Synthesis, characterization and adsorption studies of amino functionalized silica nano hollow sphere as an efficient adsorbent for removal of imidacloprid pesticide

Covalent organic framework-functionalized magnetic MXene nanocomposite for efficient pre-concentration and detection of organophosphorus and organochlorine pesticides in tea samples before gas chromatography-triple quadrupole mass spectrometry analysis

In this study, a hydrophobic covalent organic framework-functionalized magnetic composite (CoFe2O4@Ti3C2@TAPB-TFTA) with a high specific area with 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,3,5,6-tetrafluoroterephthalaldehyde (TFTA) was designed and synthesized through Schiff base reaction. An efficient magnetic solid-phase extraction method was established and combined with gas chromatography-triple quadrupole mass spectrometry to sensitively determine 10 organochlorine and organophosphorus pesticides in tea samples. The established method exhibited good linearity in the range of 0.05-120 μg/L and had low limits of detection (0.013-0.018 μg/L). The method was evaluated with tea samples, and the spiked recoveries of pesticides in different tea samples reached satisfactory values of 85.7-96.8%. Moreover, the adsorption of pesticides was spontaneous and followed Redlich-Peterson isotherm and pseudo-second-order kinetic models. These results demonstrate the sensitivity, effectiveness, and reliability of the proposed method for monitoring organochlorine and organophosphorus pesticides in tea samples, providing a preliminary basis for researchers to reasonably design adsorbents for the efficient extraction of pesticides.

Imidacloprid removal by modified graphitic biochar with Fe/Zn bimetallic oxides

Coping with the critical challenge of imidacloprid (IMI) contamination in sewage treatment and farmland drainage purification, this study presents a pioneering development of an advanced modified graphitic white melon seed shells biochar (Fe/Zn@WBC). The Fe/Zn@WBC demonstrates a substantial enhancement in adsorption efficiency for IMI, achieving a remarkable removal rate of 87.69% within 30 min and a significantly higher initial adsorption rate parameter h = 4.176 mg g-1·min-1. This significant improvement outperforms WBC (12.22%, h = 0.115 mg g-1·min-1) and highlights the influence of optimized adsorption conditions at 900 °C and the graphitization degree resulting from Fe/Zn bimetallic oxide modification. Characterization analysis and batch sorption experiments including kinetics, isotherms, thermodynamics and pH factors illustrate that chemical adsorption is the main type of adsorption mechanism responsible for this superior ability to remove IMI through pore filling, hydrogen bonding, hydrophobic interaction, electrostatics interaction, π-π interactions as well as complexation processes. Furthermore, we demonstrate exceptional stability of Fe/Zn@WBC across a broad pH range (pH = 3-11), co-existing ions presence along with humic acid under various real water conditions while maintaining high removal efficiency. This study presents an advanced biochar adsorbent, Fe/Zn@WBC, with efficient adsorption capacity and easy preparation. Through three regeneration cycles via pyrolysis method, it demonstrates excellent pyrolysis regeneration capabilities with an average removal efficiency of 92.02%. The magnetic properties enable rapid separation facilitated by magnetic analysis. By elucidating the efficacy and mechanistic foundations of Fe/Zn@WBC, this research significantly contributes to the field of environmental remediation by providing a scalable solution for IMI removal and enhancing scientific understanding of bimetallic oxides-hydrophilic organic pollutant interactions.

Mesoporous silica nanospheres-mediated insecticide and antibiotics co-delivery system for synergizing insecticidal toxicity and reducing environmental risk of insecticide

Mesoporous silica nanoparticles (MSNs) are efficient carriers of drugs, and are promising in developing novel pesticide formulations. The cotton aphids Aphis gossypii Glover is a world devastating insect pest. It has evolved high level resistance to various insecticides thus resulted in the application of higher doses of insecticides, which raised environmental risk. In this study, the MSNs based pesticide/antibiotic delivery system was constructed for co-delivery of ampicillin (Amp) and imidacloprid (IMI). The IMI@Amp@MSNs complexes have improved toxicity against cotton aphids, and reduced acute toxicity to zebrafish. From the 16S rDNA sequencing results, Amp@MSNs, prepared by loading ampicillin to the mesoporous of MSNs, greatly disturbed the gut community of cotton aphids. Then, the relative expression of at least 25 cytochrome P450 genes of A. gossypii was significantly suppressed, including CYP6CY19 and CYP6CY22, which were found to be associated with imidacloprid resistance by RNAi. The bioassay results indicated that the synergy ratio of ampicillin to imidacloprid was 1.6, while Amp@MSNs improved the toxicity of imidacloprid by 2.4-fold. In addition, IMI@Amp@MSNs significantly improved the penetration of imidacloprid, and contributed to the amount of imidacloprid delivered to A. gossypii increased 1.4-fold. Thus, through inhibiting the relative expression of cytochrome P450 genes and improving penetration of imidacloprid, the toxicity of IMI@Amp@MSNs was 6.0-fold higher than that of imidacloprid. The greenhouse experiments further demonstrated the enhanced insecticidal activity of IMI@Amp@MSNs to A. gossypii. Meanwhile, the LC50 of IMI@Amp@MSNs to zebrafish was 3.9-fold higher than that of IMI, and the EC50 for malformation was 2.8-fold higher than IMI, respectively, which indicated that the IMI@Amp@MSNs complexes significantly reduced the environmental risk of imidacloprid. These findings encouraged the development of pesticide/antibiotic co-delivery nanoparticles, which would benefit pesticide reduction and environmental safety.

