Aqueous adsorption of aniline, phenol, and their substitutes by multi-walled carbon nanotubes

Support based metal incorporated layered nanomaterials for photocatalytic degradation of organic pollutants

An effective approach to producing sophisticated miniaturized and nanoscale materials involves arranging nanomaterials into layered hierarchical frameworks. Nanostructured layered materials are constructed to possess isolated propagation assets, massive surface areas, and envisioned amenities, making them suitable for a variety of established and novel applications. The utilization of various techniques to create nanostructures adorned with metal nanoparticles provides a secure alternative or reinforcement for the existing physicochemical methods. Supported metal nanoparticles are preferred due to their ease of recovery and usage. Researchers have extensively studied the catalytic properties of noble metal nanoparticles using various selective oxidation and hydrogenation procedures. Despite the numerous advantages of metal-based nanoparticles (NPs), their catalytic potential remains incompletely explored. This article examines metal-based nanomaterials that are supported by layers, and provides an analysis of their manufacturing, procedures, and synthesis. This study incorporates both 2D and 3D layered nanomaterials because of their distinctive layered architectures. This review focuses on the most common metal-supported nanocomposites and methodologies used for photocatalytic degradation of organic dyes employing layered nanomaterials. The comprehensive examination of biological and ecological cleaning and treatment techniques discussed in this article has paved the way for the exploration of cutting-edge technologies that can contribute to the establishment of a sustainable future.

Preparation of GO/COFs composites by interlayer-confined strategy for the adsorption of nitro aromatic pollutants

With the continuous development of industrialization, the excessive emission of nitro aromatic with strong toxicity, high carcinogenicity and non-degradability has attracted great attention. How to efficiently remove nitro aromatic pollutants is an important research topic. In this work, graphene oxide/covalent organic frameworks (GO/COFs) composites were successfully synthesized via interlayer confinement strategy selecting GO, 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTP) and 1,3,5-tri(4-aminophenyl)benzene (TPB) as raw materials. Due to high specific surface area, hierarchical porous structure and good thermal stability, GO/COFs were utilized to adsorb and remove nitro aromatic hydrocarbons in the water environment. The adsorption behavior of GO/COFs for o-nitrophenol, 1,3-dinitrobenzene and 2,4,6-trinitrophenol were further investigated. The GO/COFs composites showed the strongest adsorption capacity for 2,4,6-trinitrophenol, and the maximum adsorption capacity for 2,4,6-trinitrophenol, o-nitrophenol, and 1,3-dinitrobenzene were 438, 317, and 173 mg g-1, respectively. The experimental results indicated that the GO/COFs composites provided great adsorption capability for nitro aromatic pollutants and can be reused, rendering it an extremely potential adsorbent for organic pollutants.

A QSAR prediction model for adsorption of organic contaminants on microplastics: Dubinin-Astakhov plus linear solvation energy relationships

Numerous pharmaceuticals and personal care products (PPCPs) co-exist with various types of microplastics (MPs) in the environment, making it extremely hard to experimentally measure all their adsorption interactions. Thus, a precise prediction model is on demand. In this study, we combined the commonly used Dubinin-Astakhov (DA) model and the linear solvation energy relationships (LSERs) model to predict the adsorption capacity (Q0) and adsorption affinity (E) of MPs for PPCPs, including the key parameters of MP (specific surface area, oxygen-containing functional groups), and the Kamlet-Taft solvation parameters of organic contaminants. The model was validated with the experimental data of 8 PPCPs and 8 MPs (i.e. pristine and aged PE, PET, PS, PVC) plus some published adsorption data. This new model also indicated that the adsorption of PPCPs on those MPs was primarily governed by hydrophobic interaction and hydrogen bonding. The developed model can predict the adsorption of PPCPs onto MPs with a high accuracy and can also provide insights into the understanding of interaction forces in the adsorption process.

Redox potential model for guiding moderate oxidation of polycyclic aromatic hydrocarbons in soils

In-situ chemical oxidation is an important approach to remediate soils contaminated with persistent organic pollutants, e.g., polycyclic aromatic hydrocarbons (PAHs). However, massive oxidants are added into soils without an explicit model for predicting the redox potential (Eh) during soil remediation, and overdosed oxidants would pose secondary damage by disturbing soil organic matter and acidity. Here, a soil redox potential (Eh) model was first established to quantify the relationship among oxidation parameters, crucial soil properties, and pollutant elimination. The impacts of oxidant types and doses, soil pH, and soil organic carbon contents on soil Eh were systematically clarified in four commonly used oxidation systems (i.e., KMnO4, H2O2, fenton, and persulfate). The relative error of preliminary Eh model was increased from 48-62% to 4-16% after being modified with the soil texture and dissolved organic carbon, and this high accuracy was verified by 12 actual PAHs contaminated soils. Combining the discovered critical oxidation potential (COP) of PAHs, the moderate oxidation process could be regulated by the guidance of the soil Eh model in different soil conditions. Moreover, the product analysis revealed that the hydroxylation of PAHs occurred most frequently when the soil Eh reached their COP, providing a foundation for further microorganism remediation. These results provide a feasible strategy for selecting oxidants and controlling their doses toward moderate oxidation of contaminated soils, which will reduce the consumption of soil organic matter and protect the main structure and function of soil for future utilization. ENVIRONMENTAL IMPLICATIONS: This study provides a novel insight into the moderate chemical oxidation by the Eh model and largely reduces the secondary risks of excessive oxidation and oxidant residual in ISCO. The moderate oxidation of PAHs could be a first step to decrease their toxicity and increase their bioaccessibility, favoring the microbial degradation of PAHs. Controlling the soil Eh with the established model here could be a promising approach to couple moderate oxidation of organic contaminants with microbial degradation. Such an effective and green soil remediation will largely preserve the soil's functional structure and favor the subsequent utilization of remediated soil.

