Efficient encapsulation of toxic dye from wastewater using biodegradable polymeric adsorbent

Guanylated chitosan derivatives for the adsorption of anionic dyes: Performance and mechanism

Chitosan is an emerging adsorbent in pollution management, but its solubility in acidic aqueous solutions and its weak affinity towards pollutants limit its adsorption performance. The development of novel cationic chitosan containing guanidinium groups, has facilitated the advancement of various applications. This work presents a comprehensive methodology for chitosan guanylation through the reaction of neat chitosan with carbodiimide reagents in ionic liquid media. The resulting two guanidinium chitosan derivatives, guanidinium chitosan containing dicyclohexyl and guanidinium chitosan containing dimethylaminopropyl hydrochloride were thoroughly characterized by FT-IR, XRD, thermogravimetry, solid-state NMR and scan electron microscopy, and then investigated as adsorbents for anionic dyes, i.e. methyl orange. The impact of pH, contact time, dye concentration and temperature on the adsorption of methyl orange dye were explored. Both materials showed high adsorption efficiency of 274 and 320 mg/g, respectively. Due to the lower acidity of the guanidinium groups, the gunaylated materials display efficient anion exchange properties even at basic pH. Furthermore, the guanylation leads to decreased solubility via the construction of intermolecular hydrogen bonds. The adsorption properties of cationic chitosan derivatives are outstanding, displaying a high degree of recyclability. The utilization of guanylated chitosan derivatives presents new opportunities in the field of water purification.

Construction of chitosan based magnetic bio adsorbent for efficient recovery of Ni(II)

Nowadays, efficient harnessing of heavy metal contamination is an urgent environmental task. Herein, magnetic bio adsorbent Fe3O4-graphene oxide-chitosan composite (FGOC) was constructed via one step solvothermal procedure for adsorptive recovery of Ni(II). Subsequently, interaction mechanism between FGOC and Ni(II) was deeply elucidated via combining adsorption fitting, the hard-soft acid-base (HSAB) theory calculation and spectroscopic analysis (XPS, UV-Vis and fluorescent emission spectra). Results indicate, FGOC prevails single Fe3O4, chitosan and graphene oxide in Ni(II) scavenging efficiency when pH > 6. Particularly, maximum adsorption percent and quantity 96.52 % and 386.09 mg·g-1 is reached at pH = 10. After six consecutive cycles, adsorption percent and quantity are 88.41 % and 353.63 mg·g-1. Moreover, FGOC demonstrates favorable selectivity towards Ni(II) under the coexistence of common interfering substances. Adsorption isotherm and kinetic fittings propose chemical adsorption with heterogeneous affinity. HSAB theory discloses, groups -OH, -COOH, -C(=O)NH-, -NH2 provide strong adsorptive affinity, with electron flowing from adsorbent towards Ni(II). Furthermore, the overall affinity provided by the potential adsorption sites in each constituents are in following order: Fe3O4 < CS < GO. Above findings were substantiated by spectroscopic tests. This work provides reference for fabricating magnetic graphene oxide-chitosan composite towards valuable metal recovery from wastewater.

A CeFe2O4-CeO2 composite for the electrochemical detection and advanced oxidation of the antibiotic Sparfloxacin

Antibiotics, such as fluoroquinolones, are frequently found in aquatic environments, making their detection and removal crucial from both an environmental and health perspective. In this study, a CeFe2O4 spinel was combined with CeO2 to give a new composite material (CFO), which was then supported by carbon nanofibers (CNFs). This CFO-CNFs composite facilitated the selective and sensitive electrochemical detection of sparfloxacin, a third-generation fluoroquinolone. A linear concentration range extending from 0.06 to 240 μM with a limit of detection of 49.0 nM and a sensitivity of 0.524 μA μM-1 cm-2 were observed. Excellent selectivity in the presence of various inorganic ions, commonly found in aquatic systems, was achieved, while good recovery (90.4-96.2 %) from real water samples was also evident. The CFO with additional CeO2 was immobilised onto carbon cloth, a sustainable and environmentally acceptable substrate, and successfully used in the activation of peroxymonosulfate (PMS) to generate radical species that degraded the sparfloxacin. The optimal removal was seen at a pH of 7.0, with a first-order rate constant of 0.075 min-1 in 0.1 mM PMS and 50 μM sparfloxacin. The immobilised catalyst was easily regenerated using a dilute solution of NaBH4 (0.5 mM). Interestingly, this immobilised catalyst at carbon cloth also facilitated the electrochemical detection of sparfloxacin, with an impressive LOD of 14.0 nM.

Metal-organic framework-based tunable platform for the immobilization of lipase with enhanced activity in non-aqueous systems

Nowadays, metal-organic frameworks (MOFs) have been emerged as an efficient platform for enzyme immobilization due to their high porosity, tunability, and chemical versatility. In this study, a series of hybrid lipase@NKMOF-101-M (M = Mg, Mn, Zn, Co, or Ni) biocatalysts were constructed through a facile in situ encapsulation method, and the encapsulation and immobilization of lipase in MOFs were carefully validated. The catalytic activity of lipase@NKMOF-101-Mn was 2-fold higher than that of lipase@ZIF-8 and 3-fold higher than that of lipase@MCM-41 due to its excellent dispersibility and hydrophobicity in hexane. The reduced Km value demonstrated a superior affinity of lipase@NKMOF-101s toward to the substrate in non-aqueous reaction system. Moreover, the effects of MOF particle size, metal ions, and enzyme distribution on the catalytic performance of the immobilized lipase were systematically investigated. The results demonstrated that as the particle size of lipase@NKMOF-101s decreased, the apparent enzyme activity increased dramatically. Metal ions in MOFs exhibited activation effect toward to enzyme activity and an approximate 12-fold increase in activity was achieved when transesterification was performed using lipase@NKMOF-101-Mn compared with free lipase. Notably, lipase@NKMOF-101-Co and lipase@NKMOF-101-Ni exhibited substrate selectivity owing to the specific distribution of the lipase in the MOF carriers. Lipase@NKMOF-101s can maintain >80 % of its initial activity even after 5 recycles and a long-term storage (30 days). Consequently, NKMOF-101 is a tunable and sustainable platform for the construction of enzyme@MOFs biocatalysts with superior catalytic performance.

Biodegradable taro stem cellulose aerogel: A simple approach for adsorbing microplastics and dyestuffs contaminants

Water pollution and agricultural waste are pressing global issues. Herein, a biomass aerogel derived from waste taro stem microcrystalline cellulose (TS-MCC) was fabricated, in which, the effects of cellulose amount, cross-linker content, pre-freezing protocols on the aerogel's property were studied. The optimized TS-MCC2.0 aerogel exhibited a hierarchical porous structure with good mechanical property (65.04 kPa) and adsorption capacities, with the qm towards microplastics (Polystyrene, PS) and dye (Congo red, CR) being 418.6 mg/g and 951.51 mg/g at 298 K, respectively. Meanwhile, it exhibited good applicability under different pH (3-11) and ionic strength environments, as well as the retained notably simultaneous adsorption ability even under mixed contaminant systems. The mathematical models suggested that the adsorption of PS and CR both fitted pseudo-second-order kinetics, and the adsorption isotherms could be described by the Langmuir and Freundlich models, respectively. Hydrogen bonding, electrostatic attraction, and π-π interactions were inferred as the main adsorption mechanisms towards PS and CR according to Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy analysis. Moreover, the adsorption efficiencies were 92.37 % for PS and 88.34 % for CR after 5 reuse cycles. Therefore, this study provides a green aerogel sorbent for adsorbing microplastics and dyes contaminants.

