Removal of safranin dye from water using polypyrrole nanofiber/Zn-Fe layered double hydroxide nanocomposite (Ppy NF/Zn-Fe LDH) of enhanced adsorption and photocatalytic properties

Progress in layered double hydroxides (LDHs): Synthesis and application in adsorption, catalysis and photoreduction

Layered double hydroxides (LDHs), also known as anionic clays, have attracted significant attention in energy and environmental applications due to their exceptional physicochemical properties. These materials possess a unique structure with surface hydroxyl groups, tunable properties, and high stability, making them highly desirable. In this review, the synthesis and functionalization of LDHs have been explored including co-precipitation and hydrothermal methods. Furthermore, extensive research on LDH application in toxic pollutant removal has shown that modifying or functionalizing LDHs using materials such as activated carbon, polymers, and inorganics is crucial for achieving efficient pollutant adsorption, improved cyclic performance, as well as effective catalytic oxidation of organics and photoreduction. This study offers a comprehensive overview of the progress made in the field of LDHs and LDH-based composites for water and wastewater treatment. It critically discusses and explains both direct and indirect synthesis and modification techniques, highlighting their advantages and disadvantages. Additionally, this review critically discusses and explains the potential of LDH-based composites as absorbents. Importantly, it focuses on the capability of LDH and LDH-based composites in heterogeneous catalysis, including the Fenton reaction, Fenton-like reactions, photocatalysis, and photoreduction, for the removal of organic dyes, organic micropollutants, and heavy metals. The mechanisms involved in pollutant removal, such as adsorption, electrostatic interaction, complexation, and degradation, are thoroughly explained. Finally, this study outlines future research directions in the field.

Advancements in textile dye removal: a critical review of layered double hydroxides and clay minerals as efficient adsorbents

The textile industry is responsible for producing large volumes of wastewater that contain a wide variety of dye compounds. This poses a significant environmental hazard and risks harming both ecosystems and living organisms. This review study explores the advancements in adsorption research for dye removal, with a particular emphasis on the development of various adsorbents. The article provides detailed insights into the toxicity and classification of dyes, different treatment techniques, and the characteristics of numerous adsorbents, with special attention to layered double hydroxides (LDH) and clay minerals. A comprehensive list of adsorbents, encompassing natural materials, agricultural by-products, industrial waste, and activated carbon, is discussed for effective removal of different dyes. Furthermore, the review extensively examines the influence of various adsorption variables, such as pH, initial dye concentration, adsorbent dosage, temperature, contact time, ionic strength, and pore volume of the adsorbent. Additionally, the application of response surface methodology for optimizing adsorption variables is elucidated. Commonly, electrostatic attraction, π-π interactions, n-π interactions, van der Waals forces, H-bonding, and pore diffusion play a major role in adsorption mechanism. The review also found that LDH can eliminate a wide range of dyes from wastewater, achieving excellent uptake capacities often exceeding 500 mg/g, with a removal efficiency of 99%. The Langmuir isotherm and pseudo-second-order kinetic equations gave the best fit to most of the adsorption data. Overall, this review serves as a valuable resource for researchers and practitioners seeking sustainable solutions to address the environmental challenges posed by textile dye contamination.

Synthesis and Characterization of Iron-Rich Glauconite Nanorods by a Facile Sonochemical Method for Instantaneous and Eco-friendly Elimination of Malachite Green Dye from Aquatic Environments

Novel glauconite nanorods (GNRs) were synthesized by the sonication-induced chemical expansion and scrolling process of natural glauconite. The synthetic nanostructure was characterized by different analytical techniques as a superior adsorbent for the malachite green dye (MG). The synthetic GNRs were detected as porous nanorods with an average length of 150 nm to 5 μm, an average diameter of 25 to 200 nm, and a specific surface area of 123.7 m2/g. As an adsorbent for MG, the synthetic GNRs showed superior uptake capacity up to 1265.6 mg/g at the saturation stage, which is higher than most of the recently developed highly adsorbent dyes. The adsorption behavior and mechanistic properties were depicted by using modern and traditional equilibrium modeling. The kinetic assumption of the pseudo-first-order model (R2 > 0.94) and the classic isotherm of the Langmuir equilibrium model (R2 > 0.97) were used to describe the adsorption reactions. The steric investigation demonstrates that each active site on the surface of GNRs can adsorb up to three MG molecules (n = 2.19-2.48) in vertical orientation involving multimolecular mechanisms. Also, the determined active site density (577.89 mg/g) demonstrates the enrichment of the surface of GNRs with numerous adsorption receptors with strong affinity for the MG dye. The energetic study, including Gaussian energy (6.27-7.97 kJ/mol) and adsorption energy (9.45-10.43 kJ/mol), revealed that GNRs had physically adsorbed the dye, which might involve electrostatic attraction, hydrogen bonding, van der Waals forces, and dipole forces. The internal energy, enthalpy, and entropy determined the exothermic and spontaneous uptake of MG.

Recent Progress of Layered Double Hydroxide-Based Materials in Wastewater Treatment

Layered double hydroxides (LDHs) can be used as catalysts and adsorbents due to their high stability, safety, and reusability. The preparation of modified LDHs mainly includes coprecipitation, hydrothermal, ion exchange, calcination recovery, and sol-gel methods. LDH-based materials have high anion exchange capacity, good thermal stability, and a large specific surface area, which can effectively adsorb and remove heavy metal ions, inorganic anions, organic pollutants, and oil pollutants from wastewater. Additionally, they are heterogeneous catalysts and have excellent catalytic effect in the Fenton system, persulfate-based advanced oxidation processes, and electrocatalytic system. This review ends with a discussion of the challenges and future trends of the application of LDHs in wastewater treatment.

