Microwave-assisted degradation of acid orange using a conjugated polymer, polyaniline, as catalyst

Advanced oxidation/reduction processes (AO/RPs) for wastewater treatment, current challenges, and future perspectives: a review

Advanced oxidation/reduction processes (AO/RPs) are considered as effective water treatment technologies and thus could be used to solve the problem of water pollution. These technologies of wastewater treatment involve the production of highly reactive species such as •OH, H•, e-aq, SO4•-, and SO3•-. These radicals can attack the targeted contaminants present in aqueous media and result in their destruction. The efficiency of AO/RPs is highly affected by various operational parameters such as initial concentration of contaminant, solution pH, catalyst amount, intensity of light source, nature of oxidant and reductant used, and the presence of various ionic species in aquatic media. Among AO/RPs, the solar light-based AO/RPs are most widely used nowadays for contaminant removal from aqueous media because of their high environmental friendliness and cost effectiveness. By using these techniques, almost all types of pollutants can be easily removed from aquatic media within short intervals of time, and hence, the problem of water pollution can be solved effectively. This review focuses on various AO/RPs used for wastewater treatment. The effects of different operational parameters that affect the efficiency of these processes toward contaminant removal have been discussed. Besides, challenges and future recommendations are also briefly provided for the researchers in order to improve the efficiency of these processes.

Visible-light induced degradation of diphenyl urea and polyethylene using polythiophene decorated CuFe2O4 nanohybrids

The present work reports facile synthesis of CuFe₂O₄ nanoparticles via co-precipitation method and formulation of its nanohybrids with polythiophene (PTh). The structural and morphological properties were investigated using fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectra (SEM-EDS) and UV-Vis spectroscopy. The band gap was found to decrease with increase in the loading of PTh and was found to be 2.52 eV for 1-PTh/CuFe₂O₄, 2.15 eV for 3-PTh/CuFe₂O₄ and 1.89 eV for 5-PTh/CuFe₂O₄. The nanohybrids were utilized as photocatalysts for visible light induced degradation of diphenyl urea. Diphenyl urea showed 65% degradation using 150 mg catalyst within 120 min. Polyethylene (PE) was also degraded using these nanohybrids under visible light as well as microwave irradiation to compare its catalytic efficiency under both conditions. Almost 50% of PE was degraded under microwave and 22% under visible light irradiation using 5-PTh/CuFe₂O₄. The degraded diphenyl urea fragments were analyzed using LCMS and a tentative mechanism of degradation was proposed.

Theoretical Studies of Conducting Polymers: A Mini Review

The present short review discusses the computational studies carried out on polyacetylene (PAc), polyaniline (PANI), polypyrrole (PPy), and other conducting polymers for predicting their electronic, optoelectronic and structural properties. Studies...

Significance of conducting polyaniline based composites for the removal of dyes and heavy metals from aqueous solution and wastewaters - A review

Dyes and heavy metals pollution have become a major environmental concern worldwide. Various methods, such as advanced oxidation, biodegradation, precipitation, flocculation, ultra filtration, ion-exchange, electro-chemical degradation and coagulation, have been proposed for the removal of dyes and heavy metals from contaminated wastewater. Of these methods, adsorption and detoxification are considered as the most promising and economically viable. Polyaniline-based composites, a material prepared by combining polyaniline with one or more similar or disimilar materials, have been reported as good adsorbents to remove and detoxify different groups of pollutants due to their unique physical and chemical properties. In the last decade, several studies have reported the effective adsorption (∼95%) of dyes and heavy metals onto polyaniline based composites. Furthermore, some polyaniline -composites reduced the adsorbed heavy metals into less toxic state. This review compiles the application of different polyaniline composites for adsorption and/or detoxifcation of dyes and heavy metals and documents composite preparation methods, morphology and properties of the composites, and mechanism of dyes and heavy metals adsorption. Based on the avilabile literature, this review suggests that more studies are warranted to understand the influence of various conditions and experimental variables on dyes and heavy metals removal from wastewater and/or aqueous solution.

A comprehensive review on the photocatalytic activity of polythiophene-based nanocomposites against degradation of organic pollutants

Photocatalytic activity of polythiophene-based nanocomposites.

