Fabrication and characterization of a nanocomposite hydrogel for combined photocatalytic degradation of a mixture of malachite green and fast green dye

Starch-based hydrogels for environmental applications: A review

Water sources have become extremely scarce and contaminated by organic and inorganic industrial and agricultural pollutants as well as household wastes. Poisoning water resources by dyes and metals is a problem because contaminated water can leak into subsurface and surface sources, causing serious contamination and health problems. Therefore, developing wastewater treatment technologies is valuable. Today, hydrogels have attracted considerable attention owing to their broad applications. Hydrogels are polymeric network compositions with significant water-imbibing capacity. Hydrogels have potential applications in diverse fields such as biomedical, personal care products, pharmaceuticals, cosmetics, and biosensors. They can be prepared by using natural (biopolymers) and synthetic polymers. Synthetic polymer-based hydrogels obtained from petrochemicals are not environmentally benign; thus, abundant plant-based polysaccharides are found as more suitable compounds for making biodegradable hydrogels. Polysaccharides with many advantages such as non-toxicity, biodegradability, availability, inexpensiveness, etc. are widely employed for the preparation of environmentally friendly hydrogels. Polysaccharides-based hydrogels containing chitin, chitosan, gum, starch (St), etc. are employed to remove pollutants, metals, and dyes. Among these, St has attracted a lot of attention. St can be mixed with other compounds to make hydrogels, which remove dyes and metal ions to variable degrees of efficiency. Although St has numerous advantages, it suffers from drawbacks such as low stability, low water solubility, and fast degradability in water which limit its application as an environmental adsorbent. As an effective way to overcome these weaknesses, various modification approaches to form starch-based hydrogels (SBHs) employing different compounds have been reported. The preparation methods and applications of SBH adsorbents in organic dyes, hazardous materials, and toxic ions elimination from water resources have been comprehensively discussed in this review.

Metal/metal oxide-carbohydrate polymers framework for industrial and biological applications: Current advancements and future directions

Recently, the development and consumption of metal/metal oxide carbohydrate polymer nanocomposites (M/MOCPNs) are withdrawing significant attention because of their numerous salient features. Metal/metal oxide carbohydrate polymer nanocomposites are being used as environmentally friendly alternatives for traditional metal/metal oxide carbohydrate polymer nanocomposites exhibit variable properties that make them excellent prospects for a variety of biological and industrial uses. In metal/metal oxide carbohydrate polymer nanocomposites, carbohydrate polymers bind with metallic atoms and ions using coordination bonding in which heteroatoms of polar functional groups behave as adsorption centers. Metal/metal oxide carbohydrate polymer nanocomposites are widely used in woundhealing, additional biological uses and drug delivery, heavy ions removal or metal decontamination, and dye removal. The present review article features the collection of some major biological and industrial applications of metal/metal oxide carbohydrate polymer nanocomposites. The binding affinity of carbohydrate polymers with metal atoms and ions in metal/metal oxide carbohydrate polymer nanocomposites has also been described.

Synthesis of highly fluorescent carbon quantum dots from rubber seed shells for the adsorption and photocatalytic degradation of dyes

The potentials of biomass-based carbon quantum dot (CQD) as an adsorbent for batch adsorption of dyes and its photocatalytic degradation capacity for dyes which are congo red (CR) and methylene blue (MB) have been conducted in this study. The CQDs properties, performance, behaviour, and photoluminescence characteristics were assessed using batch adsorption experiments which were carried out under operating conditions including, temperature, pH and dosage. The morphological analysis revealed that CQDs are highly porous, uniform, closely aligned and multi-layered. The presence of hydroxyl, carboxyl and carbonyl functional groups indicated the significance of the oxygenated functional groups. Spectral analysis of photoluminescence for CQDs confirmed their photoluminescent quality by exhibiting high excitation intensity and possessing greenish-blue fluorescence under UV radiation. The removal percentage of the dyes adsorbed for both CR and MB dyes was 77% and 75%. Langmuir isotherm and pseudo-second-order models closely fitted the adsorption results. Thermodynamics analysis indicated that the adsorption process was exothermic and spontaneous, with excellent reusability and stability. The degradation efficiency of CQDs on both dyes was more than 90% under sunlight irradiation and obeyed the first-order kinetic model. These results demonstrated CQDs to be an excellent adsorbent and outstanding photocatalyst for organic dye degradation.