Bimetallic metal-organic frameworks as electrode modifiers for enhanced electrochemical sensing of chloramphenicol

An electrochemical sensor is presented for the detection of the chloramphenicol (CAP) based on a bimetallic MIL-101(Fe/Co) MOF electrocatalyst. The MIL-101(Fe/Co) was prepared by utilizing mixed-valence Fe (III) and Co (II) as metal nodes and terephthalic acid as ligands with a simple hydrothermal method and characterized by SEM, TEM, XRD, FTIR, and XPS. Electrochemical measurements such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) showed that bimetallic MIL-101(Fe/Co) had the faster electron transfer, larger electroactive area, and higher electrocatalytic activity compared with  their monometallic counterparts due to the strong synergistic effect between bimetals. Inspired by these results, the MIL-101(Fe/Co)-based sensor was used to detect CAP. Some experiment parameters of pH, Fe and Co molar ratio, MIL-101(Fe/Co) volume, and DPV quiet time were optimized. The direct reduction mechanism of CAP was verified to involve four electrons and four protons process. Finally, the sensitive and selective CAP detection in the concentration range 1 to 200 μM with a detection limit of 0.3 μM was realized by the proposed sensor. The satisfactory recoveries in tap water and lake water indicated the practicability of the proposed electrochemical sensor. It is expected that this work may open up a paradigm for the preparation of MOF-based electrode modifiers with desired electrocatalytic performance for environmental pollution monitoring.

An overview of recent advances in treatment of complex dye-containing wastewater and its techno-economic assessment

Industries such as textiles, polymers, pharmaceuticals, papers, and tanneries are the key contributors to the global economy. These industries utilize various types of synthetic dyes in their processes, leading to discharge of dyes-contaminated wastewater. The wastewater generally contains various types of dyes (such as methyl orange, congo red, malachite green, etc.), which have a detrimental impact on the ecosystem and human health due to their toxic, carcinogenic, and mutagenic nature. As the result, it is crucial to treat the dyes-contaminated wastewater to protect the environment and render it suitable for reuse, mitigating the escalating global demand for clean water. This review provides a comprehensive overview of dyes and their treatment technologies (i.e., physical, chemical, and biological treatment). Among various treatment methods, the biological treatment is widely employed due to its energy efficiency and eco-friendliness. However, biological treatment faces challenges such as slow processing rates and limited effectiveness in handling low-biodegradability pollutants (BOD5/COD <0.2). This review also highlighted recent advancements in treatment technologies and explored the emerging integrated treatment method that aims to achieve higher removal efficiency for a low biodegradability index dye-contaminated wastewater. Additionally, a techno-economic assessment is presented, analyzing the cost-effectiveness of the emerging technologies in real-world applications. Further, the critical research gaps and future outlooks are also discussed. Overall, the review aims to contribute to the ongoing efforts to improve wastewater treatment processes and promote sustainable water management practices.

Eco-friendly engineering of micro composite-based hydroxyapatite bio crystal and polyaniline for high removal of OG dye from wastewater: Adsorption mechanism and RSM@BBD optimization

The presence of harmful substances such as dyes in water systems poses a direct threat to the quality of people's lives and other organisms living in the ecosystem. Orange G (OG) is considered a hazardous dye. The existing paper attempts to evaluate a low-cost adsorbent for the effective removal of OG dye. The developed adsorbent Polyaniline@Hydroxyapatite extracted from Cilus Gilberti fish Scale (PANI@FHAP) was elaborated through the application of the in situ chemical polymerization method to incorporate PANI on the surface of naturally extracted hydroxyapatite FHAP. The good synthesis of PANI@FHAP was evaluated through multiple techniques including X-ray diffraction (XRD), Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS), Fourier Transforms Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) coupled with thermal differential analysis (DTA) analysis. The results reveal a highly ordered disposition of PANI chains on FHAP, resulting in a well-coated FHAP in the PANI matrix. Furthermore, the presence of functional groups on the surface of PANI such as amine (-NH2) and imine (=NH) groups would facilitate the removal of OG dye from contaminated water. The adsorption of OG onto PANI@FHAP was conducted in batch mode and optimized through response surface methodology coupled with box-Behnken design (RSM/BBD) to investigate the effect of time, adsorbent dose, and initial concentration. The outcomes proved that OG adsorption follows a quadratic model (R2 = 0.989). The kinetic study revealed that the adsorption of OG fits the pseudo-second-order model. On the other hand, the isotherm study declared that the Freundlich model is best suited to the description of OG adsorption. For thermodynamic study, the adsorption of OG is spontaneous in nature and exothermic. Furthermore, the regeneration-reusability study indicates that PANI@FHAP could be regenerated and reused up to five successive cycles. Based on the FTIR spectrum of PANI@FHAP after OG adsorption, the mechanism governing OG adsorption is predominantly driven by π-π interaction, electrostatic interaction, and hydrogen bonding interactions. The obtained results suppose that PANI@FHAP adsorbent can be a competitive material in large-scale applications.

Surfactant-modified coconut coir powder (SMCCP) as a low-cost adsorbent for the treatment of dye-contaminated wastewater: parameters and adsorption mechanism

The dye-contaminated wastewater discharged from various industries such as dye manufacturing, paint, textile, paper, and cosmetic is a prime source of surface water pollution having serious detrimental effects on both the environment and human beings. These hazardous dyes when exposed to water obstruct the penetration of sunlight into the water and thus restrain aquatic plants from generating photosynthetic compounds. Moreover, some dyes are potential cancer-causing and also negatively impact the human nervous and respiratory systems. In this current study, modification of coconut coir powder (CCP) was carried out through cationic surfactant treatment and was successively utilized as the adsorbent for decoloring anionic dye (acid blue 185 (AB 185)) containing waste stream. Further, a comparative investigation of the dye removal efficiency of raw CCP and surfactant-modified coconut coir powder (SMCCP) as the adsorbent was studied. On surfactant treatment, using a very minimal SMCCP dosage of 8.3 g/L, a very high percentage dye removal of 98.4% is possible, whereas with raw CCP, even after using a higher dosage of 14 g/L, only 70.1% dye removal can be achieved. Characterization of SMCCP adsorbent was done by Fourier transform infrared, thermogravimetric, X-ray, and scanning electron microscope analyses. Furthermore, the optimization of critical operating parameters was investigated for the effective adsorption of AB 185 dye in batch mode. The adsorption of AB 185 onto SMCCP was a thermodynamically spontaneous endothermic process, following the Langmuir isotherm and pseudo-second-order kinetic model. Moreover, regeneration of exhausted SMCCP by 0.1 (M) NaOH was achieved with a satisfactorily high recovery of 97% in the first cycle. Subsequently, SMCCP can be successfully reutilized for five consecutive cycles with a loss of 17.6% in the total adsorption capacity. With all such advantages, the present study delivers a new paradigm to utilize the novel adsorbent SMCCP as a promising eco-friendly adsorbent aided by its advantage of regeneration and reusability for the treatment of dye-contaminated wastewater.

Algal-derived dissolved organic matter accelerates mercury methylation under cyanobacterial blooms in the sediment of eutrophic lakes

Mercury (Hg), especially in the form of methylmercury (MeHg), poses a significant threat to both organisms and the environment due to its extreme toxicity. While methylation process of Hg in sediments has been extensively studied, recognition of its associated risks and mechanisms during cyanobacterial blooms remains limited. This study investigated the distribution characteristics of Hg and MeHg in sediments of Taihu Lake, China. The concentration of Hg and MeHg varied within the range of 96.0-212.0 ng g-1 and 0.1-0.5 ng g-1, respectively. Higher ecological risks of Hg were found in algal-dominated regions compared to macrophyte areas. The significant correlations observed between Hg, MeHg, and algal-derived dissolved organic matter (ADOM) components C1 and C2 in algal-dominated regions indicate a close association between ADOM components and the Hg methylation process. These components are involved in the absorption or complexation of Hg, participate in redox reactions, and modulate microbial activity. The dsrB gene in sulfate-reducing bacteria (SRB) was found to accelerate the metabolic pathways of Hg methylation. These findings indicate that ADOM could enhance the methylation process of Hg during cyanobacterial blooms, which warrants attention.

