Photocatalytic degradation of water pollutants using conducting polymer-based nanohybrids: A review on recent trends and future prospects

Synthesis, Characterization, and In Silico Studies of Cysteine Modified Polyaniline Against Bovine Serum and Human Serum Albumin

In this paper, oligomers of polyaniline (PANI) modified with cysteine (Cys) were synthesized via using different mole ratios of aniline: Cysteine (80:20, 50:50, and 20:80) followed by ultrasound-assisted polymerization of PANI. The structure and morphological properties of Cys-PANI were confirmed from FTIR and scanning electron microscopy (SEM). Fluorescence quenching of bovine serum albumin (BSA) and human serum albumin (HSA) was carried out using different concentrations of the Cys-PANI oligomers. There was a slight difference in the static quenching of HSA as compared to BSA, which was attributed to the different structures of the two serum albumins. The quenching rate constant was found to increase with cysteine content in the polymer, showing that the loading of higher amount of Cys increased the solubility of the Cys-PANI oligomers. This led to electrostatic attraction between the water molecules shielding the serum albumins and the Cys-PANI oligomers. The docking studies confirmed the binding to be hydrogen bonding, π-alkyl and π-amide stacked interactions. The binding energy of the Cys-PANI oligomers with mole ratio 50:50 and 20:80 was found to be better as compared to the Cys-PANI oligomer. The binding energy values showed that these polymers could potentially be used in fabricating protein sensors.

Thermophysical properties of graphene reinforced with polymethyl methacrylate nanoparticles for technological applications: a molecular model

CONTEXT

"Nanostructure of graphene-reinforced with polymethyl methacrylate" (PMMA-G), and vice versa, is investigated using its molecular structure, in the present work. The PMMA-G nanostructure was constructed by bonding PMMA with graphene nanosheet in a sense to get three different configurations. Each configuration consisted of polymeric structures with three degrees of polymerization (such as monomers, dimers, and trimers polymers, respectively). The results obtained make this new PMMA-G material more reliable and useful for several important technological applications, such as the construction of devices for hydrogen storage, batteries, super-capacitors, sensors and solar cells, and dental materials, among others. The PMMA reinforcement with graphene favors its thermal stability maintaining greater dimensional stability against thermal variations (minimal deformation); this is crucial for electronic devices and for packaging systems that undergo repeated thermal cycles during their manufacture, and also they are good thermal insulators. For microelectronic devices, such as chips and sensors, with low thermal expansion coefficients, it may prevent unwanted deformation. The PMMA density increases when it is reinforced with graphene, the polymers tend to be stiffer and stronger, important for applications where greater structural strength is required, and also become less soluble in solvents than pure PMMA and more resistant to the action of chemicals. Comparing a common polyvinyl chloride (PVC) material with the PMMA-G polymer, we found more advantages, such as the PMMA-G is less expensive, it has improved aesthetics, it is less rigid, it has more stable color, and it is less prone to keeping microorganisms alive, among others advantages.

METHODS

Materials Studio (MS) software is used as the best and most reliable computational tool in the sense of analyzing some thermophysical properties of graphene reinforced with polymethyl methacrylate nanoparticles. The most stable PMMA nanostructures, graphene and PMMA-G, were obtained by applying density functional theory methods implemented by a DMol3 computational code under the MS software. The Synthia computational code, also under MS software, which is based on connectivity indices methods derived from graph theory combined with geometric variables, was also applied, to each polymerized structure, obtaining some of the important thermophysical properties; i.e., Van der Waals volume, molar volume, coefficient of volumetric thermal expansion, density, solid phase molar heat capacity at constant pressure, thermal conductivity, glass transition temperature, secondary relaxation temperature, and half decomposition temperature. The best-used hardware was a T7500 Dell Workstation, with 3.47 GHz Quad-Core Processors, 96 Gb RAM memory, and a perpetual MS software license.

Elimination of antibiotic contaminants from wastewater using polycarbazole nanocomposites as microwave-activated catalysts

