Open access peer-reviewed chapter

Polyaniline-Based Nanocomposites for Environmental Remediation

Written By

Thabiso C. Maponya, Mpitloane J. Hato, Thabang R. Somo, Kabelo E. Ramohlola, Mogwasha D. Makhafola, Gobeng R. Monama, Arjun Maity, Kwena D. Modibane and Lebogang M. Katata-Seru

Submitted: April 6th, 2018Reviewed: November 4th, 2018Published: November 11th, 2019

DOI: 10.5772/intechopen.82384

Chapter metrics overview

843 Chapter Downloads

View Full Metrics

Abstract

With growth in civilisation and industrialisation, there is an increase in the release of toxic heavy metal ions and dyes into water system, which is of public concern. As a result, appropriate treatment methods have to be implemented in order to mitigate and prevent water pollution. The discovery of nanotechnology has led to the development and utilisation of various nanoadsorbent for the removal of pollutants from water. PANI nanostructures and nanocomposites are noble adsorbents that have gained popularity in addressing water pollution issues and have been reported in literature. In this chapter, the main focus is on the synthesis of PANI nanocomposites and nanostructures and their application as efficient adsorbents for water treatment. Detailed discussions on different synthetic routes and characterisation have been dedicated to applications of these materials and are compared for the adsorptive removal of heavy metal ions and dyes from water.

Keywords

  • conducting polymers
  • polyaniline
  • composites
  • water remediation

1. Introduction

The existence of various toxic pollutants in natural water systems originating from different activities such as textile industry, mining operation and steel manufacturing is still a global challenge [1]. Hence, it is vital to develop efficient technologies to remove these pollutants from wastewater prior release into the environment. Among several water treatment processes (coagulation, membrane filtration, chemical reduction and precipitation, reverse osmosis), adsorption technology is deemed an efficient technology to treat wastewater due to exceptional advantages such as low cost, high removal efficiency and regeneration [1]. For many years, there has been an ongoing research on the development of high affinity materials towards water pollutants, which can effectively adsorb and remove them from industrial wastewater [2]. Conducting polymers (CPs) including polypyrrole (PPy), polythiophene (PTh), polyacetylene (PA) and polyaniline (PANI) have attained great attention for water treatment, owing to their intriguing properties such as ease synthesis, tunable structure and the presence of ideal functional groups [3]. Hence, CPs have been widely applied in materials such as rechargeable batteries, chemical sensors, electrochromic devices, surface coating for corrosion protection and water treatment [4]. Among these conducting polymers, PANI has been widely studied due to its low cost, ease of synthesis, good environmental stability, unique doping/de-doping property and relatively high conductivity [5]. The discovery of PANI dates back to about 180 years ago to the experiments made by Runge [6]. From his work reported in 1834, he discovered that a dark green PANI changed to black when the mixture of copper(II) chloride and aniline nitrate is heated on a porcelain plate to 100°C [6, 7]. Anciently, PANI was known as ‘aniline black’, after forming an undesirable black powder deposit on the anode during oxidation of aniline [8, 9] and is the most stable CP that can be easily protonated (with an acid) to increase conductivity or deprotonated (with a base) to reduce its conductivity [10]. In 1862, Letheby prepared it through oxidation of aniline under mild conditions [9, 11]. Attempt to control the synthesis conditions of polyaniline grew until in the 1910s when Green and Woodhead managed successfully to control the conditions, which led to the discovery of its four oxidation states [8]. This was followed by Jozefowic’s group in the 1960s and 1970s for better understanding of the material [6, 8]. After this, the study of polyaniline with other (intrinsic conducting polymers) ICPs increased tremendously worldwide and were studied for different applications.

Advertisement

2. Synthesis of polyanilines

Polyaniline have different chemical structures which is attributed to the oxidation state of the polymer backbone, hence it exists in different states [12, 13]. The general representation of the polyaniline structure can be described by the following structural formula (Figure 1):

Figure 1.

The general structure of polyaniline.

were y = 1, 0.5 and 0 correspond to fully reduced polyaniline (leucoemeraldine), the half oxidised polyaniline (emeraldine) and fully oxidised polyaniline (pernigraniline), respectively [13]. Upon doping, PANI can be interconverted from one oxidation state to another [13]. The interconversions can be clearly deduced as presented in Figure 2.

Figure 2.

Oxidation of aniline monomer during polymerisation of aniline [21,22].

There are two general methods which are employed to synthesise conducting polymers through electrochemical oxidation of the monomers or chemical oxidation of the monomers, namely: electrochemical polymerisation and chemical polymerisation.

2.1 Electrochemical polymerisation

Electrochemical polymerisation or method can be carried out by employing one of the three techniques: (i) applying a constant current (galvanostatic), or (ii) applying a constant potential (potentiostatic), and lastly (iii) by applying a potential scanning/cycling to the aqueous solution of aniline [14]. Polymerisation process is performed in strongly acidic aqueous electrolyte using a radical polymerisation mechanism which allows a formation of anilinium radical cation by aniline oxidation on the electrode[15, 16]. Electrochemical polymerisation strongly depends on the following factors:

  1. low pH which is needed for preparation of conductive polymeric materials,

  2. the dopant anion incorporated into polymer to determine the morphology, conductivity, rate of polymerisation growth and influences degradation process and

  3. inert electrode such as Pt, Au and graphite [17].