Molten salt mediated single-step synthesis of reusable nanostructured CaTiO3 for the removal and recovery of Sr2+: A potential adsorbent for the contaminated water bodies

The facile synthesis approach for the adsorbent preparation and recyclability during decontamination of radioactive pollutants is a significant concern in water treatment. The objective of this study is to, synthesis via solid-state reaction of the nanostructured CaTiO3 for the removal and recovery of strontium (Sr2+) from the various water sources. The influence of the adsorption-dependent parameters including, initial concentration, adsorbent dose, pH, contact time and co-existing ions interference were investigated. The prepared adsorbent was characterized by different analytical techniques like FT-IR, SEM with EDAX, TEM, TGA-DTG, Powder XRD and BET surface analysis. The kinetic models were also used, and according to the kinetic models, a pseudo-second-order kinetic model (R2 = 0.999) was better fitted to the adsorption of Sr2+ ions onto CaTiO3 rather than pseudo-first-order kinetics, which could properly represent the observed adsorption of Sr2+. For the isotherm study, the results are best fitted to the Langmuir isotherm model (R2 = 0.98) with a maximum adsorption capacity of 102.04 mg/g. The common ions (Na+, Mg2+, Ca2+, and K+) and Sr2+ having a concentration of 1:2, 1:3, and 1:4, where 82.8, 79.5, and 68.2 % removal was achieved of Sr2+ in each respective matrix. In addition, the adsorption and corresponding recovery and removal for the different Sr2+spiked matrices in deionized water, tap water, well water, lake water, and seawater were investigated with 97, 65.6, 76.5, 73.9 and 17.8 % removal respectively. Also, the CaTiO3 showed excellent recyclability with minimal loss even after 5 consecutive recyclability cycles and >90% removal of strontium achieved. Hence, prepared nanostructured CaTiO3 could be considered a promising adsorbent for the removal and recovery of Sr2+ions from contaminated water bodies.

Phenanthrene sorption studies on coffee waste- and diatomaceous earth-based adsorbents, and adsorbent regeneration with cold atmospheric plasma

Phenanthrene (PHE) is a polycyclic aromatic hydrocarbon categorized as a high priority organic pollutant being toxic for the ecosystem and human health, and its sorption on natural organic or inorganic substances seems a well-promising method for its removal from water streams. The goals of the present work are (i) to assess the capacity of low-cost adsorbents fabricated by treating coffee wastes and diatomaceous earth to remove PHE from water; (ii) to elucidate the role of the pore structure on PHE sorption dynamics; and (iii) to assess the potential to regenerate adsorbents loaded with PHE, by using the novel technology of cold atmospheric plasma (CAP). Diatomaceous earth (DE) and DE pre-treated with sodium hydroxide (NaOH) or phosphoric acid (H3PO4) were chosen as inorganic adsorbents. Coffee waste (CW) and activated carbons (AC) produced from its pyrolysis at 800 °C (CWAC), either untreated (CWAC-800) or pre-treated with NaOH (CWAC-NaOH-800) and H3PO4 (CWAC-H3PO4-800), were chosen as organic adsorbents. The adsorbents were characterized with nitrogen adsorption-desorption isotherms, attenuated total reflectance-Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. Based on the PHE sorption capacity and pore structure/surface characteristics, the CWAC-NaOH-800 was chosen as the most efficient adsorbent for further equilibrium and kinetic sorption studies. The multi-compartment model was used to describe the PHE sorption dynamics in CWAC-NaOH-800 by accounting for the pore/surface diffusion and instantaneous sorption. The CWAC-NaOH-800 exhibited remarkable values for (i) the specific surface area (SBET = 676.5 m2/g) and meso- and micro-pore volume determined by nitrogen sorption (VLN2 = 0.415 cm3/g); (ii) the macro- and meso-pore volume determined by mercury intrusion porosimetry (VMIP = 3.134 cm3/g); and (iii) the maximum PHE sorption capacity (qmax = 142 mg/g). The percentage of adsorbent recovery after its regeneration with CAP was found to be ~ 35%. From the simulation of sorption dynamics, it was found that at early times, the sorption kinetics is governed by the film diffusion towards the external surface of grains, but at late times, most of the adsorbed mass is transferred primarily to meso-/macro-pores via diffusion, and secondarily to micro-porosity via surface diffusion. Based on the adsorbent characteristics, effect of pH on sorption efficiency, and numerical analysis of sorption dynamics, it was concluded that probably the dominant adsorption mechanism is the π-π interactions between hydrophobic PHE aromatic rings and CWAC-NaOH-800 graphene layers. The high PHE removal efficiency of CWAC-NaOH-800, the successful interpretation of sorption dynamics with the multi-compartment model, and the potential to regenerate PHE-loaded adsorbents with the green and economic technology of CAP motivate a strategy for testing CWACs towards the adsorption of other PAHs, application of adsorbents to real wastewaters, and scaling-up to pilot units.

Sustainable adsorbent frameworks based on bio-resourced materials and biodegradable polymers in selective phosphate removal for waste-water remediation

Phosphorus to an optimum extent is an essential nutrient for all living organisms and its scarcity may cause food security, and environmental preservation issues vis-à-vis agroeconomic hurdles. Undesirably excess phosphorus intensifies the eutrophication problem in non-marine water bodies and disrupts the natural nutrient balance of the ecosystem. To overcome such dichotomy, biodegradable polymer-based adsorbents have emerged as a cost-effective and implementable approach in striking a "desired optimum-undesired excess" balance pertaining to phosphate in a sustainable manner. So far, the reports on adopting such adsorbent-approach for wastewater remediation remained largely scattered, unstructured, and poorly correlated. In this background, the contextual review comprehensively discusses the current state-of-the-art in utilizing biodegradable polymeric frameworks as an adsorbent system for phosphate removal and its efficient recovery from the aquatic ecosystem, while highlighting their characteristics-specific functional efficiency vis-à-vis easiness of synthetic and commercial viability. The overview further delves into the sources and environmental ramifications of excessive phosphorus in water bodies and associated mechanistic pathways of phosphorus removal via adsorption, precipitation, and membrane filtration enabled by biodegradable (natural and synthetic) polymeric substrates. Finally, functionality optimization, degradability tuning, and adsorption selectivity of biodegradable polymers are highlighted, while aiming to strike a balance in "removal-recovery-reuse" dynamics of phosphate. Thus, the current review not only paves the way for future exploration of biodegradable polymers in sustainable cost-effective adsorbents for phosphorus removal but also can serve as a guide for researchers dealing with this critical issue.

Novel Chitosan-ZnO nanocomposites derived from Nymphaeaceae fronds for highly efficient removal of Reactive Blue 19, Reactive Orange 16, and Congo Red dyes

The primary aim of this investigation was to synthesise novel adsorbent by incorporating greenly synthesized zinc oxide nanoparticles into chitosan matrix (G-ZnO-Cs). The production of ZnO Nanoparticles via a green approach involved the utilization of extracts derived from Nymphaeaceae fronds. This assertion was substantiated by the application of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD) analytical techniques. Several Analytical methods such as Fourier Transform Infrared spectroscopy (FT-IR), Energy Dispersive X-ray Analysis (EDAX), FESEM, Thermogravimetric Analysis (TGA), XRD, Brunauer-Emmett-Teller (BET) analysis, and point-of-zero charge determination were used to characterize G-ZnO-Cs. Further study investigates the impact of five key processing parameters, namely pH, interaction duration, G-ZnO-Cs dosage, temperature, and initial concentration of dyes, on the removal of three organic dyes Reactive Blue 19 (RB 19), Reactive Orange 16 (RO 16), and Congo Red (CR) The adsorption process of Reactive Blue 19 (RB 19), Reactive Orange 16 (RO 16), and Congo Red (CR) dyes on G-ZnO-Cs were determined to comply to the pseudo-second-order (PSO) and Langmuir models, as determined through equilibrium and kinetic experiments. The highest adsorption capabilities for RB 19, RO 16 and CR dye were revealed to be 219.6 mg/g, 129.6 mg/g, and 118.8 mg/g, respectively. The elimination success rate of the fixed-bed column approach for treating huge volumes was highlighted in the conducted research. Moreover, the G-ZnO-Cs composite exhibited significant reusability due to its ability to undergo elution and simultaneous regeneration processes.

