Adsorption Of Pollutants Research Articles

Recent Advances on the Adsorption of Pollutants from Aqueous Media Using Clay-Based Adsorbents

The sequestration of pollutants from wastewater remains an active research topic recently owing to persistent disposal of industrial wastewater to waterbodies without adequate management strategies available especially in the developing countries. Different technologies have been employed in which adsorption has found a wide range of application. Today, various low cost adsorbents have been developed and evaluated for the adsorption processes. Clay mineral is one of the low cost natural adsorbents requiring minimum modification to enhance its adsorptive capacities. To maintain a clean and safe environment the water bodies must be free of contaminants of emerging concern. The availability of potable water is a global effort, as two of the UN's seventeen Sustainable Development Goals (SDG) are centered on water which is not surprising. Goal 6 focuses on clean water and sanitation whereas Goal 14 focuses on life below the water. With this in view, the availability of potable water highlights the significance of this study, which analyzes the potential of clay minerals as a good precursor for water treatment. Therefore, this review focuses on the clay minerals, its availability in Nigeria, classification and modification of the clay adsorbent.

Novel poly(2-ethyl-2-oxazoline) and poly(diallyldimethylammonium chloride) polymer functionalized montmorillonite: Physicochemical aspects and near-IR study of hydration properties

The novel functionalized montmorillonites (Mts) with non-ionic poly(2-ethyl-2-oxazoline) (PEtOx) and cationic poly(diallyldimethylammonium) (PDDA) were created via an intercalation method with different loading ratio of both polymers. A comprehensive investigation into their physicochemical properties was conducted using Carbon analysis (CA), Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), Simultaneous thermal analysis (TGA/DSC) and BET-N2 adsorption analysis. The impact of hydration on PEtOx-Mts and PDDA-Mts was assessed through gravimetric analysis and near-infrared spectroscopy (NIR) spectroscopy. PXRD analysis revealed a significant increase in 001 diffraction of PDDA-Mt corresponding to a PDDA interlayer with a basal spacing ranging from 1.47 to 1.49 nm. Conversely, the basal spacing exceeding 2 nm for PEtOx suggested, that the PEtOx polymer was intercalated in a larger amount and packed in a less compact manner compared to PDDA. After modification of Na-Mt with PEtOx polymer, FTIR spectroscopy confirmed the presence of the carbonyl CO group (3265 and 1641 cm-1) and the stretching (2982, 2942 and 2883 cm-1) and bending (1480–1200 cm-1) vibrations of the CH2 and CH3 groups. The vibrations of CH groups were further verified following PDDA modification. NIR spectroscopy also confirmed the vibrational bands attributed to both modifiers after intercalation of PEtOx and PDDA. The results of BET-N2 adsorption revealed a significant decrease in the specific surface area (SSA) after intercalation with a non-ionic PEtOx polymer. On the contrary, in the case of saturation of Na-Mt with polycation PDDA, SSA increased slightly in two instances. TGA analysis confirmed greater weight loss for PEtOx-Mts compared to PDDA-Mts. Derivative thermogravimetry (DTG) revealed the release of physisorbed bound water around 100 °C, decomposition of the organic phase within the 250–550 °C range and dehydroxylation of OH groups around 550–800 °C in both cases. The results obtained from the gravimetry and NIR analysis indicated a greater hydrophobic nature for PEtOx-Mts compared to PDDA-Mts. These findings hold substantial potential for enhancing the properties of novel organo-montmorillonites, thereby facilitating their application as adsorbents for pollutants, surface coatings, biodegradable materials, fillers in polymer nanocomposites, drug carriers, anticancer agents and various other significant applications.

Adsorption and desorption of phenanthrene and 1-hydroxyphenanthrene by goethite-coated polyvinyl chloride