Microwave-assisted rapid degradation of DDT using nanohybrids of PANI with SnO2 derived from Psidium Guajava extract

The present work reports microwave-assisted synthesis of SnO₂ nanoparticles via green route using Psidium Guajava extract. For the enhancement of catalytic activity, nanohybrids of SnO₂ were formulated using different ratios of polyaniline (PANI) via ultrasound-assisted chemical polymerization. Formation of nanohybrids was confirmed via IR and XPS studies. The UV-vis DRS spectra of PANI/SnO₂ revealed significant reduction in the optical band gap upon nanohybrid formation. Microwave-assisted catalytic efficiency of pure SnO₂, PANI, PANI/SnO₂ nanohybrids was investigated using DDT as a model persistent organic pollutant. The degradation efficiency of PANI/SnO₂ was found to increase with the increase in the loading of PANI. Around 87% of DDT degradation was achieved within a very short period of 12 min under microwave irradiation using PANI/SnO₂-50/50 as catalyst. The effect of DDT concentration was explored and the degradation efficiency of PANI/SnO₂-50/50 catalyst was noticed to be as high as 82% in presence of 100 mg/L of DDT. The effect of microwave power on the degradation efficiency revealed 79% degradation using the same nanohybrid when exposed to microwave irradiation for 5 min under 1110 W microwave power. Scavenging studies confirmed the generation of OH, O₂^- radicals. The fragments with m/z values as low as 86 and 70 were confirmed by LCMS analysis. Recyclability tests showed that PANI/SnO₂-50/50 nanohybrid exhibited 81% degradation of DDT (500 mg/L) even after the third cycle, which reflected high catalytic efficiency as well as remarkable stability of the catalyst. This green nanohybrid could therefore be effectively utilized for the rapid degradation of persistent organic pollutants.

Simultaneous decolorization and desalination of dye wastewater through electrochemical process

Salt-containing dye wastewater discharged from textile industries causes serious environmental problems. Simultaneous decolorization and desalination of dye wastewater in a laboratory scale electrochemical cell are realized for the first time with boron-doped diamond anode. With initial methyl orange (MO) and NaCl of 50 and 3000 mg L^-1, decolorization and desalination efficiencies of 70.2 and 88.7% were achieved after 6-h treatment with applied voltage of 6 V. Increasing applied voltages resulted in the improvements of both color and salt removal, while higher MO concentrations suppressed decolorization and higher NaCl concentration accelerated desalination rate. MO dissociated into anions transferred through the anion exchange membrane into the anode compartment and reacted with the active species as ·OH, H₂O₂, and ClO^- generated in anode compartment, leading to color removal. Component analysis confirmed the destruction of MO, with generation of low molecular weight compounds such as phenol and indole. Ions balance analysis indicated that Cl^- and Na⁺ moved to the anode and the cathode compartments respectively through the employed membranes driven by external voltage, realizing salt removal. This study has collectively demonstrated an efficient alternative for satisfactory treatment of salt-containing dye wastewater based on electrochemical technology.

Facile synthesis of novel polypyrrole dispersed AgFeO2nanohybrid with highly efficient photocatalytic activity towards 2,4,6-trichlorophenol degradation

Synthesis of polypyrrole dispersed AgFeO₂nanohybrids for highly efficient visible light driven eco-friendly photocatalysis.

Highly Efficient Photocatalytic Degradation of Amido Black 10B Dye Using Polycarbazole-Decorated TiO2 Nanohybrids

The present study reports the synthesis of polycarbazole (PCz)-decorated TiO₂ nanohybrids via in situ chemical polymerization of carbazole monomers in TiO₂ dispersions. The ratio of the polymer in the nanohybrid varied between 0.5 and 2 wt %. The synthesized nanohybrids were characterized using infrared and diffuse reflectance spectroscopies, whereas the morphology was analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. XRD revealed changes in the peak corresponding to the d(001) plane of TiO₂ owing to the interaction between the two components. TEM confirmed the formation of PCz-decorated nanohybrids. Amido Black 10B (AB-10B) was chosen as a model dye for the degradation studies. Sonophotocatalytic degradation of the dye was studied by varying the catalyst and dye concentrations. Results showed that PCz/TiO₂ nanohybrids exhibited a complete degradation of AB-10B dye within a short span of 60-90 min, which was faster than pure TiO₂ and the reported decorated TiO₂ nanohybrids synthesized by other authors. The degraded dye fragments were identified using liquid chromatography-mass spectrometry (LCMS). By varying the loading of PCz in TiO₂, the nanohybrids could be tuned to achieve visible light-driven degradation.

