Synthesis and characteristics of polyaniline/zirconium oxide conductive nanocomposite for dye adsorption application

Adsorbent biochar derived from corn stalk core for highly efficient removal of bisphenol A

Environmental-friendly biochar (BC) with low cost was obtained by simple pyrolysis of corn stalk core, which was employed as an adsorbent for efficiently removing organic pollutants in water. The physicochemical properties of BCs were characterized by various techniques, including X-ray diffractometer (XRD), Fourier transforms infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Raman, Thermogravimetric (TGA), N₂ adsorption-desorption and zeta potential tests. The influence of pyrolysis temperature on the structure and adsorption efficiency of the adsorbent was emphasized. The graphitization degree and sp² carbon content of BCs were enhanced by increasing the pyrolysis temperature, which was favorable for the enhancement of the adsorption efficiency. The adsorption results showed that corn stalk core calcined at 900 °C (BC-900) displayed exceptional adsorption efficiency toward bisphenol A (BPA) in wide pH (1-13) and temperature (0-90 °C) ranges. Moreover, adsorbent BC-900 could adsorb various pollutants from water, including antibiotics, organic dyes, and phenol (50 mg·L^-1). The adsorption process of BPA over BC-900 matched well with the Langmuir isotherm and pseudo-second-order kinetic model. Mechanism investigation suggested that large specific surface area and pore filling acted the foremost role in the adsorption process. Adsorbent BC-900 has the potential application in wastewater treatment due to its simple preparation, low cost, and excellent adsorption efficiency.

Mesoporous carbon structure impregnated with 2D engineered zirconium: A sustainable adsorbent for the removal of dyes from the aqueous solution

The key designing of new breeds of the adsorbents aimed to improve the physical, chemical and textural morphology along with surface functionalization, selectivity toward the contaminants, and regenerations efficiency. In this aspect, two adsorbents named wet oxidative and ultrasonicated zirconium impregnated composite, have been synthesized through two routes, i.e., wet oxidation and ultrasonication. In wet oxidation method, carbon-based materials are oxidized using an oxidant followed by impregnation, while in ultrasonication assisted route, the impregnation is carried out using acoustic phenomenon. The characterization study revealed that the wet oxidation process is more competent in impregnating zirconium and developing diverse porosity and functionalities. The maximum adsorption capacity of wet oxidative adsorbent was 812 mg/g for Reactive Blue 19 and 203.18 mg/g for Methylene Blue, that accentuated the efficiency of the adsorbent over raw activated carbon. The electrostatic interaction, hydrogen-bonding and ligand exchange phenomenon are the involved adsorption mechanism for dyes. The regeneration study finally asserts that the wet oxidative adsorbent shows an insignificant decrease in its capacity up to the 5^th-cycle (i.e., 87.67% removal at 5^th cycle) as compared to raw AC (46.71% removal at 5th cycle). Further, a continuous fixed-bed column study revealed a significant correlation between experimental breakthrough data and kinetic data. Thus, the developed adsorbent has a sedulous adsorption capacity to remove the most stubborn toxic dyes and can be used in industrial-scale applications.

Role of polyaniline in accomplishing a sustainable environment: recent trends in polyaniline for eradicating hazardous pollutants

Attaining a sustainable environment has become a prime area of research interest, as it is an utmost necessity for a healthy life. Hence, ample studies have been carried out in adopting different processes and utilizing various materials to attain the goal. Herein, we present an exclusive discussion on one such material, i.e., polyaniline (PANI) and its derivatives. Being an intrinsic conducting type, it has grabbed more attention due to its durability in different doped/un-doped states, promptness in structural alteration, and solution processability. This review presents an exhaustive discussion on published reports showing utilization of PANI and its derivative in various forms like pure and composites, for cleaning the environment through adsorption, photodegradation, etc., and the various methods adopted in order to achieve an optimum operating condition to obtain the maximum outcome. In addition to these merits and demerits, various technical challenges faced with materials have been also presented. Therefore, it is expected that this piece of work, presenting the exhaustive discussion on PANI and; its derivatives would help to develop a better understanding of this excellent conducting polymer PANI and provide a state of art on the role of this material for attaining sustainable surroundings for the living beings.