MOF-on-MOF heterostructure boosting AIE sensing and triggered structural collapse for histamine detection

We explored a novel preparation method for MOF-on-MOF heterostructured material (Zn-BTEC@ZIF-8). This prepared heterostructured material acts as a container, capable of adsorbing tetracycline hydrochloride molecules into its backbone through hydrogen bonding and π-π interactions. This phenomenon triggers an aggregation induced emission (AIE) effect, leading to the formation of luminescent bodies. The coordination between histamine and MOF was found to collapse the originally stabilized MOF-on-MOF structure. This collapse causes the splitting of the initially stabilized MOF-on-MOF structure from the aggregated state into fragments, resulting in the quenching of fluorescence in the fluorophore. Remarkably, the fluorescence quenching efficiency of this composite surpasses that of single-layer metal-organic framework (MOF) zeolitic imidazolate framework-8 (ZIF-8) or zinc-based MOF of pyromellitic acid (Zn-BTEC), enabling more sensitive detection of histamine. In this investigation, we constructed a label-free fluorescent sensor specifically designed for the detection of histamine, capitalizing on the AIE effect inherent in MOF-on-MOF architecture and the presence of tetracycline hydrochloride (Tet). The sensor demonstrates a rapid, straightforward, and stable response, allowing for histamine detection within 20 min. Notably, the sensor covers a detection range of 2-400 mg L-1, achieving a low detection limit of 1.458 mg L-1 The practical application of this sensor for quantitative detection of histamine in river water and various fish species exhibited robust performance, ensuring reliability and accuracy in real samples. Its potential application in food safety and environmental monitoring is evident, making it a valuable tool for addressing histamine-related challenges in these domains.

Assessment of heavy metals accumulation by vegetables irrigated with different stages of textile wastewater for evaluation of food and health risk

Wastewater irrigation for vegetable cultivation is greatly concerned about the presence of toxic metals in irrigated soil and vegetables which causes possible threats to human health. This study aimed to ascertain the accumulation of heavy metals (HMs) in edible parts of vegetables irrigated with different stages of textile dyeing wastewater (TDW). Bio-concentration factor (BCF), Estimated daily intake (EDI), and target hazard quotient (THQ) were computed to estimate human health risks and speculate the hazard index (HI) of adults and children with the consumption of HMs contaminated vegetables at recommended doses. Five vegetables (red amaranth, Indian spinach, cauliflower, tomato, and radish) in a pot experiment were irrigated with groundwater (T1) and seven stages of TDW (T2∼T8) following a randomized complete block design (RCBD) with three replications. Among the TDW stages, T8, T7, T4, and T5 exhibited elevated BCF, EDI, THQ, and HI due to a rising trend in the accumulation of Pb, Cd, Cr, and Ni heavy metals in the edible portion of the red amaranth, followed by radish, Indian spinach, cauliflower, and tomato. The general patterns of heavy metal (HM) accumulation, regarded as vital nutrients for plants, were detected in the following sequence: Zn > Mn/Cu > Fe. Conversely, toxic metals were found to be Cd/Cr > Ni > Pb, regardless of the type of vegetables. Principal Component Analysis (PCA) identified T8, T7, and T4 of TDW as the primary contributors to the accumulation of heavy metals in the vegetables examined. Furthermore, the analysis of the heavy metals revealed that the BCF, THQ, and HI values for all studied metals were below 1, except for Pb. This suggests that the present consumption rates of different leafy and non-leafy vegetables, whether consumed individually or together, provide a low risk in terms of heavy metal exposure. Nevertheless, the consumption of T8, T7, and T4 irrigated vegetables, specifically Indian spinach alone or in combination with red amaranth and radish, by both adults and children, at the recommended rate, was found to pose potential health risks. On the other hand, T2, T3, and T6 irrigated vegetables were deemed safe for consumption. These findings indicated that the practice of irrigating the vegetables with T8, T7, and T4 stages of TDW has resulted in a significant buildup of heavy metals in the soils and edible parts of vegetables which are posing health risks to adults and children. Hence, it is imperative to discharge the T8, T7, and T4 stages of TDW after ETP to prevent the contamination of vegetables and mitigate potential health risks.

Bacterial cellulose based TiO2-CdS nanocomposite gel with enhanced photocatalytic activity for adsorptive degradation of cationic dye

Dye released by industrial is one of the main known pollutants in wastewater, which is harmfully affected to the human health. Adsorptive method by absorbents and photocatalytic degradation technique are advanced technologies to remove dyes from wastewater. However, the single technique mentioned above has imperfections limiting its application. Herein, in order to integrate the two techniques and take both advantages, bacterial cellulose (BC) based titanium dioxide (TiO2)‑cadmium sulfide (CdS) nanocomposite gel was prepared by microwave-assisted solvothermal synthesis. The BC@TiO2-CdS nanocomposite gel was characterized by SEM, EDS, XRD, XPS, Raman spectral and TG, its photocatalytic mechanism was proved by PL. The results showed the TiO2-CdS nanophotocatalyst exhibited binary hierarchical structure and followed the Z-scheme type photocatalytic system. The Z-scheme heterojunction is advantageous for photo-generated charge separation and migration. The photocatalytic performance of BC@TiO2-CdS nanocomposite gel was evaluated by MB degradation under visible light irradiation. Due to synergistic effect of BC matrix and TiO2-CdS, the as-prepared BC@TiO2-CdS nanocomposite gel possesses enhanced photocatalytic activity with 94.47 % removal of methylene blue (MB) after 180 min visible light irradiation. Therefore, this work provides a facile route to fabricate bio-mass based efficient nanophotocatalytic material for pretreating the water pollution.

Changes in microcystin concentration in Lake Taihu, 13 years (2007-2020) after the 2007 drinking water crisis

Since the 2007 water crisis occurred in Lake Taihu, substantial measures have been taken to restore the lake. This study evaluates the effectiveness of these restoration activities. We examined the physicochemical parameters and the distribution of microcystin and Microcystis in both the water column and sediment during the bloom period of May 2020 to October 2020. The mean value of extracellular and intracellular microcystin content was 0.12 μg L-1 and 16.26 μg L-1, respectively. The mean value of microcystin in sediment was 172.02 ng g-1 and peaked in August. The concentration in the water and sediment was significantly lower than the historical average concentration. The abundance of toxigenic Microcystis and total Microcystis in the water column ranged from 2.61 × 102 to 2.25 × 109 copies·L-1 and 8.28 × 105 to 2.76 × 109 copies·L-1, respectively. The proportion of toxic Microcystis in the sediment ranging from 31.2% to 19.12%. The highest and lowest region was Meiliang Bay and Grass-algae type zone, respectively. The copy number of the 16S rRNA gene was 1-4 orders of magnitude higher than that of mcyA gene in populations of Microcystis, indicating that non-toxic Microcystis was the dominant form in the majority of the lake. The abundance of toxic Microcystis in the water column was positively correlated with total phosphorus, PO43--P and pH, while the water temperature played distinct role to the distribution of toxic Microcystis in sediment. Our research indicated phosphorus remains a key factor influencing the toxic Microcystis and microcystins in the water column. pH played distinct roles in the distribution of microcystins in sediment and water column. The increasing water temperature is a threat. Explicit management actions and policies, which take into account nutrient concentrations, pH, and increasing temperatures, are necessary to understand and control the distribution of microcystin and Microcystis in Lake Taihu.