The electrochemical process is more advantageous since film properties such as thickness and conductivity can be controlled by the synthesis parameters, including the current density, substrate, pH, nature and concentration of electrolyte [18].

2.2 Chemical polymerisation

Like electrochemical polymerisation, chemical polymerisation is also carried out in an acidic medium such as hydrochloric acid (HCl) and formic acid which helps in yielding primary polymer [19]. For this process to occur, a dopant or oxidant is required. The dopant reagents used during this process are the oxidising agents such as ammonium persulfate (APS), ferric chloride (FeCl3), hydrogen peroxide (H2O2) and ceric nitrate (Ce(NO3)3). The principal function of the oxidant is to withdraw a proton from an aniline molecule, without forming a strong coordination bond either with the substrate intermediate or with the final product [20].

The general mechanism involved during polymerisation of aniline proceeds dominantly via radical mechanisms. Radical mechanisms can be subdivided into initiation, chain propagation and termination steps, which results in stable intermediate resonance structures. The three different stages of polymerisation are illustrated from Figures 24.

2.2.1 Step 1: initiation step (oxidation of aniline monomer)

The initial step of aniline oxidative polymerisation is the generation of the aniline cation radical in the oxidation of aniline with an oxidant as shown in Figure 2 [21, 22]. The aniline cation radical undergoes resonance to attain the most stable and reactive radical cation which is free from steric hindrances [23]. This step is the slowest step in the reaction, hence it’s deemed as the rate determining step in aniline polymerisation [24].

2.2.2 Step 2: radical coupling and re-aromatisation

Head to tail coupling of the N- and para- radical cations takes place (Figure 3), yielding a dicationic dimer species. This dimer further undergoes the process of re-aromatisation which causes it to revert to its neutral state, yielding an intermediate referred to as p-aminodiphenylamine (PADPA) [25, 26]. These processes are also accompanied by the elimination of two protons.

Figure 3.

Formation of a dimer [25,27].

2.2.3 Step 3: chain propagation

The dimers are immediately oxidised and then react with a stable aniline cation radical via an electrophilic aromatic substitution, followed by deprotonation and rearrangements to afford the trimer as seen in Figure 4 [27]. The trimer further undergoes oxidation and reacts with aniline cation radical to form a tetramer and so on.

Figure 4.

Formation of a trimer and polymer formation [27].

Advertisement

3. Synthesis and characterisation of polyaniline nanocomposites

Different nanocomposites based on polyaniline have been reported for wastewater remediation in order to enhance the removal efficiency of polyaniline. Depending on the method of synthesis, a variety of PANI based nanostructures and nanocomposites can be developed. For example, Ren et al. [28] reported PANI/PAN (polyacrylonitrile) nanocomposite synthesised via in–situ polymerisation of ANI monomer using DBSA and APS to obtain a nanofibrous structures as depicted in Figure 5a. Rachna and co-workers [29] reported zinc ferrite-PANI nanocomposite prepared following similar preparation method and monomer using toluene as a solvent and CuSO4. The SEM image (Figure 5b) showed that the nanocomposite had a smooth surface. Tanzifi et al. [30] prepared PANI/carboxymethyl cellulose/titanium dioxide PANI/CMC/TiO2 nanocomposite in acidic medium using the same polymerisation route and APS as an oxidising agent. The nanocomposite structure formed uniform spherical particles as indicated in Figure 5c. PANI@Ni(OH)2 nanocomposite was prepared by Bhaumik et al. [2] via in–situ polymerisation using APS and hydrazine hydrate. The SEM image showed a tubular structure as represented in Figure 5d.

Figure 5.

SEM images of different structures of PANI nanocomposites (a) fibres [28], (b) smooth surface [29], (c) spherical [30] and (d) tubular [2].

Hallajiqomi et al. [31] synthesised PANI/PVP nanocomposite via in–situ polymerisation using KIO3 and PVP as oxidising agent and surfactant, respectively. The nanocomposite showed irregular structural morphology. PANI/reduced graphene oxide (RGO) nanocomposite was synthesised by Li et al. [32] following the same polymerisation route using APS as an oxidising agent. The nanocomposite exhibited a lamellar structure. In another study, Harijan and Chandra [33] reported a PANI-GO nanocomposite synthesised by similar preparation method and the nanocomposite was composed of sheet-like morphology. Wang et al. [34] synthesised PANI/α-ZrP with plate–like structures via in–situ polymerisation using the same oxidising agent. In another study, Abdolahi et al. [35] synthesised uniform PANI nanofibers through interfacial polymerisation with different sizes ranging from micro- to nanometers. Gold-polyaniline (AuPANI) nanocomposite was prepared by simple interfacial polymerisation, performed in an immiscible water/toluene biphasic system using tetrachloroaurate, as an oxidant [36]. The TEM images of AuPANI nanocomposite showed rod-like Au nanoparticles embedded in a PANI matrix (see Figure 6ad). Dhachanamoorthi et al. [37] prepared PANI-iron oxide (Fe3O4) ternary nanocomposites with improved crystallinity upon addition of Fe3O4 by mechanical mixing approach. Similar method was used for the synthesis of PANI-zinc oxide (ZnO) nanocomposites with enhanced electrical conductivity and homogeneous distribution on ZnO nanoparticles in the polymer matrix [38]. Basavaiah et al. [39] prepared polyaniline nanorods and magnetite nanoparticles via self-assembly route.