Efficient photocatalytic degradation of ciprofloxacin by graphite felt-supported MnS/Polypyrrole composite: Dominant reactive species and reaction mechanisms

The accumulation of antibiotics in aquatic environments poses a serious threat to human health. Photocatalytic degradation is a promising method for removing antibiotics from water, but its practical implementation requires improvements in photocatalyst activity and recovery. Here, a novel graphite felt-supported MnS/Polypyrrole composite (MnS/PPy/GF) was constructed to achieve effective adsorption of antibiotics, stable loading of photocatalyst, and rapid separation of spatial charge. Systematic characterization of composition, structure and photoelectric properties indicated the efficient light absorption, charge separation and migration of the MnS/PPy/GF, which achieved 86.2% removal of antibiotic ciprofloxacin (CFX), higher than that of MnS/GF (73.7%) and PPy/GF (34.8%). The charge transfer-generated 1O2, energy transfer-generated 1O2, and photogenerated h+ were identified as the dominant reactive species, which mainly attacked the piperazine ring in the photodegradation of CFX by MnS/PPy/GF. The •OH was confirmed to participate in the defluorination of CFX via hydroxylation substitution. The MnS/PPy/GF-based photocatalytic process could ultimately achieve the mineralization of CFX. The facile recyclability, robust stability, and excellent adaptability to actual aquatic environments further confirmed MnS/PPy/GF is a promising eco-friendly photocatalyst for antibiotic pollution control.

Room temperature fabrication of cobalt mullite for the snappy adsorption of cationic and anionic dyes

Cobalt mullite adsorbent for the robust adsorption performance toward Victoria Blue (VB) and Metanil Yellow (MY) is fabricated by the sol-gel method at room temperature using dipropylamine as a structure-directing agent. The synthesized adsorbent is characterized by XRD, FT-IR, and HRTEM. From these analyses, it is found that dipropylamine binds with the alumina and cobalt oxide, which makes it into tetrahedral to octahedral form. This interaction causes the formation of cobalt mullite. It is observed that trigonal alumina and orthorhombic cobalt mullite are interlinked to form a hybrid network. The special feature of adopting this adsorbent for the adsorption of VB and MY is that it has a large amount of Brønsted acid site because of the octahedral coordination of Al and Co. The large availability of acid sites in the framework and hybridization of two different network systems favors robust adsorption. The rate of adsorption (K₂ = 0.00402 g/mg.min for VB and K₂ = 0.004 g/mg.min for MY) and adsorption capacity (Q_e = 102.041 mg/g for VB and Q_e = 19.0406 mg/g for MY) are greater for VB than MY. This may be due to the more steric factor involved in MY than VB. Thermodynamic parameter indicated that the adsorption of VB and MY is spontaneous, endothermic, and increased randomness in the adsorbent-adsorbate interface. The results from the enthalpy value (ΔH° = 65.43 kJ/mol for VB and ΔH° = 44.729 kJ/mol for MY) revealed that the chemisorption is involved in the adsorption process.

Intercalated-Laurate-Enhanced Photocatalytic Activities of Ni/Cr-Layered Double Hydroxides

Laurate (LA−)-intercalated nickel–chromium-layered double hydroxides (LDHs) were synthesized using the co-precipitation method and investigated as a potential photocatalyst for methylene orange (MO) degradation. For comparison, a series of LDHs with various molar ratios of Ni2+(or Mg2+)/Cr3+(or Fe3+)/LA−(or CO32−) were prepared. X−ray diffraction (XRD) and element analysis showed that Ni/Cr(2/1)−1.0 LA LDH had the most ordered crystal structure, and showed the same photocatalytic decolorization performance as Mg/Cr(2/1)−1.0LA LDH towards MO, which was significantly superior to Ni/Cr−CO3 LDH, Ni/Fe(2/1)−1.0LA LDH, and Ni/Cr−CO3 LDH with LA−, and Cr3+ with LA−. The photocatalytic removal rate of MO with the initial concentration of 100 mg/L by Ni/Cr(2/1)−1.0LA LDH (0.5 g/L) could be up to 80% with UV light irradiation for 3 h, which was almost twice higher than that of the sorption test. The photocatalytic reaction was in accordance with the pseudo-first-order kinetics, which implied that the catalytic process took place on the surface of the catalyst. All the results indicate the photodegradation of MO by Ni/Cr−LA LDHs was enhanced by the sorption of MO onto the intercalated LA− in the interlayer. The free radical capture experiments suggest that the main role of the photocatalytic mechanism of Ni/Cr−LA LDHs could be the •O2− with high oxidation activity produced by the electron-hole pairs of LDH, as excited by UV light. Additionally, the •O2− further reacted with the adjacent MO molecule pre-sorbed on the intercalated LA.

Photocatalytic degradation of remdesivir nucleotide pro-drug using [Cu(1-methylimidazole)4(SCN)2] nanocomplex synthesized by sonochemical process: Theoretical, hirshfeld surface analysis, degradation kinetic, and thermodynamic studies

The first ultrasonic synthesis of [Cu(L)₄(SCN)₂] (L = 1-methylimidazole) nanocomplex was carried out under ultrasonic irradiation, and its photocatalytic performance for the degradation of remdesivir (RS) under sunlight irradiation was comprehensively investigated for the first time in this study. The physicochemical properties of the synthesized photocatalyst were examined by Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. The band gap of the synthesized [Cu(L)₄(SCN)₂] nanocomplex was determined to be 2.60 eV by the diffuse reflectance spectroscopy method using Kubelka-Munk formula. The photocatalytic performance of nanocomplex was examined for the removal of remdesivir under sunlight from water for which the results indicated that an amount of 0.5 gL^-1 of the [Cu(L)₄(SCN)₂] nanocomplex was sufficient to remove more than 96% remdesivir from its 2 mg L^-1 concentration within 20 min, at pH = 6. The kinetic data showed that the photodegradation onto the [Cu(L)₄(SCN)₂] nanocomplex has a high correlation (0.98) with the pseudo-second-order kinetic model. The decrease in chemical oxygen demand (COD) (from 70.5 mg L^-1 to 36.4 mg L^-1) under optimal conditions clearly confirmed the mineralization of the RS drug. The values of ΔS° (-0.131 kJ mol^-1 K^-1) and ΔH° (-49.750 kJ mol^-1) were negative, indicating that the adsorption process was spontaneous and more favorable in lower temperatures. Moreover, the RS structure in the open shell state and the high HOMO and LUMO gaps based on the M06/6-31 + G (d) level of theory may be a confirmation of this fact. In addition, the Hirshfeld surface analysis (HSA) of the crystal packing of the prepared complex was discussed in detail to evaluate the interactions between the crystal packings. The results of this study confirm that the [Cu(L)₄(SCN)₂] nanocomplex can be successfully used for the photodegradation of pharmaceutical contaminants.

