Polyaniline Composites Research Articles

Improvement in the performance of indium free dye sensitized solar cell by the use of polyaniline composite

The photovoltaic study of the fabricated dye sensitized solar cells is revealed in this paper. To provide indium free approach, fluorine doped tin oxide (FTO) and aluminium doped zinc oxide (AZO) glass substrate were used as charge collectors for counter electrodes and photoanode respectively. Also, a novel and natural mixed dye was used as sensitizer and mixture of doped polymer (polyaniline with metallic oxides of tin, vanadium and cerium) and iodide-triiodide couple was utilized as electrolyte for the cell. Optical band gap and light absorption performance of dyes were studied by ultraviolet-visible (UV-vis) spectroscopy. Surface morphology and elemental composition of polymer composites was studied using scanning electron microscopic (SEM) with energy dispersive X ray (EDX) analysis. Phase analysis of the composites was determined by X-ray diffraction and thermal behavior with the help of thermo gravimetric analysis (TGA). Photovoltaic characteristics (I-V) and induced photon to current efficiency (IPCE) measurements were also investigated. Highest IPCE of 17.7% was observed when polyaniline was doped with oxide of vanadium. Hence an efficient, green, indium free and novel cell is fabricated by the usage of different charge collector substrate, natural dye sensitizer and quasi solid-state electrolyte.

Exploring the potential of SnSe/PANi composite counter electrodes for improved efficiency in dye-sensitized solar cells

This paper investigates the synthesis and characterization of novel counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), focusing on composite polyaniline (PANi) nanofibers integrated with tin selenide (SnSe). Three CEs, namely SnSe, PANi, and their composite, were prepared via facile hydrothermal and cyclic voltammetry methods and compared with a standard platinum (Pt) CE. The efficiencies obtained were 4.20 %, 5.63 %, 8.39 %, and 7.72 % for SnSe, PANi, SnSe/PANi, and Pt CEs, respectively. The improved efficiencies, particularly in the case of the SnSe/PANi composite, were attributed to increased short-circuit density of the composite sample. The materials and devices prepared in this study are characterized using various methods including FESEM, TEM, XRD, Raman and FTIR spectroscopies, EIS, Tafel, OCVD, IPCE and etc to support our proposed CE structure. Our findings demonstrate the promising potential of SnSe/PANi composite CEs in enhancing the performance and affordability of DSSCs.

Reactivity of polyaniline composites with attractive cyclic nitramines

Composite microcrystals of the nitramines (NAs) RDX, HMX, BCHMX and CL-20 with electrically conductive polyaniline (PANi) are a charge transfer complexes in composite crystals (CACs). The activation energies of thermolysis, Ea, of the pure NAs and their PANi-composites were determined using the Kissinger method, and decomposition processes are discussed. Except for the RDX/PANi CAC, all the other CACs show higher Ea values for decomposition compared to their pure NA counterparts. For all CACs, relationships are specified between the Ea values, on the one hand, and the squares of the detonation velocities, enthalpies of formation, spark energy and impact sensitivities, on the other. The relationships between their low-temperature heats of decomposition, ΔH, from DSC, and their enthalpy of formation, logarithm of impact sensitivity, electric spark energy, as well as detonation energy, are described. The PANi favorably influences the density of the corresponding CAC; surprisingly close linear correlations were found, and explained, between these densities and the Ea values. This presence of PANi strongly increased the electrical spark sensitivity of the CACs in comparison to the base NAs. Based on the results obtained, it can be noted in particular the exceptional desensitization of HMX to impact and the increased sensitivity to electrical spark by coating its crystals with polyaniline.

Electro-Co-Polymerisation of Polypyrrole-Polyaniline Composites in Ionic Liquids for Metal-Free Hydrogen Evolution Electrodes.

Pure organic films consisting of polypyrrole, polyaniline and a composite of polypyrrole and polyaniline electrodeposited in the ionic liquid EMIM-TFSI onto mesoporous carbon electrodes are tested for their hydrogen evolution reaction capabilities. The use of these intrinsically conducting polymers is seen as a way of stepping away from expensive and rare metallic catalysts. Co-polymerisation of polypyrrole and polyaniline in a 1 : 10 ratio in EMIM-TFSI was found to be doped with the TFSI- anion and be much more active to the hydrogen evolution reaction when compared to pure polymers. Tafel analysis of the composite gave a value of 144 mV/dec indicating that the Volmer step is the rate limiting step. However, stability tests showed an improvement in the composite's overpoential performance for the hydrogen evolution reaction.