Figure 6.

TEM images of AuPANI nanocomposite with different magnifications (a, b, c) showing rod-like Au nanoparticles embedded in a PANI synthesised by interfacial polymerisation and (d) corresponding selected area electron diffraction (SAED) [36].

Table 1 shows some of the PANI based nanocomposites reported for the removal of pollutants from wastewater. The most commonly used method is the in–situ chemical polymerisation, which can result in various morphological structures. The structure of the nanocomposite is strongly affected by the type of oxidant, surfactant or stabiliser, the precursor and the ratio of the precursor to that of ANI.

AdsorbentSynthesis method, oxidant and/or other reagentsMorphologyRefs.
PANI-PPya, FeCl3Fibres[40]
PANI nanoadsorbenta, APS, stabiliserSpherical particles[41]
PANI/tin(II)molybdophosphateIn-situ methodSpherical particles[42]
PANI/Fe0a, FeCl3Fibrous structure[43]
PANI/ZrO2Direct mixing, APSIrregular rougher surface[44]
PANI–ZnOa, APSFlaky structure[45]
PANI/SiO2a, APS, NaCMCNaUniform spherical particles[46]
Fe3O4/G/PANIa, APSMixture of sheets and spherical particles[47]
PANI/zeolitea, APSMixture of sheets and tubular particles[48]
PANI/MnO2/TiO2a, KMnO2Aggregated spherical particles[49]
PPy-PANI/Fe3O4a, FeCl3roughly spherical particles[3]

Table 1.

Some of PANI nanocomposites and their reported structures.

a = in-situ polymerisation, NaCMCNa = sodium carboxymethyl cellulose sodium.

Advertisement

4. Polyaniline and its composites for wastewater treatment

The application of PANI for wastewater treatment has been widely studied owing to its exceptional structure that comprises abundant amine and imine functional groups [50, 51]. The nitrogen atoms on these functional groups have lone pairs of electrons to facilitate chelation and adsorption of pollutants [28, 52]. However, PANI has disadvantages such as poor mechanical properties and processability as well as low solubility. These limitations emanate from its high conjugation and strong electrostatic interaction between chains, which decreases its performance and limit its commercial application [51, 53]. Composites formation offers potential in addressing the above shortfalls. Polyaniline composites can be regarded as a material consisting of PANI matrix and one or more components such as semiconductors, metal nanoparticles, organic compounds, inorganic compounds as well as biological and natural products in order to improve polymer backbone properties or extend its functionalities [51, 54]. In order to prepare the composite materials successfully, several methods like physical mixing, sol–gel technique, in–situchemical polymerisation, emulsion technology, sonochemical process and irradiation technique are employed [55]. Since then, various PANI composites have been reported for the removal of pollutants from wastewater using membrane technology [56, 57], chemical reduction [50], photocatalytic degradation [58, 59] and adsorption technology [60, 61]. Among these methods, adsorption has been identified as a prestigious technology, due to its flexibility and simplicity of design, initial cost, ease operation and insensitivity to toxic pollutants [62]. Different polyaniline-based composites for adsorption of pollutants have been widely studied. Samani et al. [60] reported PANI/PEG (polyethylene glycol) composite for the removal of hexavalent chromium ions (Cr(VI)), which had the maximum adsorption capacity (qmax) of 68.97 mg/g. Debnath et al. [63] reported a PANI/lignocellulose composite with qmax of 1672.5 mg/g for Congo red (CR) removal. PANI/chitosan was studied by Janaki et al. [64] for the removal of dyes (CR, Coomassie Brilliant Blue (CBB), and Remazol Brilliant Blue R (RBBR)). They obtained the maximum capacities to be 322.58, 357.14 and 303.03 for CR, CBB and RBBR, respectively. PANI/silica (SiO2) gel was reported by Karthik et al. [52] with qmax = 63.41 mg/g for the removal of Cr(VI). However, most of these PANI composites have lower removal efficiency and adsorption capacity, owing to their irregular structure resulting from agglomeration, poor water dispersion and reduced surface area [35]. Numerous researches have been focussed on the development of nanostructured PANI composites with improved surface area and maximum adsorption capacity [35, 53, 65, 66].

Advertisement

5. Application of polyaniline nanocomposites as adsorbents for water treatment

In recent years, polyaniline nanocomposites have been used as adsorbents for the removal of various pollutants from wastewater [30]. More studies have been focussed on the adsorption of organic dyes and heavy metals ions due to their good interaction with PANI nanocomposites functional groups [52]. In the study of interaction between PANI nanocomposites and pollutants, various adsorption parameters such as pH, contact time, adsorbent dose, temperature, nature of the adsorbent and concentration of the pollutants are investigated [38]. From these parameters, the efficiency and adsorption capacity of nanocomposites can be determined to confirm the potential of the PANI nanocomposites as adsorbents for water purification.

5.1 Adsorption of heavy metals

The general sources of heavy metals are weathering of rocks due to their abundance in nature and mining industries as a result of mineral process of metal ores [61]. Various heavy metals known to pollute water include nickel, cadmium, lead, mercury, chromium, arsenic and copper. The water pollution by these toxic metals is a global concern owing to their acute toxicity and enduring accumulation [67]. Heavy metals are problematic since they are mutagenic, carcinogenic, are not biodegradable and can form various species [68].