Application of Polypyrrole-Based Electrochemical Biosensor for the Early Diagnosis of Colorectal Cancer

Although colorectal cancer (CRC) is easy to treat surgically and can be combined with postoperative chemotherapy, its five-year survival rate is still not optimistic. Therefore, developing sensitive, efficient, and compliant detection technology is essential to diagnose CRC at an early stage, providing more opportunities for effective treatment and intervention. Currently, the widely used clinical CRC detection methods include endoscopy, stool examination, imaging modalities, and tumor biomarker detection; among them, blood biomarkers, a noninvasive strategy for CRC screening, have shown significant potential for early diagnosis, prediction, prognosis, and staging of cancer. As shown by recent studies, electrochemical biosensors have attracted extensive attention for the detection of blood biomarkers because of their advantages of being cost-effective and having sound sensitivity, good versatility, high selectivity, and a fast response. Among these, nano-conductive polymer materials, especially the conductive polymer polypyrrole (PPy), have been broadly applied to improve sensing performance due to their excellent electrical properties and the flexibility of their surface properties, as well as their easy preparation and functionalization and good biocompatibility. This review mainly discusses the characteristics of PPy-based biosensors, their synthetic methods, and their application for the detection of CRC biomarkers. Finally, the opportunities and challenges related to the use of PPy-based sensors for diagnosing CRC are also discussed.

Superior removal of methylene blue using green fabricated pomegranate peel/nano-hematite composite: reusability, isotherm and kinetics study

Green hematite nanoparticles were synthesized using pomegranate peel extract of different concentrations (2 g, 4 g, and 6 g) and in the presence of the peel residuals. The obtained products defined as PP/GNH (I), PP/GNH (II), and PP/GNH (III) referring to the hematite nanoparticles at different concentrations compositing with pomegranate peel residuals. The products were addressed as green adsorbents for methylene blue dye contaminants in water. They exhibit superior adsorption properties with theoretical q_max of 666, 1111, and 909 mg/g for PP/GNH (I), PP/GNH (II), and PP/GNH (III), respectively. The equilibration times were attained after 480 min for the three products. The isotherm and kinetic studies indicate that the adsorption systems for the synthetic materials are of chemisorption type. The adsorption behaviors of these systems can be demonstrated according to Pseudo-second order as well as Elovich kinetic model. Furthermore, the adsorption results reflected a mono-layer uptake form which was more suitable for the Langmuir model than other investigated models. The products also showed high performances when it comes to remove the dyes investigated such as methylene blue Congo red, safranin, methyl orange, and crystal violet. Finally, green fabricated nano hematite/pomegranate peel composites are of high stability and can be reused for five cycles.Communicated by Ramaswamy H. Sarma.

Enhancement of photocatalytic activities of ZnFe2O4 composite by incorporating halloysite nanotubes for effective elimination of aqueous organic pollutants

ZnFe₂O₄ is a highly desirable catalyst due to its exceptional photo-response in the visible light region, but various drawbacks, such as rapid recombination of photo-generated electron-hole pairs and severe particle agglomeration, make it difficult to use. In this study, a co-precipitation approach was used to create ZnFe₂O₄/HNT (ZF/HNTs) composites. XRD, SEM, TEM, FTIR, BET, and DRS were used to characterize the ZF/HNT composites. Furthermore, the effectiveness of removing crystal violet under simulated visible light irradiation was used to assess photocatalytic activity. The results showed that ZnFe₂O₄ with typical diameters of around 20 nm was significantly distributed on halloysite nanotubes. Because of the synergistic impact of the improved agglomeration phenomena of ZnFe₂O₄ and the decreased recombination rate of photo-generated electrons and holes, all of the composites had superior photocatalytic performance than pure ZnFe₂O₄. The ZF/HNTs-11 composite exhibited the highest removal performance, removing 96.7% of the sample in less than 150 min. In addition, the composite was very stable and reusable. Consequently, ZF/HNTs-11 composite is an effective catalyst for treating pollutants found in wastewater.

Renewable and eco-friendly ZnO immobilized onto dead sea sponge floating materials with dual practical aspects for enhanced photocatalysis and disinfection applications

In this study, we have investigated the role of natural dead sea sponge (DSS, Porifera) as a three-dimensional (3D) porous host substrate for the immobilization of nanostructured ZnO material towards the development of ZnO based floating photocatalysts for efficient removal of methylene blue (MB) dye under the illumination of sunlight. After photodegradation, the treated water after dye degradation contains several pathogens, different disinfectants or chemical reagents that are essentially used. This is not the case for DSS as it can naturally kill any pathogens during the wastewater treatment process. To explore these functions, ZnO nanosheets were incorporated onto DSS via hydrothermal protocol and the as prepared ZnO/DSS hybrid material exhibited approximately ∼100% degradation efficiency for the removal of MB. Importantly, the degradation kinetics associated with the fabricated ZnO/DSS was remarkably accelerated as evidenced by the high values of degradation reaction rate constants (3.35 × 10^-2min^-1). The outperformance of ZnO/DSS could be attributed to the adsorption caused by its 3D porous structure together with the high rapid oxidation of MB. Furthermore, the high charge separation of electron-hole pairs, natural porosity, and abundant catalytic sites offered by the hybrid ZnO/DSS floating photocatalyst have enabled quantitative (∼100%) degradation efficiency for MB. Finally, the excellent reusability results confirm the feasibility of using natural ZnO/DSS-based photocatalyst for practical solution of wastewater treatment and other environmental problems.