Chitosan-Polyaniline (Bio)Polymer Hybrids by Two Pathways: A Tale of Two Biocomposites.

Previous research highlights the potential of polyaniline-based biocomposites as unique adsorbents for humidity sensors. This study examines several preparative routes for creating polyaniline (PANI) and chitosan (CHT) composites: Type 1-in situ polymerization of aniline with CHT; Type 2-molecular association in acidic aqueous media; and a control, Type 3-physical mixing of PANI and CHT powders (without solvent). The study aims to differentiate the bonding nature (covalent vs. noncovalent) within these composites, which posits that noncovalent composites should exhibit similar physicochemical properties regardless of the preparative route. The results indicate that Type 1 composites display features consistent with covalent and hydrogen bonding, which result in reduced water swelling versus Type 2 and 3 composites. These findings align with spectral and thermogravimetric data, suggesting more compact structure for Type 1 materials. Dye adsorption studies corroborate the unique properties for Type 1 composites, and 1H NMR results confirm the role of covalent bonding for the in situ polymerized samples. The structural stability adopts the following trend: Type 1 (covalent and noncovalent) > Type 2 (possible trace covalent and mainly noncovalent) > Type 3 (noncovalent). Types 2 and 3 are anticipated to differ based on solvent-driven complex formation. This study provides greater understanding of structure-function relationships in PANI-biopolymer composites and highlights the role of CHT as a template that involves variable (non)covalent contributions with PANI, according to the mode of preparation. The formation of composites with tailored bonding modalities will contribute to the design of improved adsorbent materials for environmental remediation to versatile humidity sensor systems.

Study of Graphene Oxide/Polymer Composite Membranes in Air Filtration of PM2.5

pollution, particularly the issue of fine particulate matter (PM2.5), which has emerged as a significant environmental and public health concern globally. It is particularly important to develop efficient, economical and sustainable air filtration materials to reduce the concentration of PM2.5. In this study, we investigated the potential application of some polymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and polyaniline (PANI) composites with graphene oxide (GO) for efficient PM2.5 filtration. These composites were found to have excellent filtration performance, thermal stability. PVDF/ GO/PI nanofiber membranes maintained stable performance under repetitive filtration cycles and high temperature conditions. PAN/GO/PI nanofiber membranes exhibited good mechanical properties and stable cycling performance.PANI/GO composites took advantage of the unique properties of the conductive polymers, and in TGA experiments, they showed minimal mass loss. Their durability and efficiency remain high even after multiple wash cycles, highlighting their potential for practical applications.

Analysis of Electrochemical Deposition of Polyaniline and Polyaniline Composites in Sodium Tungstate and Sodium Molybdate Solutions

Although polyaniline has a high electroactivity in environments below pH 5, it loses its electroactivity in neutral and basic environments. In addition, polyaniline film does not give physically stable film when it becomes thick. For these reasons, polyaniline has been synthesized in the presence of other monomers or inorganic/organic species, leading to the obtaining of composite polymers with some new electrochemical and physical properties. In this study, novel composite polymer films of polyaniline were synthesized electrochemically in the presence of different concentrations of Na2MoO4.2H2O and Na2WO4.2H2O, and these composite polymer films were examined in monomer-free solutions for electrochemical investigation. As a result, the cathodic charge of polyaniline increased from 0.25 mC to 1.50 mC in the presence of 0.05 M Na2MoO4.2H2O. Also, the polyaniline/WO3 composite achieved a charge transfer of 0.42 mC in the presence of 0.25 M NiSO4.2H2O, 0.05 M NiCl2.6H2O, Na2WO4, Na2MoO4.2H2O, 0.4 M Na3C6H5O7.2H2O and 0.05 Na2WO4.2H2O as a metal source. These prove the better charge transfer during the redox reaction of the polyaniline composite film.