5.1.1 PANI nanocomposites for adsorption of heavy metals ions

A PANI/RGO nanocomposite was reported by Li et al. [32] for the removal of Hg(II) ions from aqueous solution. It was shown that the PANI/RGO had high equilibrium adsorption capacity in comparison to PANI (Figure 7a). The obtained monolayer maximum adsorption capacity was 1000 mg/g at pH 4, 33°C and 400 mg/L for 200 mg adsorbent dose. Bhaumik et al. [38] reported a PANI/Fe0 nanocomposite for the removal of arsenic (As), which had Langmuir maximum adsorption capacity of 232.5 and 227.7 mg/g for both As(III) and As(V) at pH 7, 25°C and 1 mg/L for 10 mg of PANI/Fe0 nanocomposite. The obtained pH effects results (Figure 7b) showed higher removal efficiency by the nanocomposite in comparison to the neat PANI. Harijan and Chandra [33] reported a PANI/GO for the removal Cr(VI) from aqueous solution. It was demonstrated that the nanocomposite had high Langmuir maximum capacity of 192 mg/g at pH 6.5, 30°C and 100 mg/L for 25 mg of PANI/GO in comparison to the neat PANI (Figure 7c). Table 2 shows some of the PANI nanocomposites reported for removal of various heavy metal ions under different experimental conditions.

Figure 7.

Comparison of PANI and PANI nanocomposites for the removal of various pollutants (a) kinetics [32], (b) pH effect [43], (c) isotherms [33] and (d) equilibrium adsorption capacity [34].

AdsorbentPollutantqmax (mg/g)pHConc. (mg/L)Adsorbent dose (mg)Refs.
PANI/PANCr(VI)67.032510[28]
PAMpDA@Fe3O4Co(II)116.365050[69]
PPy-PANI/Fe3O4Cr(VI)303.0210050[3]
Fe3O4/GO/PANICr(VI)153.46.510050[47]
PANI@Ni(OH)2Cr(VI)625.0410010[2]
PANI/zeoliteCr(VI)250200[48]
PANI/PVPMn(II)50.307100250[31]

Table 2.

Some of the PANI nanocomposites for heavy metals adsorption.

5.2 Adsorption of organic dyes

Organic pollutants are generally materials that comprise of aromatic rings in their structure. Numerous organic pollutants including dyes, chlorinated, aliphatic and phenolic compounds are carcinogenic and mutagenic [70]. Dyes are of major concern due to their wide application in textile, paper, pigment and plastic industries. Their presence in water systems results in water decolouration, which can negatively affect aquatic life by influencing the photosynthetic process [71]. Some of PANI based nanocomposites for dye removal are given in Table 3.

AdsorbentPollutantqmax (mg/g)pHConc. (mg/L)Adsorbent dose (mg)Refs.
PANI/MWCNTsCR1472507[74]
PANI/PA 6MO48.81030[54]
ZnFe2O4-PANIRhodamine B RHB1000210500[29]
PANI/CMC/TiO2CR94.282.682140[30]
PANI/Fe0CR99.671001000[75]
PPy–PANI NFsCR222.2242001000[35]
Starch/PANIReactive Black 5811.3051060[76]

Table 3.

Some of the PANI based nanocomposites for dye adsorption.

5.2.1 PANI nanocomposites for adsorption of dyes

Wang et al. [34] reported PANI/α-ZrP for the removal of methyl orange (MO) cationic dye. It was demonstrated by Figure 7d that the nanocomposite (5 mg) had high removal efficiency capacity at pH 4 and 25°C for 100 mg/L MO solution. The monolayer maximum adsorption capacity was obtained to be 377 mg/g. Tanzifi et al. [46] reported PANI/SiO2 nanocomposite for the removal of amido black 10B. The obtained Langmuir maximum adsorption capacity was 42.24 mg/g at pH 2, 25°C and 30 mg/L for a 100 mg adsorbent dose. Gharbani [37] reported PANI/tin(II)molybdophosphate for the removal of malachite green (MG). It was demonstrated that the removal efficiency was 93% for 50 mg/L of MG at pH 10 and the adsorption process followed Freundlich isotherm model. In another study, Ballav et al. [72] synthesised PANI coated ligno-cellulose composite (PLC) via in-situ polymerisation of aniline monomer for the removal of Reactive Black 5 (RB-5) from aqueous solutions. The authors reported that the equilibrium adsorption isotherm studies revealed that the Langmuir isotherm provided the best fit with monolayer adsorption capacity of 312 mg/g. The Maity’s research group also reported the use of PANI-coated lignin-based adsorbent for the uptake of reactive dye eosin yellow (EY) from aqueous solution [73]. The adsorption capability of the adsorbent was found to be more effective than the unmodified adsorbent at lower pH.