Optimizing the algae-bacteria biofilm reactor for imidacloprid wastewater treatment: An evaluation of hydraulic retention times for enhanced efficiency and energy savings

Recent observations have highlighted the rapidly growing prevalence of emerging contaminants such as Imidacloprid (IMI) within our environment. These insecticidal pollutants, coexisting with more traditional contaminants, have become predominant in aquatic systems, posing risks to both human and ecological well-being. Among the various wastewater treatment approaches tested, biofilm reactors are currently gaining prominence. In this study, we employed an Algae-Bacteria Biofilm Reactor (ABBR) to concurrently address both conventional and emergent contaminants, specifically IMI, over an extended timeframe. Following a 60-day assessment, the ABBR consistently demonstrated removal efficiencies exceeding 85% for total dissolved nitrogen, ammonia nitrogen, and total dissolved phosphorus, and also achieved removal efficacy for the soluble chemical oxygen demand (sCOD). Despite the removal efficiency of IMI (with initial concentration is 1.0 mg/L) in ABBR showed a gradual decline over the extended period, it remained consistently effective over 50% due to the microalgae-mediated free radical reactions, indicating the ABBR's sustained efficiency in long-duration operations. Additionally, applying some non-conventional modifications, like aeration removal and reducing light exposure, demonstrated minimal impact on the reactor's pollutant removal efficiencies, achieving comparable results to the control group (which utilized aeration with a 14:10 light/dark ratio), 0.92 kW h/L/d of electricity can be saved economically, which accentuated the potential for energy conservation. An in-depth analysis of the treated effluents from the ABBRs, using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technique, uncovered four potential transformation pathways for IMI. Overall, our findings suggest that these optimized processes did not influence the transformation products of IMI, thereby reaffirming the viability of our proposed optimization.

Novel hydrophilic straw biochar for the adsorption of neonicotinoids: kinetics, thermodynamics, influencing factors, and reuse performance

Nitenpyram (NIT) is the most water-soluble neonicotinoid (NEO). It has been shown to pose a serious threat to human health and the environment but was always ignored due to its limited market share. There were few experts who studied NIT's transport behavior on biochar. In this study, two types of biochar were co-activated separately using zinc chloride combined with phosphoric acid and potassium hydroxide combined with acetic acid, marked as ZBC and KBC. Characterizations suggested that hydrophilic ZBC and KBC had more surface functional groups than unmodified biochar (BC), and specific surface areas of ZBC (456.406 m²·g^-1) and KBC (750.588 m²·g^-1) were significantly higher than of BC (67.181 m²·g^-1). The pore structures of KBC and ZBC were hierarchical porous structures with different pore sizes and typical microporous structure, respectively. The adsorption performance of either NIT or IMI on KBC was better than that on ZBC. Only 0.4 g·L^-1 of KBC can absorb 89.62% of NIT in just 5 min. The equilibrium adsorption amounts of NIT on ZBC and KBC were 17.995 mg·g^-1 and 82.910 mg·g^-1. Elovich and Langmuir models were used to evaluate the whole adsorption process, which was attributed to the chemisorption mechanism. In addition, removal rates of NIT were negatively correlated to NIT's initial concentration and positively correlated to the dose of biochar. pH had almost no effect on adsorption, but the presence of salt ions can inhibit the removal of NIT. Long-term stabilities of biochars were also acceptable. These findings will promote the development in the preparation of biochar fields and provide a positive reference value for NEO removal.

Various hydrogen bonds make different fates of pharmaceutical contaminants on oxygen-rich nanomaterials

Various hydrogen bonds, especially charge-assisted hydrogen bond (CAHB), is considered as one of vital mechanisms affecting the environmental behavior and risk of pharmaceutical contaminants (PCs). Herein the sorption/desorption of three PCs including clofibric acid (CA), acetaminophen (ACT), and sulfamerazine (SMZ) on three Oxygen-rich (O-rich) nanoparticles (nano-silica: Nano-SiO₂, nano-alumina: Nano-Al₂O₃, and oxidized carbon nanotubes: O-CNTs) were investigated to explore the effect of various hydrogen bonds with different strengths on environmental behaviors of PCs. The results indicated that although solvent-assisted CAHB, solvent-uninvolved CAHB, and ordinary hydrogen bond (OHB) all played a crucial role in sorption of PCs on three O-rich nanomaterials, they showed significantly different effects on the desorption behaviors of PCs from three sorbents. Compared with OHB (hysteresis index ≤0.0766), the stronger CAHB (hysteresis index ≥0.1981) between PCs and O-rich nanoparticles having comparable pK_a with PCs, caused obvious desorption hysteresis of PCs, resulting in their better immobilization on O-rich nanomaterials. The FTIR characterization found that both solvent-assisted and solvent-uninvolved CAHB formation resulted in a new characteristic peak appeared in the high frequency (3660 cm^-1 for Nano-SiO₂, 3730 cm^-1 for Nano-Al₂O₃, and 3780 cm^-1 for O-CNTs). Also, density functional theory (DFT) calculation verified that the smaller |ΔpK_a| between PCs and O-rich sorbents, the shorter bond length, and the larger bond angle resulted in the stronger hydrogen bond formed, thereby leading to the greater immobilization of PCs. These results provide in-depth understanding of the environmental behavior and risk of PCs, and light new idea for designed materials to control PCs pollution in the environment.