Removal of pharmaceuticals (diclofenac and amoxicillin) by maltodextrin/reduced graphene and maltodextrin/reduced graphene/copper oxide nanocomposites

Due to the scarcity of water and the growing industrialization, pharmaceutical wastewater treatment is of particular importance. For this reason, it is necessary to achieve an efficient method to eliminate all types of pharmaceutical pollutants. Herein, synthetic nano-composite is proposed to take a step towards improving the operation of removing pharmaceutical contaminants from the environment and aquatic and industrial effluents. Binary (maltodextrin/reconstituted graphene nanocomposite) and ternary (maltodextrin/reconstituted graphene nanocomposite/copper oxide) nanocomposites were prepared and characterized using, FT-IR, FESEM-EDS, TEM, DLS, and XRD. The nanocomposites were used to eliminate diclofenac and amoxicillin as Pharmaceuticals. The removal of amoxicillin at a concentration of 30 mg/L with an adsorbent dose of 0.05 g and a pH of 7.4 and an optimal temperature of 20 °C in 10 min has the highest removal rate of 86%. In addition, diclofenac with nano-adsorbents prepared under optimal conditions, including an initial concentration of 20 mg/L, adsorbent dose of 0.05 g, adsorption time of 7 min, a temperature of 20 °C and a pH of 7, has the highest removal efficiency of 94%. The results indicated that the prepared nanocomposites are alternative adsorbents to remove Pharmaceuticals from water.

Photocatalytic degradation of methylene blue using polyaniline-based silver-doped zinc sulfide (PANI-Ag/ZnS) composites

This study set out to determine the photocatalytic degradation potential of polyaniline-based silver-doped zinc sulfide composite (PANI-Ag/ZnS) for effective degradation of methylene blue. The heterogeneous photocatalytic experiments were carried out by irradiating aqueous dye solutions with ultraviolet light (UV-254 nm). The catalysts (ZnS, Ag/ZnS, PANI-ZnS, and PANI-Ag/ZnS) were prepared successfully and characterized by Fourier Transforms Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray diffraction (EDX). Combined with density functional theory calculations, a set of calculations has been performed for optimization, computation, and accuracy of the structure. After the optimization, the equilibrium lattice were a=b= (0.54447 nm), in good agreement with experimental results (a=b=c=0.54093 nm). Fermi energy levels E_f, indicating Ag-doped in ZnS as the impurity acceptor and for better visible-light photo-catalysis, narrow bandgap, and acceptor states are beneficial. The optimization of effective parameters like pH, catalyst dose, oxidant dose, dye concentration, and reaction time was carried out. The best degradation efficiency (> 95%) of PANI-Ag/ZnS composite against methylene was achieved within 60 min of reaction time under optimized conditions. The optimized conditions were recoded as follows: pH = 7, catalysts dose = 30 mg/L, oxidant dose = 3 mM, and irradiation time = 60 min under UV-254 nm for all catalysts. The central composite design (CCD) under the Response Surface Methodology (RSM) was chosen as a statistical tool to obtain the correlation of influential parameters. Five successive reusability trials were carried out to check the stability of catalysts.

The Adsorption Performance of Polyaniline/ZnO Synthesized through a Two-Step Method

Polyaniline/Zinc oxide (PANI/ZnO) were prepared using a two-step method, and the morphology and the structure of PANI/ZnO composites were characterized through a scanning electron microscope (SEM) and X-ray diffraction (XRD). Factors such as the content of ZnO, the adsorption time and the mass of the adsorbent, and the kinetic equation of PANI/ZnO as adsorbents for the adsorption of methyl orange solution were studied. The results showed that the adsorption efficiency of methyl orange by polyaniline with the increase of adsorbent mass firstly increased and then decreased. Among the composites with the same quality, PANI composites with 8% ZnO have a better adsorption effect for methyl orange, and the maximum adsorption ratio can reach 69% with the increase of adsorption time at 0.033 g; With the increase of adsorbent mass, the adsorption efficiency of PANI composites with 8% ZnO increased continuously. When the mass increased from 0.033 g to 0.132 g, the adsorption rate increased from 69% to 93%, and the adsorption of the methyl orange solution by PANI/ZnO composites was more in line with the quasi-second-order kinetic equation.

Preparation and Characterization of a Novel Activated Carbon@Polyindole Composite for the Effective Removal of Ionic Dye from Water

The present study is aimed at the synthesis and exploring the efficiency of a novel activated carbon incorporated polyindole (AC@PIN) composite for adsorptive removal of Malachite Green (MG) dye from aqueous solution. An AC@PIN hybrid material was prepared by in situ chemical oxidative polymerization. The physico-chemical characteristics of the AC@PIN composite were assessed using Fourier-transform infrared spectrometer, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet visible spectroscopy, and determination of point of zero charge (pH_PZC). A series of adsorption studies was conducted to evaluate the influence of operational parameters such as pH, contact time, initial dye concentration, AC@PIN dosage, and temperature on dye adsorption behavior of developed composite. A maximum dye removal percentage (97.3%) was achieved at the pH = 10, AC@PIN dosage = 6.0 mg, initial dye concentration 150 mg L⁻¹, and temperature = 20 °C. The kinetic studies demonstrated that the adsorption of MG on AC@PIN followed pseudo-second-order model (R² ≥ 0.99). Meanwhile, Langmuir isotherm model was founded to be the best isotherm model to describe the adsorption process. Finally, the recyclability test revealed that the composite exhibits good recycle efficiency and is stable after 5 cycles. The obtained results suggest that AC@PIN composite could be a potential candidate for the removal of MG from wastewater.