Advertisement

6. Conclusions

This chapter encompasses the work done on PANI nanocomposites/nanostructures for the removal of heavy metal ions and dyes from aqueous solution. Adsorption technology was widely studied due to its flexibility in design and operational simplicity. The use of PANI nanocomposites as adsorbents has been investigated for adsorption of pollutants owing to their inherent properties such as high surface area, environmental stability, easy preparation and good water dispersion. The literature showed that a variety of morphological structures can be obtained, which depend strongly on the method of synthesis, and thus have various effects on the adsorption of the pollutant. For example, PANI based nanocomposites and nanostructures are preferable prepared via in-situ polymerisation. It was demonstrated that the pH, contact time, temperature, adsorbent dosage, concentration, nature of adsorbent and the presence of competing ions have an influence on the removal efficiency of nanocomposites. Hence, optimisation of adsorption parameters has been studied for the removal of heavy metals such Cr(VI), Hg(II), As(V), Co(II) and dyes such as CR, MB, MO, MG and RB5 from wastewater using various PANI nanocomposites and nanostructures. Overall, these nanocomposites display improved removal efficiency towards heavy metals and dyes adsorption. Hence, data in this chapter provides insight into PANI based materials for potential use as economically valuable adsorbents for the removal of dyes and heavy metals ions from wastewater.

Advertisement

Acknowledgments

KDM and MJH greatly acknowledge the financial support from the National Research Foundation (NRF) (Grant Nos. 117727 and 118113), Sasol Inzalo Foundation and University of Limpopo, South Africa.

Advertisement

Conflict of interest

We declare that there is no conflict of interest.