Sodium titanate: A proton conduction material for ppb-level NO2 detection with near-zero power consumption

Constrained by the traditional charge transfer sensing mechanism, it is quite challenging to fabricate NO2 sensors that simultaneously exhibit high sensitivity, rapid response/recovery, and low power consumption. Herein, sodium titanate (NTO), a layered material with abundant surface-rooted OH groups (OHR), is demonstrated to be a promising NO2 sensing material. To understand the sensing behavior of NTO, the influences of operating temperature, applied voltage, and relative humidity are investigated, and a novel OHR-enabled proton conduction sensing mechanism is proposed. The sensing process mainly involves selective NO2 adsorption on OHR, thereby lowering the activation energy for proton transportation along the NTO surface. Meanwhile, the moderate intermolecular interaction makes NO2 both easily adsorbed and desorbed at room temperature. Hence, NTO exhibits a highly sensitive, rapid, and fully recoverable response (∼5.7-1 ppm NO2 within 3 s), wide detection range (1 ppb-20 ppm), good stability (>2 months), and near-zero power consumption (0.5 nW). Finally, we demonstrate that NTO has an excellent practical indoor/outdoor NO2 sensing ability. This work offers a new pathway to resolve the inherent conflicts in available NO2 sensors by using NTO via the OHR-enabled proton conduction sensing mechanism, which may also provide insight into designing high-performance sensors for other gases.

Investigating the effect of type of fish and different cooking methods on the residual amount of polycyclic aromatic hydrocarbons (PAHs) in some Iranian fish: A health risk assessment

The aim of this study was to assess the level of PAHs and associated health risks in different types of fish cooked with different methods, using the MSPE-GC/MS technique (magnetic solid phase extraction with gas chromatography/mass spectrometry). The limits of detection (LODs), limits of quantification (LOQs) and recovery percentages ranged from 0.1 to 0.63 μg/kg, 0.3-1.89 μg/kg, and 93.7 to 102.6%, respectively. The results showed that the mean of ƩPAHs in all samples was 20.31 ± 6.60 µg/kg. Additionally, PAH4 and BaP levels in all samples were 4.58 ± 1.40 and 1.08 ± 0.36 µg/kg, respectively, which were below the European Union (EU) standard level (12 and 2 µg/kg, respectively). The results showed that among 5 types of fish, starry sturgeon had highest average total PAHs (13.24 ± 1.84 µg/kg), while Caspian Sea sprat had the lowest average total PAHs (1.24 ± 0.8 µg/kg). In terms of cooking methods (charcoal-grilled fish, fried fish and oven-grilled fish), charcoal-grilled fish had the highest average total PAH level at 25.41 ± 7.31 µg/kg, while the lowest average total PAH was found in the raw fish sample at 16.44 ± 4.63 µg/kg. The Monte Carlo Simulation was used to determine the 95% ILCRs (Incremental Lifetime Cancer Risk) due to ingestion of fish. The results showed that the ILCR for adults was 2.85E-9, while for children it was 1.32E-8. Therefore, based on these findings, it can be concluded that the consumption of fish cooked with different methods does not pose a risk to human health in terms of the amount of PAHs (ILCR < 1 × 10-4).

Toxicity assessment of poultry-waste biosynthesized nanosilver in Anabas testudineus (Bloch, 1792) for responsible and sustainable aquaculture development-A multi-biomarker approach

The current study investigates the potential utilization of poultry intestines for the synthesis of stable silver nanoparticles (AgNPs) and their impact on fish physiology. The AgNPs were synthesized and characterized using various analytical techniques. The toxicity of AgNPs on Anabas testudineus was evaluated, determining a 96-h LC50 value of 25.46 mg l-1. Subsequently, fish were exposed to concentrations corresponding to 1/10th, 1/25th, 1/50th, and 1/100th of the estimated LC50 for a duration of 60 days in a sub-acute study. A comprehensive range of biomarkers, including haematological, serum, oxidative stress, and metabolizing markers, were analyzed to assess the physiological responses of the fish. Additionally, histopathological examinations were conducted, and the accumulation of silver in biomarker organs was measured. The results indicate that silver tends to bioaccumulate in all biomarker organs in a dose- and time-dependent manner, except for the muscle tissue, where accumulation initially increased and subsequently decreased, demonstrating the fish's inherent ability for natural attenuation. Analysis of physiological data and integrated biomarker responses reveal that concentrations of 1/10th, 1/25th, and 1/50th of the LC50 can induce stress in the fish, while exposure to 1/100th of the LC50 shows minimal to no stress response. Overall, this study provides valuable insights into the toxicity and physiological responses of fish exposed to poultry waste biosynthesized AgNPs, offering potential applications in aquaculture while harnessing their unique features.

Porous polymer magnetic adsorbents for dye wastewater treatment

Dye wastewater discharged from industries has caused serious environmental problems. The recent decade has witnessed adsorption technology emerging as an advanced dye wastewater treatment method with great potential Therefore, we fabricated two kinds of magnetic porous adsorbents (HSF and HSVF) with different specific surface areas and activity sites. Both of which exhibit excellent performance with remarkable dye adsorption capacities, especially HSVF. We further investigated their adsorption kinetic and isotherm in detail. Therein, HSVF showed a nice desorption capacity, and it could be recycled rapidly by magnetism, which exhibited the advantages of effective, easy operation, and low cost. In addition, their adsorption kinetic and isotherm were further studied and compared in detail. The results revealed that introducing strong active sites could improve both the adsorption capacity and rate effectively even though sacrificing part of specific surface areas, indicating that active sites might play a dominant role during the dye adsorption process.

Current trends in the detection and removal of heavy metal ions using functional materials

The shortage of freshwater resources caused by heavy metal pollution is an acute global issue, which has a great impact on environmental protection and human health. Therefore, the exploitation of new strategies for designing and synthesizing green, efficient, and economical materials for the detection and removal of heavy metal ions is crucial. Among the various methods for the detection and removal of heavy ions, advanced functional systems including nanomaterials, polymers, porous materials, and biomaterials have attracted considerable attention over the past several years due to their capabilities of real-time detection, excellent removal efficiency, anti-interference, quick response, high selectivity, and low limit of detection. In this tutorial review, we review the general design principles underlying the aforementioned functional materials, and in particular highlight the fundamental mechanisms and specific examples of detecting and removing heavy metal ions. Additionally, the methods which enhance water purification quality using these functional materials have been reviewed, also current challenges and opportunities in this exciting field have been highlighted, including the fabrication, subsequent treatment, and potential future applications of such functional materials. We envision that this tutorial review will provide invaluable guidance for the design of functional materials tailored towards the detection and removal of heavy metals, thereby expediting the development of high-performance materials and fostering the development of more efficient approaches to water pollution remediation.

Decoration of polystyrene with nanoparticles of cobalt hydroxide as new composites for the removal of Fe(iii) and methylene blue from industrial wastewater

Effluent water from different industries is considered one of the most serious environmental pollutants due to its non-safe disposal. Therefore, proper treatment methods for such wastewater are strongly stimulated for its potential reuse in industries or agriculture. This study introduces a composite fabricated via doping of polystyrene with nanoparticles of cobalt hydroxide as a novel adsorbent for dye and heavy metal decontamination from wastewater. The adsorbent fabrication involves the preparation of polystyrene via high-internal phase emulation (HIPE) polymerization followed by its intercalation with particles of alkali cobalt. The chemical composition and structural properties of the synthesized composite were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). Moreover, scanning electron microscopy (SEM) and N2 adsorption-desorption surface area analysis were performed to identify the surface and morphological characteristics of the composite. Then, the ability of this structure toward the removal of methylene blue dye (MB) and heavy metal (iron iii) species from waste aqueous solutions was investigated. Successful elimination for both MB and Fe(iii) was achieved by the presented composite. Elevated adsorption capacities of 75.2 and 112.3 mg g-1, toward MB and Fe(iii) respectively, were detected for the presented polymer-metal hydroxide composite. The increased values of the composite are attributed to the presence of both organic and inorganic functional groups within its structure. Kinetic and isotherm studies for the removal of both cationic species revealed that adsorption processes fit the pseudo-second-order kinetic model and Langmuir isotherm model. Additionally, thermodynamics measurements indicated that the adsorption process of methylene blue and Fe ions is feasible, spontaneous, physisorption, and endothermic.