Electromagnetic interference shielding properties of PMMA modified-Co0.5Zn0.5Fe2O4 − polyaniline composites

Present work reports solution combustion synthesis (SCS) of Co0.5Zn0.5Fe2O4 spinel ferrite, its chemical modification with polymethylmethacrylate (PMMA), synthesis of polyaniline (PANI), and electromagnetic interference (EMI) shielding properties of their composites. Both as-prepared and PMMA-modified Co0.5Zn0.5Fe2O4 adopt cubic spinel structure as shown by X-ray diffraction studies. Field emission scanning electron microscopy images show the agglomerated and microporous nature of the ferrites. High resolution transmission electron microscopy image of as-prepared Co0.5Zn0.5Fe2O4 shows lattice fringes related to (311) plane of the spinel structure. X-ray photoelectron spectroscopy studies reveal the presence of Co2+, Zn2+, and Fe3+ in tetrahedral and octahedral coordinations in the ferrite. EMI shielding properties are evaluated for PMMA-modified Co0.5Zn0.5Fe2O4 and PANI composites in different weight ratios. Composites containing PMMA-modified ferrite and PANI with 50:50 and 10:90 weight ratios show the best performance among all the composites in 2−20 GHz frequency range. Optimized PMMA-modified Co0.5Zn0.5Fe2O4 and PANI composite with the ratio of 10:90 shows shielding effectiveness (SE) values of −16.6 to −24.2 dB in 2−20 GHz frequency region.Graphical

Poly(aniline/aminophenol)-wrapped graphene nanoplates loaded with gabapentin inhibitor as a filler in poly(aniline/vinylalcohol/aminophenol)/acrylic coating to endow corrosion/wear durability by triple protection mechanism

A coating with excellent tribological behavior and corrosion durability was synthesized by chemical/electrochemical method from the composition of polyaniline (PANI), polyaminophenol (PAP), polyvinylalcohol (PVA), and reinforced with PANI/PAP/Gabapentin-functionalized Graphene nanoplates. Acrylic (AC) covered the composite coating as a top layer. According to the evaluations, G@PANI/PAP/GP-reinforced coating has 5 times more corrosion resistance than unreinforced one (on the 1st and 30th days). Not only has the corrosion resistance of PANI/PVA/PAP contained G@PANI/PAP/GP not decreased over time, but it has increased by ∼20 %. The defect density of passive film under (PANI/PVA/PAP)/Acrylic coating containing G@PANI/PAP/GP is 10 times less than that of the (PANI/PVA/PAP)/Acrylic coating. G@PANI/PAP/GP decreased the friction coefficient and wear rate of PANI composite coating over time by ∼47 % and 84 %. Furthermore, the simultaneous presence of graphene and gabapentin has increased the lubrication (Rsk = -0.24 µm) and adhesion (13 %) of the coating. It is how a polyaniline-based composite coating with three mechanisms of passivation, corrosion barrier, and inhibition protects the 304 SS over time.

Layered double hydroxide assembled on a metal–organic framework coupled with polyaniline as pseudocapacitive anode for phosphorus capture

Excessive phosphorus is detrimental to supporting the proper function of aquatic ecosystems. Capacitive deionization (CDI) is an emerging, highly efficient, eco-friendly electrochemical technology that eliminates phosphorus from wastewater. In this work, a novel LDH@MOF/PANI composite was successfully fabricated by utilizing polyaniline (PANI) as a conductive substrate and metal–organic framework (MOF) as a self-sacrificial template for layered double hydroxide (LDH). The results demonstrated that LDH and PANI are favorable for improving the pore structure features, enriching the phosphorus binding sites, and strengthening the electrochemical performance of the electrode materials. Accordingly, the LDH@MOF/PANI electrode presented a superior phosphorus capture capacity than LDH@MOF and MOF. The isotherm and kinetic experiments revealed that the phosphorus capture by LDH@MOF/PANI is a chemisorption-dominated process associated with heterogeneous adsorption. The potential interference with phosphorus uptake was also assessed by focusing on several vital factors. Eventually, the possible mechanism suggested that ligand exchange, anion exchange, hydrogen bond, electrostatic attraction, and electric field assistance participate in the phosphorus uptake process. This work presents promising insight into the assembly design and rational construction of LDH-based pseudocapacitive anode for phosphorus capture.