Engineered biochar supported layered double hydroxide-cellulose nanocrystals composite-: Synthesis, characterization and azo dye removal performance

In this work, engineered biochar decorated layered double hydroxides and cellulose nanocrystals (B-CuFe-CNC) biocomposites were synthesized by the facile ultrasonicated-co-precipitation technique. The biocomposite was investigated for purification of Eriochrome Black T (EBT) dye from water. The characterization results showed that the presence of CNC in biochar-layered double hydroxides resulted in a two-dimensional rod-like structure with excellent crystallinity, improved surface functionalities, and provides an attractive platform for the enhanced adsorption of azo anionic dye molecules. The adsorption system was appropriately demonstrated by the BBD-RSM (R² > 0.994). The biocomposite exhibited higher EBT adsorption in the acidic pH range (2-5) due to strong electrostatic and chemical interactions. The kinetic and isotherm results were well demonstrated by pseudo-second order, Freundlich, and Redlich Peterson models. The maximum adsorption capacity of biocomposite was 876.2 mg/g achieved within 45 min. The spectroscopic analyses imply that the high removal of EBT by biocomposite is mainly governed by electrostatic attraction, hydrogen bonding, and chemical/metal complexation mechanisms. The biocomposite maintained high EBT removal after six successive adsorption cycles and excellent dye adsorption in the different water matrices. The results suggest that tailoring biochar properties with layered double hydroxide and CNC is a promising way for the enhanced removal of dye contaminants from wastewater.

Investigation of Citrus reticulata peels as an efficient and low-cost adsorbent for the removal of safranin orange dye

Safranin orange (SO) is a cationic dye widely used in industrial sectors. It becomes a threat to the aquatic ecosystem once it reaches water resources, directly affecting photosynthetic activity and dissolved oxygen rate. In view of this scenario and considering the large production of agro-industrial waste, which provides significant disposal costs and environmental impacts, the agricultural by-products such as mandarin peels (MP) are being used as biosorbent materials. Thus, this work proposed the use of MP for SO adsorption. The material was characterized by SEM, zeta potential, and FTIR analysis, in which it was possible to verify heterogeneous porous morphology, predominantly negative surface, and organic functional groups that facilitate adsorption. The results were promising, wherein the maximum adsorption capacity was 464 mg g^-1 (318 K), 0.4 g L^-1 adsorbent concentration, 120 min equilibrium time and removal percentage of 84.75%. The experimental data showed a better fit to the Langmuir and pseudo-second order mathematical models. The thermodynamic analysis inferred spontaneous, endothermic, and reversible character for SO adsorption onto MP. The main proposed adsorptive mechanisms were hydrogen bonds, π-interactions, and electrostatic interactions. In addition, the reuse of MP showed good efficiency since the adsorption capacity was maintained above 50% after four cycles (from 77.90 to 41.55 mg g^-1). Moreover, when evaluating the effect of pH and ionic strength, it verified that the adsorption efficiency was not reduced. Therefore, when compared with other materials, the versatility and potential applicability of MP as a low-cost adsorbent for wastewater treatment is notable.

Preparation and evaluation of the antimicrobial activity of sodium alginate-grafted diphenylamine embedded with silver nanoparticles

Antibiotic nanocomposite polymers show great promise in treating a variety of pathogens that cause widespread disease. Sodium alginate-grafted diphenylamine (NaAlg-g-DPA) embedded with different ratios of silver nanoparticles (AgNPs) was fabricated and characterized through different techniques including FTIR, XRD, and SEM techniques for investigating the antimicrobial activity. XRD confirmed the crystallinity of these compounds, and the average crystal size of Na Alg-g-DPA/Ag was estimated to be 48.6 nm. Then it was applied as an antimicrobial agent and evaluated through two ways (inhibition zone and MIC techniques) against Staphylococcus aureus as gram-positive bacteria with an inhibition zone of 19.31.6 mm and 18.60.63 mm against Escherichia coli as gram-negative bacteria while with increasing the Ag ratio 2:1 there was an enhancement in their biological activity to be 21.90.69 mm against Staphylococcus aureus and with an inhibition zone of 21.32.1 mm against Escherichia coli. The outcomes of this investigation are important for the development of new composite materials with antibacterial properties for industrial applications.

Activated carbon derived from sugarcane and modified with natural zeolite for efficient adsorption of methylene blue dye: experimentally and theoretically approaches

The introduction of activated carbon/natural zeolite (AC/NZ) as an efficient and reliable nanoadsorbent for enhancing methylene blue (MB) dye adsorption. By calcining sugarcane waste at various temperatures between 500 and 900 °C, activated carbons (ACs) are formed. Both XRD and SEM were used for the characterization of the prepared adsorbents. Adsorption measurements for the removal of MB dye were made on the impact of pH, beginning MB concentration, and contact time. The maximum AC500/NZ adsorption capacity for MB dye at 25 °C, pH 7, and an AC500/NZ mass of 50 mg was found to be approximately 51 mg/g at an initial concentration of 30 ppm. The pseudo-second-order kinetics model and the Temkin isotherm model describe the adsorption process. The Temkin model shows that the adsorption energy is 1.0 kcal/mol, indicating that the MB-to-AC500/NZ adsorption process occurs physically. Our Monte Carlo (MC) simulation studies supported our findings and showed that the Van der Waals dispersion force was responsible for the MB molecule's physical adsorption. The AC500/NZ adsorbent is thought to be a strong contender for water remediation.