Ectopic expression of an Old Yellow Enzyme (OYE3) gene from Saccharomyces cerevisiae increases the tolerance and phytoremediation of 2-nitroaniline in rice

2-nitroaniline (2-NA) is an environmental pollutant and has been extensively used as intermediates in organic synthesis. The presence of 2-NA in the environment is not only harmful for aquatic life but also mutagenic for human beings. In this study, we constructed transgenic rice expressing an Old Yellow Enzyme gene, ScOYE3, from Saccharomyces cerevisiae. The ScOYE3 transgenic plants were comprehensively investigated for their biochemical responses to 2-NA treatment and their 2-NA phytoremediation capabilities. Our results showed that the rice seedlings exposed to 2-NA stress, showed growth inhibition and biomass reduction. However, the transgenic plants exhibited strong tolerance to 2-NA stress compared to wild-type plants. Ectopic expression of ScOYE3 could effectively protect transgenic plants against 2-NA damage, which resulted in less reactive oxygen species accumulation in transgenic plants than that in wild-type plants. Our phytoremediation assay revealed that transgenic plants could eliminate more 2-NA from the medium than wild-type plants. Moreover, omics analysis was performed in order to get a deeper insight into the mechanism of ScOYE3-mediated 2-NA transformation in rice. Altogether, the function of ScOYE3 during 2-NA detoxification was characterized for the first time, which serves as strong theoretical support for the phytoremediation potential of 2-NA by Old Yellow Enzyme genes.

Carbon nanotubes buckypapers: A new frontier in wastewater treatment technology

Occurrence of contaminants in water is one of the major global concerns humanity is still facing today: most of them are extremely toxic and dangerous for human health, obliging their removal for a proper and correct process of sanitation. Among wastewater treatment technologies, in the view of development of sustainable and environmentally friendly processes, membrane adsorption has proved to be a fast and simple method in the removal of pollutants, offering great contaminants recovery percentages, fast adsorbent regeneration and recycle, and easy scale-up. Due to their large surface area and tunable chemistry, carbon nanotubes (CNTs)-based materials revealed to be extraordinary adsorbents, exceeding by far performances of ordinary organic and inorganic membranes such as polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, ceramics, currently employed in membrane technologies for wastewater treatment. In consideration of this, the review aims to summarize recent developments in the field of carbon nanotubes-based materials for pollutants recovery from water through adsorption processes. After a brief introduction concerning what adsorption phenomenon is and how it is performed and governed by using carbon nanotubes-based materials, the review discusses into detail the employment of three common typologies of CNTs-based materials (CNTs powders, CNTs-doped polymeric membranes and CNTs membranes) in adsorption process for the removal of water pollutants. Particularly focus will be devoted on the emergent category of self-standing CNTs membranes (buckypapers), made entirely of carbon nanotubes, exhibiting superior performances than CNTs and CNTs-doped polymeric membranes in terms of preparation strategy, recovery percentages of pollutants and regeneration possibilities. The extremely encouraging results presented in this review aim to support and pave the way to the introduction of alternative and more efficient pathways in wastewater treatment technologies to contrast the problem of water pollution.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

A two-stage Fe(VI) oxidation process enhances the removal of bisphenol A for potential application

Ferrate (Fe(VI)) has been extensively studied as a green oxidant to treat wastewater. But Fe(VI) oxidation still faces several challenges for application, such as the sensitivity of Fe(VI) to pH and the restrictions on the Fe(VI) utilization efficiency for pollutant elimination at low concentration levels. This study proposed a two-stage Fe(VI) oxidation process to enhance the bisphenol A (BPA) removal for potential applicability, consisting of the adsorption by CNTs of stage I and the degradation by Fe(VI) of stage II. The Fe(VI) utilization efficiency in the two-stage process (0.848) was higher than that in one-stage processes (0.727) and Fe(VI) alone system (0.504) at pH 9. In stage I, the adsorption process had good compliance with the Langmuir isotherm model and pseudo-second-order kinetic model. In stage II, the effective utilization of low-concentration Fe(VI) was 2.45 times more than Fe(VI) alone, and the reduction of reaction volume was beneficial to further enhance utilization. The probe experiments (sulfoxide) and the degradation experiments of other electron-donating/withdrawing pollutants (e.g., atrazine, benzoic acid) demonstrated that Fe(IV) and Fe(V) were major oxidizing species in the two-stage process. The regeneration experiments showed that CNTs still had acceptable adsorption and catalytic capabilities after five cycles. Finally, the intermediate products in the two-stage process were detected and four possible degradation pathways of BPA were proposed. These findings were meaningful for the practical application of Fe(VI) oxidation to overcome the conditional limitation and improve the utilization.