Iron-modified biochar derived from sugarcane bagasse for adequate removal of aqueous imidacloprid: sorption mechanism study

Adsorption has been considered as a promising remediation technology to separate organic and inorganic agrochemicals from contaminated soil and water. Low-cost adsorbents, including waste derived materials, clay composites, biochar, and biochar modified materials, have attracted enormous attention for the removal of organic contaminants, including pesticides. In this study, iron-modified base-activated biochar (FeBBC) was prepared by pyrolysis (at 400 °C for 1 h) of iron-doped base (KOH) activated sugarcane bagasse for the removal of a widely used insecticide, namely imidacloprid (IMI) from water. The maximum adsorption capacity of the adsorbent (FeBBC) was calculated as 10.33 (± 1.57) mg/g from Langmuir isotherm model. The adsorbents could remove up to ~ 92% of IMI from aqueous solution at 23.8 mg/L IMI. Experimental data fitted well with the Freundlich model and pseudo-second-order model, demonstrating physisorption, as well as chemosorption, contributed to the sorption process. Even at highly acidic/basic solution pH, the FeBBC could remove substantial amount of IMI demonstrating hydrophobic interaction and pore diffusion play vital role for removal of IMI. The slight improving of IMI sorption with increasing solution pH indicated the sorption was also facilitated through ionic interaction alongside physical sorption. However, physical sorption including hydrophobic interaction and pore-filling interaction plays a vital role in the sorption of IMI.

Synthesis and application of a carbon composite containing molecularly imprinted poly(methacrylic acid) for efficient removal of fenpyroximate pesticide

This work describes fabrication steps of the carbon composite based on molecular imprinted poly(methacrylic acid) (MIP-CC) as a new adsorbent for the selective removal of fenpiroxymate pesticide (Fen). The prepared composite was characterized using Brunauer-Emmett-Teller (BET), zeta sizer and Field Emission Scanning Electron Microscopy (FESEM) techniques. The influence of operational parameters such as solution pH, contact time, amount MIP for preparation of carbon composite and amount MIP- CC toward removal of Fen have been evaluated and optimized via central composite design (CCD) as an optimization tool of response surface method. The optimum removal (87%) was achieved at pH 6.5, 1.53 g/L carbon composite prepared with 3.4 wt % MIP at 70 min. The maximum adsorption of Fen by the fabricated MIP-CC was 254 mg/g. Compared with the corresponding non-imprinted polymer (NIP-CC), the MIP-CC exhibited higher adsorption capacity and outstanding selectivity toward Fen. Langmuir isotherm best fitted the adsorption equilibrium data of MIP-CC and the kinetics followed a pseudo-second-order model. The calculated thermodynamic parameters showed that adsorption of Fen pesticide was spontaneous and exothermic under the studied conditions.

Efficient removal of Imidacloprid and nutrients by algae-bacteria biofilm reactor (ABBR) in municipal wastewater: Performance, mechanisms and the importance of illumination

Neonicotinoids, such as Imidacloprid (IMI), are frequently detected in water and wastewater, posing a threat on both the environment and the health of living things. In this work, a novel algae-bacteria biofilm reactor (ABBR) was constructed to remove IMI and conventional nutrients from municipal wastewater, aiming to explore the removal effect and advantage of ABBR. Results showed that ABBR achieved 74.9% removal of IMI under 80 μmol m^-2·s^-1 light, higher than photobioreactor (PBR) without biofilm (61.2%) or ABBR under 40 μmol m^-2·s^-1 light (48.4%) after 16 days of operation. Moreover, it also showed that ABBR allowed a marked improvement on the removal of total dissolved nitrogen (TDN), total dissolved phosphorus (TDP) and soluble chemical oxygen demand (sCOD). ABBR showed different IMI removal efficiencies and bacterial communities under different light conditions, indicating that light played an important role in driving ABBR. The merits of ABBR are including (i) ABBR showed rapid pollutant removal in a short time, (ii) in ABBR, stable consortiums were formed and chlorophyll content in effluent was very low, (iii) compared with PBR, degradation products in ABBR showed lower biological toxicity. Our study highlights the benefits of ABBR on IMI removing from municipal wastewater and provides an effective and environment-friendly engineering application potential of IMI removal.