Ciprofloxacin (CIP) is a widely used antibiotic, and its presence in water bodies poses a risk due to its resistance to conventional wastewater treatment processes. The accumulation of such pharmaceuticals can disrupt aquatic ecosystems, harm aquatic life, and contribute to ecological imbalances. Therefore, the degradation of CIP is of immense environmental significance. This study presents the microwave-assisted catalytic degradation of the antibiotic drug CIP using nanocomposites of carbazole copolymerized with pyrrole (PCz-co-PPy) and with thiophene (PCz-co-PTh). The PCz-co-PPy and PCz-co-PTh nanocomposites were synthesized through an ultrasound-assisted method. The resulting nanocomposites were characterized using spectral and morphological analyses. FT-IR and UV-Vis spectroscopy confirmed successful intercalation and copolymerization, while FESEM images revealed a chain-like morphology. These copolymer nanocomposites were employed as microwave-active catalysts for CIP degradation, achieving an optimal degradation efficiency of 95% within 21 min using PCz-co-PPy-50/50 and PCz-co-PTh-50/50 at 600 W microwave power. The degradation followed pseudo-first-order kinetics, with rate constants calculated as 0.031 min-1, 0.020 min-1, 0.030 min-1, 0.056 min-1, and 0.071 min-1for PCz, PPy, PTh, PCz-co-PPy-50/50, and PCz-co-PTh-50/50 nanocomposites, respectively, for a 50 mg l-1CIP solution. The catalytic efficiency is attributed to the formation of microwave-induced active species, including hot spots, electrons (e-), holes (h+), superoxide radicals (•O2-), and hydroxyl radicals (•OH). Scavenger analysis verified that •OH and •O2-radicals play a crucial role in CIP degradation. A possible degradation mechanism and pathway for the nanocomposite system is proposed.

Enhanced Degradation of Norfloxacin Under Visible Light by S-Scheme Fe2O3/g-C3N4 Heterojunctions

S-scheme Fe2O3/g-C3N4 heterojunctions were successfully fabricated by the ultrasonic assistance method to remove norfloxacin (NOR) under visible light irradiation. The synthesized catalysts were well studied through various techniques. The obtained Fe2O3/g-C3N4 heterojunctions exhibited an optimal photocatalytic degradation of 94.7% for NOR, which was 1.67 and 1.28 times higher than using Fe2O3 and g-C3N4 alone, respectively. In addition, the kinetic constant of NOR removal with Fe2O3/g-C3N4 composites was about 0.6631 h-1, and NOR photo-deegradation was still 86.7% after four cycles. The enhanced photocatalytic activity may be mainly attributed to the formation of S-scheme Fe2O3/g-C3N4 heterojunctions with built-in electric fields, which were beneficial to the separation and transfer of photostimulated charge carriers. Furthermore, a possible photo-degradation mechanism of NOR for S-scheme Fe2O3/g-C3N4 heterojunctions is described.

Investigation of Doehlert matrix conception in novel intrinsically conducting polymers based on selenium nanoparticles for wastewater treatment: Synthesis, characterization, kinetic and chemometric study

The synthesis of robust intrinsically conducting polymers (ICPs) based on nanoparticles is becoming increasingly attractive to the research community due to the unique properties of these nanocomposites. Indeed, as organic semiconductors, ICPs combine both polymer and metal properties in a single structure. This study presents an innovative approach in which the Doehlert Matrix (DM) is applied to a novel ICP nanocomposite based on polyaniline (Pani) coupled with selenium (Se) loaded mesoporous titania (TiO2) for wastewater treatment by photocatalysis. It includes both the elaboration routes of ICP nanocomposites, characterization of materials by X-ray diffraction (XRD), BET analysis, thermogravimetric analysis (TGA), RAMAN spectroscopy and Fourier transform infrared spectroscopy (FTIR) and photodegradation of methylene blue (MB) as a representative of dye pollutant. In addition, the photocatalytic process has been optimized by a novel DM conception. The effect of the pH of the solution, the catalyst dosage and the initial pollutant concentration was investigated. The optimum conditions were found to be: initial MB concentration of 15 mg/L, the catalyst dosage of 69 mg and pH of 9.6 with an operating time of 75 min, with a coefficient of determination R2 equal to 0.9985. The removal efficiency of BM was close to 97 %. The study shows that the new ICP nanocomposites improve the photocatalytic efficiency compared to pure titania and/or pure Pani. In addition, as the ternary Pani-Se-TiO2 nanocomposite could be obtained from a low-cost synthesis, it is a very promising material for use in wastewater treatment.