Nanotechnology as an efficient and effective alternative for wastewater treatment: an overview

The increase in the surface and groundwater contamination due to global population growth, industrialization, proliferation of pathogens, emerging pollutants, heavy metals, and scarcity of drinking water represents a critical problem. Because of this problem, particular emphasis will be placed on wastewater recycling. Conventional wastewater treatment methods may be limited due to high investment costs or, in some cases, poor treatment efficiency. To address these issues, it is necessary to continuously evaluate novel technologies that complement and improve these traditional wastewater treatment processes. In this regard, technologies based on nanomaterials are also being studied. These technologies improve wastewater management and constitute one of the main focuses of nanotechnology. The following review describes wastewater's primary biological, organic, and inorganic contaminants. Subsequently, it focuses on the potential of different nanomaterials (metal oxides, carbon-based nanomaterials, cellulose-based nanomaterials), membrane, and nanobioremediation processes for wastewater treatment. The above is evident from the review of various publications. However, nanomaterials' cost, toxicity, and biodegradability need to be addressed before their commercial distribution and scale-up. The development of nanomaterials and nanoproducts must be sustainable and safe throughout the nanoproduct life cycle to meet the requirements of the circular economy.

Functional Carbon from Nature: Biomass-Derived Carbon Materials and the Recent Progress of Their Applications

Biomass is considered as a promising source to fabricate functional carbon materials for its sustainability, low cost, and high carbon content. Biomass-derived-carbon materials (BCMs) have been a thriving research field. Novel structures, diverse synthesis methods, and versatile applications of BCMs have been reported. However, there has been no recent review of the numerous studies of different aspects of BCMs-related research. Therefore, this paper presents a comprehensive review that summarizes the progress of BCMs related research. Herein, typical types of biomass used to prepare BCMs are introduced. Variable structures of BCMs are summarized as the performance and properties of BCMs are closely related to their structures. Representative synthesis strategies, including both their merits and drawbacks are reviewed comprehensively. Moreover, the influence of synthetic conditions on the structure of as-prepared carbon products is discussed, providing important information for the rational design of the fabrication process of BCMs. Recent progress in versatile applications of BCMs based on their morphologies and physicochemical properties is reported. Finally, the remaining challenges of BCMs, are highlighted. Overall, this review provides a valuable overview of current knowledge and recent progress of BCMs, and it outlines directions for future research development of BCMs.

Bio-sorbent from castor oil polyurethane foam containing cellulose-halloysite nanocomposite for removal of manganese, nickel and cobalt ions from water

In order to mitigate the contamination of water with heavy metals, caused by mining dam failures in Brumadinho and Mariana in Brazil, eco-friendly bio-based castor oil polyurethane foams, containing a cellulose-halloysite green nanocomposite were prepared. Polyurethane foams containing none (PUF-0), 5%wt (PUF-5), and 10%wt (PUF-10) of the nanocomposite were obtained. The application of the material in aqueous media was verified through an investigation of the efficiency of adsorption, the adsorption capacity, and the adsorption kinetics in pH= 2 and pH= 6.5 for manganese, nickel, and cobalt ions. An increase of 5.47 times in manganese adsorption capacity was found after only 30 min in contact with a solution having this ion at pH= 6.5 for PUF-5 and 11.38 times for PUF-10 when both were compared with PUF-0. Adsorption efficiency was respectively 68.17% at pH= 2 for PUF-5% and 100% for PUF-10 after 120 h, while for the control foam, PUF-0, the adsorption efficiency was only 6.90%.

Metabolomic analysis and ecofriendly enrichment of sunflower meal extract

BACKGROUND

The presence of phenolic compounds in sunflower is well reported in the literature; however, knowledge is scarce when it comes to the composition of other secondary metabolites in this species and their by-products. This work evaluated, for the first time, the phytochemical composition of sunflower meal produced in Brazil. A combination of mixture design and central composite rotatable design 2³ models was then applied to maximize the recovery of bioactive compounds using ecologically friendly solvents and concentrating by applying activated carbon, a sustainable adsorbent. The product of this extraction-concentration was also evaluated by an untargeted metabolomic approach using ultra-performance liquid chromatography coupled to mass spectrometry.

RESULTS

A diverse and abundant profile of phenolic compounds was obtained from Brazilian sunflower meal: in total, 51 natural products were tentatively identified, 35 of which for the first time in sunflower. The sorption capacity of the activated charcoal, in the optimized process conditions, was effective in the separation and concentration of minority secondary metabolites. The ecofriendly extract proved to be enriched in plumberoside, p-coumaric acid, and alkaloids.

CONCLUSIONS

Investigation of the phytochemical profile of sunflower meal produced in Brazil pointed to several secondary metabolites reported for the first time in sunflower samples, including phenolic compounds, alkaloids, and terpenes. The use of activated charcoal in an alkaline medium as an adsorbent for the concentration of these phytochemicals, from an aqueous extract, generated a potentially cost-effective, ecofriendly extract, enriched in minor metabolites, indicating a possible innovative way to selectively obtain these compounds from sunflower meal. © 2022 Society of Chemical Industry.

Nanomaterials as a Sustainable Choice for Treating Wastewater: A Review

The removal of dyes from textile effluents utilizing advanced wastewater treatment methods with high efficiency and low cost has received substantial attention due to the rise in pollutants in water. The purpose of this work is to give a comprehensive analysis of the different treatments for removing chemical dyes from textile effluents. The capability and potential of conventional treatments for the degradation of dyeing compounds in aqueous media, as well as the influence of multiple parameters, such as the pH solution, initial dye concentration, and adsorbent dose, are presented in this study. This study is an overview of the scientific research literature on this topic, including nanoreductive and nanophotocatalyst processes, as well as nanoadsorbents and nanomembranes. For the purpose of treating sewage, the special properties of nanoparticles are currently being carefully researched. The ability of nanomaterials to remove organic matter, fungus, and viruses from wastewater is another benefit. Nanomaterials are employed in advanced oxidation techniques to clean wastewater. Additionally, because of their small dimensions, nanoparticles have a wide effective area of contact. Due to this, nanoparticles' adsorption and reactivity are powerful. The improvement of nanomaterial technology will be beneficial for the treatment of wastewater. This report also offers a thorough review of the distinctive properties of nanomaterials used in wastewater treatment, as well as their appropriate application and future possibilities. Since only a few types of nanomaterials have been produced, it is also important to focus on their technological feasibility in addition to their economic feasibility. According to this study, nanoparticles (NPs) have a significant adsorption area, efficient chemical reactions, and electrical conductivity that help treat wastewater effectively.