Emerging Trends in the Remediation of Persistent Organic Pollutants Using Nanomaterials and Related Processes: A Review

Persistent organic pollutants (POPs) have become a major global concern due to their large amount of utilization every year and their calcitrant nature. Due to their continuous utilization and calcitrant nature, it has led to several environmental hazards. The conventional approaches are expensive, less efficient, laborious, time-consuming, and expensive. Therefore, here in this review the authors suggest the shortcomings of conventional techniques by using nanoparticles and nanotechnology. Nanotechnology has shown immense potential for the remediation of such POPs within a short period of time with high efficiency. The present review highlights the use of nanoremediation technologies for the removal of POPs with a special focus on nanocatalysis, nanofiltration, and nanoadsorption processes. Nanoparticles such as clays, zinc oxide, iron oxide, aluminum oxide, and their composites have been used widely for the efficient remediation of POPs. Moreover, filtrations such as nanofiltration and ultrafiltration have also shown interest in the remediation of POPs from wastewater. From several pieces of literature, it has been found that nano-based techniques have shown complete removal of POPs from wastewater in comparison to conventional methods, but the cost is one of the major issues when it comes to nano- and ultrafiltration. Future research in nano-based techniques for POP remediation will solve the cost issue and will make it one of the most widely accepted and available techniques. Nano-based processes provide a sustainable solution to the problem of POPs.

Adsorption isotherm models: A comprehensive and systematic review (2010-2020)

Among numerous methods developed in purification and separation industries, the adsorption process has received considerable attention due to its inexpensive, facile, and eco-friendly nature. The importance of the adsorption process causes extraordinary endeavors for modeling the adsorption isotherms during the years; thus, myriads of research have been conducted and many reviews have been published. In this paper, we have attempted to gather the most widely used adsorption isotherms and their related definitions, along with examples of correlated work of the recent decade. In the present review, 37 adsorption isotherms with about 400 references have been collected from the research published in the period of 2010-2020. The adsorption isotherms utilized are alphabetically organized for ease of access. The parameters of each isotherm, as well as the applicable definitions, are presented in the table, in addition to being discussed in the text. Another table is provided for the practical use of researchers, featuring the usage of the related isotherms in peer-reviewed studies.

Visible-light-assisted peroxymonosulfate activation by metal-free bifunctional oxygen-doped graphitic carbon nitride for enhanced degradation of imidacloprid: Role of non-photochemical and photocatalytic activation pathway

Bifunctional oxygen-doped graphitic carbon nitride (OCN) was fabricated to activate peroxymonosulfate (PMS) for degrading imidacloprid (IMD). The modulated electronic structure of OCN promoted the adsorption, electron transfer, and formation of the redox site of PMS. The light absorption capacity, and the separation and migration speed of photogenerated carriers of OCN were increased. Consequently, 94.5% of IMD (3.0 mg/L) was removed by OCN-10/PMS process in 2.0 h. Compared with g-C₃N₄/PMS (0.048 h^-1), the IMD degradation rate constant of OCN-10/Vis/PMS system (1.501 h^-1) was increased by 30.3 times. The PMS oxidation on electron-deficient C atoms and holes, the PMS reduction around electron-rich O atoms and photogenerated electrons, and the multiple reactions of superoxide radical were the sources of the main active species singlet oxygen. Moreover, even under different pH conditions, coexisting anions, humic acid, and other neonicotinoid pesticides, the OCN-10/Vis/PMS system still showed acceptable applicability. Finally, mass spectrometry identified that hydroxylation and N-dealkylation of amines were the primary degradation pathways of IMD. This paper demonstrates an environmental-friendly combined activation strategy of PMS that can be operated day and night with low energy consumption, aiming to pave the way for developing metal-free photocatalysts for high-efficient environmental purification based on advanced oxidation coupling technology.

Application of chitosan-alginate bio composite for adsorption of malathion from wastewater: Characterization and response surface methodology

Agricultural effluents in aqueous media have caused serious threats due to adversely affect human health and the ecosystem. In this study, the low-cost easily accessible chitosan-alginate adsorbent was prepared for the removal of malathion from agricultural effluents using microemulsion method. The adsorbent was characterized using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The optimum experimental conditions, including adsorbent dosage (0.05-0.25 g), contact time (5-25 min), and concentration of malathion (5-25 mg L^-1) at five levels were studied using the composite central design (CCD) based on the response surface methodology (RSM). The highest removal percentage was obtained 82.35 with an adsorbent dosage of 0.18 g, contact time of 20 min, and initial concentration of 10 mg L^-1. The analysis of variance (ANOVA) was applied to assess the significance and adequacy of the model. The results revealed that quadratic model was proper for the prediction removal of malathion. The adsorption kinetics and isotherms were examined under optimal conditions. The Langmuir with a coefficient of determination (R²) = 0.99 and pseudo-second-order with R² = 0.99 were achieved as the best isotherm and kinetic models, respectively. The results showed that the chitosan-alginate biopolymer can be effective and affordable adsorbent for the removal of malathion from aqueous solution.