Microplastics loaded with phenanthrene and derivatives are widely detected in aquatic environments, and the coating of natural minerals or organic macromolecules may change the environmental behavior of microplastics. In this study, three kinds of composites with different coverage were prepared by coating goethite on the surface of polyvinyl chloride microplastics to investigate the adsorption and desorption behavior of phenanthrene (PHE) and 1-hydroxyphenanthrene (1-OHPHE), and the effect of mucin on desorption was investigated. The results showed that goethite promoted the adsorption of PHE and 1-OHPHE by increasing the specific surface area of the composites. With the increase of the cover degree, the adsorption of PHE decreased because of the decrease in hydrophobicity; while the adsorption of 1-OHPHE initially increased and then decreased with the contributions of hydrophobic interaction and hydrogen bond. The adsorption of 1-OHPHE could be influenced by the pH and ionic strength primarily through electrostatic interactions and Ca2+ bridging. The goethite significantly increased the desorption hysteresis for two chemicals due to the complicated pore structures and increased adsorption affinity. Mucin promoted the desorption of PHE through competitive adsorption, and inhibit the desorption of 1-OHPHE through hydrophobic interaction, hydrogen bonding and Ca2+ bridging. This study elucidated the effects of natural minerals on the adsorption and desorption behavior of organic pollutants on microplastics, briefly discussed the effects of organic macromolecules on the desorption behavior of pollutants with different properties, and emphasized the different environmental behaviors of pollutants.

Ti3C2TX MXene/loofah-derived carbon aerogel for high-efficiency adsorption of organic pollutants in wastewater

The contamination of wastewater by organic pollutants significantly impacts human health and the environment due to their carcinogenic nature and various adverse effects. To address this issue, this study offers a high-efficiency and low-cost biomass-based carbon aerogel adsorbent, which was prepared through the hydrothermal carbonization of loofah, followed by Ti3C2TX MXene impregnation. The aerogel features a porous three-dimensional network structure and a substantial specific surface area, facilitating broad-spectrum adsorption capabilities for various dyes and drugs. The aerogel achieved impressive adsorption capacities of 175.29 and 75.73 mg/g for cationic methylene blue and Rhodamine B dyes, and 106.33 and 93.29 mg/g for anionic methyl orange and Congo red dyes, as well as 86.25 mg/g for tetracycline hydrochloride, surpassing other reported biomass-based aerogels. Furthermore, it demonstrated effective decolorization ability for wastewater containing mixed dyes. Notably, it exhibited excellent recycling and regeneration properties, maintaining a high removal rate after multiple cycles of adsorption–desorption. The adsorption process of dye/drug by the aerogel followed Langmuir’s monomolecular layer adsorption model, exhibiting spontaneous, endothermic, and disorder-increasing behavior in alignment with the pseudo-second-order kinetic model. This study presents an efficient biomass-based aerogel for the removal of organic pollutants from wastewater.

Role of Nanoparticle Size in the Photocatalytic Degradation of Pollutants

Purpose: The aim of the study was to assess the role of nanoparticle size in the photocatalytic degradation of pollutants. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study indicated that smaller nanoparticles exhibit a higher surface area-to-volume ratio, providing more active sites for pollutant interaction and adsorption, which enhances the overall degradation process. Additionally, smaller nanoparticles tend to have higher charge carrier mobility and reduced recombination rates of electron-hole pairs, further improving photocatalytic activity. This increased efficiency is critical in environmental applications, as it allows for the effective breakdown of various contaminants, including dyes, pesticides, and pharmaceuticals, at lower catalyst loadings and shorter reaction times. The optimization of nanoparticle size, therefore, plays a crucial role in developing advanced photocatalytic systems for environmental remediation. Implications to Theory, Practice and Policy: Optical absorption theory, surface area and reaction kinetics theory and charge carrier dynamics theory may be used to anchor future studies on assessing the role of nanoparticle size in the photocatalytic degradation of pollutants. Develop robust methodologies for synthesizing nanoparticles with precise control over size distribution. Establish standardized protocols for evaluating the performance and safety of nanoparticle-based photocatalytic materials. This includes setting benchmarks for degradation efficiency, durability, and potential environmental impacts.

Catalytic ozonation performance and mechanisms of Cu-Co/γ-Al2O3 to achieve antibiotics and ammonia simultaneously removal in aquaculture wastewater