Adsorption of fulvic acid on mesopore-rich activated carbon with high surface area

The loss of dissolved organic matter (DOM), especially fulvic acid (FA), from soil by rainfall and runoff will reduce soil fertility and result in water pollution of DOM. Carbon materials including biochars (BCs) and activated carbons (ACs) are widely suggested for soil remediation and carbon immobilization. However, these suggested carbon materials are dominated by micropores, and largely limiting the adsorption capacity for FA. Therefore, a mesopore-rich activated carbon (KAC) with high surface area was prepared from bamboo chips to investigate the adsorption of FA. This KAC can adsorb FA more than ACs and BCs investigated in this study and reported in previous studies not only because of the high surface area (3108 m²/g), but also the higher mesopore volume proportion (57%). The negative pH effect on adsorption performance of KAC was weaker than that on AC and BC, because of the less polarity of KAC. Moreover, KAC was favorable to adsorb FA fractions with various molecular weights, higher aromaticity and higher polarity. This study indicated that KAC was a promising adsorbent for FA, and revealed the underlying adsorption mechanism of FA on KAC, which are helpful for the carbon immobilization and pollution control in soil.

Dispersive Membrane Microextraction of Substituted Phenols from Honey Samples and a Brief Outlook on Its Sustainability Using Analytical Eco-Scale and Analytical GREEnness Metric Approach

Honey is part and parcel of our daily nutrition, but in recent times it has been reported to be tainted by the presence of polar substituted phenols purported from the use of pesticides, herbicides, antimicrobial agents, etc. Honey's viscous nature and matrix complexity often result in analytical chemists resorting to derivatization for the detection of polar analytes such as substituted phenols. This study aims to overcome the matrix effect without derivatization and offer a more sustainable solution with notable sensitivity and selectivity using dispersive membrane microextraction alongside high-performance liquid chromatography (DMME-HPLC) with sporopollenin-methylimidazolium-based mixed matrix membrane (Sp-MIM-MMM). The DMME-HPLC approach successfully determined the presence of mono- and disubstituted phenols from unspiked honey samples with concentrations ranging from 7.8 to 154.7 ng/mL. The sustainability of the proposed method was also validated using the Analytical Eco-Scale (AES) and the Analytical GREEnness Metric (AGREE) where an excellent score of 94 and the encouraging score of 0.72 were recorded, respectively.

Understanding Carbon Nanotube Voltammetry: Distinguishing Adsorptive and Thin Layer Effects via "Single-Entity" Electrochemistry

Cyclic voltammetry of ensembles of nanotube-modified electrodes fails to distinguish between signals from electroactive material adsorbed on the tubes from those due to a thin-layer response of analyte material occluded in the pores of the ensemble. We demonstrate that the distinction can be clearly made by combining cyclic voltammetry with single-entity measurements and provide proof of concept for the case of b-MWCNTs and the oxidation of 4-hexylresorcinol (HR), where the increased signals seen at the modified electrode are concluded to arise from thin-layer diffusion and not adsorptive effects. The physical insights are generic to porous, conductive composites.

Robust antibacterial activity of functionalized carbon nanotube- levofloxacine conjugate based on in vitro and in vivo studies

A new nano-antibiotic was synthesized from the conjugation of multi-walled carbon nanotubes with levofloxacin (MWCNT-LVX) through covalent grafting of drug with surface-modified carbon nanotubes in order to achieve an effective, safe, fast-acting nano-drug with the minimal side effects. This study is the first report on the evaluation of in vitro cell viability and antibacterial activity of nano-antibiotic along in addition to the in vivo antibacterial activity in a burn wound model. The drug-loading and release profile at different pH levels was determined using an ultraviolet–visible spectrometer. MWCNT-LVX was synthesized by a simple, reproducible and cost-effective method for the first time and characterized using various techniques, such as scanning electron microscope, transmission electron microscopy, and Brunauer–Emmett–Teller analysis, and so forth. The noncytotoxic nano-antibiotic showed more satisfactory in vitro antibacterial activity against Staphylococcus aureus compared to Pseudomona aeruginosa. The novel synthetic nano-drug possessed high loading capacity and pH-sensitive release profile; resultantly, it exhibited very potent bactericidal activity in a mouse S. aureus wound infection model compared to LVX. Based on the results, the antibacterial properties of the drug enhanced after conjugating with surface-modified MWCNTs. The nano-antibiotic has great industrialization potential for the simple route of synthesis, no toxicity, proper drug loading and release, low effective dose, and strong activity against wound infections. In virtue of unique properties, MWCNTs can serve as a controlled release and delivery system for drugs. The easy penetration to biological membranes and barriers can also increase the drug delivery at lower doses compared to the main drug alone, which can lead to the reduction of its side effects. Hence, MWCNTs can be considered a promising nano-carrier of LVX in the treatment of skin infections.