A State-of-Art Review of the Metal Oxide-Based Nanomaterials Effect on Photocatalytic Degradation of Malachite Green Dyes and a Bibliometric Analysis

A wide range of hard contaminants in wastewater is generated from different industries as byproducts of the organic compound. In this review, various metal oxide-based nanomaterials are employed for the photocatalytic removal of malachite green (MG) dye from wastewater. Some cost-effective and appropriate testing conditions are used for degrading these hard dyes to get higher removal efficiency. The effects of specific parameters are considered such as how the catalyst is made, how much dye is in the solution at first, how much nanocatalyst is needed to break down the dye, the initial pH of the dye solution, the type of light source used, the year of publications, and how long the dye has to be exposed to light to be removed. This study suggests that Scopus-based core collected data employ bibliometric methods to provide an objective analysis of global MG dye from 2011 to 2022 (12 years). The Scopus database collects all the information (articles, authors, keywords, and publications). For bibliometric analysis, 658 publications are retrieved corresponding to MG dye photodegradation, and the number of publications increases annually. A bibliometric study reveals a state-of-art review of metal oxide-based nanomaterials' effects on photocatalytic degradation of MG dyes (12 years).

A green approach for the preparation of ZnO@C nanocomposite using agave americana plant extract with enhanced photodegradation

The present study demonstrates the crucial role of agave americana extract in enhancing the optical properties of zinc oxide (ZnO) through thermal treatment method. Various analytical and surface science techniques have been used to identify the morphology, crystalline structure, chemical composition, and optical properties, including scanning electron microscopy, x-ray diffraction, high resolution transmission electron microscopy (HRTEM), x-ray spectroscopy (EDS) and UV-visible spectroscopy techniques. The physical studies revealed the transformation of ZnO nanorods into nanosheets upon addition of an optimized amount of agave americana extract, which induced large amount of amorphous carbon deposited onto ZnO nanostructures as confirmed by HRTEM analysis. The use of increasing amount of americana extract has significantly reduced the average crystallite size of ZnO nanostructures. The resultant hybrid system of C@ZnO has produced a significant effect on the ultraviolet light-assisted photodegradation of malachite green (MG) dye. The photocatalyst dose was fixed at 10 mg for each study whereas the amount of agave americana extract and MG dye concentration are varied. The functionality of hybrid system was greatly enhanced when the amount of agave americana extract increased while dye concentration kept at lower level. Ultimately, almost 100% degradation efficiency was achieved via the prepared hybrid material, revealing combined contribution from synergy, stabilization of ZnO due to excess of carbon together with the high charge separation rate. The obtained results suggest that the driving role of agave americana extract for surface modification of photocatalyst can be considered for other nanostructured photocatalysts.

Visible-light driven dual heterojunction formed between g-C3N4/BiOCl@MXene-Ti3C2 for the effective degradation of tetracycline

In the present study, we have successfully formulated a dual heterojunction of g-C₃N₄/BiOCl@MXene-Ti₃C₂ (GCBM) which was found to be highly active in the visible region. GCBM was found to be highly efficient for the degradation of an antibiotic, tetracycline (TC) as compared to the individual constituting units; g-C₃N₄ and BiOCl. Maximum of 97% TC degradation rate was obtained within 90 min of visible light irradiation for initial concentration of 10 mg/L of TC. Optical analysis exhibited that the synthesized heterojunction showed high absorption in the complete spectrum. The reactive species specified by the scavenger study showed the major involvement of ^•O₂^- and ^•OH radicals. The charge transfer mechanism showed that 2 schemes were majorly involvement in which Z-scheme was formed between g-C₃N₄ and BiOCl and Schottky junction was formed between g-C₃N₄ and Mxene-Ti₃C₂. The formation of Schottky junction helped in inhibiting the back transfer of photogenerated charges and thus, helped in reducing the recombination rate. The synthesized photocatalyst was found to be highly reusable and was studied for consecutive 5 cycles that generalized the high proficiency even after repetitive cycles.