Tailoring structural and optical properties of Cu(II)-induced MgAl2O4 nanoparticles and their response to toxic dyes under solar illumination

Worldwide environmental challenges pose critical problems with the growth of the global economy. Addressing these issues requires the development of an eco-friendly and sustainable catalyst for degrading organic dye pollutants. In this study, copper-doped magnesium aluminates (CuxMg1-xAl2O4) with x = 0.0-0.8 were synthesized using a citrate-based combustion route. The inclusion of Cu(II) significantly impacted the structural, microstructural, optical, and photocatalytic activity of the catalyst. Rietveld analysis of X-ray diffraction powder profiles revealed single-phase spinels crystallized in the face-centered cubic unit cell with Fd 3 ¯ m space group. Chemical states of the ions, surface morphology, and elemental investigation were analyzed by X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy, respectively. UV-visible and diffuse reflectance spectroscopies confirmed the reduction of the band gap due to Cu(II) doping, validated by first-principle investigations using the WIEN2k code. The catalyst with x = 0.8 showed higher photocatalytic efficacy (90% and 93%) for removing two azo organic dye pollutants, rhodamine B and methyl orange, respectively, within 120 min. Degradation kinetics followed a pseudo-first-order mechanism. The doped (0.8) sample was structurally and morphologically stable and reusable under visible irradiation, retaining performance after three runs. Scavenger studies confirmed hydroxyl and superoxide radicals' involvement in the degradation. This work presents an effective approach to enhancing CuxMg1-xAl2O4 catalysts' photodegradation performance, with potential applications in pharmaceuticals and wastewater remediation.

Recent insights into mechanism of modified bio-adsorbents for the remediation of environmental pollutants

Rapid industrialization has exacerbated the hazard to health and the environment. Wide spectrums of contaminants pose numerous risks, necessitating their disposal and treatment. There is a need for further remediation methods since pollutant residues cannot be entirely eradicated by traditional treatment techniques. Bio-adsorbents are gaining popularity due to their eco-friendly approach, broad applicability, and improved functional and surface characteristics. Adsorbents that have been modified have improved qualities that aid in their adsorptive nature. Adsorption, ion exchange, chelation, surface precipitation, microbial uptake, physical entrapment, biodegradation, redox reactions, and electrostatic interactions are some of the processes that participate in the removal mechanism of biosorbents. These processes can vary depending on the particular biosorbent and the type of pollutants being targeted. The systematic review focuses on the many modification approaches used to remove environmental contaminants. Different modification or activation strategies can be used depending on the type of bio-adsorbent and pollutant to be remediated. Physical activation procedures such as ultrasonication and pyrolysis are more commonly used to modify bio-adsorbents. Ultrasonication process improves the adsorption efficiency by 15-25%. Acid and alkali modified procedures are the most effective chemical activation strategies for adsorbent modification for pollution removal. Chemical modification increases the removal to around 95-99%. The biological technique involving microbial culture is an emerging field that needs to be investigated further for pollutant removal. A short evaluation of modified adsorbents with multi-pollutant adsorption capability that have been better eliminated throughout the adsorption process has been provided.

New Insights on Designing the Next-Generation Materials for Electrochemical Synthesis of Reactive Oxidative Species Towards Efficient and Scalable Water Treatment: A Review and Perspectives

Electrochemical water remediation technologies offer several advantages and flexibility for water treatment and degradation of contaminants. These technologies generate reactive oxidative species (ROS) that degrade pollutants. For the implementation of these technologies at an industrial scale, efficient, scalable, and cost-effective in-situ ROS synthesis is necessary to degrade complex pollutant mixtures, treat large amount of contaminated water, and clean water in a reasonable amount of time and cost. These targets are directly dependent on the materials used to generate the ROS, such as electrodes and catalysts. Here, we review the key design aspects of electrocatalytic materials for efficient in-situ ROS generation. We present a mechanistic understanding of ROS generation, including their reaction pathways, and integrate this with the key design considerations of the materials and the overall electrochemical reactor/cell. This involves tunning the interfacial interactions between the electrolyte and electrode which can enhance the ROS generation rate up to ~ 40% as discussed in this review. We also summarized the current and emerging materials for water remediation cells and created a structured dataset of about 500 electrodes and 130 catalysts used for ROS generation and water treatment. A perspective on accelerating the discovery and designing of the next generation electrocatalytic materials is discussed through the application of integrated experimental and computational workflows. Overall, this article provides a comprehensive review and perspectives on designing and discovering materials for ROS synthesis, which are critical not only for successful implementation of electrochemical water remediation technologies but also for other electrochemical applications.

Photocatalytic membrane coated with α-Fe2O3/Fe3O4 for enhanced filtration performance and antifouling property in surface water treatment

