Comparative performance of bare and functionalize ZnO nanoadsorbents for pesticide removal from aqueous solution

Sunlight-mediated photocatalytic removal of phenanthrene from wastewater using carbon-doped zinc oxide (C-ZnO) nanoparticles

In an effort for efficient solar energy harvesting, carbon-doped zinc oxide (C-ZnO) nanoparticles with intriguing properties were synthesized by sonicated sol-gel technique with the aid of activated charcoal. Compared to pure ZnO, the incorporation of carbon has drastically promoted the photocatalytic activity of C-ZnO towards the degradation of phenanthrene under illumination of both UV and sunlight. The characterization of the as-synthesized nanoparticles by scanning electron microscope (SEM), UV-vis spectra, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS) confirmed the carbon doping of C-ZnO. The highest degradation rate of phenanthrene was obtained at pH 7 and C-ZnO loading of 0.5 g L^-1. Finally, the kinetic studies of the photocatalytic degradation of phenanthrene by using C-ZnO were well-fitted with the Langmuir-Hinshelwood model and followed the pseudo-first-order rate expression.

Rice Straw as Green Waste in a HTiO2@AC/SiO2 Nanocomposite Synthesized as an Adsorbent and Photocatalytic Material for Chlorpyrifos Removal from Aqueous Solution

A nano-HTiO2@activated carbon-amorphous silica nanocomposite catalyst (HTiO2@AC/SiO2) is utilized to photo breakdown catalytically and adsorb chlorpyrifos insecticide. SEM, TEM, and X-ray diffraction were used to examine HTiO2@AC/SiO2, synthesized through sol–gel synthesis. With an average size of 7–9 nm, the crystallized form of HTiO2 is the most common form found. At varied pH, catalyst doses, agitation speed, initial pesticide concentrations, contact periods, and temperatures, HTiO2@AC/SiO2 was examined for efficiency under visible light and in darkness. Because of the pseudo-second-order kinetics observed for chlorpyrifos, chemisorption is believed to dominate the adsorption process, as indicated by an estimated activation energy of 182.769 kJ/mol, which indicates that chemisorption dominates the adsorption process in this study. The maximal adsorption capacity of chlorpyrifos is 462.6 mg g−1, according to the Langmuir isotherms, which infer this value. When exposed to visible light, the adsorption capacity of HTiO2@AC/SiO2 increased somewhat as the temperature rose (283 k 323 k 373 k), indicating an exothermic change in Gibbs free energy during the process (−1.8 kJ/mol), enthalpy change (−6.02 kJ/mol), and entropy change (0.014 J/mol K), respectively, at 298.15 K. Negative (ΔS) describes a process with decreased unpredictability and suggests spontaneous adsorption. HTiO2@AC/SiO2 may be a promising material.

Removing the Oxamyl from Aqueous Solution by a Green Synthesized HTiO2@AC/SiO2 Nanocomposite: Combined Effects of Adsorption and Photocatalysis

The photocatalytic degradation and adsorption of the oxamyl pesticide utilizing a nano-HTiO2@activated carbon-amorphous silica nanocomposite catalyst (HTiO2@AC/SiO2). Sol-gel Synthesis was used to produce HTiO2@AC/SiO2, which was examined using Scanning Electron Microscopy, Transmission Electron Microscopy, and an X-ray diffractometer. The analyses confirmed that HTiO2 is mainly present in its crystalline form at a size of 7–9 nm. The efficiency of HTiO2@AC/SiO2 was assessed at various pHs, catalyst doses, agitating intensities, initial pesticide concentrations, contact times, and temperatures under visible light and in darkness. Oxamyl adsorption kinetics followed a pseudo-second-order kinetic model, suggesting that the adsorption process is dominated by chemisorption, as supported by a calculated activation energy of −182.769 kJ/mol. The oxamyl adsorption is compatible with Langmuir and Freundlich isotherms, suggesting a maximum adsorption capacity of 312.76 mg g−1. The adsorption capacity increased slightly with increasing temperature (283 K < 323 K < 373 K), suggesting an exothermic process with the Gibbs free energy change ΔG, enthalpy change ΔH, and entropy change ΔS°, being –3.17 kJ/mol, −8.85 kJ/mol, and −0.019 J/mol K, respectively, at 310 K for HTiO2@AC/SiO2 under visible light. This indicates spontaneous adsorption, and negative (ΔS) explain a decreased randomness process. HTiO2@AC/SiO2 would be a promising material.

Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview

The ecological toxicity imparted by non-biodegradable organic dyes has been considered as a major risk to handle in front of mankind. In this view, the low-cost zinc oxide nanoparticles (ZnO-NPs) were facially synthesized by coating the surface with surfactant (CTAB) and ionic liquid (BMTF) molecules for the effective removal of Eriochrome Black T (EBT) from aqueous media. Various advanced characterization techniques have given insight into the morphological features, crystalline structure and physio-chemical properties of as-synthesized ZnO-NPs. The systematic analysis of the adsorption isotherms and kinetics models specifies that the adsorption of EBT follow Freundlich model and pseudo-second-order kinetics. The intraparticle diffusion model displayed a linear relationship (R² = 0.98, 0.97 and 0.94 for BMTF@ZnO, CTAB@ZnO and bare ZnO-NPs), which shows that pore diffusion rate is affected by surface modification and effects the overall EBT adsorption process. Furthermore, after the removal of 87% and 84% of EBT dye by BMTF@ZnO-NPs and CTAB@ZnO-NPs, the fabricated nanoadsorbents of ZnO were successfully regenerated and reused after the treatments up to four times. The adsorption aptitude of ZnO-NPs towards EBT dye was systematically explored in real wastewater samples and interference study of inorganic metallic salts was also performed. The toxicity estimations of the treated dye solutions were made using floral and fungal activities, to ascertain their non-toxic nature before releasing into the environment. These outcomes have supported the immense potential of ZnO-NPs towards the removal of EBT in a cost effective manner.

Toxicity and remediation of pharmaceuticals and pesticides using metal oxides and carbon nanomaterials

The worldwide development of agriculture and industry has resulted in contamination of water bodies by pharmaceuticals, pesticides and other xenobiotics. Even at trace levels of few micrograms per liter in waters, these contaminants induce public health and environmental issues, thus calling for efficient removal methods such as adsorption. Recent adsorption techniques for wastewater treatment involve metal oxide compounds, e.g. Fe2O3, ZnO, Al2O3 and ZnO-MgO, and carbon-based materials such as graphene oxide, activated carbon, carbon nanotubes, and carbon/graphene quantum dots. Here, the small size of metal oxides and the presence various functional groups has allowed higher adsorption efficiencies. Moreover, carbon-based adsorbents exhibit unique properties such as high surface area, high porosity, easy functionalization, low price, and high surface reactivity. Here we review the cytotoxic effects of pharmaceutical drugs and pesticides in terms of human risk and ecotoxicology. We also present remediation techniques involving adsorption on metal oxides and carbon-based materials.

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.

Nanoparticles Based Extraction Strategies for Accurate and Sensitive Determination of Different Pesticides

Sample preparation methods have become indispensable steps in analytical measurements not only to lower the detection limit but also to eliminate the matrix effect although more sophisticated instruments are being commonly used in routine analyses. Solid phase extraction (SPE) is one of the main extraction/preconcentration methods used to extract and purify target analytes along with simple and rapid procedures but some limitations have led to seek for an easy, sensitive and fast extraction methods with analyte-selective sorbents. Nanoparticles with different modifications have been used as spotlight to enhance extraction efficiency of target pesticides from complicated matrices. Carbon-based, metal and metal oxides, silica and polymer-based nanoparticles have been explored as promising sorbents for pesticide extraction. In this review, different types of nanoparticles used in the preconcentration of pesticides in various samples are outlined and examined. Latest studies in the literature are discussed in terms of their instrumental detection, sample matrix and limit of detection values. Novel strategies and future directions of nanoparticles used in the extraction and preconcentration of pesticides are also discussed.

Emerging nanobiotechnology in agriculture for the management of pesticide residues

Utilization of pesticides is often necessary for meeting commercial requirements for crop quality and yield. However, incessant global pesticide use poses potential risks to human and ecosystem health. This situation increases the urgency of developing nano-biotechnology-assisted pesticide formulations that have high efficacy and low risk of side effects. The risks associated with both conventional and nanopesticides are summarized in this review. Moreover, the management of residual pesticides is still a global challenge. The contamination of soil and water resources with pesticides has adverse impact over agricultural productivity and food security; ultimately posing threats to living organisms. Pesticide residues in the eco-system may be treated via several biological and physicochemical processes, such as microbe-based degradation and advanced oxidation processes. With these issues in mind, we present a review that explores both existing and emerging techniques for management of pesticide residues and environmental risks. These techniques can offer a sustainable solution to revitalize the tarnished water/soil resources. Further, state-of-the-art research approaches to investigate biotechnological alternatives to conventional pesticides are discussed along with future prospects and mitigation techniques are recommended.