Facile Synthesis of Gold Nanoparticles for Anticancer, Antioxidant Applications, and Photocatalytic Degradation of Toxic Organic Pollutants

In the current study, a facile, rapid, and ecologically safe photosynthesis of gold nanoparticles (AuNPs) that remained stable for 3 months is reported to advocate the main aspects of green chemistry, such as safer solvents and auxiliaries, and the use of renewable feedstock. Zi-AuNPs were phytosynthesized by the aqueous extract of Ziziphus spina-christi leaves, and numerous techniques were employed for their characterization. The results demonstrated the successful phytofabrication of crystalline AuNPs with brownish-black color, spherical nanoparticles with a size between 0 and 10 nm, a plasmon peak at 540 nm, and a surface charge of -25.7 mV. Zi-AuNPs showed an effective photodegradation efficiency (81.14%) against malachite green and a good recycling capacity of 69.2% after five cycles of regeneration. The cytotoxicity test by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay signified a high anticancer efficiency for both Zi-AuNPs and Z. spina-christi extract against human breast cancer cells (MCF7 cell line) with IC₅₀'s of 48 and 40.25 μg/mL, respectively. Highly efficient antioxidant capabilities were proven with 2,2-diphenyl-1-picrylhydrazyl (DPPH) removal percentages of 67.5% for Zi-AuNPs and 92.34% for Z. spina-christi extract.

SnO2nanorods/graphene nanoplatelets nanocomposites: towards fast removal of malachite green and pathogen control

The world is facing alarming challenges of environmental pollution due to uncontrolled water contamination and multiple drug resistance of pathogens. However, these challenges can be addressed by using novel nanocomposites materials such as, SnO₂/graphene nanopaletelets (GNPs) nanocomposites remarkably. In this work, we have prepared SnO₂nanorods and SnO₂/GNPs nanocomposites (GS-I and GS-II) with size of 25 ± 6 nm in length and 4 ± 2 nm in diameter. The optical bandgap energies change from 3.14 eV to 2.80 eV in SnO₂and SnO₂/GNPs nanocomposite. We found that SnO₂/GNPs nanocomposite (GS-II) completely removes (99.11%) malachite green in 12 min, under UV light exposure, while under same conditions, SnO₂nanorods removes only 37% dye. Moreover, visible light exposure resulted in 99.01% removal of malachite green in 15 min by GSII as compared to 24.7% removal by SnO₂. In addition, GS-II nanocomposite inhibits 79.57% and 78.51% growth ofP. aeruginosaandS. aureusrespectively. A synchronized contribution of SnO₂and GNPs makes SnO₂/GNPs nanocomposites (GS-II) an innovative multifunctional material for simultaneous fast and complete removal of malachite green and inhibition of drug resistant pathogens.

Comparative studies on adsorptive and photocatalytic potential of differently synthesized ferric oxide nanoparticles for malachite green

In the present work, effect of different fuels on the structural, morphological, magnetic, adsorptive and photocatalytic properties of ferric oxide nanoparticles (Fe₂O₃ NPs) was evaluated. Fe₂O₃ NPs were synthesized via combustion method by using oxalyl dihydrazide (ODH), polyethylene glycol (PEG) and urea as fuels. The indigenously synthesized NPs were characterized by different analytical tools. XRD patterns confirmed the presence of α- and γ-Fe₂O₃ phases. TEM micrographs displayed average particle size was less than 30 nm. Saturation magnetization amplified with increase in the γ-Fe₂O₃ content, which was correlated to the fuel used for synthesis. Adsorptive and photocatalytic activity of synthesized NPs was studied using malachite green (MG) dye as a model compound. The uptake behavior for MG dye was influenced by the solution pH, contact time, adsorbent dose, temperature and dye concentration. Thermodynamic studies indicated the endothermic nature of the adsorption phenomenon. The adsorption was well defined with Langmuir and Freundlich isotherms in comparison to Dubinin-Radushkevitch adsorption isotherm model. The trend for percentage removal of MG dye using NPs synthesized by different fuels was: urea > PEG > ODH. Fe₂O₃ NPs facilitated photo degradation of dye solution in ultra-violet and visible light irradiations.