CdO Decorated with Polypyrrole Nanotube Heterostructure: Potent Electrocatalyst for the Detection of Antihistamine Drug Promethazine Hydrochloride in Environmental Samples

In the realm of electrochemical sensor application, the development and fabrication of semiconducting metal oxides with the integration of conducting polymers for the trace-level detection of pharmaceutical medicines garnered considerable interest. Herein, we reported facile cadmium oxide decorated with polypyrrole nanotubes fabricated on a glassy carbon electrode (CdO@PPy/GCE) for efficient determination of antihistamine drug promethazine hydrochloride (PMH). The as-synthesized CdO@PPy composite was characterized by various analytical tools like X-ray powder diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, the electrocatalytic activity of the modified electrode for PMH detection was examined by voltammetry and amperometric methods, and the modified electrode exhibited lower charge transfer resistance compared to the bare GCE. Under the optimized condition, the fabricated electrode shows a wide linear range (50-550 μM), better sensitivity (0.13 μAμM-1 cm-2), low detection limit (10.83 nM) (S/N = 3), and excellent selectivity and reproducibility toward PMH detection. Moreover, the modified GCE depicted eminent practical ability for PMH detection in lake water and pharmaceutical tablets.

High-efficiency foam fractionation of anthocyanin from perilla leaves using surfactant-free active Al2O3 nanoparticle as collector and frother: Performance and mechanism

Anthocyanin (ACN) is a natural pigment with significant industrial applications. However, foam fractionation of ACN from perilla leaves extract presents theoretical challenges due to its limited surface activity and foaming capacity. This work developed a surfactant-free active Al₂O₃ nanoparticle (ANP) as a collector and frother, which was modified with adipic acid (AA). The ANP-AA efficiently collected ACN through the electrostatic interaction, condensation reaction, and hydrogen bonding, with a Langmuir maximum capacity of 129.62 mg/g. Moreover, ANP-AA could form a stable foam layer by irreversibly adsorbing on the gas-liquid interface, reducing surface tension, and alleviating liquid drainage. Under the appropriate conditions of ANP-AA 400 mg/L and pH 5.0, we achieved a high ACN recovery of 95.68% with an enrichment ratio of 29.87 after ultrasound-assisted extraction of ACN from perilla leaves. Additionally, the recovered ACN displayed promising antioxidant properties. These findings hold significant importance in the food, colorant, and pharmaceutical industries.

Green synthesize of nano-MOF-ethylcellulose composite fibers for efficient adsorption of Congo red from water

Two novel MOF- ethyl cellulose (EC)- based nanocomposites have been designed and synthesized in water by electrospinning and applied for adsorption of congo red (CR) in water. Nano- Zeolitic Imidazolate Framework-67 (ZIF-67), and Materials of Institute Lavoisier (MIL-88A) were synthesized in aqueous solutions by a green method. To enhance the dye adsorption capacity and stability of MOFs, they have been incorporated into EC nanofiber to prepare composite adsorbents. The performance of both composites in the absorption of CR, a common pollutant in some industrial wastewaters, has then been investigated. Various parameters including initial dye concentration, the dosage of the adsorbent, pH, temperature and contact time were optimized. The results indicated 99.8 and 90.9% adsorption of CR by EC/ZIF-67 and EC/MIL-88A, respectively at pH = 7 and temperature at 25 °C after 50 min. Furthermore, the synthesized composites were separated conveniently and successfully reused five times without significant loss of their adsorption activity. For both composites, the adsorption behavior can be explained by pseudo-second-order kinetics, Intraparticular diffiusion and Elovich models demonstrated that the experimental data well matched to the pseudo-second-order kinetics. Intraparticular diffiusion model showed that the adsorption of CR on EC/ZIF-67 and EC/MIL-88a took place in one and two steps, respectively. Freundlich isotherm models and thermodynamic analysis indicated exothermic and spontaneous adsorption.

Alkali-oxygen cooking coupled with ultrasonic etching for directly defibrillation of bagasse parenchyma cells into cellulose nanofibrils

A scheme combining alkali‑oxygen cooking and ultrasonic etching cleaning was developed for the short range preparation of CNF from bagasse pith, which has a soft tissue structure and is rich in parenchyma cells. This scheme expands the utilization path of sugar waste sucrose pulp. The effect of NaOH, O₂, macromolecular carbohydrates, and lignin on subsequent ultrasonic etching was analyzed, and it was found that the degree of alkali‑oxygen cooking was positively correlated with the difficulty of subsequent ultrasonic etching. The mechanism of ultrasonic nano-crystallization was found to be the bidirectional etching mode from the edge and surface cracks of the cell fragments by ultrasonic microjet in the microtopography of CNF. The optimum preparation scheme was obtained under the condition of 28 % NaOH content and 0.5 MPa O₂, which solves the problem of low-value utilization of bagasse pith and environmental pollution, providing a new possibility for the source of CNF.

Effective Adsorption and Removal of Doxorubicin from Aqueous Solutions Using Mesostructured Silica Nanospheres: Box-Behnken Design Optimization and Adsorption Performance Evaluation

The aim of this study is to evaluate the efficacy of mesoporous silica nanospheres as an adsorbent to remove doxorubicin (DOX) from aqueous solution. The surface and structural properties of mesoporous silica nanospheres were investigated using BET, SEM, XRD, TEM, ζ potential, and point of zero charge analysis. To optimize DOX removal from aqueous solution, a Box-Behnken surface statistical design (BBD) with four times factors, four levels, and response surface modeling (RSM) was used. A high amount of adsorptivity from DOX (804.84 mg/g) was successfully done under the following conditions: mesoporous silica nanospheres dose = 0.02 g/25 mL; pH = 6; shaking speed = 200 rpm; and adsorption time = 100 min. The study of isotherms demonstrated how well the Langmuir equation and the experimental data matched. According to thermodynamic characteristics, the adsorption of DOX on mesoporous silica nanospheres was endothermic and spontaneous. The increase in solution temperature also aided in the removal of DOX. The kinetic study showed that the model suited the pseudo-second-order. The suggested adsorption method could recycle mesoporous silica nanospheres five times, with a modest reduction in its ability for adsorption. The most important feature of our adsorbent is that it can be recycled five times without losing its efficiency.

Modified glucose as a sensor to track the metabolism of individual living endothelial cells - Observation of the 1602 cm−1 band called “Raman spectroscopic signature of life”

A relatively new approach to subcellular research is Raman microscopy with the application of sensors called Raman probes. This paper describes the use of the sensitive and specific Raman probe, 3-O-propargyl-d-glucose (3-OPG), to track metabolic changes in endothelial cells (ECs). ECs play a significant role in a healthy and dysfunctional state, the latter is correlated with a range of lifestyle diseases, particularly with cardiovascular disorders. The metabolism and glucose uptake may reflect the physiopathological conditions and cell activity correlated with energy utilization. To study metabolic changes at the subcellular level the glucose analogue, 3-OPG was used, which shows a characteristic and intense Raman band at 2124 cm^-1.3-OPG was applied as a sensor to track both, its accumulation in live and fixed ECs and then metabolism in normal and inflamed ECs, by employing two spectroscopic techniques, i.e. spontaneous and stimulated Raman scattering microscopies. The results indicate that 3-OPG is a sensitive sensor to follow glucose metabolism, manifested by the Raman band of 1602 cm^-1. The 1602 cm^-1 band has been called the "Raman spectroscopic signature of life" in the cell literature, and here we demonstrate that it is attributed to glucose metabolites. Additionally, we have shown that glucose metabolism and its uptake are slowed down in the cellular inflammation. We showed that Raman spectroscopy can be classified as metabolomics, and its uniqueness lies in the fact that it allows the analysis of the processes of a single living cell. Gaining further knowledge on metabolic changes in the endothelium, especially in pathological conditions, may help in identifying markers of cellular dysfunction, and more broadly in cell phenotyping, better understanding of the mechanism of disease development and searching for new treatments.