Antibiotics and ammonia are generally co-existed in aquaculture tailwater; moreover, ammonia would also be produced from during ozonation, and should be simultaneously removed before discharge or reuse. In this study, catalyst Cu-Co/γ-Al2O3 was screened from a variety of metal oxides and applied in catalytic ozonation of three kinds of antibiotics and NH+4-N. Factors that affected their removal, including catalyst dosages, O3 concentration, initial pH as well as co-existing ions, were investigated. Moreover, the mechanisms were probed by exploring free radicals’ role as well as intermediates identification; and the characteristics of catalysts before and after use were evaluated using SEM, EDS, XRD, XPS, and BET. Results demonstrated that Cu-Co/γ-Al2O3 could significantly stimulate the degradation of the selected antibiotics and NH+4-N during ozonation. The degradation efficiencies of ciprofloxacin (CIP), tetracycline (TC), sulfamethoxazole (SMX) and NH+4-N can reach up to 95.0 %, 100.0 %, 96.2 %, and 75.7 %, respectively. Plenty of oxygen vacancy (Ovs) and sufficient alkaline sites on the surface of catalyst facilitated the adsorption of pollutants. Furthermore, the transformation of metal ions Cu+/Cu2+ and Co2+/Co3+ enhanced the electron transfer capacity and favored the formation of reactive oxygen species (ROS) during catalytic ozonation reaction, and their roles in catalytic ozonation has also been verified. The radical quenching experiments demonstrated that ·OH was the main contributor for enhancing pollutants removal. The results of Gaussian calculation coincided with those intermediates detected by UPLC-Q-TOF-MS, the pollutants’ removal mechanisms by catalytic ozonation were proposed basing on them. The overall toxicities were compared for ozone only/catalytic ozonation by zebrafish embryo experiment. The results of this study would provide new a feasible way for treating antibiotics and NH+4-N simultaneously in aquaculture wastewater.

Lignin-Derived Sustainable Nano-Platforms: A Multifunctional Solution for an Efficient Dye Removal.

In contrast to conventional non-biobased adsorbents, lignin emerges as a cost-effective and environmentally benign alternative for water treatment. This study identifies unexpected and unpredicted multifunctional properties of lignin nanoparticles (LNPs). LNPs, which are prepared by simple physical processes, demonstrated for the first time to behave as multifunctional materials able to adsorb and photodegrade methylene blue (MB) in aqueous medium upon UV irradiation. Furthermore, the synthetic approach adopted to synthesize LNPs - and therefore their surface properties - strongly affects their performances. More specifically, LNPs obtained by solvent-antisolvent nanoprecipitation (SLNPs) show the highest MB adsorption properties (98 % removal), reaching a maximum adsorption capacity of 43.0 mg g-1, and the fastest adsorption kinetics with respect to other lignin-based adsorbents. Conversely, hydrotropic LNPs (HLNPs) exhibit exceptional photocatalytic activity, resulting in 98 % MB degradation over 6 hours of UV irradiation, combined with the ability to be easily recycled and reused. The present effort paves the way for the use of LNPs as efficient multifunctional materials able to perform concurrently adsorption and photocatalytic degradation of dye pollutants, toward the creation of a sustainable biobased water treatment platform.

The fate of organic compounds in organic waste during torrefaction and implications for its valorization

Torrefaction is commonly used to improve biomass properties, applications, and economy. The characteristics and subsequent applications of torrefied biomass are largely contingent on the organic compounds in parent biomass and their evolution during torrefaction. Yet, the evolution of organic compounds in biomass particularly minor components (e.g., polyphenols) is far less investigated for torrefaction. To address such issues, a superheated steam (SHS) boosted torrefaction process at different temperatures (200, 250, and 300 °C) and residence times (15, 30, and 60 min) was performed on spent coffee ground (SCG), which is an emerging biowaste and is rich in various organic compounds. Results found that both temperature and residence time determine SHS torrefaction performance. SHS torrefaction could effectively remove volatile matters to upgrade SCG for solid fuel. The relatively high content of N and S in torrefied SCG may negatively affect fuel quality but may benefit its adsorption of environmental pollutants. SHS boosted torrefaction could facilitate cellulose and lipids degradation compared to conventional torrefaction. Efficient reduction/removal of labile carbon and ecotoxic chemicals (e.g., phenols and caffeine) in SCG was successfully achieved with SHS torrefaction. As a result, SHS-torrefied SCG with higher biostability and lower phytotoxicity was evaluated as soil amendments and additives to soilless growing substrate. Implications for subsequent application by revealing the evolution of organic compounds during SHS torrefaction were discussed. This study highlighted the potentiality of SHS torrefaction as a pretreatment of biomass for versatile applications.