HCH Removal in a Biochar-Amended Biofilter

This study evaluated the efficiency of two biofilter systems, with and without biochar chambers installed, at degrading and removing HCH and its isomers in natural drainage water. The biochar biofilter proved to be 96% efficient at cleaning HCH and its transformation products from drainage water, a significant improvement over classic biofilter that remove, on average, 68% of HCH. Although iron- and sulfur-oxidizing bacteria, such as Gallionella and Sulfuricurvum, were dominant in the biochar bed outflows, they were absent in sediments, which were rich in Simplicispira, Rhodoluna, Rhodoferax, and Flavobacterium. The presence of functional genes involved in the biodegradation of HCH isomers and their byproducts was confirmed in both systems. The high effectiveness of the biochar biofilter displayed in this study should further encourage the use of biochar in water treatment solutions, e.g., for temporary water purification installations during the construction of other long-term wastewater treatment technologies, or even as final solutions at contaminated sites.

Degradation of synthetic dyes using nanoparticles: a mini-review

The industrial revolution has marked a strong impact on financial upgradation of several countries, and increase in the industrial establishment globally has direct impact on environment because of the release of unwanted product in air and inside the water bodies. The use of dyes has increased tremendously in various industries ranging from food, leather, textile, paper, cosmetic, pharmaceuticals, etc. The problem has emerged due to disposing of the dyes in the open environment, and mostly it is disposed along with the industrial wastes into the water bodies, which becomes harmful for animals, aquatic life and human health. This review highlights the role of the nanoparticles particularly biosynthesized nanoparticles for eliminating the dyes from the industrial wastewater. There are several methods for the synthesis of nanoparticle including physical, chemical and green synthesis of nanoparticles commonly known as biological method. Among all, the biological method is considered as the rapid, easy, eco-friendly and is being performed at mild conditions. The uses of nanoparticles for removal of dyes from water minimize the hazardous impact and thus considered to be the best approach as far as water quality and safety of environment is concerned.

Sorption of organic compounds by pyrolyzed humic acids

Humic acids (HAs) are frequently subjected to pyrolysis and carbonization by wildfires, which could significantly change the sorption of organic contaminants and their environmental risks in natural system. In previous studies, sorption of organic compounds was investigated for HAs pyrolyzed at temperature below 330 °C, but not for HAs pyrolyzed at higher temperature. Therefore, in this study, sorption of 22 typical organic compounds by HAs pyrolyzed at a series of temperatures from 300 to 700 °C was investigated. Sorption of organic compounds was dominated by nonlinear partition for HAs pyrolyzed at low temperature (e.g., 300 and 400 °C) due to the aliphatic and nonporous structures of pyrolyzed humic acids (PyHAs), while it was dominated by pore-filling adsorption for HAs pyrolyzed at high temperature (e.g., 700 °C) due to the aromatic and porous structures of PyHAs. For HAs pyrolyzed at moderate temperature (e.g., 450, 500 and 600 °C), both nonlinear partition and pore-filling adsorption were responsible for the sorption of organic compounds. Meanwhile, the contribution of pore-filling adsorption to overall sorption increased but the contribution of nonlinear partition decreased with the increasing pyrolytic temperature of PyHAs, attributed to the structure change of PyHAs from aliphatic and nonporous to the aromatic and porous. Moreover, with the increasing pyrolytic temperature of PyHAs, sorption affinity of organic compounds increased, while the change of sorption capacity could be explained by the decrease of nonlinear partition and the increase of pore-filling adsorption. The obtained results could help to evaluate the transport, bioavailability and health risks of organic contaminants in the environment.

Use of Electrocoagulation for Treatment of Pharmaceutical Compounds in Water/Wastewater: A Review Exploring Opportunities and Challenges

Increasing dependency on pharmaceutical compounds including antibiotics, analgesics, antidepressants, and other drugs has threatened the environment as well as human health. Their occurrence, transformation, and fate in the environment are causing significant concerns. Several existing treatment technologies are there with their pros and cons for the treatment of pharmaceutical wastewater (PWW). Still, electrocoagulation is considered as the modern and decisive technology for treatment. In the EC process, utilizing electricity (AC/DC) and electrodes, contaminants become coagulated with the metal hydroxide and are separated by co-precipitation. The main mechanism is charge neutralization and adsorption of contaminants on the generated flocs. The range of parameters affects the EC process and is directly related to the removal efficiency and its overall operational cost. This process only could be scaled up on the industrial level if process parameters become optimized and energy consumption is reduced. Unfortunately, the removal mechanism of particular pharmaceuticals and complex physiochemical phenomena involved in this process are not fully understood. For this reason, further research and reviews are required to fill the knowledge gap. This review discusses the use of EC for removing pharmaceuticals and focuses on removal mechanism and process parameters, the cost assessment, and the challenges involved in mitigation.

An azine-based polymer derived hierarchically porous N-doped carbon for hydrophilic dyes removal

In this study, a novel hierarchically porous N-doped carbon (HPNC) material was successfully prepared by soft-templating method. The commercial triblock copolymer of Pluronic F127 and a polyazine derived from hydrazine hydrate & glyoxal were used as soft template and precursor, respectively. The obtained materials were fully characterized and tested as a sorbent for the removal of hydrophilic dyes of Methylene blue (MB), Basic Fuchsin (BF), Eosin Y (EY) and Rhodamine B (RB) from their aqueous effluents. According to the characterization results, the synthesized material of HPNC-1000 presented thick fibrous morphology with micron size in diameter, hierarchically porous structure with surface area of 1853 m²/g, pore volume of 1.59 cm³/g and nitrogen content of 4.5 wt%. Adsorption-desorption investigation reveals that synergistic effect of hydrophobic interaction and hydrogen-bonding formation of the dye molecules with the sorbent was most pronounced in the adsorptions. The maximum adsorption capacities for MB, BF, EY and RB reached 0.83, 0.92, 1.23 and 1.83 mmol g^-1, respectively. The adsorption processes well fitted by the pseudo first-order kinetic model and the Liu's isotherm. The sorbent can be regenerated by above 90% of the initial adsorption efficiency after six regeneration cycles.