Insight into the Effect of Sulfonation Techniques on the Adsorption Properties of -SO3H Surface-Functionalized Coal as Adsorbent for Malachite Green Dye: Steric and Energetic Investigation

Natural coal (N.C) was sulfonated with sulfuric acid by normal stirring (MS.C) and sonication waves (SS.C) to obtain -SO₃H functionalized coal as enhanced adsorbents of malachite green dye (MG). The sulfonated products exhibit enhanced surface area (MS.C (27.2 m²/g) and SS.C (45.8 m²/g)) as compared to N.C. SS.C achieved higher acid density (14.2 mmol/g) and sulfur content (13.2 wt. %) as compared to MS.C. The impact of the sulfonation processes on the adsorption of MG was assessed based on the monolayer isotherm model of one energy. The MG Q _sat of N.C (121.3 mg/g), MS.C (226.3 mg/g), and SS.C (296.4 mg/g) validate the significant effect of the sulfonation processes by the sonication waves. This is in agreement with the active site densities that reflect the saturation of SS.C by more active sites (180.74 mg/g) than MS.C (120.38 mg/g) and N.C (70.84 mg/g). The MS.C and SS.C can adsorb three MG molecules as compared to two molecules per site of N.C. The Gaussian energy (<8 kJ/mol) and adsorption energy (<40 kJ/mol)) reflects the physisorption of MG involving van der Waals forces, hydrogen bonding, and dipole bonding forces. The thermodynamic functions demonstrate the uptake of MG by exothermic, spontaneous, feasible reactions.

Recent Literature Review of Significance of Polypyrrole and Its Biocomposites in Adsorption of Dyes from Aqueous Solution

The usage of dyes has been tremendously augmented due to industrialization and human’s intrinsic fascination with colors. Owing to their excessive usage in industries like textiles, food, cosmetics, paints, printing etc., it is indisputably a contributing factor in aquatic pollution. Dyes effluents have emerged as a burgeoning challenge. Owing to issues such as toxicity, mutagenicity, and disturbed photosynthesis associated with dye contamination, it is crucial to look for an explication to deal with this challenge. Polypyrrole-based biocomposites have been reported as good adsorbents for textile wastewater treatment. In the last decade, numerous studies have stated the effective removal of dyes via Polypyrrole-based biocomposites. This review concentrates on the implication of different Polypyrrole-based biocomposites for decontamination of dyes and synthesis methods, characteristics, and mechanism of dyes degradation by these biocomposites from wastewater.

An electroactive montmorillonite/polypyrrole ion exchange film: Ultrahigh uptake capacity and ion selectivity for rapid removal of lead ions

Contact with trace heavy metal contaminants will also lead to extremely bad health influence on human body and aquatic life. Although various adsorbents have been synthesized for the recovery of heavy metal ions, most of them shows deficient adsorption capacity, sluggish uptake rate and low selectivity. In this study, a montmorillonite/polypyrrole (MMT/PPy) film was successfully synthesized by intercalating polymers PPy into the interlayer of MMT nanosheets for selective and rapid capture of Pb²⁺. The electroactive film has ultrahigh uptake capacity (1373.29 mg⋅g^-1), which is much higher than most conventional Pb²⁺ adsorbents. Meanwhile, it had an extreme selectivity towards Pb²⁺ due to the MMT/PPy film can accurately identified Pb²⁺. Through characterization testing and data analysis, the selective and rapid uptake/release of Pb²⁺ should be realized through three ways: (1) negatively-charged laminates of MMT can generate electrostatic attraction to Pb²⁺; (2) -OH on the surface of MMT laminates can accurately identified and bonded with Pb²⁺ (M-O-H↔ M-O-Pb); (3) PPy doped by PSS^n- and protic acid can rapidly catch Pb²⁺ (PPy⁺·PSS^n-+Pb²⁺+e^-→ PPy·PSS^n-·Pb²⁺). Therefore, such a novel MMT/PPy nanocomposite film could has evident application prospect to remove Pb²⁺ from various water bodies.

Self-supported trimetallic NiZnLa nanosheets on hierarchical porous graphene oxide-polymer composite fibers for enhanced phosphate removal from water

Phosphate-induced water eutrophication has attracted global attention. Fabricating adsorbents with both high phosphate adsorption affinity and accessible separation property is challenging. Herein, PG@NZL, a hierarchical nanocomposite fibrous membrane, was fabricated via in-situ growth of La-doped NiZn-LDH (NiZnLa_0.1) over electrospun graphene oxide-polymer composite fibers (PG). The porous surface of the PG fibers provided abundant anchor sites for the vertical self-supported growth of NiZnLa_0.1 nanosheets, contributing to a high surface area. The La-doped NiZnLa_0.1 trimetallic LDH achieved a much higher adsorption capacity than NiZn-LDH. The negative adsorption energy (-1.45 eV), calculated with DFT, confirmed its spontaneous adsorption potential for phosphate. Interestingly, the PG fibers contributed to oxygen vacancies and the metal center electronic structure evolution of NiZnLa_0.1, thus strengthening the coordination with phosphate. Mechanistic analysis revealed that the high adsorption capacity of PG@NZL is attributed to its superior anion exchange property, oxygen vacancies, and inner-sphere complexation. Therefore, the flexible and easily separated PG@NZL nanocomposite fibrous membrane is a promising adsorbent for effectively treating phosphate-bearing wastewater.