A photocatalytic membrane coated with α-Fe2O3/Fe3O4 nanoparticles has been developed to address the challenges of membrane fouling and organic removal in the treatment of natural surface water. The photocatalytic and filtration properties of the membranes were investigated through a variety of methods. The successful preparation of iron oxide was confirmed by UV-vis diffuse reflectance spectra and X-ray diffractometry, with α-Fe2O3 identified as the primary photocatalytic agent. A commercial ultrafiltration (UF) membrane was employed as a comparison to evaluate the photocatalytic performance and filtration properties of the modified membrane. Results showed that the photocatalytic membrane achieved better removal rates for UV254 (22.0%) and specific fluorescent organic compounds, such as component 2 (19.38%) and component 3 (16.89%), compared to the control group. Furthermore, both irreversible and reversible fouling resistances of the prepared membranes were significantly lower than that of the control group, with reductions of 39.4% and 50.2%, respectively. The membrane coated with α-Fe2O3/Fe3O4 nanoparticles exhibited moderate removal of protein-like and terrestrially derived humic-like fluorescent organics while controlling membrane fouling. Although the α-Fe2O3/Fe3O4 nanoparticles-coated photocatalytic membrane demonstrated good anti-fouling properties, the removals of organic matters were not as effective as anticipated due to the shorter hydraulic retention time. This study provides valuable insights for enhancing pollutant degradation and anti-fouling properties of membranes through the utilization of solar photocatalytic α-Fe2O3/Fe3O4 surface-modified membranes in the treatment of natural surface water.

A critical review on the removal of toxic pollutants from contaminated water using magnetic hybrids

The persistence of organic/inorganic pollutants in the water has become a serious environmental issue. Among the different pollutants, dyes and heavy metal pollution in waterways are viewed as a global ecological problem that can have an impact on humans, plants, and animals. The necessity to develop a sustainable and environmentally acceptable approach to remove these toxic contaminants from the ecosystem has been raised. In the past two decades, rapid industrialization and anthropogenic activities in developed countries have aggravated environmental pollution. Industrial effluents that are discharged directly into the natural environment taint the water, which has a consequence for the water resources. Magnetic nanohybrids are broadly investigated materials used in the adsorption and photocatalytic degradation of poisonous pollutants present across water effluents. In the present review, the toxic health effects of heavy metals and dyes from the water environment have been discussed. This paper reviews the role of magnetic nanohybrids in the removal of pollutants from the water environment, providing an adequate point of view on their new advances regarding their qualities, connection methodologies, execution, and their scale-up difficulties.

Preparation of gallotannin loaded chitosan/zinc oxide nanocomposite for photocatalytic degradation of organic dye and antibacterial applications

Chitosan functionalization is a growing field of interest to enhance the unique characteristics of metal oxide nanoparticles. In this study, a facile synthesis method has been used to develop a gallotannin loaded chitosan/zinc oxide (CS/ZnO) nanocomposite. Initially, white color formation confirmed the formation, and physico-chemical natures of the prepared nanocomposite were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Crystalline of CS amorphous phase and ZnO patterns were demonstrated by XRD. FTIR revealed the presence of CS and gallotannin bio-active groups in the formed nanocomposite. Electron microscopy study exhibited that the produced nanocomposite had an agglomerated sheets like morphology with an average size of 50-130 nm. Further, the produced nanocomposite was assayed for methylene blue (MB) degradation activity from aqueous solution. After 30 min of irradiation, the efficiency of nanocomposite degradation was found to be 96.64 %. Moreover, prepared nanocomposite showed a potential and concentration-dependent antibacterial activity against S. aureus. In conclusion, our findings revealed that prepared nanocomposite can be used as an excellent photocatalyst as well as a bactericidal agent in industrial and clinical sectors.

Novel morphological mono-metallic substituted polyoxometalate immobilized 3-(aminopropyl)-imidazole photocatalysts for visible-light driven degradation: Anti-bacterial activity, membrane bacterial activity applications

A novel keggin-type tetra-metalates substituted polyoxometalate was functionalized by 3-(aminopropyl)-imidazole (3-API) supporting a ligand substitution method. In this paper, polyoxometalate (POMs) (NH₄)₃ [PMo₁₂O₄₀] and transition metal substituted of (NH₄)₃ [{PM^IVMo₁₁O₄₀}.(H₂O)] (M = Mn, V) are used as one of the adsorbents. The 3-API/POMs hybrid have been synthesized and used as adsorbent for the photo-catalysis of azo-dye molecule degradation after visible-light illumination as a simulated organic contaminant in water. The transition metal (M = M^IV, V^IV) substituted keggin-type anions (MPOMs) were synthesized, which reveals the degradation of methyl orange (MO) of about 94.0 % and 88.6 %. Immobilizing high redox ability POMs as an efficient acceptor of photo generated electron, on metal 3-API. In the presence of visible light irradiation result reveals that 3-API/POMs (89.9 %) have incredibly achieved after certain irradiation time and at specific conditions (3)-API/POMs; photo-catalysts dose = 5mg/100 ml, pH = 3 and MO dye concentration = 5 ppm). As the surface of POM catalyst has strong absorption of azo-dye MO molecule engaged as a molecular exploration through photo catalytic reactant. From the SEM images it is clear that the synthesized POMs based materials and POMs conjugated MO have varieties of morphological changes observed such as flakes, rods and spherical like structures. Anti-bacterial study reveals that the process of targeted microorganism occur higher activity against pathogenic bacterium for 180 min of visible-light irradiation is measured in terms of zone of the inhibition. Furthermore, the photo catalytic degradation mechanism of MO using POM, metaled POMs and 3-API/POMs also has been discussed.