Vapor-phase reduction synthesis of N, S co-doped graphene/MWCNT hybrid membrane for all-solid-state supercapacitors and adsorption of organic pollutants

Owing to the limited reserves of fossil fuels, many researchers are focused on seeking advanced materials to relieve the drawbacks caused by the imbalance between the supply and demand of fossil fuels. In this study, a N, S co-doped graphene/multi-walled carbon nanotubes hybrid membrane (GMHE) was synthesized by flow-directed assembly followed by vapor-phase reduction. The resulting hybrid membrane not only exhibited excellent capacitance performance, but also good adsorption capacity for organic pollutants owing to its high electrochemical activity, well-developed pore structure, and rich surface state. The assembled GMHE all-solid-state symmetric supercapacitor delivered a high power density of 6000 W·kg−1 at an energy density of 16.0 W·h·kg−1 and superior capacitance stability (retaining 97.2 % of its initial capacitance value at 3 A·g−1). The adsorption capacity of the GMHE for organic pollutants was 50 times (chlorobenzene) its own mass. In addition, the hybrid membrane exhibited remarkable reusability over in adsorption–combustion cycles. The judiciously designed bifunctional membrane material developed herein can be directly applied in energy storage and oil pollution cleanup, supporting sustainable economic development.

Deep Cleaning of Crystal Violet and Methylene Blue Dyes from Aqueous Solution by Dextran-Based Cryogel Adsorbents.

Polysaccharides have recently attracted growing attention as adsorbents for various pollutants, since they can be extracted from a variety of renewable sources at low cost. An interesting hydrophilic and biodegradable polysaccharide is dextran (Dx), which is well-known for its applications in the food industry and in medicine. To extend the application range of this biopolymer, in this study, we investigated the removal of crystal violet (CV) and methylene blue (MB) dyes from an aqueous solution by Dx-based cryogels using the batch technique. The cryogel adsorbents, consisting of cross-linked Dx embedding a polyphenolic (PF) extract of spruce bark, were prepared by the freeze-thawing approach. It was shown that the incorporation of PF into the Dx-based matrix induced a decrease in porosity, pore sizes and swelling ratio values. Moreover, the average pore sizes of the DxPF cryogels loaded with dyes further decreased from 42.30 ± 7.96 μm to 23.68 ± 2.69 μm, indicating a strong interaction between the functional groups of the cryogel matrix and those of the dye molecules. The sorption performances of the DxPF adsorbents were evaluated in comparison to those of the Dx cryogels and of the PF extract. The experimental sorption capacities of the DxPF cryogel adsorbents were higher in comparison to those of the Dx cryogels and the PF extract. The DxPF cryogels, particularly those with the highest PF contents (sample DxPF2), demonstrated sorption capacities of 1.2779 ± 0.0703 mmol·g-1, for CV, and 0.3238 ± 0.0121 mmol·g-1, for MB. The sorption mechanisms were analyzed using mathematical models, including Langmuir, Freundlich, Sips and Dubinin-Radushkevich isotherms, and kinetic models, like pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD). The sorption process was best described by the Sips isotherm and PSO kinetic models, indicating chemisorption as the dominant mechanism. This study outlines the importance of developing advanced renewable materials for environmental applications.

Economical and rapid mechanochemical synthesis of porous organic adsorbents with high hydrophilicity for ultra-fast removal of organic micro-pollutants from water

Various porous adsorbent materials have shown excellent adsorption performance for the removal of organic micro-pollutants in water. However, the practical application was hindered by the high cost or slow adsorption kinetics for most of porous adsorbents. Therefore, it is of great significance to develop economic adsorbent materials with characteristic like low-cost, easier preparation method, excellent adsorption kinetics etc.Herein, based on the Friedel-Crafts alkylation reaction, we reported three novel hydrophilic organic porous adsorbent frameworks (PAF-210, PAF-211 and PAF-212) with high Brunauer-Emmet-Teller (BET) surface area (956 ∼ 1384 m2/g) for phenolic micro-pollutants (bisphenol A (BPA), 2,4-dichlorophenol (2,4-DCP) and 2-naphthol (2-NO)) adsorption in water, which were prepared by using cheap trimethyl orthoformate (TMOF) as crosslinker and one-step simple ball milling synthetic method under room temperature within 15 min. Rich oxygen content promotes the resulting polymers to possess excellent hydrophilicity and wettability through water vapor adsorption and water contact angle analysis. The excellent hydrophilicity and proper porous properties made the resulting frameworks suitable as porous organic adsorbents to rapidly remove organic phenolic micro-pollutants from water. Among the resulting polymers, the PAF-210 exhibited ultra-fast adsorption (>94.0 % within 5 s), ultra-rapid adsorption kinetics with pseudo-second-order rate constants (K2, up to 7.72g/mg min−1 for 2,4-DCP), high pollutant adsorption capacity (up to 867.03 mg g−1 for BPA) and excellent recyclability (10 cycles with slight loss in adsorption capacity) through systematically characterization. The adsorption performances of PAF-210 are much better than these of the commercial activated carbons and β-cyclodextrin-based porous adsorbents (K2 = 1.50g/mg min−1 for P-CDP) etc. The favorable hydrophilicity, surface wettability, and adsorption performance of PAF-210 were significantly better than the comparative material constructed by using benzene and formaldehyde dimethyl acetal (FDA) through conventional thermal synthetic method, which is a very classic synthesis strategy in the field of porous materials. More importantly, the PAF-210 exhibited relatively superior adsorption performance on BPA, and it still presented excellent adsorption performance (removal efficiency ≥ 96.8 % within 5 s after 10 cycles) even at the safe range of BPA quantified in drinking water (BPA≤10 μg L−1, Standards for drinking water quality, GB5749-2022, China). XPS analysis and theoretical simulations proved that the excellent adsorption performance and ultra-fast adsorption rate stem from interactions including π-π interactions, hydrogen bonding and van der Waals interactions between PAF-210 and micro-pollutants.