References

  1. 1.Bhaumik M, Maity A, Srinivasu VV, Onyango MS. Removal of hexavalent chromium from aqueous solution using polypyrrole-polyaniline nanofibers. Chemical Engineering Journal. 2012;181(182):323-333. DOI: 10.1016/j.cej.2011.11.088
  2. 2.Bhaumik M, Kumar V, Maity A. Synergetic enhancement of Cr(VI) removal from aqueous solutions using polyaniline@Ni(OH)2 nanocomposites adsorbent. Journal of Environmental Chemical Engineering. 2018;6:2514-2527. DOI: 10.1016/j.jece.2018.03.047
  3. 3.Kera NK, Bhaumik M, Pillay P, Ray SS, Maity A. Selective removal of toxic Cr(VI) from aqueous solution by adsorption combined with reduction at a magnetic nanocomposite surface. Journal of Colloid and Interface Science. 2017;503:214-228. DOI: 10.1016/j.jcis.2017.05.018
  4. 4.Krishnani KK, Srinives S, Mohapatra BC, Boddu VM, Hao J, Meng X, et al. Hexavalent chromium removal mechanism using conducting polymers. Journal of Hazardous Materials. 2013;252(253):99-106. DOI: 10.1016/j.jhazmat.2013.01.079
  5. 5.Thambidurai S, Pandiselvi K. Polyaniline/natural polymer composites and nanocomposites. In: Polyaniline Blends, Composites, and Nanocomposites. 2018. pp. 235-256. DOI: 10.1016/B978-0-12-809551-5.00009-6
  6. 6.Rasmussen SC. The early history of polyaniline: Discovery and origins. Substantia. 2017;1:99-109. DOI: 10.13128/substantia-30
  7. 7.Ciri G. Recent advances in polyaniline research: Polymerization mechanisms, structural aspects, properties and applications. Synthetic Metals. 2013;177:1-47. DOI: 10.1016/j.synthmet.2013.06.004
  8. 8.Kang ET, Neoh KG, Tan KL. Polyaniline: A polymer with many interesting intrinsic redox states. Progress in Polymer Science. 1998;23:277-324. DOI: 10.1016/s0079-6700(97)00030-0
  9. 9.Li D, Huang J, Kaner RB. Polyaniline nanofibers: A unique polymer nanostructure for versatile applications. Accounts of Chemical Research. 2009;42:135-145. DOI: 10.1021/ar800080n
  10. 10.Parel MMP, Gillado AV, Herrera MU. Morphology and electrical conductivity of polyaniline coating on acetate film. Surfaces and Interfaces. 2018;10:74-77. DOI: 10.1016/j.surfin.2017.12.00
  11. 11.Trojanowicz M. Application of conducting polymers in chemical analysis. Microchimica Acta. 2003;143:75-91. DOI: 10.1007/s00604-003-0066-5. Review article
  12. 12.Sattari S, Reyhani A, Khanlari MR, Khabazian M, Heydari H. Synthesis of polyaniline-multi walled carbon nanotubes composite on the glass and silicon substrates and methane gas sensing behavior of them at room temperature. Journal of Industrial and Engineering Chemistry. 2014;20:1761-1764. DOI: 10.1016/j.jiec.2013.08.029
  13. 13.Bhadra S, Khastgir D, Singha NK, Lee JH. Progress in preparation, processing and applications of polyaniline. Progress in Polymer Science. 2009;34:783-810. DOI: 10.1016/j.progpolymsci.2009.04.003
  14. 14.Liu X, Zhang L, Li Y, Bian L, Su Z, Zhang L. Electropolymerization of aniline in aqueous solutions at pH 2 to 12. Journal of Materials Science. DOI: 10.1007/s10853-005-0854-x
  15. 15.Gurunathan K, Murugan AV, Marimuthu R, Mulik UP, Amalnerkar DP. Electrochemically synthesised conducting polymeric materials for applications towards technology in electronics, optoelectronics and energy storage devices. Materials Chemistry and Physics. 1999;61:173-191. DOI: 10.1016/SO254-0584(99)00081-4
  16. 16.Gvozdenovi MM, Jugovi BZ, Stevanovi JS, Grgur BN. Electrochemical synthesis of electroconducting polymers. Hemijska Industrija. 2014;68:673-684. DOI: 10.2298/HEMIND131122008G
  17. 17.Jaymand M. Recent progress in chemical modification of polyaniline. Dedicated to professor Dr. Ali Akbar Entezami. Progress in Polymer Science. 2013;38:1287-1306. DOI: 10.1016/j.progpolymsci.2013.05.015
  18. 18.Toshima N, Hara S. Direct synthesis of conducting polymers from simple monomers. Progress in Polymer Science. 1995;20:155-183. DOI: 10.1016/0079-6700(94)00029-2
  19. 19.Campos TLA, Kersting DF, Ferreira CA. Chemical synthesis of polyaniline using sulphanilic acid as dopant agent into the reactional medium. Surface and Coatings Technology. 1999;122:3-5. DOI: 10.1016/S0257-8972(99)00399-0
  20. 20.Ciri G, Konyushenko EN, Trchov M. Chemical oxidative polymerization of anilinium sulfate versus aniline: Theory and experiment. Synthetic Metals.2008;158:200-211. DOI: 10.1016/j.synthmet.2008.01.005
  21. 21.Mazur M, Michota-kami A, Bukowska J. Surface-catalyzed growth of poly(2-methoxyaniline) on gold. Electrochimica Acta. 2007;52:5669-5676. DOI: 10.1016/j.electacta.2006.10.043
  22. 22.Nicolas-debarnot D, Poncin-Epaillard F. Polyaniline as a new sensitive layer for gas sensors. Analytica Chimica Acta. 2003;475:1-15. DOI: 10.1016/S0003-2670(02)01229-1
  23. 23.Cordeiro MA, Goncalves D, Bulhoes LO, Cordeiro JM. Synthesis and characterisation of poly-o-toulidine: Kinetics and structural aspects. Materials Science. 2005;8:5-10
  24. 24.Sapurina IY, Stejskal J. The effect of pH on the oxidative polymerization of aniline and the morphology and properties of products. Russian Chemical Reviews. 2010;79:1123-1143. DOI: 10.1070/RC2010v079n12ABEH004140
  25. 25.Tang HJ, Wang AT, Lin SY, Huang KY, Yang CC, Yeh JM, et al. Polymerization of aniline under various concentrations of APS and HCl. Polymer Journal. 2011;43:667-675. DOI: 10.1038/pj.2011.43
  26. 26.Ahmed SM. Mechanistic investigation of the oxidative polymerization of aniline hydrochloride in different media. Polymer Degradation and Stability. 2004;85:605-614. DOI: 10.1016/j.polymdegradstab.2004.01.003