Surface-Enhanced Biocompatibility and Adsorption Capacity of a Zirconium Phosphate-Coated Polyaniline Composite

The present study deals with the synthesis, characterization, and testing of a novel composite, zirconium(IV) phosphate-coated polyaniline (ZrPO4@PANI), toward the adsorption- and surface-controlled toxicity applications. Following the synthesis of the ZrPO4@PANI composite using the sol-gel route, various characterization techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction were employed to confirm its surface functionality, morphology and agglomeration, and crystallinity and crystal nature, respectively. The composite was found to be effective toward the adsorptive removal of the methylene blue dye (an organic pollutant) as against the changes in the dye concentration, dose, pH, and so forth. Also, to understand the MB adsorption kinetics, the experimental data were evaluated using the Langmuir and Freundlich models and the results were described in accordance with the Langmuir isotherm model (an adsorption capacity of 120.48 mg/g at ambient temperature). In addition, the tests conducted using pseudo-first- and pseudo-second-order kinetic models confirmed the existence of pseudo-second-order rates. Furthermore, the calculation of thermodynamic parameters for the MB adsorption, namely, changes in enthalpy, entropy, and Gibbs' free energy, exhibited a spontaneous, feasible, and exothermic nature. Finally, the comparative studies of in vitro toxicity and flow cytometry confirmed that the copresence of ZrPO4 along with PANI significantly improved the biocompatibility. The outcome of the experimental results implies that the composite is capable enough of serving as the safe and low-cost adsorbent, in addition to supporting the effective capping of the surface toxicity of PANI.

Preparation of novel and highly active magnetic ternary structures (metal-organic framework/cobalt ferrite/graphene oxide) for effective visible-light-driven photocatalytic and photo-Fenton-like degradation of organic contaminants

Herein, MIL-101(Fe), CoFe₂O₄, novel binary (MIL-101(Fe)/CoFe₂O₄, MIL-101(Fe)/GO and CoFe₂O₄/GO), and ternary (MIL-101(Fe)/CoFe₂O₄/(3%)GO and MIL-101(Fe)/CoFe₂O₄/(7%)GO) magnetic composites based upon the MIL-101(Fe) were synthesized. The XRD, FESEM, TEM, EDX, BET-BJH, FTIR, VSM, DRS, PL, EIS and other electrochemical analyses were applied to characterize samples. The MIL/CoFe₂O₄/(3%)GO demonstrated the best performance compared to other samples for visible light photocatalytic and photo-Fenton-like degradation of Direct Red 23 (DtR-23), Reactive Red 198 (ReR-198) dyes as well as Tetracycline Hydrochloride (TC-H) antibiotic. Degradation of dyes using the ternary composite after 70 min of visible light irradiation was greater than that of 99%. The presence of the optimum GO as a strong electron acceptor in MIL/CoFe₂O₄/(3%)GO not only led to the effective separation of charge carriers and thus reduction of their recombination but also increased the absorption of visible light. The composite possessed good durability in terms of stability and reusability. The PL, EIS and electrochemical analyses indicated that the MIL/CoFe₂O₄/(3%)GO improved the optical properties and photocatalytic performance.

Conductive Polymers and Their Nanocomposites as Adsorbents in Environmental Applications

Proper treatment and disposal of industrial pollutants of all kinds are a global issue that presents significant techno-economical challenges. The presence of pollutants such as heavy metal ions (HMIs) and organic dyes (ODs) in wastewater is considered a significant problem owing to their carcinogenic and toxic nature. Additionally, industrial gaseous pollutants (GPs) are considered to be harmful to human health and may cause various environmental issues such as global warming, acid rain, smog and air pollution, etc. Conductive polymer-based nanomaterials have gained significant interest in recent years, compared with ceramics and metal-based nanomaterials. The objective of this review is to provide detailed insights into different conductive polymers (CPs) and their nanocomposites that are used as adsorbents for environmental remediation applications. The dominant types of CPs that are being used as adsorbent materials include polyaniline (PANI), polypyrrole (Ppy), and polythiophene (PTh). The various adsorption mechanisms proposed for the removal of ODs, HMIs, and other GPs by the different CPs are presented, together with their maximum adsorption capacities, experimental conditions, adsorption, and kinetic models reported.