Adsorption Behavior of Methylene Blue Cationic Dye in Aqueous Solution Using Polypyrrole-Polyethylenimine Nano-Adsorbent

In this work, a polypyrrole-polyethyleneimine (PPy-PEI) nano-adsorbent was successfully synthesized for the removal of methylene blue (MB) from an aqueous solution. Synthetic dyes are among the most prevalent environmental contaminants. A new conducting polymer-based adsorbent called (PPy-PEI) was successfully produced using ammonium persulfate as an oxidant. The PEI hyper-branched polymer with terminal amino groups was added to the PPy adsorbent to provide more effective chelating sites for dyes. An efficient dye removal from an aqueous solution was demonstrated using a batch equilibrium technique that included a polyethyleneimine nano-adsorbent (PPy-PEI). The best adsorption parameters were measured at a 0.35 g dosage of adsorbent at a pH of 6.2 and a contact period of 40 min at room temperature. The produced PPy-PEI nano-adsorbent has an average particle size of 25–60 nm and a BET surface area of 17 m²/g. The results revealed that PPy-PEI nano-composite was synthesized, and adsorption was accomplished in the minimum amount of time. The maximum monolayer power, qmax, for MB was calculated using the isothermal adsorption data, which matched the Langmuir isotherm model, and the kinetic adsorption data, which more closely fitted the Langmuir pseudo-second-order kinetic model. The Langmuir model was used to calculate the maximum monolayer capacity, or qmax, for MB, which was found to be 183.3 mg g⁻¹. The as-prepared PPy-PEI nano-adsorbent totally removes the cationic dyes from the aqueous solution.

Enhanced sorption and reduction of Cr(VI) by the flowerlike nanocomposites combined with molybdenum disulphide and polypyrrole

Developing high-performance adsorbent for hexavalent chromium (Cr(VI)) elimination presents an enticing prospect in environmental remediation. Herein, three-dimensional flowerlike nanospheres composed of molybdenum disulphide and polypyrrole (MoS₂@PPy) were successfully prepared via a one-pot hydrothermal and subsequent carbothermal reduction process for the removal of Cr(VI). The effects of pH, adsorbent dosage, co-existing ions, initial Cr(VI) concentration and temperature were investigated systematically by batch experiments. Benefiting from the incorporation of MoS₂, the obtained MoS₂@PPy composites showed a dramatic increase of specific surface area (149.82 m²·g^-1) and adsorption capacity (230.97 mg·g^-1) when compared with the pure PPy nanoparticles. Based on the thermodynamics study and X-ray photoelectron spectroscopy analyses, the removal process of Cr(VI) was proved to be exothermic and spontaneous, and accessible under-coordinated Mo(IV) and pyrrolic N groups coupled with redox reactions were conducive to the efficient removal of Cr(VI). Attractively, the MoS₂@PPy acted as the electron donor could also activate peroxymonosulphate for the efficient degradation of organic contaminants. These results suggested that the MoS₂@PPy was promising in Cr(VI) elimination and other kinds of organic pollutants removal in wastewater.

Green Synthesis of CS-TiO2 NPs for Efficient Photocatalytic Degradation of Methylene Blue Dye

The development of a non-malignant and sustainable treatment approach for eradicating mephitic organic dyes from freshwater resources is a daunting task. In a similar vein, the current work investigates the mitigation of methylene blue (MB) dye utilizing titanium dioxide nanoparticles (CS-TiO₂ NPs) synthesized using cannabis sativa (bhang) leaf extract via a greener approach. The CS-TiO₂ NPs are well characterized through XRD, FE-SEM, HR-TEM, UV-Vis spectroscopy, FTIR spectroscopy, and EDS spectroscopy. Microscopic studies confirm that the average particle size distribution of the individual particles was found to be in the range of 12.5 ± 1.5 nm, whereas the average size of the CS-TiO₂ NPs aggregates is 24.5 ± 11.5 nm. Additionally, the synthesized CS-TiO₂ NPs manifested remarkable photocatalytic degradation potential against methylene blue dye with a degradation efficiency of 98.2% and an apparent rate constant of 0.0398 min⁻¹. As a result, this research offers a green/sustainable alternative for water purification.

Bioaugmented removal of 17β-estradiol, nitrate and Mn(II) by polypyrrole@corn cob immobilized bioreactor: Performance optimization, mechanism, and microbial community response

The coexistence of nitrate and endocrine substances (EDCs) in groundwater is of global concern. Herein, an efficient and stable polypyrrole@corn cob (PPy@Corn cob) bioreactor immobilized with Zoogloea sp. was designed for the simultaneous removal of 17β-estradiol (E2), nitrate and Mn(II). After 225 days of continuous operation, the optimal operating parameters and enhanced removal mechanism were explored, also the long-term toxicity and microbial communities response mechanisms under E2 stress were comprehensively evaluated. The results showed that the removal efficiencies of E2, nitrate, and Mn(II) were 84.21, 82.96, and 47.91%, respectively, at the optimal operating conditions with hydraulic retention time (HRT) of 8 h, pH of 6.5 and Mn(II) concentration of 20 mg L^-1. Further increased of initial E2 (2 and 3 mg L^-1) resulted in the inhibiting effect of denitrification and manganese oxidation, but excellent E2 removal efficiencies maintained, which were associated with the formation and continuous accumulation of biomanganese oxides (BMO). Characterization analysis of biological precipitation demonstrated that adsorption and redox conversion on the BMO surface played key roles in the removal of E2. In addition, different levels of E2 exposure are decisive factors in community evolution, and bioaugmented bacterial communities with Zoogloea as the core group can dynamically adapt to E2 stress. This study offers the possibility to better utilize microbial metabolism and to advance opportunities that depend on microbial physiology and material characterization applications.

