced graphene oxide

To investigate the adsorption behavior of contaminants with different adsorbents and co-adsorbates under identical conditions, the adsorption capacities of anionic orange II (OII) dye onto graphene oxide (GO) and photoreduced GO (PRGO) in a single-component system and in the presence of cationic methylene blue (MB) dye as well as heavy metal ion Pb²⁺ were explored. In this work, PRGO was prepared by solar light irradiation of a GO dispersion. GO and PRGO were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. The adsorption isotherms of OII, MB, and Pb²⁺ onto GO and PRGO in single and binary systems have been studied and analyzed by the Langmuir model. In the single system, the adsorption capacity of OII on GO can be promoted from 8.4 mg g⁻¹ to 32.5 mg g⁻¹ after solar light irradiation. While the adsorption capacities of MB and Pb²⁺ are not affected by the photoreduction process. In the binary system, a marked synergistic effect for the adsorption of OII has been determined in the presence of both MB and Pb²⁺, where the adsorption capacity of OII on PRGO has been improved from 8.4 mg g⁻¹ to 295 mg g⁻¹ and 105 mg g⁻¹, enhancements of 35- and 12.5-fold, respectively. In contrast, the presence of OII leads to a mildly antagonistic effect on the adsorption of MB and Pb²⁺. These findings show that the adsorption of anionic dyes by graphene-based materials can be strongly improved in the presence of either cationic dyes or heavy metal ions, which will be of great value in practical applications.

The adsorption capacity of graphene oxide (GO) for orange II (OII) can be remarkably enhanced in the presence of methylene blue (MB) and Pb²⁺.

Performance of metal–organic frameworks for the adsorptive removal of potentially toxic elements in a water system: a critical review

Elevated levels of potentially toxic elements (PTEs) in aqueous environments have drawn attention recently due to their presence and toxicity to living beings. There have been numerous attempts to remove PTEs from aqueous media. The potential of metal–organic frameworks (MOFs) in removing PTEs from aqueous media has been recognized due to their distinctive advantages (e.g., increased removal capability, large surface area, adjustable porosity, and recyclability). Because of the poor stability of MOFs in water, pre and post synthetic modification and functionalization of MOFs have also been developed for water treatment investigations. This review addresses the performance and mechanisms of PTE removal in various modified MOFs in detail. In order to compare the performance of MOFs, here we used partition coefficient (PC) instead of maximum adsorption capacity, which is sensitively influenced by initial loading concentrations. Therefore, the PC of each material was used to evaluate the adsorption performance of different MOFs and to compare with other sorbents. Furthermore, it discusses the scale-up issues and forthcoming pathway for the research and development needs of MOFs for effective PTE removal. This review further elucidates the main removal mechanisms of PTEs by MOFs. Commercial or domestic water treatment systems or water filters can utilize engineered MOFs to treat water by adsorptive removal. However, marketable products have yet to be investigated thoroughly due to limitations of the large-scale synthesis of MOFs.

This review examines the performance of metal–organic frameworks based on partition coefficient data over the classic maximum adsorption capacities.

Kinetic, equilibrium, and thermodynamic performance of sulfonamides adsorption onto graphene

With the extensive production and consumption of sulfonamide antibiotics, their existence in aquatic environments has received increasing attention due to their acute and chronic toxic effects. In this study, graphene was characterized and applied for sulfamethazine (SMT) removal from aqueous solution. The effect of the contact time (0-1440 min), initial concentration (2-100 mg L^-1), and temperature (298-318 K), as well as pH (2-9) and ionic strength (0-0.2 M NaNO₃), have been examined. The maximum adsorption capacity was calculated to be 104.9 mg g^-1 using the Langmuir model. The endothermic adsorption process (△H = 10.940 kJ mol^-1) was pH- and temperature-dependent, and the adsorption data fitted well with the Langmuir isothermal and the pseudo second-order kinetic models. Additionally, ionic strength (0.01 to 0.2 M NaNO₃) had no obvious influence on SMT adsorption by graphene. Ultimately, graphene proved to be an effective adsorbent for sulfonamide antibiotics removal from aqueous solutions.

Steam activation of waste biomass: highly microporous carbon, optimization of bisphenol A, and diuron adsorption by response surface methodology

Highly microporous carbons were prepared from argan nut shell (ANS) using steam activation method. The carbons prepared (ANS@H2O-30, ANS@H2O-90, and ANS@H2O-120) were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared, nitrogen adsorption, total X-ray fluorescence, and temperature-programmed desorption (TPD). The ANS@H2O-120 was found to have a high surface area of 2853 m2/g. The adsorption of bisphenol A and diuron on ANS@H2O-120 was investigated. The isotherm data were fitted using Langmuir and Freundlich models. Langmuir isotherm model presented the best fit to the experimental data suggesting micropore filling of ANS@H2O-120. The ANS@H2O-120 adsorbent demonstrated high monolayer adsorption capacity of 1408 and 1087 mg/g for bisphenol A and diuron, respectively. The efficiency of the adsorption was linked to the porous structure and to the availability of the surface adsorption sites on ANS@H2O-120. Response surface method was used to optimize the removal efficiency of bisphenol A and diuron on ANS@H2O-120 from aqueous solution. Graphical abstract ᅟ.