Polyaniline Supported Ag-Doped ZnO Nanocomposite: Synthesis, Characterization, and Kinetics Study for Photocatalytic Degradation of Malachite Green

Ag-ZnO/PANI nanocomposite was prepared via the sol-gel technique following in situ oxidative polymerization of polyaniline (PANI). XRD, UV-Vis, and FT-IR spectroscopy were employed to study the crystal size, bandgap energy, and bond structure of as-synthesized nanocomposites. The mean crystallite size of the nanocomposite determined from XRD was 35.68 nm. Photocatalytic degradation of malachite green (MG) dye using as-synthesized photocatalysts was studied under visible light irradiation. The highest degradation efficiency was recorded for Ag-ZnO/PANI nanocomposites (98.58%) than Ag-ZnO nanoparticles (88.23%) in 120 min. The kinetics of photocatalytic degradation of MG follows pseudo-first-order reaction with rate order of 1.16 10−2 min−1. Moreover, the photocatalytic activity of Ag-ZnO/PANI nanocomposites was evaluated and compared with Ce-Cd oxide, electrospun P(3HB)-TiO2, and with other catalysts in the literature. The optimal conditions for photocatalytic degradation are as follows: the concentration of malachite green (0.2 g/l), pH (8), and the concentration of catalyst load (0.2 g/l) under visible light with an irradiation time of 120 min.

Stimulation of Bacillus sp. by lipopeptide biosurfactant for the degradation of aromatic amine 4-Chloroaniline

This study aims to reveal that the biosurfactant act as a stimulant in aromatic amine 4-Chloroaniline (4-CA) degradation. Isolated degrading strain Bacillus sp. was used for the production of biosurfactant with help of substrate such as engine oil. The surfactant production by the strain was studied by using various screening methods and the results showed best emulsification activity (75%), surface tension reduction activity (28.6 mNm^-1) and oil spreading activity (5.9 cm). The obtained surfactant was characterized using Fourier transform infrared spectroscopy (FT-IR), Gas chromatography-Mass Spectrometry (GC-MS), Matrix-Assisted Laser Desorption/ Ionization Time of Flight (MALDI-TOF) which confirmed that the nature of surfactant is lipopeptide. The maximum removal of 4-CA was achieved in different environmental conditions at concentration 100 mg L^-1, neutral pH and temperature 30 °C. In the degradation studies, the 4-CA was removed upto 76% by Bacillus sp but in the presence of lipopeptide surfactant, the Bacillus sp removed 4-CA upto 100%. The degraded metabolites were further characterized using High-Pressure Liquid Chromatography (HPLC) and GC-MS. This research indicated that strain Bacillus sp along with the lipopeptide biosurfactant possesses higher potential in the bioremediation of 4-CA compound from the environment.

Adsorption characteristics of methylene blue by a dye-degrading and extracellular polymeric substance -producing strain

Biosorption of dye by microbes and the extracellular polymeric substances (EPS) were of great environmental significance, especially for the dye-degrading and EPS-producing strain. Previous studies were mainly focused on the adsorption capacities and regeneration properties of pure culture, few were on the biosorption of dyes by the dye-degraders and the contributions of EPS on adsorption. In this study, a dye-degrading and EPS-producing strain i.e., Klebsiella oxytoca was used to evaluate its removal capacity to methylene blue. The maximum adsorption capacity (q_e) by the strain was calculated as 145 mg g^-1, which is superior to many reported bio-adsorbents and some synthetic materials. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results suggested that CO, -NH₂ and P-OH groups were involved in the adsorption. High pressure steam sterilization (HPSS) increased the hydrophilicity of cell wall but did not significantly change the cell structure. Compared with the dead resting cell (DRC), the relative higher q_e obtained by live resting cell (LRC) possibly due to the loss of some cell structure during the HPSS process. Adsorption experiments by EPS-free LRC, confocal laser microscope and three-dimensional excitation-emission matrix fluorescence spectroscopy results confirmed that the EPS played a role in the adsorption of MB dye. The adsorption characteristics of the dye-degrader and the contributions of EPS on adsorption were investigated in detail in this study. The results were benefit for better understanding of the interaction mechanisms between the dye molecules and cells that before the biodegradation process, which were of great significance for the practical usage of residual sludge on removal of dyes.