Coupling experiments with calculations to understand the thermodynamics evolution for the sorption of zwitterionic ciprofloxacin on oxidizing-aged pyrogenic chars in the aquatic system

Oxidized aging due to the long-term exposure can significantly alter the sorption of pyrogenic chars (i.e., biochar, BC) towards antibiotics, which determined their fates in natural environments. In this study, the sorption of ciprofloxacin (CIP) on the oxidizing-aged BCs was studied linking the experimental thermodynamics and theoretical calculations. Results revealed that Q₀ of CIP negatively correlated with their average site energies (E_m), while pore-normalized Q₀ on aged BCs were 2-6 folds higher than fresh BCs. From competitive sorption, it is proposed that the transformation of CIP^± to CIP⁺ occurred and the π⁺-π electron donor-acceptor interaction and Coulombic attraction onto the aged BCs played a critical role. These two specific interactions with CIP were thermodynamically improved when aging degree increased and favored the free energies (Δ_aG) of sorption by 2-5 kJ mol^-1. Based on the identified relationship between experimental Δ_OA-ΔG⁰ with E_a through DFT calculations, the contributions of the specific interactions to antibiotic sorption on aged BCs were quantified. This study provided an in-depth understanding of how the aging process affects the sorption of zwitterionic antibiotics on BCs and also possibilities to predict the fate of antibiotics in the presence of BCs over a long-term period.

Theoretical study of small aromatic molecules adsorbed in pristine and functionalised graphene

Small aromatic molecules are precursors for several biological systems such as DNA, proteins, drugs, and are also present in several pollutants. The understanding of the interaction of these small aromatic molecules with pristine and functionalised graphene (fGr) can generate different applications. We performed ab initio simulations based on the density functional theory to evaluate the interaction between the aromatic compounds, benzene, benzoic acid, aniline and phenol, with pristine and fGr. The results show that the binding energy for all cases is less than 103.24 kJ/mol (1.07 eV) without substantial modification of the electronic properties, indicating that the interaction occurs through a physical adsorption regime. The results are promising because they suggest that pristine graphene and functionalised graphene are suitable for removing these pollutants, or for carrying molecules for biological applications influenced by π-π and H-bonds interaction.

Coating magnetite alters the mechanisms and site energy for sulfonamide antibiotic sorption on biochar

Magnetite-coating biochar (MBC) is a promising remediator for antibiotic contamination. Accurate models describing the sorption affinity are required to better understand the role of minerals. In this study, the presence of magnetite led to the improvements of oxygen-containing groups (i.e. C˭O) and regulation of π-systems within BC. Based on Dubinin-Ashtakhov (DA) model, the differences of site energy (E_m) and sorption heterogeneity (σ_e*) led to the variances between sorption capacities of sulfonamides (SAs). The positive correlations between E_m and the oxygen content or pore volume of MBCs indicated that π-π interactions, H-bonding, and pore-filling may act as the high energy sites. Moreover, σ_e* was related to the distribution of magnetite on BC and their porosities. These results suggested that compared to BCs, the coating minerals improved the π-interaction assisted H-bonding and proton configuration of antibiotic when sorbing on MBC. The negative correlations between the E_m of different SAs with their molecular sizes and solubilities resulted from steric effects and competition with water, which further confirmed the proposed high energy sites on MBCs. This study provided the insightful information of site energy distribution and understanding of fate and transport of organic pollutants on BC when the iron minerals were embedded or coated.

Nonlinear partition of nonionic organic compounds into humus-like substance humificated from lignin

Nonlinear sorption of nonionic organic compounds (NOCs) by soil organic matter (SOM) is a significant behaviour that affecting their distribution, transport and fate in the environment. Sorption of typical NOCs, including phenols, anilines, nitrobenzenes and polycyclic aromatic hydrocarbons (PAHs) by Lig48, a humus-like substance humificated from lignin (the principal component of plant precursors of SOM), is nonlinear and without desorption hysteresis, and interpreted by nonlinear partition mechanism in this study. The positively linear relationship between sorption capacity and water solubility of NOCs is a distinguish characteristic for their nonlinear partition into Lig48. Moreover, the nonlinear partition capacity of NOCs is mainly dependent on the aromaticity of humus-like substances with a positively linear relationship, while the nonlinear partition affinity is mainly dependent on the polarity of humus-like substances with a negatively linear relationship. Competition between phenols, anilines, nitrobenzenes and PAHs was observed for their nonlinear partition into Lig48. In addition to van der Waals force, specific interactions, i.e., hydrogen-bonding and π-π interactions are responsible for the nonlinear partitioning of NOCs into humus-like substances including Lig48. These novel observations are helpful for understanding the nonlinear sorption of NOCs by SOM and elucidating the migration and transport of NOCs in the environment.