Potential use of ZnO@activated carbon nanocomposites for the adsorptive removal of Cd2+ ions in aqueous solutions

Nowadays, the pollution in water resources has become a major concern, both environmentally and in perspective of human health. The bioaccumulation of pollutants, especially heavy metal ions through the food chain, poses a hazardous risk to humans and other living organisms. Nanomaterials and their composites have been recognized for their potential to resolve such problems. Herein, ZnO nanoparticles were synthesized and characterized via different microscopic/spectroscopic techniques. ZnO nanoparticles (i.e., 20 to 50 nm) were obtained in high yield via a facile chemical approach. The ratio of ZnO nanoparticles and activated carbon was optimized to achieve enhanced electrostatic interactions for the effective adsorption of cadmium ions (Cd²⁺). The adsorptive performance of the nanocomposite was further assessed in relation to several key parameters (e.g., contact time, solution pH, and adsorbent/adsorbate dosage). The nanocomposites (1 mg/ml) offered amaximum adsorption capacity of 96.2 mg/g for Cd²⁺ ions as confirmed through adsorption isotherms for a best interpretation of the adsorption phenomenon. The favourable adsorption capacity of the synthesized ZnO/activated carbon (9:1) nanocomposites supported their use as an efficient sorbent material in practical performance metrics (e.g., partition coefficient of 0.54 mg g^-1μM^-1) for the adsorption of Cd²⁺ ions.

Removal of emerging contaminants from the environment by adsorption

Emerging contaminants (EC's) are pollutants of growing concern. They are mainly organic compounds such as: pesticides, pharmaceuticals and personal care products, hormones, plasticizers, food additives, wood preservatives, laundry detergents, surfactants, disinfectants, flame retardants, and other organic compounds that were found recently in natural wastewater stream generated by human and industrial activities. A majority of ECs does not have standard regulations and could lead to lethal effects on human and aquatic life even at small concentrations. The conventional primary and secondary water treatment plants do not remove or degrade these toxic pollutants efficiently and hence need cost effective tertiary treatment method. Adsorption is a promising method worldwide for EC removal since it is low initial cost for implementation, highly-efficient and has simple operating design. Research has shown that the application of different adsorbents such as, activated carbons(ACs), modified biochars (BCs), nanoadsorbents (carbon nanotubes and graphene), composite adsorbents, and other are being used for EC's removal from water and wastewater. The current review intends to investigate adsorption process as an efficient method for the treatment of ECs. The mechanism of adsorption has also been discussed.

Nanotechnology-based recent approaches for sensing and remediation of pesticides

Pesticides are meant to control and destroy the pests and weeds. They are classified into different categories on the basis their origin and type of pest they target. Chemical pesticides such as insecticides, herbicides and fungicides are commonly used in agricultural fields. However, the excessive use of these agrochemicals have adverse effects on environment such as reduced population of insect pollinators, threat to endangered species and habitat of birds. Upon consumption; chemical pesticides also cause various health issues such as skin, eye and nervous system related problems and cancer upon prolonged exposure. Various techniques in the past have been developed on the basis of surface adsorption, membrane filtration and biological degradation to reduce the content of pesticides. However, slow response, less specificity and sensitivity are some of the drawbacks of such techniques. In recent times, Nanotechnology has emerged as a helping tool for the sensing and remediation of pesticides. This review focuses on the use of this technology for the detection, degradation and removal of pesticides. Nanomaterials have been classified into nanoparticles, nanotubes and nanocomposites that are commonly used for detection, degradation and removal of pesticides. The review also focuses on the chemistry behind the sensing and remediation of pesticides using nanomaterials. Different types of nanoparticles, viz. metal nanoparticles, bimetallic nanoparticles and metal oxide nanoparticles; nanotubes such as carbon nanotubes and halloysite nanotubes have been used for the detection, degradation and removal of pesticides. Further, various enzyme-based biosensors for detection of pesticides have also been summarized.