Polyaniline coated tungsten trioxide as an effective adsorbent for the removal of orange G dye from aqueous media

In this work, the core–shell PANI@WO₃ composite was obtained from the reaction of aniline monomer polymerization with WO₃ particles; sodium persulfate was used as an oxidant. Various analytical techniques such as scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-prepared PANI@WO₃ adsorbent, which well confirmed that the WO₃ particles were coated by polyaniline polymer. The PANI@WO₃ composite was tested as an adsorbent to remove reactive orange G (OG) for the first time. pH, adsorbent dose, contact time, initial dye concentration, and temperature were systematically investigated in order to study their effect on the adsorption process. The experimental findings showed that the PANI@WO₃ composite has considerable potential to remove an aqueous OG dye. Langmuir and Freundlich's models were used to analyze the equilibrium isotherms of OG dye adsorption on the PANI@WO₃ composite. As a result, the best correlation of the experimental data was provided by the Langmuir model, and the maximum capacity of adsorption was 226.50 mg g⁻¹. From a thermodynamic point of view, the OG dye adsorption process occurred spontaneously and endothermically. Importantly, PANI@WO₃ still exhibited an excellent adsorption capability after four regeneration cycles, indicating the potential reusability of the PANI@WO₃ composite. These results indicate that the as prepared PANI@WO₃ composite could be employed as an efficient adsorbent and was much better than the parent material adsorption of OG dye.

In this work, the core–shell PANI@WO₃ composite was obtained from the reaction of aniline monomer polymerization with WO₃ particles; sodium persulfate was used as an oxidant.

Photocatalytic Degradation of Organic Dyes and Antimicrobial Activities by Polyaniline-Nitrogen-Doped Carbon Dot Nanocomposite

Nitrogen-doped carbon nanodots (N@CDs) were prepared by hydrothermal processing of bovine serum albumin (Mw: 69,324 with 607 amino acids). A polyaniline (PANI-N@CDs) nanocomposite was then synthesized by ultrasonication and used to degrade Congo red (CR), methylene blue (MB), Rhodamine B (RhB), and crystal violet (CV) four common organic dyes. The PANI-N@CD nanocomposite simultaneously adsorbed and concentrated the dye from the bulk solution and degraded the adsorbed dye, resulting in a high rate of dye degradation. The combination of holes (h+), hydroxyl (OH•), and O2•- was involved in the N@CD-mediated photocatalytic degradation of the dyes. Under visible light illumination at neutral pH, the PANI-N@CDs were proven as an efficient adsorbent and photocatalyst for the complete degradation of CR within 20 min. MB and RhB were also degraded but required longer treatment times. These findings supported the design of remediation processes for such dyes and predicted their fate in the environment. The nanocomposite also exhibited antimicrobial activities against Gram-negative bacterium E. coli and Gram-positive bacterium S. aureus.

Study of the methylene blue adsorption mechanism using ZrO2/Polyaniline nanocomposite

ZrO2 (Zirconia) nanoparticles (NPs), PANI (polyaniline), and ZrO2/PANI nanocomposites (NCs) were successfully synthesized using CTAB (Hexadecyltrimethylammonium bromide) and SDS (Sodium dodecyl sulfate) surfactants by following the co-precipitation method. The structural phase analysis of as-prepared, annealed nanoparticles, and nanocomposites was done using the XRD (x-ray diffraction) technique. The crystallite size of pure SDS and CTAB assisted ZrO2 NPS comes out to be 19 and 17 nm, respectively. After the formation of NCs, the size has been reduced to 15.7 and 15.9 nm, respectively for the same samples. The effect of surfactants on the dye adsorption mechanism was studied using XRD and UV–vis spectroscopy. The prepared NPs and NCs were utilized as an adsorbent for the removal of organic dye methylene blue (MB) which is used as a model compound. UV–vis spectra of the supernatant solution were taken and studied to detect the relative decrease in the dye concentration with time. The as-prepared CTAB assisted ZrO2/PANI NCs show higher adsorption activity than annealed CTAB assisted ZrO2/PANI whereas a reversal trend in the adsorption activity was observed for SDS-assisted ZrO2/PANI NCs. Various kinetic models were implemented and correlated to the experimental data to elucidate the working mechanism for dye adsorption and to set up, a relation in the adsorption activity of surfactant modified NPs and NCs.