Promoting adsorption of organic pollutants via tailoring surface physicochemical properties of biomass-derived carbon-attapulgite

Biomass-derived carbon-attapulgite adsorbent was developed for organic pollutants removal. All the batch assays were performed to evaluate the effects of organic components, contact time, and initial concentration of organic pollutants on the adsorption performance of the as-prepared adsorbent. The samples were characterized via Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). The results demonstrated that the acid-treated carbon-attapulgite adsorbent (H-ATP/BC) showed a large specific surface area (237 m² g^-1) and possessed abundant oxygen-containing functional groups and silicon-oxygen bonds (i.e., O-Si-O and O-Si), which provided more active sites and conduced to the adhesive of organic pollutants. Both physical adsorption and chemical adsorption were involved in the adsorption process, and competitive adsorption occurred when two or more target pollutants coexist. Especially, phenol and/or aniline with an aromatic ring were much more likely to adhere to the H-ATP/BC surface than pyridine, and the selectivity order of H-ATP/BC for these pollutants was phenol > aniline > pyridine. From the model fitting, it was observed that the adsorption data could be described well by a pseudo-second-order model and Freundlich isotherms. The theoretical maximum phenol, aniline, and pyridine adsorption capacities of the H-ATP/BC were 14.31 mg g^-1, 15.21 mg g^-1, and 20.74 mg g^-1, respectively. Comparison among the commercial adsorbents price also illustrated that H-ATP/BC could be a promising material for efficient treatment of organic pollutants.Graphical abstract.

Bismuth molybdate incorporated functionalized carbon nanofiber as an electrocatalytic tool for the pinpoint detection of organic pollutant in life samples

Herein, we fabricated a feasible and accurate sensing platform for the quantification of toxic organic pollutant 2-nitroaniline (2-NA) in water samples through electrocatalyst made up of bismuth molybdate (Bi₂MoO₆, BMO) functionalized carbon nanofiber (f-CNF) modified electrode. The preparation of BMO/f-CNF composite is of two methods, such as co-precipitation (C-BMO/f-CNF) and ultrasonication method (U-BMO/f-CNF). The physicochemical properties of the composites were characterized by XRD, FTIR, Raman, BET, FE-SEM, and HR-TEM techniques. At U-BMO/f-CNF, the charge transfer resistance was low (R_ct = 12.47 Ω) compared to C-BMO/f-CNF because nanosized U-BMO particles correctly aim at the defective sites of the f-CNF surface wall. Further, the electrocatalytic activity of C&U-BMO/f-CNF composites was examined by cyclic voltammetry (CV) and differential pulse voltammetry techniques (DPV) for the electrochemical detection of 2-nitroaniline (2-NA). The U-BMO/f-CNF/GCE shows a higher cathodic current, wide dynamic linear range of 0.01-168.01 µM, and superior electrocatalytic activity with a low detection limit (0.0437 µM) and good sensitivity (0.6857 μA μM^-1 cm^-2). The excellent selectivity nature of U-BMO/f-CNF/GCE was observed in the presence of various organic pollutants and a few toxic metal cations. The practical applicability such as stability, repeatability towards 2-NA outcomes with accepted results. Besides, the practical viability of as proposed U-BMO/f-CNF sensor was investigated in soil and lake water samples delivers good recovery results. Hence from these analyses, we conclude that U-BMO/f-CNF/GCE potential for the determination of hazardous environmental pollutant 2-NA.

Nonlinear sorption of phenols and anilines by organobentonites: Nonlinear partition and space limitation for partitioning

Organobentonites, i.e., bentonites coated with surfactants such as cetyltrimethylammonium (CTAB), are superior and low-cost sorbents for removal of organic contaminants from wastewater. Nonlinear sorption of polar organic compounds such as phenols and anilines by organobentonites were widely observed and interpreted by adsorption mechanism. However, in this study, it was observed that the nonlinear sorption of phenols and anilines by CTAB coated bentonites (CTAB-bentonites) should be attributed to nonlinear partition mechanism with the additional space limitation in CTAB-bentonites for nonlinear partitioning, rather than adsorption mechanism. This nonlinear partition mechanism is supported by that (i) organobentonites is a partition medium, identified by the linear isotherms of polycyclic aromatic hydrocarbons (PAHs) and nitrobenzenes; (ii) sorption coefficients (logK_d), the ratio of adsorbed amount (q_e) to equilibrium concentration (C_e), and Dubinin-Ashtakhov (DA) model fitted sorption capacity (logQ⁰) of organic compounds, by a given CTAB-bentonite, are positively correlated with their octanol-water distribution coefficients (logK_OW) and solubility in octanol (logS_o) respectively; (iii) logK_d and logQ⁰ of a given organic compound by CTAB-bentonites are positively correlated with organic carbon contents (f_oc) of CTAB-bentonites, but not specific surface area. Specific interaction (i.e., hydrogen-bonding interaction), in addition to van der Waals force, is responsible for the nonlinear partitioning of phenols and anilines into CTAB-bentonites, because of the positively linear relationship between DA model fitted sorption affinity (E) and hydrogen-bonding donor parameter (α_m) of organic compounds. These results could help the recognizing of the nonlinear sorption behaviors of organic compounds by organobentonites and promote their environmental applications in wastewater treatment.