Enhancing electrochemical performance of graphene oxide/polyaniline composite through plasma-assisted chemical cross-linking and surface modification

The composite of graphene oxide (GO) and polyaniline (PANI) is a promising electrode material for supercapacitors. A high loading of PANI can provide large specific capacitance, but it is a pervasive challenge to reconcile long-term cycling stability and high-rate discharge. Herein, we focus on a GO/PANI composite with low PANI content (∼25 wt%), developing a stable network of GO with an even distribution of PANI. Moreover, significantly enhanced electrochemical performance is achieved by utilizing plasma technology. The specific capacitance increases by 99 % to 433 F g−1 at 1.5 A g−1 after Argon (Ar) plasma treatment. Even at 15 A g−1, a capacitance retention rate of 91 % is obtained. After 15,000 cycles, the capacitance retention rate is 93 %, surpassing most previously reported GO/PANI composite electrodes. The further assembled all-solid-state supercapacitors can deliver a high energy density of 13.6 Wh kg−1 and exceptional cycling stability. According to results of characterization, it is demonstrated that Ar plasma imparts GO/PANI better surface morphology and achieves etching, reduction of GO, and cross-linking of GO and PANI, thereby activating the electrochemical activities of GO and PANI while ensuring stability. In this regard, the synergistic effects of cross-linking, reduction, and etching, and the mechanism are theoretically illustrated by dynamic differential equations. This work presents plasma processing unique charm for designing graphene-based materials via a customized strategy, exploiting an effectual approach to drive the applications of graphene-based materials in energy storage.

Optimizing pH sensor performance with PANI/PMMA composite thin films: Impedimetric and capacitive transduction approaches

The continuous search for novel materials to meet the requirements of modern technological applications has led to the widespread use of polyaniline (PANI) composites for sensing purposes. Although research has been carried out on both chemical sensors using PANI/polymer composites and chemical sensors with impedimetric/capacitive transduction using PANI composites, there is still a gap in the use of PANI/polymer composites in impedimetric and capacitive transduction platforms for pH sensing. In this study, the influence of composite thin films consisting of PANI and poly(methyl methacrylate) (PMMA) on the sensitivity and linearity of pH sensors based on electrochemical impedance and capacitance spectroscopy (EIS/ECS) was evaluated. The sensitivity and linearity of the devices showed a dependence on the polymer content. For PANI:PMMA equal to 30:70, the EIS and ECS sensitivity reached 12.6 ± 2.7 and 18.7 ± 4.9 %/pH, respectively, after reaching its minimum value for the 50:50 sample. Similarly, the linearity values for the 30:70 sample were 92.7 % and 99.8 % for EIS and ECS, respectively. We were able to encapsulate the PANI in the PMMA matrix, which improved the control of ion diffusion and analyte access to the active redox quinoid rings on the PANI. As a result, the saturation effect of the polymer was reduced. By adjusting the relative content of PANI and PMMA, the structure and properties of the composite can be controlled, directly affecting the sensor parameters. These materials have potential applications in sensors for various fields such as food, biomedical and environmental monitoring, with the ability to tailor their properties for optimal response.

Enhanced degradation of crystal violet using PANI-ZnO nanocomposites: Electro-oxidation and photocatalysis studies

This work compares the transformation capabilities of crystal violet (CV), a toxic cationic dye of the triphenylmethane family, by advanced oxidation processes, especially heterogeneous photocatalysis and electrochemical oxidation, on new nanocomposite materials with a composition of zinc oxide (ZnO) and polyaniline (PANI) by chemical polymerization in solution. Concerning the synthesis of PANI, we have exploited the radical oxidative polymerization method; this latter is functional and uncomplex, as it does not require expensive equipment, using ammonium persulfate as an oxidant with a part of monomer (Aniline) to remove pollutants present in the environment. After physicochemical analyses including FTIR, SEM, and electrochemical characterizations by cyclic voltammetry and conductimetry, the results show that the photocatalytic activity of PANI-ZnO 5 % resulted in a better yield (85 %) compared to PANI alone and other composites (PANI-ZnO 10 % and PANI-ZnO 20 %). However, the electro-oxidation discoloration rates on all PANI alone and PANI-ZnO composite electrodes (5 %, 10 %, and 20 %) reached almost 99 %. To deepen our understanding, computational DFT calculations were employed, complementing experimental findings, and together, they contribute to elucidating the intricate mechanisms underlying the enhanced performance of these nanocomposite materials in both photocatalysis and electrochemical oxidation processes.