A Water-Soluble Schiff Base Turn-on Fluorescent Chemosensor for the Detection of Al3+ and Zn2+ Ions at the Nanomolar Level: Application in Live-Cell Imaging

A water-soluble Schiff base, 2,3-bis((E)-(2-hydroxy-3-methoxybenzylidene)amino) propanoic acid (ODA) prepared by condensing o-vanillin and DL-2,3-diaminopropionic acid was evaluated as an efficient "turn on" fluorescent chemosensor for the selective recognition of Al3+ and Zn2+ ions in presence of several interfering metal ions (detection limit; for Al3+ = 1.82 nM, Zn2+ = 7.06 nM). The probe also shows a selective chromogenic behavior towards Al3+ and Zn2+ ions that the naked eye can view. The binding stoichiometry was determined using 1H-NMR titration and ESI-MS spectrometry. The sensing mechanism is due to the inhibition of ESIPT and isomerization of -C=N of ODA on complexation with Al3+/Zn2+. The intramolecular hydrogen bonding energy and the critical bond energy in ODA-Al3+/Zn2+ were calculated using QTAIM analysis. The Thin Layer Chromatography (TLC) plates and strip papers loaded with ODA were used to test the practical applications for sensing Al3+ and Zn2+ ions. Moreover, the probe has been used for live-cell imaging to detect Al3+ and Zn2+ ions in hepatoma C3A and human glioblastoma U87 cells.

Multiple Roles of Mesoporous Silica in Safe Pesticide Application by Nanotechnology: A Review

Pollution related to pesticides has become a global problem due to their low utilization and non-targeting application, and nanotechnology has shown great potential in promoting sustainable agriculture. Nowadays, mesoporous silica-based nanomaterials have garnered immense attention for improving the efficacy and safety of pesticides due to their distinctive advantages of low toxicity, high thermal and chemical stability, and particularly size tunability and versatile functionality. Based on the introduction of the structure and synthesis of different types of mesoporous silica nanoparticles (MSNs), the multiple roles of mesoporous silica in safe pesticide application using nanotechnology are discussed in this Review: (i) as nanocarrier for sustained/controlled delivery of pesticides, (ii) as adsorbent for enrichment or removal of pesticides in aqueous media, (iii) as support of catalysts for degradation of pesticide contaminants, and (iv) as support of sensors for detection of pesticides. Several scientific issues, strategies, and mechanisms regarding the application of MSNs in the pesticide field are presented, with their future directions discussed in terms of their environmental risk assessment, in-depth mechanism exploration, and cost-benefit consideration for their continuous development. This Review will provide critical information to related researchers and may open up their minds to develop new advances in pesticide application.

CaFu MOF as an efficient adsorbent for simultaneous removal of imidacloprid pesticide and cadmium ions from wastewater

Heavy metal ions and pesticides are the noteworthy toxic substances which must be removed from contaminated water for safeguarding public health. The higher levels of these substances in natural water may adversely affect the human health, climate and the eco-framework. The adsorptive removal of hazardous constituents employing metal organic frameworks has drawn considerable attention of researchers during the last decade. From this point of view, single crystal of calcium fumarate [Ca(C₄H₄O₄)_1.5 (H₂O)(CH₃OH)₂] has been developed and analyzed by single crystal X-ray crystallography which confirmed the formation of 3-D metal organic frameworks (MOFs). The synthesized MOFs was employed for simultaneous adsorptive removal of imidacloprid, a high consumption pesticide, and highly toxic Cd (II) from aqua ecosystem. The effect of variation in experimental conditions such as solution pH, adsorbent dosage, contact time, initial concentration and temperature on adsorption was systematically evaluated. Both the imidacloprid and Cd(II) exhibited maximum adsorption at pH 6.5 and 7.8, respectively. The equilibrium empirical data was fitted into Langmuir, Freundlich and Temkin isotherms. The adsorption capacity of CaFu MOFs was observed to be 467.23 and 781.2 mg g^-1 for imidacloprid and cadmium ions, respectively. The adsorbed pollutants were desorbed from the adsorbent using dilute HCl, and the material was reused for five adsorption-desorption cycles without any appreciable loss of adsorption capacity. Therefore, the 3-D CaFu MOFs could be utilized as a novel material for adsorptive removal of imidacloprid pesticide as well as Cd (II) from wastewater.

Highly efficient removal of imidacloprid using potassium hydroxide activated magnetic microporous loofah sponge biochar

Extensive application of imidacloprid (IMI) in pest control and its undesirable removal efficiency enabled it to be a critical global challenge. Low cost, efficient, sustainable and environment-friendly technologies are urgently needed to be developed to remove IMI from water. A novel adsorbent of potassium hydroxide activated magnetic microporous loofah sponge biochar (KOH+Fe/Zn-LBC) was synthesized, as well as its adsorption capacity and mechanisms for IMI were investigated in this study. KOH+Fe/Zn-LBC had the superior pore structure (surface area and pore volume) and its maximum adsorption capacity for IMI could reach 738 mg g^-1 at 298 K. Kinetics, isotherms, thermodynamics and characterization analysis suggested that pore filling, hydrogen bonding and π-π conjugation were its main adsorption mechanisms. Additionally, the thermodynamic parameters described that IMI adsorption was a spontaneous, endothermic and less random process. Particularly, the magnetic separation of KOH+Fe/Zn-LBC was beneficial for its reuse. Ultrasound and ethanol co-processing could effectively regenerate the used KOH+Fe/Zn-LBC and maintain its stable sustainable adsorption capacity (99.4% of its fresh adsorption capacity after five reuse cycles). Besides, KOH+Fe/Zn-LBC exhibited a stable adsorption capacity and environmental safety in a wide pH range. Therefore, KOH+Fe/Zn-LBC has the potential to be an efficient, green and sustainable adsorbent for neonicotinoids removal.