Enhanced Adsorption and Evaluation of Tetracycline Removal in an Aquatic System by Modified Silica Nanotubes

In the present study, a nanocomposite adsorbent based on mesoporous silica nanotubes (MSNTs) loaded with 3-aminopropyltriethoxysilane (3-APTES@MSNTs) was synthesized. The nanocomposite was employed as an effective adsorbent for the adsorption of tetracycline (TC) antibiotics from aqueous media. It has an 848.80 mg/g maximal TC adsorption capability. The structure and properties of 3-APTES@MSNT nanoadsorbent were detected by TEM, XRD, SEM, FTIR, and N₂ adsorption-desorption isotherms. The later analysis suggested that the 3-APTES@MSNT nanoadsorbent has abundant surface functional groups, effective pore size distribution, a larger pore volume, and a relatively higher surface area. Furthermore, the influence of key adsorption parameters, including ambient temperature, ionic strength, initial TC concentration, contact time, initial pH, coexisting ions, and adsorbent dosage, had also been investigated. The 3-APTES@MSNT nanoadsorbent's ability to adsorb the TC molecules was found to be more compatible with Langmuir isothermal and pseudo-second-order kinetic models. Moreover, research on temperature profiles pointed to the process' endothermic character. In combination with the characterization findings, it was logically concluded that the 3-APTES@MSNT nanoadsorbent's primary adsorption processes involved interaction, electrostatic interaction, hydrogen bonding interaction, and the pore-fling effect. The synthesized 3-APTES@MSNT nanoadsorbent has an interestingly high recyclability of >84.6 percent up to the fifth cycle. The 3-APTES@MSNT nanoadsorbent, therefore, showed promise for TC removal and environmental cleanup.

Efficient Removal of Ciprofloxacin from Contaminated Water via Polystyrene Anion Exchange Resin with Nanoconfined Zero-Valent Iron

Ciprofloxacin (CIP), an important emerging contaminant, has been frequently detected in water, and its efficient removal has become an issue of great concern. In this study, a nanocomposite material nZVI/PA was synthesized by impregnating nanoscale zero-valent iron (nZVI) inside a millimeter-sized porous host (polystyrene-based anion exchange resin (PA)) for CIP removal. The nZVI/PA composite was characterized by field emission scanning electron microscopy coupled with energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, as well as X-ray photoelectron spectroscopy, and it was confirmed that nZVI was uniformly dispersed in PA with a small particle size. Furthermore, several key factors were investigated including initial solution pH, initial CIP concentration, co-existing ions, organic ligands, and dissolved oxygen. The experimental results indicated that the nZVI/PA composites exhibited a high removal efficiency for CIP under the conditions of initial pH 5.0, and initial CIP concentration 50 mg L^-1 at 25 °C, with the maximum removal rate of CIP reaching 98.5%. Moreover, the nZVI/PA composites exhibited high efficiency even after five cycles. Furthermore, quenching tests and electron spin resonance (ESR) confirmed that CIP degradation was attributed to hydroxyl (·OH) and superoxide radicals (⋅O2-). Finally, the main degradation products of CIP were analyzed, and degradation pathways including the hydroxylation of the quinolone ring, the cleavage of the piperazine ring, and defluorination were proposed. These results are valuable for evaluating the practical application of nZVI/PA composites for the removal of CIP and other fluoroquinolone antibiotics.

Fe3O4-Halloysite Nanotube Composites as Sustainable Adsorbents: Efficiency in Ofloxacin Removal from Polluted Waters and Ecotoxicity

The present work aimed at decorating halloysite nanotubes (HNT) with magnetic Fe₃O₄ nanoparticles through different synthetic routes (co-precipitation, hydrothermal, and sol-gel) to test the efficiency of three magnetic composites (HNT/Fe₃O₄) to remove the antibiotic ofloxacin (OFL) from waters. The chemical-physical features of the obtained materials were characterized through the application of diverse techniques (XRPD, FT-IR spectroscopy, SEM, EDS, and TEM microscopy, thermogravimetric analysis, and magnetization measurements), while ecotoxicity was assessed through a standard test on the freshwater organism Daphnia magna. Independently of the synthesis procedure, the magnetic composites were successfully obtained. The Fe₃O₄ is nanometric (about 10 nm) and the weight percentage is sample-dependent. It decorates the HNT's surface and also forms aggregates linking the nanotubes in Fe₃O₄-rich samples. Thermodynamic and kinetic experiments showed different adsorption capacities of OFL, ranging from 23 to 45 mg g^-1. The kinetic process occurred within a few minutes, independently of the composite. The capability of the three HNT/Fe₃O₄ in removing the OFL was confirmed under realistic conditions, when OFL was added to tap, river, and effluent waters at µg L^-1 concentration. No acute toxicity of the composites was observed on freshwater organisms. Despite the good results obtained for all the composites, the sample by co-precipitation is the most performant as it: (i) is easily magnetically separated from the media after the use; (ii) does not undergo any degradation after three adsorption cycles; (iii) is synthetized through a low-cost procedure. These features make this material an excellent candidate for removal of OFL from water.

On As(III) Adsorption Characteristics of Innovative Magnetite Graphene Oxide Chitosan Microsphere

A magnetite graphene oxide chitosan (MGOCS) composite microsphere was specifically prepared to efficiently adsorb As(III) from aqueous solutions. The characterization analysis of BET, XRD, VSM, TG, FTIR, XPS, and SEM-EDS was used to identify the characteristics and adsorption mechanism. Batch experiments were carried out to determine the effects of the operational parameters and to evaluate the adsorption kinetic and equilibrium isotherm. The results show that the MGOCS composite microsphere with a particle size of about 1.5 mm can be prepared by a straightforward method of dropping FeCl2, graphene oxide (GO), and chitosan (CS) mixtures into NaOH solutions and then drying the mixed solutions at 45 °C. The produced MGOCS had a strong thermal stability with a mass loss of <30% below 620 °C. The specific surface area and saturation magnetization of the produced MGOCS was 66.85 m2/g and 24.35 emu/g, respectively. The As(III) adsorption capacity (Qe) and removal efficiency (Re) was only 0.25 mg/g and 5.81% for GOCS, respectively. After 0.08 mol of Fe3O4 modification, more than 53% of As(III) was efficiently removed by the formed MGOCS from aqueous solutions over a wide pH range of 5−10, and this was almost unaffected by temperature. The coexisting ion of PO43− decreased Qe from 3.81 mg/g to 1.32 mg/g, but Mn2+ increased Qe from 3.50 mg/g to 4.19 mg/g. The As(III) adsorption fitted the best to the pseudo-second-order kinetic model, and the maximum Qe was 20.72 mg/g as fitted by the Sips model. After four times regeneration, the Re value of As(III) slightly decreased from 76.2% to 73.8%, and no secondary pollution of Fe happened. Chemisorption is the major mechanism for As(III) adsorption, and As(III) was adsorbed on the surface and interior of the MGOCS, while the adsorbed As(III) was partially oxidized to As(V) accompanied by the reduction of Fe(III) to Fe(II). The produced As(V) was further adsorbed through ligand exchange (by forming Fe−O−As complexes) and electrostatic attraction, enhancing the As(III) removal. As an easily prepared and environmental-friendly composite, MGOCS not only greatly adsorbs As(III) but also effectively removes Cr(VI) and As(V) (Re > 60%) and other metals, showing a great advantage in the treatment of heavy metal-contaminated water.