The decolorization and mineralization of orange II by microwave-assisted ball milling

This study proposed an integrated technique of reduction coupled with an oxidation process in order to acquire simultaneously both decolorization and mineralization of orange II under the condition of microwave-assisted milling. Experimental variables of initial dye concentration, iron dosage, microwave power, solution pH and initial H₂O₂ concentration were systematically studied. Under the optimal operational parameters (100 mg/L aqueous solution of pH 3 containing 400 mg/L H₂O₂ while controlling microwave power at 400 W), the results showed that the decolorization efficiency is up to 91% after reaction for 2 min and the total organic carbon removal efficiencies were 72.7% and 80.5% at a reaction time of 10 min and 60 min, respectively. It indicated that the decolorization and mineralization of orange II were largely enhanced by the reduction of zero-valent iron in the ball milling process and the oxidation of hydroxyl radicals generated by hydrogen peroxide. It suggested that microwave-assisted ball milling technology has potential application for degradation of azo dye in wastewater.

Microwave energy assisted carbonization of nanostructured conducting polymers for their potential use in energy storage applications

Three well-established one-step approaches, namely, conducting polymer (CP) nanofiber (NF) synthesis by NF seeding, CP nanoclip (NC) synthesis by oxidative template, and microwave (MW) energy-assisted carbonization were systematically combined to prepare carbonaceous nanostructures from CPs, with great potential as the active material for energy storage purposes. Polypyrrole (PPy), as one of the most well-known and commonly studied members of the CP family was prepared in both NF and NC forms, as the sacrificial carbonization precursor, for different property comparison purposes. Due to conducting polymers’ high electron mobility and easily exciting nature under MW irradiation, both PPy NF and NC samples had vigorously interacted with MWs. The as-obtained carbonaceous samples from such interactions exhibited high thermal stabilities, competitive specific capacitance values and long-term stable electrochemical cyclic performances, which are crucial for the active materials used in energy storage applications. Thus, it is believed that, this well-established and well-studied process combination will dominate the large-scale manufacturing of the carbon-based, active energy storage materials from CPs.

Polyaniline–single walled carbon nanotube composite – a photocatalyst to degrade rose bengal and methyl orange dyes under visible-light illumination

PANI–SWCNT composites with varying SWCNT content were synthesized, investigated and compared with PANI as photocatalysts under visible light irradiation towards the degradation of Rose Bengal (RB) and Methyl Orange (MO) dyes.

SrTiO₃ Nanocube-Doped Polyaniline Nanocomposites with Enhanced Photocatalytic Degradation of Methylene Blue under Visible Light

The present study highlights the facile synthesis of polyaniline (PANI)-based nanocomposites doped with SrTiO₃ nanocubes synthesized via the in situ oxidative polymerization technique using ammonium persulfate (APS) as an oxidant in acidic medium for the photocatalytic degradation of methylene blue dye. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), UV⁻Vis spectroscopy, Brunauer⁻Emmett⁻Teller analysis (BET) and Fourier transform infrared spectroscopy (FTIR) measurements were used to characterize the prepared nanocomposite photocatalysts. The photocatalytic efficiencies of the photocatalysts were examined by degrading methylene blue (MB) under visible light irradiation. The results showed that the degradation efficiency of the composite photocatalysts that were doped with SrTiO₃ nanocubes was higher than that of the undoped polyaniline. In this study, the effects of the weight ratio of polyaniline to SrTiO₃ on the photocatalytic activities were investigated. The results revealed that the nanocomposite P-Sr500 was found to be an optimum photocatalyst, with a 97% degradation efficiency after 90 min of irradiation under solar light.

Synthesis of chitosan grafted-polyaniline/Co3O4 nanocube nanocomposites and their photocatalytic activity toward methylene blue dye degradation

Co₃O₄ nanocube-doped chitosan-grafted-polyaniline nanocomposites have been successfully synthesised. The synthesised polymeric nanocomposite was stable and exhibits greater photocatalytic activity to degrade MB efficiently within a short duration of time.

Synergistic effect of microwave irradiation and conjugated polymeric catalyst in the facile degradation of dyes

Degradation of Orange G under controlled conditions using microwave irradiation.