A multimodal sensing network based on synergistically sensitized polyaniline composites strategy for safety monitoring in pesticide spraying

Ensuring the safety of farmers during pesticide spraying is crucial in smart agricultural practices due to the potential risks of pesticide poison and the associated irreversible damages. However, there is a notable deficiency of efficient monitoring strategies for providing timely and cost-effective safety warnings. In this study, we have devised an advanced and real-time sensing network using polyaniline (PANI) composites to address this pressing concern. To enhance sensing performance, diverse quantum dots (QDs) sensitizers and rigid or flexible substrates are strategically integrated with PANI, resulting in sensors tailored to different sensing capabilities. Specifically, the proton conduction is heightened by incorporating carboxyl graphene QDs (GQDs) into PANI, obtaining the superior gas-sensing performance for NH3 detection. Moreover, a strain sensor employing Ti3C2Tx QDs (MQDs) and a flexible thermoplastic polyurethane (TPU) substrate has been developed for real-time monitoring of physical biosignals. Finally, a smart sensing network with real-time display integrated with the above sensors is designed to detection NH3 concentration released from pesticide volatilization and physiological tracking in cases of mild pesticide poisoning. This sensing network can wirelessly interface with a laptop for convenient safety monitoring of farmers engaged in smart agriculture. The proof of concept demonstrated by this sensing network holds promise for enhancing safety monitoring in smart agriculture.

Advanced carbo-catalytic degradation of antibiotics using conductive polymer-seaweed biochar composite: Exploring N/S functionalization and non-radical dynamics

Polyaniline (PANI) and Saccharina Japanica seaweed (kelp) biochar (KBC) composites were synthesized in-situ through polymerization. This study presents a novel approach to the degradation of sulfamethoxazole (SMX), a prevalent antibiotic, using a PANI-KBC composite to activate peroxymonosulfate (PMS). Extensive characterizations of the PANI-KBC composite were conducted, resulting in successful synthesis, uniform distribution of PANI on the biochar surface, and the multifunctional role of PANI-KBC in SMX degradation. A removal efficiency of 97.24% for SMX (10 mg L−1) was attained in 60 min with PANI-KBC (0.1 g L−1) and PMS (1.0 mM) at pH 5.2, with PANI-KBC showing effectiveness (>92%) across a pH range of 3.0–9.0. In the degradation of SMX, both radical (SO4•− and •OH) and non-radical (1O2 and electron transfer) pathways are involved. The reaction processes are critically influenced by the roles of SO4•−, 1O2 and electron transfer mechanisms. It was suggested that pyrrolic N, oxidized sulfur (−C−SO2−C−), structural defects, and O−CO were implicated in the production of 1O2 and electron transfer processes, respectively, and a portion of 1O2 originated from the conversion of O2•−. The study evaluated by-product toxicity, composite reusability, and stability, confirming its practical potential for sustainable groundwater remediation.

Synergism in the electrocatalytic properties of cobalt phthalocyanine-carbon nanotube-polymeric electrospun nanofibers immobilized on a gold electrode for the detection of lead(II) ions

Core-shelled electrospun nanofibers (ENFs) comprising of a polyvinyl acetate (PVA) shell encapsulating a composite of polyaniline (PANI), tetra-4-(3-oxyflavonephthalocyaninato)cobalt(II) (CoPc-flav), carboxylic acid functionalized multiwalled carbon nanotubes (f-MWCNTs) and an annealed conductive top layer of Nafion (Nf) were used to fabricated a chemically modified gold electrode (Au|ENFs-1-Nf) via the adsorption method. The electrocatalytic sensing capabilities of the Au|ENFs-1-Nf electrode towards Pb(II) ions were evaluated. In comparison to the bare gold electrode and other chemically modified electrodes (CMEs), the Au|ENFs-1-Nf electrode was less prone to fouling showing more stable analyte signal and less compromised background electrolyte currents. The Au|ENFs-1-Nf electrode could detect the Pb(II) cations in a reproducible manner ranging from 8 to 125 μM where limits of detection and quantification of 0.51 and 1.55 μM were obtained, respectively. The analytical performance of the aforementioned CME rendered a comparable percentage recovery (103 %) with that of Inductively coupled plasma-optical emission spectroscopy (ICP-OES) (115 %).