A novel, efficient and sustainable magnetic sludge biochar modified by graphene oxide for environmental concentration imidacloprid removal

Environmental concentration imidacloprid (IMI) has become a potential risk to ecological safety and human health, therefore an efficient, sustainable and environment friendly approach was urgently needed for its removal. In this study, a novel graphene oxide supported magnetic sludge biochar composite (GO/CoFe₂O₄-SBC) was first time synthesized and assessed for IMI removal at environmental concentration level. The maximum adsorption capacity of GO/CoFe₂O₄-SBC for IMI was 8.64 × 10³ μg g^-1. Physicochemical characteristics, kinetics (pseudo-second-order), isotherms (Freundlich and Temkin), thermodynamics and environmental factors analysis suggested that its outstanding adsorption performance was mainly attributed to pore filling, π-π conjugation and functional groups interaction. The mechanisms analysis indicated that intraparticle diffusion was the main rate-limiting step and its adsorption was a spontaneous, endothermic and randomness increased process. The magnetic sensitivity enabled it to be easily separated from water. The sustainable adsorption capacity (>90% of the initial adsorption capacity) of GO/CoFe₂O₄-SBC was well maintained by ethanol extraction even after five reuse cycles. GO/CoFe₂O₄-SBC also exhibited environmental security with its leaching concentrations of Fe and Co were below 0.5 mg L^-1 in a wide pH range. The performance of GO/CoFe₂O₄-SBC suggested that it could be served as a promising adsorbent for environmental concentration IMI removal.

Anionic polyacrylamide influence on the lead(II) ion accumulation in soil - the study on montmorillonite

PURPOSE

Polymeric substances, as soil conditioners, limit the erosion process as well as improve the soil structure. The same macromolecular compounds may influence the heavy metal accumulation in soil environment. The main aim of this study was investigation of anionic polyacrylamide (AN PAM) effect on the lead(II) ion sorption on the montmorillonite surface. The effects of Pb(II) ion concentration, sequence of heavy metal and anionic polymer addition into the system as well as anionic group content in the PAM macromolecules were also studied.

MATERIALS AND METHODS

The study was performed on montmorillonite (clay mineral). Two types of polymers were used: AN PAM 5% and AN PAM 30% containing 5% and 30% of carboxylic groups, respectively. The adsorbed amounts of Pb(II) ions or AN PAM on the solid were determined spectrophotometrically. Electrokinetic properties of the examined systems were established using potentiometric titration and microelectrophoresis method. The montmorillonite aggregation without and with selected substances was described based on the sedimentation study.

RESULTS

At pH 5 the Pb(II) adsorbed amount on montmorillonite equaled 0.05 mg/m² (for the initial concentration 10 ppm). Anionic polyacrylamide increased this value significantly (it was 0.11 mg/m² with AN PAM 5% and 0.11 mg/m² with AN PAM 30%). The lead(II) ions presence causes a slight increase of the anionic PAM adsorption on the montmorillonite surface. For example, for the initial polymer concentration 100 ppm, the AN PAM 5% adsorbed amount without Pb(II) equaled 0.49 mg/m², whereas with Pb(II) - 0.57 mg/m². What is more, anionic polyacrylamide and lead(II) ions affected electrokinetic properties and stability of the montmorillonite suspension.

CONCLUSIONS

Anionic polyacrylamide makes the Pb(II) accumulation on the montmorillonite surface larger and, as a consequence, reduces the Pb(II) availability to organisms. Therefore, this macromolecular compound can certainly be used to remediate soils contaminated with heavy metals.

Activation of peroxymonosulfate using drinking water treatment residuals modified by hydrothermal treatment for imidacloprid degradation

In this study, water treatment residuals (WTRs), a safe and valuable by-product containing iron, was used as a precursor for preparing effective activator (HWTRs) of peroxymonosulfate (PMS) for imidacloprid (IMD) degradation by hydrothermal treatment. Several affecting parameters on IMD degradation including PMS concentration, HWTRs dosage, initial pH and water matrix were discussed. The results of degradation experiments demonstrated that within the reaction time of 4 h, 97.64% of IMD could be removed with 0.5 g L^-1 HWTRs and 1.5 mM PMS, and the acidic conditions were favorable for IMD degradation. Both sulfate radicals (SO₄^•-) and hydroxyl radicals (·OH) were generated to attack the target pollutant IMD, and ·OH was the dominating radical in the HWTRs/PMS system, which was confirmed by the results of radicals scavenging experiments, electron spin-resonance spectroscopy (ESR) tests and quantitative analysis. What's more, X-ray photoelectron (XPS) spectroscopy was used to further verify the activation mechanism. Consequently, the activation by Fe(II) on the surface of HWTRs might dominate the reaction was confirmed. In addition, the possible degradation pathways of IMD were proposed on the basis of the degradation intermediates identified by LC-MS. This study offers an innovative idea for modifying raw WTRs to prepare efficient catalysts to activate PMS under relatively mild conditions.