Heterogeneous photocatalytic oxidation for the removal of organophosphorus pollutants from aqueous solutions: A review

Organophosphorus pollutants (OPs), which are compounds containing carbon‑phosphorus bonds or phosphate derivatives containing organic groups, have received much attention from researchers because of their persistence in the aqueous environment for long periods of time and the threat they pose to human health. Heterogeneous photocatalysis has been widely applied to the removal of OPs from aqueous solutions due to its better removal effect and environmental friendliness. In this review, the removal of OPs from aqueous matrices by heterogeneous photocatalysis was presented. Herein, the application and the heterogeneous photocatalysis mechanism of OPs were described in detail, and the effects of catalyst types on degradation effect are discussed categorically. In particular, the heterojunction type photocatalyst has the most excellent effect. After that, the photocatalytic degradation pathways of several OPs were summarized, focusing on the organophosphorus pesticides and organophosphorus flame retardants, such as methyl parathion, dichlorvos, dimethoate and chlorpyrifos. The toxicity changes during degradation were evaluated, indicating that the photocatalytic process could effectively reduce the toxicity of OPs. Additionally, the effects of common water matrices on heterogeneous photocatalytic degradation of OPs were also presented. Finally, the challenges and perspectives of heterogeneous photocatalysis removal of OPs are summarized and presented.

Polymerization and Applications of Poly(methyl methacrylate)-Graphene Oxide Nanocomposites: A Review

Graphene oxide (GO)-incorporated poly(methyl methacrylate) (PMMA) nanocomposites (PMMA-GO) have demonstrated a wide range of outstanding mechanical, electrical, and physical characteristics. It is of interest to review the synthesis of PMMA-GO nanocomposites and their applications as multifunctional structural materials. The attention of this review is to focus on the radical polymerization techniques, mainly bulk and emulsion polymerization, to prepare PMMA-GO polymeric nanocomposite materials. This review also discusses the effect of solvent polarity on the polymerization process and the types of surfactants (anionic, cationic, nonionic) and initiator used in the polymerization. PMMA-GO nanocomposite synthesis using radical polymerization-based techniques is an active topic of study with several prospects for considerable future improvement and a variety of possible emerging applications. The concentration and dispersity of GO used in the polymerization play critical roles to ensure the functionality and performance of the PMMA-GO nanocomposites.

Polymer Composite-Based Materials with Photocatalytic Applications in Wastewater Organic Pollutant Removal: A Mini Review

The development of new technologies using nanomaterials has allowed scientists to design advanced processes with many applications in environmental protection, energy production and storage, and medicinal bio-mediated processes. Due to their significant potential applications in different branches of science, the development of new polymer composites represents a priority, especially for nano-technological processes. Interest in polymeric composites was outlined by the synthesis of a large number of nano- or mezzo-scale materials with targeted functional properties for polymer matrix hybridization. The present mini review explores some of the most representative and recent papers reporting the photocatalytic activity of polymer composites toward different organic compounds (dyes, pharmaceutically active molecules, phenol, etc.). The polymer composites were divided based on their composition and photocatalytic activity. TiO2- and ZnO-based polymeric composites have been described here in light of their photocatalytic activity toward different pollutants, such as rhodamine B, phenol, or methyl orange. Polymeric composites based on WO3, Fe2O3, or Bi2MoO6 were also described. The influence of different polymeric composites and photocatalytic parameters (light spectra and intensity, pollutant molecule and concentration, irradiation time, and photocatalyst dosage) on the overall photocatalytic efficiency indicates that semiconductor (TiO2, ZnO, etc.) insertion in the polymeric matrix can tune the photocatalytic activity without compromising the structural integrity. Future perspectives and limitations are outlined considering the systematic and targeted description of the reported results. Adopting green route synthesis and application can add economic and scientific value to the knowledgebase by promoting technological development based on photocatalytic designs.

Promotion effect of free Ag+ ions on photocatalytic dechlorination processes

Free silver ions (Ag+) in the solution exhibit enhanced photocatalytic dechlorination processes of organic chloride, including 2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, over PhC2Cu under visible light irradiation.