Impact of carbonization reactor compartment size on groundnut (Arachis hypogaea) shell biochar properties

Abstract This study investigates the impact of low-temperature top-lit updraft reactor chamber size on GNSBC yield and properties. For this study, the volumes of carbonization chamber (2,364, 2,013, 1,468, and 970 cm3) in a biomass-fueled TLUD biomass gasifier were varied, and the resulting biochar was analyzed using SEM, EDX, and FTIR. The novelty of this work lies in its investigation of the unexplored impact of carbonization reactor compartment size on groundnut shell biochar properties and yield, driven by the need to optimize biochar production efficiency and support sustainable waste management practices. The results showed that carbonization chamber size variation significantly affected GNSBC yield, with an initial increase followed by diminishing returns. An increase in the carbonization compartment size led to decreased carbonization duration, increased carbonization temperature, increased porosity, and decreased oxygen content. SEM analysis revealed consistent amorphous and multi-layered morphological features across BC samples, while EDX analysis confirmed high carbon content in the samples. FTIR spectroscopy confirmed the presence of oxygenated functional groups suitable for pollutant adsorption, supporting GNSBC’s role in environmental remediation and industrial processes. This research contributes to optimizing biochar production efficiency, advancing circular economy goals, and sustainable waste management practices.

3D-printed MOF/MoS2 aerogel for dye adsorption and photocatalytic degradation

The escalating challenge of water resources contamination, attributed to toxic pollutants, requires urgent attention from both governments and society. Furthermore, the inefficacy of conventional water treatment methods emphasizes the critical necessity for exploring the development of affordable, renewable, and high-performance materials, which should, for instance, enable the mutual adsorption and photocatalytic degradation of organic pollutants. Here we employed the 3D printing technique to manufacture an aerogel based on alginate, gelatin, and carboxymethylcellulose incorporated with 5 and 7.5 wt % of MOF/MoS2. FTIR spectra and EDS analysis evidenced the presence of MOF/MoS2 in the structure of the aerogels, while Helium pycnometer analysis and SEM micrographs demonstrated that the aerogels presented low density and a porous structure with porosity above 80 %. The swelling test showed that the aerogels displayed a high water absorption capacity (1400 %) after 70 h of immersion. The rheology test demonstrated that elastic behavior prevails over viscous behavior (G' > G″) and the incorporation of 7.5 wt % MOF/MoS2 favored shear thinning and viscosity recovery in the hydrogel. Adsorption tests to methylene blue (employed as a model) showed that the aerogel (HD) without the presence of MOF/MoS2 and the aerogels HD/MOF/MoS2 5 % and MOF/MoS2 7.5 % showed removal efficiencies of 16.77 %, 28.66 %, and 95.86 %, respectively. Conversely, the photodegradation test showed that HD/MOF/MoS2 5 % and HD/MOF/MoS2 7.5 % had an efficiency of 89 % and HD of 80 %. Therefore, our results demonstrate that the developed aerogels are promising candidates for the adsorption and photodegradation of dye while being low-cost, environmentally friendly, and easy to manufacture.