Ag-Doped and Antibiotic-Loaded Hexagonal Boron Nitride Nanoparticles as Promising Carriers to Fight Different Pathogens

Utilization of antibacterial components-conjugated nanoparticles (NPs) is emerging as an attractive strategy for combating various pathogens. Herein, we demonstrate that Ag/BN NPs and antibiotic-loaded BN and Ag/BN nanoconjugates are promising carriers to fight bacterial and fungal infections. Extensive biological tests included two types of Gram-positive methicillin-resistant Staphylococcus aureus strains (B8469 and MW2), two types of Gram-negative Pseudomonas aeruginosa strains (ATCC27853 and B1307/17), and 47 types of Escherichia coli strains (including 41 multidrug-resistant ones), as well as five types of fungal cultures: Candida albicans (candidiasis-thrush) ATCC90028 and ATCC24433, Candida parapsilosis ATCC90018, Candida auris CBS109113, and Neurospora crassa wt. We have demonstrated that, even within a single genus Escherichia, there are many hospital E. coli strains with multi-drug resistance to different antibiotics. Gentamicin-loaded BN NPs have high bactericidal activity against S. aureus, P. aeruginosa, and 38 types of the E. coli strains. For the rest of the tested E. coli strains, the Ag nanoparticle-containing nanohybrids have shown superior bactericidal efficiency. The Ag/BN nanohybrids and amphotericin B-loaded BN and Ag/BN NPs also reveal high fungicidal activity against C. albicans, C. auris, C. parapsilosis, and N. crassa cells. In addition, based on the density functional theory calculations, the nature of antibiotic-nanoparticle interaction, the sorption capacity of the BN and Ag/BN nanohybrids for gentamicin and amphotericin B, and the most energetically favorable positions of the drug molecules relative to the carrier surface, which lead to lowest binding energies, have been determined. The obtained results clearly show high therapeutic potential of the antibiotic-loaded Ag/BN nanocarriers providing a broad bactericidal and fungicidal protection against all of the studied pathogens.

Biogenic synthesis of bimetallic nanoparticles and their applications

The current advancements in nanotechnology suggest a sustainable development in the green synthesis of bimetallic nanoparticles (BMNPs) through green approaches. Though challenging, nano phyto technology has versatile methods to achieve desired unique properties like optic, electronic, magnetic, therapeutic, and catalytic efficiencies. Bio-inspired, facile synthesis of bifunctional BMNPs is possible using abundant, readily available natural plant sources, bio-mass wastes and microorganisms. Synergistic effects of two different metals on mixing, bring new insight for the vast applications, which is not achievable in using monometallic NPs. By adopting bio-inspired greener approaches for synthesizing NPs, the risk of environmental toxicity caused by conventional physicochemical methods become negligible. This article hopes to provide the significance of cost-effective, one-step, eco-friendly and facile synthesis of noble/transition bimetallic NPs. This review article endows an overview of the bio-mediated synthesis of bimetallic NPs, classifications of BMNPs, current characterization techniques, possible mechanistic aspects for reducing metal ions, and the stability of formed NPs and bio-medical/industrial applications of fabricated NPs. The review also highlights the prospective future direction to improve reliability, reproducibility of biosynthesis methods, its actual mechanism in research works and extensive application of biogenic bimetallic NPs.