Insights into the Toxicity and Degradation Mechanisms of Imidacloprid Via Physicochemical and Microbial Approaches

Imidacloprid is a neonicotinoid insecticide that has been widely used to control insect pests in agricultural fields for decades. It shows insecticidal activity mainly by blocking the normal conduction of the central nervous system in insects. However, in recent years, imidacloprid has been reported to be an emerging contaminant in all parts of the world, and has different toxic effects on a variety of non-target organisms, including human beings, due to its large-scale use. Hence, the removal of imidacloprid from the ecosystem has received widespread attention. Different remediation approaches have been studied to eliminate imidacloprid residues from the environment, such as oxidation, hydrolysis, adsorption, ultrasound, illumination, and biodegradation. In nature, microbial degradation is one of the most important processes controlling the fate of and transformation from imidacloprid use, and from an environmental point of view, it is the most promising means, as it is the most effective, least hazardous, and most environmentally friendly. To date, several imidacloprid-degrading microbes, including Bacillus, Pseudoxanthomonas, Mycobacterium, Rhizobium, Rhodococcus, and Stenotrophomonas, have been characterized for biodegradation. In addition, previous studies have found that many insects and microorganisms have developed resistance genes to and degradation enzymes of imidacloprid. Furthermore, the metabolites and degradation pathways of imidacloprid have been reported. However, reviews of the toxicity and degradation mechanisms of imidacloprid are rare. In this review, the toxicity and degradation mechanisms of imidacloprid are summarized in order to provide a theoretical and practical basis for the remediation of imidacloprid-contaminated environments.

Pesticides in aquatic environments and their removal by adsorption methods

Although pesticides are widely used in agriculture, industry and households, they pose a risk to human health and ecosystems. Based on target organisms, the main types of pesticides are herbicides, insecticides and fungicides, of which herbicides accounted for 46% of the total pesticide usage worldwide. The movement of pesticides into water bodies occurs through run-off, spray drift, leaching, and sub-surface drainage, all of which have negative impacts on aquatic environments and humans. We sought to define the critical factors affecting the fluxes of contaminants into receiving waters. We also aimed to specify the feasibility of using sorbents to remove pesticides from waterways. In Karun River in Iran (1.21 × 10⁵ ng/L), pesticide concentrations are above regulatory limits. The concentration of pesticides in fish can reach 26.1 × 10³ μg/kg, specifically methoxychlor herbicide in Perca fluviatilis in Lithuania. During the last years, research has focused on elimination of organic pollutants, such as pesticides, from aqueous solution. Pesticide adsorption onto low-cost materials can effectively remediate contaminated waters. In particular, nanoparticle adsorbents and carbon-based adsorbents exhibit high performance (nearly 100%) in removing pesticides from water bodies.

Adsorption kinetic models: Physical meanings, applications, and solving methods

Adsorption technology has been widely applied in water and wastewater treatment, due to its low cost and high efficiency. The adsorption kinetic models have been used to evaluate the performance of the adsorbent and to investigate the adsorption mass transfer mechanisms. However, the physical meanings and the solving methods of the kinetic models have not been well established. The proper interpretation of the physical meanings and the standard solving methods for the adsorption kinetic models are very important for the applications of the kinetic models. This paper mainly focused on the physical meanings, applications, as well as the solving methods of 16 adsorption kinetic models. Firstly, the mathematical derivations, physical meanings and applications of the adsorption reaction models, the empirical models, the diffusion models, and the models for adsorption onto active sites were analyzed and discussed in detail. Secondly, the model validity evaluation equations were summarized based on literature. Thirdly, a convenient user interface (UI) for solving the kinetic models was developed based on Excel software and provided in supplementary information, which is helpful for readers to simulate the adsorption kinetic process.

Preparation of highly selective magnetic cobalt ion-imprinted polymer based on functionalized SBA-15 for removal Co2+ from aqueous solutions

In this research, a novel magnetic cobalt ion imprinted adsorbent (Co(II)-MIIP) was synthesized by use of magnetic SBA-15 core-shell. It was functionalized by dithizone, and after identification by various techniques was used for removal of cobalt from aquatic systems. The uptake of cobalt proceeded very fast and achieved to equilibration within 5 min at which 74 mg g-1 of cobalt was adsorbed at pH = 8 with adsorbent dose of 0.15 g. The ion imprinted sorbent exhibited good selectivity towards cobalt ions. Separation and recovery of the used sorbent was carried out respectively by use of magnetic field and by use of HNO3 (0.1 M), and 85% of the initial capacity was obtained after seven 7 regeneration cycles. Different isotherm models, and error analysis were used to evaluate the experimental data. Thermodynamic, and kinetic evaluations showed that sorption process was endothermic, and described by second order kinetic model (R2 > 0.99). The equilibrium was established within five min.