Fabrication of TiO2/NiO p-n Nanocomposite for Enhancement Dye Photodegradation under Solar Radiation

A p-n nanocomposite based on TiO₂ nanotubes (NTs) and NiO nanoparticles (NPs) was designed and optimized in this study to improve the photocatalytic performance of methylene blue (MB). The hydrothermal technique has been used to produce TiO₂/NiO nanocomposites with different NiO NPs weight ratios; 1TiO₂:1NiO, 1TiO₂:2NiO, and 1TiO₂:3NiO. The crystal phase, chemical composition, optical properties, and morphology of TiO₂/NiO were explored by various techniques. TiO₂ NTs have a monoclinic structure, while NiO NPs have a cubic structure, according to the structural study. The bandgap of TiO₂ NTs was reduced from 3.54 eV to 2.69 eV after controlling the NiO NPs weight ratio. The TiO₂/2NiO nanocomposite showed the best photodegradation efficiency. Within 45 min of solar light irradiation, the efficiency of MB dye degradation using TiO₂/2NiO hits 99.5% versus 73% using pure TiO₂ NTs. Furthermore, the catalytic photodegradation efficiency did not deteriorate significantly even after five reusability cycles, intimating the high stability of the TiO₂/2NiO nanocomposite. This suggests that the loading of NiO NPs into TiO₂ NTs lowers the recombination of photo-produced electron/hole pairs and enlarged solar spectral response range, which results in improved photocatalytic activity. The mechanism of charge transfer in the TiO₂/NiO and kinetic models were discussed for the photodegradation of MB.

Studies on the removal of acid violet 7 dye from aqueous solutions by green ZnO@Fe3O4 chitosan-alginate nanocomposite synthesized using Camellia sinensis extract

In the present study, ZnO-Fe₃O₄ nanoparticles were synthesized using the leaves of Camellia sinensis and immobilized in crosslinked alginate-chitosan polymer beads and tested for their photocatalytic applications. The prepared nanocomposite was used for the simultaneous adsorption and photocatalytic degradation of acid violet 7 (AV7) dye. The optimization of reaction conditions ensured higher dye removal efficacy up to 94.21 ± 1.02% using the nanocomposite under UV-C irradiation of 365 nm. The kinetics of the adsorption study fitted well with the pseudo-first-order reaction. The Langmuir model fitted better to the adsorption isotherms compared to the Freundlich and Temkin models. The mechanism of degradation was studied by analyzing the treated AV7 solution. The removal efficiency in tap water, groundwater, and lake water was 83.23 ± 0.4%, 69.13 ± 1.6%, and 67.89 ± 0.3%, respectively. The residual toxicity of the degraded AV7 solution was tested on model organisms like freshwater algae, Scenedesmus sp., and plant model, Allium cepa, demonstrating the lower toxicity of the degraded AV7 product. Finally, a cost-benefit analysis of the experiments was also carried out.

Mechanism of action and toxicological evaluation of engineered layered double hydroxide nanomaterials in Biomphalaria alexandrina snails

Layered double hydroxide (LDH) nanomaterials have recently become immense research area as it is used widely in industries. So, it's chance of their release into natural environment and risk assessment to nontarget aquatic invertebrate increasing. So, the present study aimed to synthesize and confirm the crystalline formation of Co-Cd-Fe LDHs and Co-Cd-Fe/PbI₂ (LDH) and then to investigate the toxic impact of the two LDH on the adult freshwater snails (Biomphalaia alexandrina). Results showed that Co-Cd-Fe/PbI₂ LDH has more toxic effect to adult Biomphalaria than Co-Cd-Fe LDHs (LC₅₀ was 56.4 and 147.7 mg/L, 72 h of exposure, respectively). The effect of LC₂₅ (117.1 mg/L) of Co-Cd-Fe LDHs exposure on the embryo showed suppression of embryonic development and induced embryo malformation. Also, it showed alterations in the tegmental architectures of the mantle-foot region of B. alexandrina snails as declared in scanning electron micrograph. Also, exposure to this sublethal concentration caused abnormalities in hemocyte shapes and upregulated IL-2 level in soft tissue. In addition, it decreased levels of nonenzymatic reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), caspase-3 activity, and total protein content in significant manner. Glutathione S-transferase (GST) activity was not affected by LDH exposure. It caused histopathological damages in both glands of snails and also caused a genotoxic effect in their cells. The results from the present study indicated that LDH has risk assessment on aquatic B. alexandrina snails and that it can be used as a biological indicator of water pollution with LDH.

Adsorption of Cationic Contaminants by Cyclodextrin Nanosponges Cross-Linked with 1,2,3,4-Butanetetracarboxylic Acid and Poly(vinyl alcohol)

Cationic organic pollutants (dyes and pesticides) are mainly hydrosoluble and easily contaminate water and create a serious problem for biotic and abiotic species. The elimination of these dangerous contaminants from water was accomplished by adsorption using cyclodextrin nanosponges. These nanosponges were elaborated by the cross-linking between 1,2,3,4-butanetetracarboxylic acid and β-cyclodextrin in the presence of poly(vinyl alcohol). Their physicochemical characteristics were characterized by gravimetry, acid-base titration, TGA, 13C NMR, ATR-FTIR, Raman, X-ray diffraction, and Stereomicroscopy. The BP5 nanosponges displayed 68.4% yield, 3.31 mmol/g COOH groups, 0.16 mmol/g β-CD content, 54.2% swelling, 97.0% PQ removal, 96.7% SO removal, and 98.3% MG removal for 25 mg/L of initial concentration. The pseudo-second-order model was suitable for kinetics using 180 min of contact time. Langmuir isotherm was suitable for isotherm with the maximum adsorption of 120.5, 92.6, and 64.9 mg/g for paraquat (PQ), safranin (SO), and malachite green (MG) adsorption, respectively. Finally, the reusability performance after five regeneration times reached 94.1%, 91.6%, and 94.6% for PQ, SO, and MG adsorption, respectively.