Silicate glass matrix@Cu2O/Cu2V2O7 p-n heterojunction for enhanced visible light photo-degradation of sulfamethoxazole: High charge separation and interfacial transfer

Focusing on the treatment of pharmaceuticals contaminated water by advanced oxidation processes, a novel three dimensional silicate glass matrix (3-DG) coupled Cu₂O/Cu₂V₂O₇ p-n heterojunction was constructed by in-situ hydrothermal technique. The optimal Cu₂O/Cu₂V₂O₇ with 30 wt % Cu₂V₂O₇ (CV-30) degrades 90.1 % sulfamethoxazole (SMX) in 60 min and nearly 100 % removal in 45 min via coupling with 3-DG. Under natural sunlight ∼ 80 % SMX removal was observed. The internal electric field of the p-n junction facilitates the electron flow via the interface. 3-D silicate glass increases the visible light absorption dramatically via internal reflection which facilitates higher exposure for the junction and shortens the diffusion length of charge carriers. The effect of reaction parameters suggests that HCO₃^- and CO₃^2- ions substantially escalate the SMX removal rate. Scavenging experiments and ESR probe suggest O₂^- as the main active species followed by OH radicals. The degradation products were detected by LC-MS analysis and a degradation mechanism was also predicted. The photocatalytic mechanism was explained in terms of the electron transfer facilitated by conventional transfer and Z-scheme. This strategy to construct such highly visible and solar active p-n heterojunctions will pave way for future opportunities for the degradation of recalcitrant pharmaceutical pollutants.

Synergic effect of Guggul gum based hydrogel nanocomposite: An approach towards adsorption-photocatalysis of Magenta-O

The article is related to sunlight and UV-visible mineralization of harmful magenta-O (FB) dye. The nanocomposite used is a cross linked network of acrylic acid synthesized inside poly(acrylamide) grafted Guggul gum in the presence of UV-visible respondent bismuth ferrite nanoparticles. The synthesis of poly(acrylamide) grafted Guggul gum (Sample I) and synthesizing a crosslinked network inside it (Sample II) involved a two-step synthesis for optimizing various reaction parameters. The maximum % water uptake obtained for polymeric samples I and II was calculated as 1227.78% and 387.97%, respectively. Average particle size of bismuth ferrite nanoparticles was 47.34 nm. The nanocomposite could maximum uptake-mineralize FB dye as 97.3% and 98.8% under sunlight and photochemical reactor, respectively for 500 mg nanocomposite dose in 10 mg/L concentrated FB solution. Dye uptake occurs through ionic interactions. However, mineralization is a consequence of advanced oxidation process involving free radical species (OH and O₂^-.). The overall process of uptake-mineralization resembled second order kinetics and Langmuir theorem (monolayer adsorption). Intraparticle diffusion model gave an idea about the multistep (three steps) process of adsorption. Physico-chemical properties of FB dye got changed after mineralization except for the pH. The maximum uptake-mineralization was observed to be 76.2% after consecutive reuse of the nanocomposite hydrogel for five cycles.

Insights into the resources generation from pulp and paper industry wastes: Challenges, perspectives and innovations

Pulp and paper industry is swiftly budding to fulfill industrial needs and with the growth of this industry, a large amount of waste has also generated which includes biological sludge generated from the wood digestion process, fly ash accumulation and lime mud produced in chemical reagent recovery circuit. There are many health hazards associated with generated wastes and this waste material can be utilized in sustainable ways to generate useful resources through technological innovations. This review highlights a few useful aspects of waste conversion to resources like the production of green energy, sorbent development, and clinker preparation. The generation of resources from such wastes is a revolutionary and innovative concept for sustainable development including valorization of the generated waste to integrate pulp and paper industry with biorefinery. This review paper focuses on the sustainable utilization of waste from such industry along with its efficiency and future challenges.