  27. 27.Song E, Choi J. Conducting polyaniline nanowire and its applications in chemiresistive sensing. Nanomaterials. 2013;3:498-523. DOI: 10.3390/nano3030498
  28. 28.Ren J, Huang X, Wang N, Lu K, Zhang X, Li W. Preparation of polyaniline-coated polyacrylonitrile fiber mats and their application to Cr(VI) removal. Synthetic Metals. 2016;222:255-266. DOI: 10.1016/j.synthmet.2016.10.027
  29. 29.Rachna K, Agarwal A, Singh NB. Preparation and characterization of zinc ferrite—polyaniline nanocomposite for removal of rhodamine B dye from aqueous solution. Environmental Nanotechnology Monitoring and Management. 2018;9:154-163. DOI: 10.1016/j.enmm.2018.03.001
  30. 30.Tanzifi M, Yaraki MT, Karami M, Karimi S, Kiadehi AD, Karimipour K, et al. Modelling of dye adsorption from aqueous solution on polyaniline/carboxymethyl cellulose/TiO2 nanocomposites. Journal of Colloid and Interface Science. 2018;519:154-173. DOI: 10.1016/j.jcis.2018.02.059
  31. 31.Hallajiqomi M, Eisazadeh H. Adsorption of manganese ion using polyaniline and its nanocomposite: Kinetics and isotherm studies. Journal of Industrial and Engineering Chemistry. 2017;55:191-197. DOI: 10.1016/j.jiec.2017.06.045
  32. 32.Li R, Liu L, Yang F. Preparation of polyaniline/reduced graphene oxide nanocomposite and its application in adsorption of aqueous Hg(II). Chemical Engineering Journal. 2013;229:460-468. DOI: 10.1016/j.cej.2013.05.089
  33. 33.Harijan DKL, Chandra V. Polyaniline functionalized graphene sheets for treatment of toxic hexavalent chromium. Journal of Environmental Chemical Engineering. 2016;4:3006-3012. DOI: 10.1016/j.jece.2016.06.014
  34. 34.Wang L, Wu X, Xu W, Huang X, Liu J, Xu A. Stable organic−inorganic hybrid of polyaniline/α-zirconium phosphate for efficient removal of organic pollutants in water environment. ACS Applied Materials and Interfaces. 2012;4:2686-2692. DOI: 10.1021/am300335e
  35. 35.Abdolahi A, Hamzah E, Ibrahim Z, Hashim S. Synthesis of uniform polyaniline nanofibers through interfacial polymerization. Materials. 2012;5:1487-1494. DOI: 10.3390/ma5081487
  36. 36.Bogdanovic U, Pasti I, Ciric-Marjanovic G, Mitric M, Ahrenkiel SP, Vodnik V. Interfacial synthesis of gold-polyaniline nanocomposite and its electrocatalytic application. ACS Applied Materials & Interfaces. 2015;7:28393-28403. DOI: 10.1021/acsami.5b09145
  37. 37.Dhachanamoorthi K, Chandra L, Suresh P, Perumal K. Facile preparation and characterization of polyaniline-iron oxide ternary polymer nanocomposites by using "mechanical mixing" approach. Mechanics: Materials Science and Engineering. 2017;9. DOI: 10.2412/mmse.41.37.672
  38. 38.Ansari SP, Mohammad F. Studies on nanocomposites of polyaniline and zinc oxide nanoparticles with supporting matrix of polycarbonate. ISRN Materials Science. 2012;2012:1-7. DOI: 10.5402/2012/129869
  39. 39.Basavaiah K, Prasad MD, Rao AVP. Simultaneous synthesis of polyaniline nanorods and magnetite nanoparticles via self-assembly method. Journal of Experimental Nanoscience. 2014;9:491-500. DOI: 10.1080/17458080.2012.670276
  40. 40.Bhaumik M, McCrindle R, Maity A. Efficient removal of Congo red from aqueous solutions by adsorption onto interconnected polypyrrole-polyaniline nanofibres. Chemical Engineering Journal. 2013;28:506-515. DOI: 10.1016/j.cej.2013.05.026
  41. 41.Tanzi M, Hosseini SH, Kiadehi AD, Olazar M, Karimipour K, Rezaiemehr R, et al. Artificial neural network optimization for methyl orange adsorption onto polyaniline nano-adsorbent: Kinetic, isotherm and thermodynamic studies. Journal of Molecular Liquids. 2017;244:189-200. DOI: 10.1016/j.molliq.2017.08.122
  42. 42.Gharbani P. Synthesis of polyaniline tin(II) molybdophosphate nanocomposite and application of it in the removal of dyes from aqueous solutions. Journal of Molecular Liquids. 2017;242:229-234. DOI: 10.1016/j.molliq.2017.07.017
  43. 43.Bhaumik M, Noubactep C, Gupta VK, McCrindle RI, Maity A. Polyaniline/Fe0 composite nanofibers: An excellent adsorbent for the removal of arsenic from aqueous solutions. Chemical Engineering Journal. 2015;271:135-146. DOI: 10.1016/j.cej.2015.02.079
  44. 44.Agarwal S, Tyagi I, Kumar V, Golbaz F. Synthesis and characteristics of polyaniline/zirconium oxide conductive nanocomposite for dye adsorption application. Journal of Molecular Liquids. 2016;218:494-498. DOI: 10.1016/j.molliq.2016.02.040
  45. 45.Mostafaei A, Zolriasatein A. Synthesis and characterization of conducting polyaniline nanocomposites containing ZnO nanorods. Progress in Natural Science: Materials International. 2012;22:273-280. DOI: 10.1016/j.pnsc.2012.07.002
  46. 46.Tanzifi M, Yaraki MT, Kiadehi AD, Hosseini SH, Olazar M, Bharti AK, et al. Adsorption of amido black 10B from aqueous solution using polyaniline/SiO2 nanocomposite: Experimental investigation and artificial neutral network modeling. Journal of Colloid and Interface Science. 2018;510:246-261. DOI: 10.1016/j.jcis.2017.09.055
  47. 47.Harijan DKL, Chandra V. Magnetite/graphene/polyaniline composite for removal of aqueous hexavalent chromium. Journal of Applied Polymer Science. 2016;133:1-7. DOI: 10.1002/app.44002
  48. 48.Shyaa AA, Hasan OA, Abbas AM. Synthesis and characterization of polyaniline/zeolite nanocomposite for the removal of chromium(VI) from aqueous solution. Journal of Saudi Chemical Society. 2015;19:101-107. DOI: 10.1016/j.jscs.2012.01.001