Graphene-enhanced manganese dioxide functional ink infused with polyaniline for high-performance screen-printed micro supercapacitor

In the world of miniature advancements in technology, a current champion has emerged: the micro supercapacitors. In order to fabricate these micro-supercapacitors, we have developed a promising and user-friendly approach for printing a conductive functional ink containing a ternary composite of manganese dioxide (MnO2) nanoparticles, Graphene, and polyaniline (PANI) as a dopant. Screen-printing technique was employed to fabricate micro-supercapacitors using the nanocomposite conductive ink. The performance of the energy storage device was examined using flexible symmetric and asymmetric, with an aqueous 1 M KOH electrolyte. According to this strategy, the characterisation and electrochemical study results revealed that doping PANI into both symmetric and asymmetric devices significantly increased the material’s capacitive performance of areal capacitance 167 mFcm−2 for MnO2/Graphene/PANI-5 composite (MGP-5) and 292.5 mFcm−2 for asymmetric supercapacitor (ASSC) at 5 mVs−1. Furthermore, the asymmetric supercapacitor displayed outstanding cyclic stability, retaining 93.6% of its capacitance after 10000 cycles. This underscores the possibility of incorporating polyaniline (PANI) into MnO2 and graphene matrices as efficient blueprints for the development of superior electrode materials. The improvement represents a significant step forward, opening avenues for the future development of novel devices and their integration into top-of-the-line flexible energy storage systems.

Design and evaluation of a polyaniline-Azadirachta indica composite for efficient dye removal: Insights from experimental and theoretical simulations

In this study, a novel composite of polyaniline and Azadirachta indica sawdust (PAIS) was synthesized to explore its potential in the adsorptive removal of methylene blue (MB) and crystal violet (CV) dyes from aqueous solution. PAIS was characterized using various instrumental techniques, including FTIR, SEM/EDXS, XRD, TEM/SAED, BET, and TGA-DTG/DTA analyses. Batch adsorption tests revealed that pH, medium temperature, initial adsorbate concentration, adsorbent dose, and contact duration significantly influence adsorption efficiency. Adsorption equilibrium was reached at 30 min for MB and 90 min for CV in an acidic medium (up to pH 7), with minimal changes observed beyond these times. The Langmuir isotherm provided the best validation, with a maximum monolayer adsorption capacity of 454.54 mg/g for MB and 370.37 mg/g for CV, showcasing superior performance compared to most reported materials. The adsorption process adhered to a pseudo-second-order approach for both dyes, with a high coefficient of determination value. The adsorption of MB and CV by this innovative adsorbent was spontaneous, endothermic, and accompanied by entropy enhancement. The adsorbent loaded with dyes was subjected to different desorbing agents (HCl, NaOH, NaCl, CH3COOH, and H2O), and HCl was the most effective. Computational studies using Density Functional Theory supported the experimental results, confirming the higher efficiency of PAIS for MB removal over CV. It is submitted that PAIS uniquely exhibits highly adaptable, recyclable, and potent low-cost adsorbent properties for eliminating both dyes from aqueous systems, representing a significant advancement in the field of dye removal.

Facile synthesis of Ce2(WO4)3-decorated polyaniline composites as promising electrode material for supercapacitor applications

Facile synthesis of Ce2(WO4)3-decorated polyaniline composites as promising electrode material for supercapacitor applications

Process modeling of direct Red-28 dye eradication by biopolymeric composite of polyaniline with mango leafy biowaste material

The use of biopolymers and synthetic adsorbents for wastewater treatment is gaining more importance due to their ease of preparation and nontoxic nature. This study focuses on developing a new biopolymeric composite using Polyaniline and a leafy mulch of mango plants (PANI/ML) and applied to remove an anionic dye, i.e.: Direct Red-28 from water on a lab scale. Samples were characterized by various spectrochemical methods, like FT-IR, UV–Vis, and SEM analysis, and then used for adsorption studies. Results indicated that PANI/ML nanomaterial removed 203.25 ± 0.57 mg/g of Direct Red-28 dye, following chemisorption and pseudo-2nd order kinetic model with inter-layer diffusion mode. Desorption studies indicated that it can be recycled three times effectively. So, this composite can be used for adsorptive bioremediation of synthetic anionic pollutants.