Advances in production and application of biochar from lignocellulosic feedstocks for remediation of environmental pollutants

Thermochemical processing of biomass results in a producing char, a typical by-product. The char can be termed as biochar when specifically applied as a soil fertility enhancement. Biochar, when utilized efficiently, is basic for enhancing financial viability and also to maintain ecosystem. The properties of carbonized biomass rely upon raw materials (feedstock) and procedure conditions. Biochar shows an incredible potential to effectively handle water contaminants taking into consideration the wide accessibility of feedstock, suitable physical/chemical surface properties and low-cost. Pyrolysis technology for converting lignocellulosic biomass into biochar has emerged as a frontier research domain for the removal of pollutants. This review focused on production of biochar from various sources of lignocellulosic biomass (cellulose, hemicellulose and lignin) and its application in various fields such as agriculture, wastewater treatment process. Biochar is a significant resource however, its application require further examination of its properties and structure and techniques to alter those factors.

Influence of ultrasound irradiation on the intrinsic viscosity of guar gum-PEG/rosin glycerol ester nanoparticles

Novel Guar Gum (GG) and polyethylene glycol (PEG) polymer blends with rosin glycerol ester (RE) nanoparticle was synthesized under ultrasonic irradiation at different composition ratios (1:1, 1:2, 1:4, 2:1, and 4:1). The intrinsic viscosities of the nanoparticles were investigated using ultrasound irradiation to determine the miscibility of the blends in solution as affected by salt, sonication time, temperature, and pH. The intrinsic viscosities of the nanosystems were compared with five different models, including Huggins, Kraemer, Tanglertpaibul-Rao, Higiro, and Rao. The Tanglertpaibul-Rao was the best model and the intrinsic viscosities of 138,27, 142,94 and 163,29 dl/g were reported for GG-PEG/RE (1:1,1:2,1:4), respectively. The viscosity results reveal that the blend containing 1:2 (GG-PEG/RE) was an optimum miscible blend. The miscibility behaviour of the polymeric nanoparticles was investigated using the voluminosity (VE), shape factor (υ), creaming index (CI) parameter, and the Krigbaum and Wall parameter (Δb), which account for the intermolecular interactions. When compared to the intrinsic viscosity results of the nanoparticles, the miscibility-improving effect of sub-300 nm GG-PEG/RE nanoparticles is clearly proven due to the ultrasonic effect. Scanning transmission electron microscopy (STEM) and Fourier transformed infrared (FTIR) spectroscopy were used for characterization of the polymeric nanoparticles.

Visible photodegradation of ibuprofen and 2,4-D in simulated waste water using sustainable metal free-hybrids based on carbon nitride and biochar

Rational designing of metal-free carbon nitride based photocatalysts can lead to an excellent optical response and a higher photocatalytic activity driven by visible and solar light. This combines green photocatalytic technology with greener materials prepared by facile approaches for environmental remediation. Herein we report utilization of star photocatalyst g-C₃N₄ (CN) to form highly efficient hetero-assemblies along with acidified g-C₃N₄ (ACN), polyaniline (PANI), reduced graphene oxide (RGO) and biochar. By use of these organic semiconductors we synthesize g-C₃N₄/ACN/RGO@Biochar (GARB), g-C₃N₄/PANI/RGO@Biochar (GPRB) and ACN/PANI/RGO@Biochar (APRB) nano-assemblies with different optical response and band edge positions for a better charge flow and reduced recombination of carriers. These synthesized catalysts were used for visible light powered degradation of 2,4-Dichlorophenoxy acetic acid (2,4-D) and ibuprofen (IBN). APRB performs the best and degrades 99.7% and 98.4% of 2,4-D and IBN (20 mg L^-1) under Xe lamp exposure in 50 min and retention of high activity in natural sunlight. Optical analysis, photoelectrochemical response and radical quenching studies show both hydroxyl and superoxide radical anions as major reactive species and a Z-scheme photocatalytic mechanism. RGO acts as an electron mediator and protects higher positioned bands of PANI and ACN in APRB for a remarkable photocatalytic activity for a metal free material. The degradation pathway was analyzed by LC-MS analysis and 42% and 40% total organic carbon was removed in 2 h for 2,4-D and IBN degradation respectively. The toxicity of degraded products was analyzed by analyzing viability of human peripheral blood cells with retaining of 99.1% cells.