Highly Efficient Photocatalyst Fabricated from the Chemical Recycling of Iron Waste and Natural Zeolite for Super Dye Degradation

In this paper, Fe2O3 and Fe2O3-zeolite nanopowders are prepared by chemical precipitation utilizing the rusted iron waste and natural zeolite. In addition to the nanomorphologies; the chemical composition, structural parameters, and optical properties are examined using many techniques. The Fe2O3-zeolite photocatalyst showed smaller sizes and higher light absorption in visible light than Fe2O3. Both Fe2O3 and Fe2O3-zeolite are used as photocatalysts for methylene blue (MB) photodegradation under solar light. The effects of the contact time, starting MB concentration, Fe2O3-zeolite dose, and pH value on photocatalytic performance are investigated. The full photocatalytic degradation of MB dye (10 mg/L) is achieved using 75 mg of Fe2O3-zeolite under visible light after 30 s, which, to the best of our knowledge, is the highest performance yet for Fe2O3-based photocatalysts. This photocatalyst has also shown remarkable stability and recyclability. The kinetics and mechanisms of the photocatalytic process are studied. Therefore, the current work can be applied industrially as a cost-effective method for eliminating the harmful MB dye from wastewater and recycling the rusted iron wires.

A comprehensive review on preparation, functionalization and recent applications of nanofiber membranes in wastewater treatment

The direct discharge of significant amounts of polluted water into water bodies causes adverse ecological and human health effects. This severe deterioration in water quality creates significant challenges to meet the growing demand for clean water. Therefore, the world urgently needs environmentally friendly advanced technology to overcome this global crisis. In this regard, nanofiber-based membrane filtration is a promising technique in wastewater remediation because of their huge surface area, extremely porous structure, amenable pore size/pore size distribution, variety of material choices, and flexibility to modification with other functional materials. However, despite their unique properties, fouling, poor mechanical properties, shrinkage, and deformation are major drawbacks of nanofiber membranes for treating wastewater. This review presents a comprehensive overview of nanofiber membranes' fabrication and function in water purification applications as well as providing novel approaches to overcoming/alleviating the mentioned disadvantages. The review first presents nanofiber membrane preparation methods, focusing on electrospinning as a versatile and viable technique alongside discussing the parameters controlling nanofiber morphology. Afterward, the functionalization of nanofiber membranes by combining them with other nanomaterials, such as metal and metal-oxide nanoparticles, carbon nanotubes, metal-organic frameworks, and biomolecules, were demonstrated and discussed. In addition, nanofiber membranes functionalized with microorganisms were highlighted. Finally, we introduced and discussed in detail the most relevant and recent advances in nanofiber applications in wastewater treatment in the context of removing different pollutants (e.g., heavy metals, nutrients, radioactive elements, pharmaceuticals, and personal care products, dyes, and pesticides). Moreover, the promising antimicrobial ability of nanofiber membranes in removing microorganisms from wastewater has been fully underscored. We believe this comprehensive review could provide researchers with preliminary data and guide both researchers and producers engaged in the nanofiber membrane industry, letting them focus on the research gaps in wastewater treatment.

g-C3N4: Properties, Pore Modifications, and Photocatalytic Applications

Graphitic carbon nitride (g-C3N4), as a polymeric semiconductor, is promising for ecological and economical photocatalytic applications because of its suitable electronic structures, together with the low cost, facile preparation, and metal-free feature. By modifying porous g-C3N4, its photoelectric behaviors could be facilitated with transport channels for photogenerated carriers, reactive substances, and abundant active sites for redox reactions, thus further improving photocatalytic performance. There are three types of methods to modify the pore structure of g-C3N4: hard-template method, soft-template method, and template-free method. Among them, the hard-template method may produce uniform and tunable pores, but requires toxic and environmentally hazardous chemicals to remove the template. In comparison, the soft templates could be removed at high temperatures during the preparation process without any additional steps. However, the soft-template method cannot strictly control the size and morphology of the pores, so prepared samples are not as orderly as the hard-template method. The template-free method does not involve any template, and the pore structure can be formed by designing precursors and exfoliation from bulk g-C3N4 (BCN). Without template support, there was no significant improvement in specific surface area (SSA). In this review, we first demonstrate the impact of pore structure on photoelectric performance. We then discuss pore modification methods, emphasizing comparison of their advantages and disadvantages. Each method's changing trend and development direction is also summarized in combination with the commonly used functional modification methods. Furthermore, we introduce the application prospects of porous g-C3N4 in the subsequent studies. Overall, porous g-C3N4 as an excellent photocatalyst has a huge development space in photocatalysis in the future.

Optimized synthesis of lignin sulfonate nanoparticles by solvent shifting method and their application for adsorptive removal of dye pollutant

Synthesis of value added products from wastes is of importance from different perspectives. Wood and paper industry produces tons of wastewaters that contains lignin. In this paper, we report a new approach, called solvent-shifting method, to synthesize lignin sulfonate nanoparticles (LS-NPs). The effective parameters on size of LS-NPs were carefully tuned and the size of LS-NPs was minimized by response surface methodology. The results suggested that LS-NPs with size of 53 nm can be synthesized at low lignin sulfonate concentration (0.28 g/mL), moderate surfactant concentration (0.32 g/mL) but relatively high anti-solvent content (92 mL of ethanol for 40 mL of the aqueous phase). The as-synthesized LS-NPs were characterized by different analytical techniques, where presence of various negatively charged functional groups on surface of LS-NPs was conformed. To investigate the potential of LS-NPs for adsorptive removal of pollutant molecules, basic red 2 (known as Safranin-O) was used as a model pollutant dye. The results suggested that the maximum removal occurs at alkaline pH, where there is strong electrostatic interactions between LS-NPs and cationic Safranin-O molecules. The adsorption capacity was 85.14 mg/gr, where the isotherm data was best described by Redlich-Peterson isotherm model. The kinetic data also revealed that the adsorption is very fast in the first 20 min, where there is three diffusional steps to complete the adsorption in 90 min. The results of this study could open up new window to the field of value-added products to synthesize waste-driven nanomaterials for environmental applications.