Superior nitrogen-doped activated carbon materials for water cleaning and energy storing prepared from renewable leather wastes

The fabrication of nitrogen-doped activated carbons (N-ACs) from leather solid wastes (LSW), a huge underutilized bioresource, by different activation methods was investigated. N-AC prepared by KOH activation (named KNAC) exhibited superior physical and chemical properties with much higher BET surface area (2247 m² g^-1) and more abundant hierarchical micropores than those activated by nano-CaCO₃ (CNAC) or by direct carbonization (NNAC). KOH activation decreased the total nitrogen content in KNAC, but it increased the ratio of surface nitrogen species. KOH activation also significantly promoted the conversion of nitrogen species in the carbon material to pyridinic N. Potential applications of the prepared N-ACs were evaluated, and they were tested as adsorbents to remove phenols from water and as the anodes of lithium batteries. The high surface area, abundant micropores, and plentiful surface pyridinic N guaranteed KNAC a superior nitrogen-doped activated carbon that could serve as an excellent adsorbent to remove phenols (282 mg/g) from waste water as well as an outstanding electrode material with a high and stable charge/discharge capacity (533.54 mAh g^-1 after 150th cycle). The strategy of LSW conversion to versatile N-ACs turns waste into treasure and could promote the sustainable development of our society.

VOCs adsorption on activated carbon with initial water vapor contents: Adsorption mechanism and modified characteristic curves

In practice, regeneration of adsorbent is always achieved by heating with hot steam, leaving some water in the adsorbent bed, which may negatively affect the VOCs adsorption. In this research, adsorption isotherms of 12 VOCs (ketones, alkanes, alcohols, halohydrocarbons, and aromatic hydrocarbons) on granular activated carbon (GAC) with different initial water contents (IWC) were conducted. Adsorption interactions between VOCs and GAC at different IWC were investigated using the combination of Linear Solvation Energy Relationship (LSER) and Dubinin-Radushkevich (DR) equation. The results showed that initial water vapor could reduce adsorption capacities and partition coefficient of 12 VOCs, especially at low VOCs concentration. According to LSER, electron acceptor ability (∑β₂^H) and dispersive force (log₁₀L¹⁶) of VOCs played major roles during adsorption. For VOCs with approximate ∑β₂^H value in the same series, the negative influence of IWC was less obvious for VOCs with higher log₁₀L¹⁶, while for VOCs with similar log₁₀L¹⁶ value in different series, the negative influence of IWC was more significant for VOCs with higher ∑β₂^H. Furthermore, characteristic curves of 12 VOCs onto dry GAC, i.e., the plots of adsorbed volume (q_v) vs adsorption potential density (ε/V_m), fell essentially onto a single curve with a high correlation coefficient, while on GAC with IWC, characteristic curves of 12 VOCs had obvious discrepancy. Considering the effect of IWC, the contribution percentage of dispersive force (W_d) to VOCs adsorption was introduced to modify adsorbed volume (q_v) in DR equation and W_d·q_v was used instead of q_v. Then, the integrative characteristic adsorption curves of 12 VOCs on GAC with initial water could be modified well and they showed better superposition with higher fitting coefficient of DR equation. The results are meaningful to estimate adsorption capacities for other VOCs adsorption onto GAC within the range of IWC in this study.

Porous carbon materials derived from olive kernels: application in adsorption of organic pollutants

Adsorption of organic pollutants (OPs), bisphenol A, and diuron, from aqueous solutions onto porous carbon materials (CMs) prepared from olive kernels, have been investigated. The effects of initial pH, initial OP concentration, temperature, and contact time on the adsorption capacity were studied. The adsorption of bisphenol A and diuron onto CMs was found to be optimal at pH 5.6 and 6.9, respectively. It was noticed that the adsorption of those organic pollutants from aqueous solution declined with increasing temperature and the process is exothermic. The rate of adsorption followed the second order kinetic equation. The equilibrium results showed that Langmuir model fits well with the data. The maximum adsorption capacities obtained using the best CM were 476 and 434 mg g^-1 for BPA and diuron, respectively. The results showed that CMs made from olive kernels are an excellent and inexpensive biomass waste-derived sorbent. Graphical abstract.

Mechanisms and Models of Adsorption: TiO2-Supported Biochar for Removal of 3,4-Dimethylaniline

Here, 3,4-dimethylaniline (3,4-DMA) was selected as a representative organic substance of aniline compounds. A biochar-titanium dioxide (BC-TiO₂) composite was prepared by the sol-gel method to investigate its adsorption ability toward the 3,4-DMA compound. Simultaneously, the prepared composite's adsorption ability and physical and physicochemical properties were also investigated. The isotherm studies confirmed that the adsorption of 3,4-DMA on both BC and BC-TiO₂ composite agrees with the Langmuir and Toth adsorption models, which means the formation of a monolayer of 3,4-DMA on the surface. The maximum adsorption capacity of 3,4-DMA was 322.58 mg g^-1 and 285.71mg g^-1 for BC and BC-TiO₂, respectively. Furthermore, the adsorption kinetics reveals that the adsorption process of 3,4-DMA on BC and the BC-TiO₂ composite is controlled by the pseudo-second-order kinetic model with an R ² of 0.99.

Biomass-derived functional porous carbons for adsorption and catalytic degradation of binary micropollutants in water

The biomass, bottlebrush flower, is exploited for the preparation of functionalized porous carbons by one-pot thermal activation using NaHCO₃ and dicyandiamide. An intensified cross-linking effect among the precursors boosts pore (especially mesopore) formation in the pyrolysis process, producing N-doped porous carbons (NPCs) with a large specific surface area (SSA, up to 2025 m²  g^-1). The biomass-derived carbon samples turn out to be highly effective in adsorption, and catalytic activation of peroxymonosulfate for degradation of aqueous phenol and p-hydroxybenzoic acid (HBA) in single and binary systems. The effects of N content, porous structure, and trace Ni species on the adsorptive and catalytic behavior of carbon are investigated. It is found that the porous structure plays a more critical role in adsorption than surface N functionality, while the contributions of various reactive species for phenol and HBA degradation are different.