Removal of hexavalent chromium from water using polyaniline/ wood sawdust/ poly ethylene glycol composite: an experimental study

Polyaniline/ Sawdust /Poly Ethylene Glycol/ (PANi/SD/PEG) composite synthesized chemically is used as an adsorbent to remove hexavalent chromium from water. Adsorption experiments have been done in batch and continuous (column) mode. Some parameter such as pH, contact time, PANi/SD/PEG dose, isotherms in batch mode and pH, column bed depth and fluid flow rate in column mode were investigated. Result shows that PANi/SD/PEG has a good performance to remove hexavalent chromium ion from aqueous media. By presence of PEG, prepared composite has been homogenized and further absorption has been occurred. The best adsorption occurs under pH 2 and optimum contact time for removal of hexavalent chromium ion in batch experiment was about 30 min. Adsorption of Cr (VI) by PANi/SD/PEG fitted well in Langmuir isotherms. Maximum adsorption of hexavalent chromium was calculated 3.2 (mg/g). In column experiments, pH and column bed depth were found to be more prominent than fluid flow rate. Though, about 22% of Cr (VI) can be recovered using 0.1 M NaOH in the batch system, the recovered Cr (VI) in column system was less than 7.9%.

Synthesis, characterization and photocatalytic application of Ag-doped Fe-ZSM-5@TiO2 nanocomposite for degradation of reactive red 195 (RR 195) in aqueous environment under sunlight irradiation

BACKGROUND

Most dyes have aromatic rings in their structures, which make them highly toxic for human being and aquatic life. Heterogeneous photodegradation using TiO₂ nanoparticles is one of the most applied methods used for dye removal. The wide band gap of TiO₂ nanoparticles disables its use of the visible light and thus the vast potential of sunlight. To overcome this deficiency, Ag doped TiO₂ nanoparticles were loaded on Fe-ZSM-5.

METHODS

Fe-ZSM-5@TiO₂-Ag photocatalyst was synthesized through sol-gel and hydrothermal methods to remove hazardous Reactive Red 195 (RR 195) from aqueous solution.

RESULTS

Pure phase of Fe-ZSM-5@TiO₂-Ag with specific surface area of 332 m²/g was successfully synthesized. Formation of Ti-O-Ag functional group in the photocatalyst structure confirmed the nanocomposite form of the product. SEM and TEM images portrayed the synthesized zeolite and photocatalyst NPs in a size range of ≤100 nm with homogenous distribution of Ag doped TiO₂ on Fe-ZSM-5 surface. The band-gap energy of Fe-ZSM-5@TiO₂-Ag was calculated 1.97 eV at λ = 630 nm. Photocatalytic activity of the photocatalyst under natural sunlight was investigated through photodecomposition of RR 195 in an aqueous solution. The dye photodecomposition of about 98% was achieved at photocatalyst concentration of 400 mg/L, pH of 3, and dye concentration of 50 mg/L at ambient temperature after 120 min under sunlight using 0.5 ml of TiO₂ and silver ammonium nitrate. The photocatalyst reusability was found significant after 5 frequent cycles.

CONCLUSION

The novel Ag-doped TiO₂-Fe-ZSM-5 nanocomposite with sunlight sensitivity can be a promising candidate to purify wastewater containing organic pollutants.

Removal of chromium(vi) from polluted wastewater by chemical modification of silica gel with 4-acetyl-3-hydroxyaniline

In the current study, a new adsorbent that is insoluble in water and many acid solutions and has a high adsorption capacity for Cr(vi) metal ions was synthesized. In the synthesis process, 3-chloropropyl-trimethoxysilane (CPTS) was first modified on a silica gel (Si) surface. Secondly, 4-acetyl-3-hydroxyaniline (AHAP) was immobilized on the modified silica gel compound (Si-CPTS). As a result of the immobilization process, a new adsorbent compound named Si-CPTS-AHAP (silica gel-3-chloropropyltrimethoxy silane 4-acetyl-3-hydroxyaniline) was obtained, which was used to separate Cr(vi) ions from aqueous solution (K₂Cr₂O₇) and industrial wastewater. The material was characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy. The amount of chromium adsorbed was detected by ultraviolet-visible spectroscopy. The adsorption was evaluated using batch methods. The effects of temperature, pH, concentration, adsorbent amount and interaction time on the adsorption of Si-CPTS-AHAP were also investigated. The adsorption of Cr(vi) ions on Si-CPTS-AHAP was investigated via adsorption kinetics, isotherm and thermodynamic studies. The value of the isotherm parameters and the highest adsorption yields were calculated from the Dubinin–Radushkevich, Freundlich and Langmuir isotherm equations. Thermodynamic features such as entropy (ΔS), enthalpy (ΔH) and free energy (ΔG) were also calculated from the experimental results. The experimental results showed that the best recoveries of Cr(vi) metal ions are under the conditions of 180 min (interaction time), 0.05 g (adsorbent amount) and 323.15 K (temperature) at pH 2. Si-CPTS-AHAP can be used for the removal of poisonous pollutants in wastewater.

Use of a newly synthesized Si-CPTS-AHAP adsorbent in the removal of Cr(vi) ions in wastewater treatment systems may potentially lead to low cost and highly efficient heavy metal removal.