Sargassum fusiforme Polysaccharide-Based Hydrogel Microspheres Enhance Crystal Violet Dye Adsorption Properties

In this study, a polysaccharide-based hydrogel microsphere (SFP/SA) was prepared using S. fusiforme polysaccharide (SFP) and sodium alginate (SA). Fourier transform infrared spectroscopy (FT-IR) demonstrated that SFP was effectively loaded onto the hydrogel microsphere. Texture profile analysis (TPA) and differential scanning calorimetry (DSC) showed that, with the increase of SFP concentration, the hardness of SFP/SA decreased, while the springiness and cohesiveness of SFP/SA increased, and the thermal stability of SFP/SA improved. The equilibrium adsorption capacity of SFP/SA increased from 8.20 mg/g (without SFP) to 67.95 mg/g (SFP accounted 80%) without swelling, and from 35.05 mg/g (without SFP) to 81.98 mg/g (SFP accounted 80%) after 24 h swelling. The adsorption of crystal violet (CV) dye by SFP/SA followed pseudo-first order and pseudo-second order kinetics (both with R2 > 0.99). The diffusion of intraparticle in CV dye was not the only influencing factor. Moreover, the adsorption of CV dye for SFP/SA (SFP accounted 60%) fit the Langmuir and Temkin isotherm models. SFP/SA exhibited good regenerative adsorption capacity. Its adsorption rate remained at > 97% at the 10th consecutive cycle while SFP accounted for 80%. The results showed that the addition of Sargassum fusiforme polysaccharide could increase the springiness, cohesiveness and thermal stability of the hydrogel microsphere, as well as improve the adsorption capacity of crystal violet dye.

Anionic Dye Removal Using a Date Palm Seed-Derived Activated Carbon/Chitosan Polymer Microbead Biocomposite

The discharge of textile wastewater into aquatic streams is considered a major challenge due to its effect on the water ecosystem. Direct blue 78 (DB78) dye has a complex structure. Therefore, it is difficult to separate it from industrial wastewater. In this study, carbon obtained from the pyrolysis of mixed palm seeds under different temperatures (400 °C and 1000 °C) was activated by a thermochemical method by using microwave radiation and an HCl solution in order to improve its adsorption characteristics. The generated activated carbon was used to synthesize a novel activated carbon/chitosan microbead (ACMB) for dye removal from textile wastewater. The obtained activated carbon (AC) was characterized by a physicochemical analysis that included, namely, particle size, zeta potential, SEM, EDX, and FTIR analyses. A series of batch experiments were conducted in terms of the ACMB dose, contact time, pH, and activated carbon/chitosan ratios in synthetic microbeads for enhancing the adsorption capacity. A remarkable improvement in the surface roughness was observed using SEM analysis. The particle surface was transformed from a slick surface with a minor-pore structure to a rough surface with major-pore structure. The zeta potential analysis indicated a higher improvement in the carbon surface charge, from -35 mv (before activation) to +20 mv (after activation). The adsorption tests showed that the dye-removal efficiency increased with the increasing adsorbent concentration. The maximum removal efficiencies were 97.8% and 98.4% using 3 and 4 g/L of AC_400°C MB-0.3:1 and AC_1000°C MB-0.3:1, respectively, with initial dye concentrations of 40 mg/L under acidic conditions (pH = 4-5), and an optimal mixing time of 50 min. The equilibrium studies for AC_400°C MB-0.3:1 and AC_1000°C MB-0.3:1 showed that the equilibrium data best fitted to the Langmuir isothermal model with R² = 0.99. These results reveal that activated carbon/chitosan microbeads are an effective adsorbent for the removal of direct blue 78 dye and provide a new platform for dye removal.

A Review of the Techno-Economic Feasibility of Nanoparticle Application for Wastewater Treatment

The increase in heavy metal contamination has led to an increase in studies investigating alternative sustainable ways to treat heavy metals. Nanotechnology has been shown to be an environmentally friendly technology for treating heavy metals and other contaminants from contaminated water. However, this technology is not widely used in wastewater treatment plants (WWTPs) due to high operational costs. The increasing interest in reducing costs by applying nanotechnology in wastewater treatment has resulted in an increase in studies investigating sustainable ways of producing nanoparticles. Certain researchers have suggested that sustainable and cheap raw materials must be used for the production of cheaper nanoparticles. This has led to an increase in studies investigating the production of nanoparticles from plant materials. Additionally, production of nanoparticles through biological methods has also been recognized as a promising, cost-effective method of producing nanoparticles. Some studies have shown that the recycling of nanoparticles can potentially reduce the costs of using freshly produced nanoparticles. This review evaluates the economic impact of these new developments on nanotechnology in wastewater treatment. An in-depth market assessment of nanoparticle application and the economic feasibility of nanoparticle applications in WWTPs is presented. Moreover, the challenges and opportunities of using nanoparticles for heavy metal removal are also discussed.

Chemically modified sugarcane bagasse-based biocomposites for efficient removal of acid red 1 dye: Kinetics, isotherms, thermodynamics, and desorption studies

Novel eco-friendly and economically favourable chemically modified biosorbents and biosomposites from sugarcane bagasse (SB) has been investigated for the first time for efficient removal of Acid red 1 dye from wastewater. As fabricated biosorbents and biocomposites were characterized analytically. Batch adsorption experiments has been performed to optimize operating parameters and the determined optimum conditions are; pH: 2, dose: 0.05 g, contact time: between 60 and 75 min, initial dye concentration: 400 mg L^-1, and temperature: 30 °C, at which maximum Acid red 1 dye removal capacities were found (within range of 143.4-205.1 mg g^-1) by as-designed SB-derived chemically modified biosorbents and biocomposites. This high adsorption capacity was accompanied due to its large specific surface area (30.19 m² g^-1) and excessive functional active binding sites. In terms of the nature of adsorption process, kinetic and isothermal studies demonstrated that experimental data shows greater fitness with pseudo 2nd order and Langmuir model. Thermodynamics analysis revealed that the adsorption process is spontaneous, feasible, and exothermic in nature. Adsorption selective studies signifies that lower concentration of co-existing metallic ions were not interfered during the removal of Acid red 1 dye, which confirms that under optimized adsorption conditions the biosorbents and biocomposites exhibited greater affinity for dye molecules. The excessive quantity (82%) of loaded dye molecules within the adsorbents were extracted within the NaOH eluting media which predicts that as designed biocomposites could have capability of reusability. Hence, it is anticipated that this type of novel SB-derived biocomposites could be considered as greener potential candidate material for commercial scale dye removal applications from industrial wastewater.

Preparation of magnetic chitosan corn straw biochar and its application in adsorption of amaranth dye in aqueous solution

In this study, the magnetic chitosan biochar (MCB) was magnetized by chemical coprecipitation after loading chitosan with Schiff base reaction. The prepared MCB was used to remove amaranth dye in solution. The synthesized MCB was characterized to define its surface morphology and specific elements. The amaranth dye adsorption system was optimized by varying the contact time, pH, and initial concentration. The adsorption of MCB on amaranth dye was measured in a wide pH range. According to Zeta potential, the surface of MCB was positively charged in the acidic pH region, which was more conducive to the adsorption of anionic amaranth dye. In addition, the adsorption data was fitted with the pseudo-first-order model and Langmuir adsorption model and the maximum adsorption capacity reached 404.18 mg/g. The adsorption efficiency of MCB was still above 95% after three cycles of adsorption and desorption. The removal percentage in the real sample of amaranth dye by MCB was within 94.5-98.6% and the RSD was within 0.14-1.08%. The MCB adsorbent with advantages of being easy to prepare, easy to separate from solution after adsorption, has good adsorption performance for amaranth dye and is effective potential adsorbent to remove organic anionic dye in wastewater.