Fabrication of self-N-doped porous biochar by synergistic pyrolysis activation for efficient tetracycline and CO2 adsorption

The development of green and economical adsorption materials with high pollutant adsorption performance is of great significance to meet environmental challenges. Herein, self N-doped porous carbon materials with excellent tetracycline and CO2 adsorption properties are successfully prepared by synergistic pyrolysis activation of corn stalk and Chlorella mixture. The addition of N-riched Chlorella significantly affects the nanopore and surface chemical structure of biochar, forming rich micro-mesopores, changing the intrinsic N doping form and surface oxygen-containing functional groups. An ultra-high tetracycline adsorption capacity of 1159.7 mg/g can be achieved by using the prepared KBC-3:1 as an adsorbent. A series of kinetic isothermal adsorption models, thermodynamic calculations, as well as comparative characterization analysis show that multiple adsorption mechanisms coexist. The pore filling of micro-mesopores (1.5–3 nm), π-π interactions of CC bonds, H bonding interactions of CO and the strong electrophilicity of pyrrolic N contribute to the excellent tetracycline adsorption performance of KBC-3:1. Furthermore, the material shows great resistance to cationic (K+, Mg2+, Cu2+) interference and excellent cycling performance. In addition, KBC-3:1 also exhibits excellent adsorption capacity for CO2, and the adsorption capacity of 5.21 mmol/g can be achieved at 273 K and 1 bar, which could be attributed to the synergistic activation effect leading to KBC-3:1 having the most abundant pyrrolic and pyridinic N species as well as the rich microporous structure. This work can provide guidance for the development of green and economical high performance carbon materials based on the intrinsic characteristics of biomass.

Advances in sustainable nano-biochar: precursors, synthesis methods and applications.

Nano-biochar, characterized by its environmentally friendly nature and unique nanostructure, offers a promising avenue for sustainable carbon materials. With its small particle size, large specific surface area, abundant functional groups and tunable pore structure, nano-biochar stands out due to its distinct physical and chemical properties compared to conventional biochar. This paper aims to provide an in-depth exploration of nano-biochar, covering its sources, transformation mechanisms, properties, applications, and areas requiring further research. The discussion begins with an overview of biomass sources for nano-biochar production and the conversion processes involved. Subsequently, primary synthesis methods and strategies for functionalization enhancement are examined. Furthermore, the applications of nano-biochar in catalysis, energy storage, and pollutant adsorption and degradation are explored and enhanced in various fields.

Enhancing chromium resistance and bulb quality in onion (Allium cepa L.) through copper nanoparticles and possible health risk

Chromium (Cr) is a toxic metal in soil–plant system, hence causing possible health risks prominently in the areas with forgoing industrial activities. Copper nanoparticles (Cu NPs) have been reported as an excellent adsorbent for pollutants. Therefore, this study investigates how copper nanoparticles enhance onion growth while decreasing chromium uptake in onion plants. Additionally, it examines the potential health risks of consuming onion plants with elevated chromium levels. The results demonstrated that the addition of CuNPs at 15 mg kg−1 significantly improved the plant height (48%), leaf length (37%), fresh weight of root (61%), root dry weight (70%), fresh weight of bulb (52%), bulb dry weight (59%), leaves fresh weight (52%) and dry weight of leaves (59%), leaf area (72%), number of onion leaves per plant (60%), Chl. a (42%), chl. b (36%), carotenoids (40%), total chlorophyll (40%), chlorophyll contents SPAD value (56%), relative water contents (35%), membrane stability index (16%), total sugars (25%), crude protein (21%), ascorbic acid (19%) and ash contents (64%) at 10 mg kg−1 Cr. Whereas, maximum decline of Cr by 46% in roots, 68% in leaves and 92% in bulb was found with application of 15 mg kg−1 of Cu NPs in onion plants under 10 mg kg−1 Cr toxicity. The health risk assessment parameters of onion plants showed minimum values 0.0028 for average daily intake (ADI), 0.001911 for Non-cancer risk (NCR), and 0.001433 for cancer risk (CR) in plants treated with Cu NPs at 15 mg kg−1 concentration grown in soil spiked with 10 mg kg−1 chromium. It is concluded that Cu NPs at 15 mg kg−1 concentration improved growth of plants in control as well as Cr contaminated soil. Therefore, use of Cu NPs at 15 mg kg−1 concentration is recommended for improving growth of plants under normal and metal contaminated soils.