Sonochemical preparation of polyaniline@TiO2 and polyaniline@SiO2 for the removal of anionic and cationic dyes

Polyaniline (PANI) synthesized by simple CDs (carbon dots) initiated polymerization has formed a composite with TiO₂ and SiO₂, respectively via a sonochemical method. These PANI@TiO₂ and PANI@SiO₂ composites were proven as effective adsorbent materials to rapidly adsorb the anionic and cationic dyes from wastewater at neutral pH and ambient temperature. Selected popular cationic and anionic organic dyes consisted of methylene blue (MB), brilliant blue (BB), Evans blue (EB), crystal violet (CV), Congo red (CR), rhodamine B (RB), and rhodamine 6G (R6G). The adsorption equilibria were governed by Langmuir and Freundlich isotherms. The kinetic results revealed that the PANI@TiO₂ and PANI@SiO₂ composite materials synthesized via the sonochemical method are efficient adsorbents compared to other adsorbent materials for the removal of organic dyes from the water. The adsorbed dyes were effectively desorbed from the composites, rendering the reusability of PANI@TiO₂ and PANI@SiO₂. The estimated adsorption capacities of PANI@TiO₂ and PANI@SiO₂ composites were 89, 93, 80, 94 and 74, 71, 61, 61 mg/g for MB, CR, CV, and R6G, respectively.

Application of polyaniline-based adsorbents for dye removal from water and wastewater-a review

Several industries release varying concentration of dye-laden effluent with substantial negative consequences for any receiving environmental compartment. The control of water pollution and tighter restriction on wastewater discharge directly into the environment to reduce the potential ecotoxicological effect of dyes is forcing processors to retreat and reuse process water and chemicals. Among the different available technologies, the adsorption process has been recognized to be one of the finest and cost-effective wastewater treatment technologies. Various adsorbents have been utilized to remove toxic dyes from water and wastewater. Here, we review the application of polyaniline-based polymeric adsorbent for the adsorption of dyes which have been received considerable attention. To date, various modifications of polyaniline have been explored to improve the adsorption properties. Review on the application of polyaniline for adsorption of dyes has not been present till date. This article provides relevant literature on the application of various polyaniline composites for removing dyes, and their adsorption capacities with their experimental conditions have been compiled. It is evident from the literature survey that polyaniline provides a better opportunity for scientists for the effective removal of various dye.

Nanoadsorbents based on conducting polymer nanocomposites with main focus on polyaniline and its derivatives for removal of heavy metal ions/dyes: A review

Water contamination by toxic heavy metal ions and dyes remains a serious public health problem for humans, so attention on specific methods and technologies to remove heavy metal ions and dyes from wastewaters/aqueous solutions are desired. Numerous adsorbents have been reported for the removal of heavy metal ions/dyes from wastewaters/aqueous solutions. Polyaniline (PANI) and its derivatives, as conducting polymers, are good adsorbents to remove various kinds of heavy metal ions and dyes from wastewaters/aqueous solutions. The nanoadsorbents based on PANI and its derivatives have received much consideration, and are extensively reported in literature. This review focuses on the PANI and its derivatives based on nanoadsorbents for water purification. Various types of these nanoadsorbents used for the removal of heavy metal ions/dyes from wastewaters/aqueous solutions are also briefly compared in this review.

Synthesis of polyaniline–magnetite nanocomposites using swollen liquid crystal templates for magnetically separable dye adsorbent applications

One dimensional iron oxide–polyaniline core–shell nanostructures enable faster adsorption of dyes and separation of the adsorbent using an external magnet.

Optimization of operational variables and kinetic modeling for photocatalytic removal of Direct Blue 14 from aqueous media by ZnS nanoparticles

Zinc sulfide nanoparticles (ZnS-NPs) were synthesized via a simple and facile co-precipitation method and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and diffuse reflectance spectroscopy (DRS). Photocatalytic activity of synthesized nanoparticles was evaluated in removal of double azo dye Direct Blue 14 (DB14) from aqueous media. Optimization of photocatalytic removal of DB14 was studied using response surface methodology (RSM). Based on the results, DB14 removal efficiency increased with increasing intensity and duration of UV light irradiation, whereas the higher pH and higher initial dye concentration were unfavorable. Under optimum conditions (initial DB14 concentration =10 mg L^-1, ZnS-NPs amount = 0.7 g L^-1, pH = 3.5, UV light intensity =16 W m^-2, and irradiation time = 48 min), dye removal efficiency reached up to 88.26%. In continuation of our researches, non-linear regression analysis was used to development a kinetics model based on the Langmuir-Hinshelwood model and an empirical equation was obtained for estimation of apparent pseudo-first-order rate constant (k_ap) as a function of the operational variables. Findings indicated a high similarity was between the model prediction and experimental results.