Research progress on the adsorption of pollutants in water by oxidized graphene

As a novel nanomaterial, oxidized graphene has attracted attention due to its unique physical properties and abundant oxygen-containing functional groups. This paper analyzes the structure of oxidized graphene, and around its structure and properties, explains the main adsorption mechanisms of oxidized graphene for metal ions and organic matter in water. It discusses and summarizes the main factors that affect the adsorption capacity of oxidized graphene, and looks forward to its application prospects and future research directions in the field of water treatment.

Engineering an A-D-A structure to enhance internal electric fields in silica-PDI-decorated vertical graphene for efficient photocatalytic oxidation

Efficient charge separation and transfer are crucial for elevating photocatalytic oxidation, and designing a photocatalyst structure with strong internal electric fields (IEF) hold promise for addressing the issue. Herein, we synthesized a silica-PDI (silica-perylene diimides) decorated vertical graphene (s-PDI@VG) architecture with an Acceptor-Donor-Acceptor (A-D-A) structure. The A-D-A configuration facilitated electron transfer from tertiary N-atom to perylene tetracarboxylic dianhydride (PTCDA) and flower-like vertical graphene (VG), resulting in a larger molecular dipole moment of s-PDI@VG compared to PTCDA and s-PDI. Consequently, an IEF with 7.5 times higher than PTCDA and 4.8 times higher than s-PDI was built, which is beneficial for photogenerated charge separation. Additionally, the valence band (VB) of s-PDI@VG deepened from 1.43 eV to 1.62 eV, enabling it to afford a strong oxidation potential. As a proof-of-concept, the 3D s-PDI@VG photocatalyst demonstrated favorable persulfate (PMS) activation and pollutant adsorption, resulting in 1.6 times higher photogenerated holes based on LSCM results. This photocatalyst also achieved 98.2 % mineralization of high-ionization-potential (h-IP) organics within 30 min. This work offers insights into a novel photocatalytic oxidation strategy with high mineralization by engineering A-D-A structure and enhancing the IEF strength of photocatalyst molecules.

Construction of magnetic recoverable porous electron-rich organic frameworks for efficiently enrichment of phenylurea herbicides from water and milk samples prior to HPLC detection

Porous electron-rich organic frameworks have attracted an increased attention in the adsorption and removal of pollutants due to their abundant electron-rich nitrogen atoms, which can effectively interact with positively charged substance. In this study, a porous electron-rich organic framework (Car-POF) and positively charged amino-functionalized magnetic nanoparticles (Fe3O4-NH2) were used to construct a magnetic electron-rich Fe3O4-NH2@Car-POF for the enrichment of some phenylurea herbicides from water and milk samples prior to high performance liquid chromatographic detection. The adsorption capacity of Fe3O4-NH2@Car-POF for the phenylureas ranged from 14.93 to 28.83 mg g−1. The LODs were observed in the range of 0.05–0.20 ng mL−1 and 0.5–1.5 ng mL−1, and LOQs in the range of 0.17–0.66 ng mL−1 and 1.7–5.0 ng mL−1 for water and milk samples with RSD less than 9.0. The adsorption studies with cationic and anionic dyes revealed that Fe3O4-NH2@Car-POF is favorable for the adsorption of positively charged compounds.

Construction dual active sites on SnO2 via Fe doping for effective ciprofloxacin photodegradation

Adjusting the electronic structure via doping and enhancing the active sites of photocatalysts are proven strategies for improving the photodegradation of pollutants. However, the photodegradation mechanism involving doping elements and their impact on pollutant adsorption and activation at active sites remain unclear. In this study, Fe-doped SnO2 photocatalysts were synthesized using the hydrothermal method, featuring small particle sizes and highly active sites. It was found that doping SnO2 with 3 mol% Fe3+ significantly enhances its photocatalytic efficiency in degrading Ciprofloxacin, outperforming pure SnO2 by approximately 18.6 times. Spectroscopy methods, combined with density functional theory calculations, revealed that the presence of Lewis acid sites and oxygen vacancies serve as active sites in the Fe-doped SnO2 samples. Furthermore, a detailed photodegradation mechanism for Fe-doped SnO2 was proposed based on the band energy structure and analysis of free radical results. This research provides new insights into the mechanism of photocatalytic degradation of Ciprofloxacin by elucidating the interactions between the active sites of the photocatalyst and Ciprofloxacin molecules.