  49. 49.Vellaichamy V, Periakaruppan P, Nagulan B. Reduction of Cr6+ from wastewater using a novel in situ-synthesized PANI/MnO2/TiO2 nanocomposite: Renewable, selective, stable, and synergistic catalysis. ACS Sustainable and Chemical Engineering. 2017;5:9313-9324. DOI: 10.1021/acssuschemeng.7b02324
  50. 50.Olad A, Nabavi R. Application of polyaniline for the reduction of toxic Cr(VI) in water. Journal of Hazardous Materials. 2007;147:845-851. DOI: 10.1016/j.jhazmat.2007.01.083
  51. 51.Tiburcio G, Santos I, Ortega MM, Castillo JM, Castro T, Romero MA, et al. Selective adsorption of metallic complex using polyaniline or polypyrrole. Materials Chemistry and Physics. 2016;182:39-48. DOI: 10.1016/j.matchemphys.2016.07.003
  52. 52.Karthik R, Meenakshi S. Removal of hexavalent chromium ions using polyaniline/silica gel composite. Journal of Water Processing and Engineering. 2014;1:37-45. DOI: 10.1016/j.jwpe.2014.03.001
  53. 53.Ayad M, El-Hefnawy G, Zaghlol S. Facile synthesis of polyaniline nanoparticles; its adsorption behavior. Chemical Engineering Journal. 2013;217:460-465. DOI: 10.1016/j.cej.2012.11.099
  54. 54.Xia Y, Li T, Chen J, Cai C. Polyaniline (skin)/polyamide 6 (core) composite fiber: Preparation, characterization and application as a dye adsorbent. Synthetic Metals. 2013;175:63-169. DOI: 10.1016/j.synthmet.2013.05.012
  55. 55.Karim MR, Lim KT, Lee MS, Kim K, Yeum JH. Sulfonated polyaniline-titanium dioxide nanocomposites synthesized by one-pot UV-curable polymerization method. Synthetic Metals. 2009;159:209-213. DOI: 10.1016/j.synthmet.2008.09.001
  56. 56.Ghaemi N, Zereshki S, Heidari S. Removal of lead ions from water using PES-based nanocomposite membrane incorporated with polyaniline modified GO nanoparticles: Performance optimization by central composite design. Process Safety and Environmental Protection. 2017;111:475-490. DOI: 10.1016/j.psep.2017.08.011
  57. 57.Tan S, Laforgue A, Bélanger D. Characterization of a cation-exchange/polyaniline composite membrane. Langmuir. 2003;19:744-751. DOI: 10.1021/la0263054
  58. 58.Soji DV, Bani ND, Lazarevi MJ, Cetojevi DD, Fin NL, Comor MI. Photocatalytic decomposition of selected biologically active compounds in environmental waters using TiO2/polyaniline nanocomposites: Kinetics, toxicity and intermediates assessment. Environmental Pollution. 2018;239:457-465. DOI: 10.1016/j.envpol.2018.04.039
  59. 59.Miao J, Xie A, Li S, Huang F, Cao J, Shen Y. A novel reducing graphene/polyaniline/cuprous oxide composite hydrogel with unexpected photocatalytic activity for the degradation of Congo red. Applied Surface Science. 2016;360:594-600. DOI: 10.1016/j.apsusc.2015.11.005
  60. 60.Samani MR, Borghei SM, Olad A, Chaichi MJ. Removal of chromium from aqueous solution using polyaniline-polyethylene glycol composite. Journal of Hazardous Materials. 2010;184:248-254. DOI: 10.1016/j.jhazmat.2010.08.029
  61. 61.Kumar PA, Chakraborty S, Ray M. Removal and recovery of chromium from wastewater using short chain polyaniline synthesized on jute fiber. Chemical Engineering Journal. 2008;141:130-140. DOI: 10.1016/j.cej.2007.11.004
  62. 62.Zare EN, Motahari A, Sillanpää M. Nanoadsorbents based on conducting polymer nanocomposites with main focus on polyaniline and its derivatives for removal of heavy metal ions/dyes: A review. Environmental Research. 2018;162:173-195. DOI: 10.1016/j.envres.2017.12.025
  63. 63.Debnath S, Ballav N, Maity A, Pillay K. Development of a polyaniline-lignocellulose composite for optimal adsorption of Congo red. International Journal of Biological and Macromolecules. 2015;75:199-209. DOI: 10.1016/j.ijbiomac.2015.01.011
  64. 64.Janaki V, Oh BT, Shanthi K, Lee KJ, Ramasamy AK, Kamala-Kannan S. Polyaniline/chitosan composite: An eco-friendly polymer for enhanced removal of dyes from aqueous solution. Synthetic Metals. 2012;162:974-980. DOI: 10.1016/j.synthmet.2012.04.015
  65. 65.Wang J, Zhang K, Zhao L. Sono-assisted synthesis of nanostructured polyaniline for adsorption of aqueous Cr(VI): Effect of protonic acids. Chemical Engineering Journal. 2014;239:123-131. DOI: 10.1016/j.cej.2013.11.006
  66. 66.Duruibe OJ, Ogwuegbu MOC, Egwurugwu JN. Heavy metal pollution and human biotoxic effects. International Journal of Physical Sciences. 2007;2:112-118
  67. 67.Sounthararajah DP, Loganathan P, Kandasamy J, Vigneswaran S. Adsorptive removal of heavy metals from water using sodium titanate nanofibres loaded onto GAC in fixed-bed columns. Journal of Hazardous Materials. 2015;287:306-316. DOI: 10.1016/j.jhazmat.2015.01.067
  68. 68.Choppala G, Kunhikrishnan A, Seshadri B, Hee J, Bush R, Bolan N. Comparative sorption of chromium species as influenced by pH, surface charge and organic matter content in contaminated soils. Journal of Geochemical Exploration. 2018;184:255-260. DOI: 10.1016/j.gexplo.2016.07.012
  69. 69.Zare EN, Lakouraj MM, Ramezani A. Effective adsorption of heavy metal cations by superparamagnetic poly(aniline-co-m-phenylenediamine)@Fe3O4 nanocomposite. Advances in Polymer Technology. 2015;34:1-11. DOI: 10.1002/adv.21501
  70. 70.Zhou Y, Zhang L, Cheng Z. Removal of organic pollutants from aqueous solution using agricultural wastes: A review. Journal of Molecular Liquids. 2015;212:739-762. DOI: 10.1016/j.molliq.2015.10.023
  71. 71.Srinivasan A, Viraraghavan T. Decolorization of dye wastewaters by biosorbents: A review. Journal of Environmental Management. 2010;1:1915-1929. DOI: 10.1016/j.jenvman.2010.05.003
  72. 72.Ballav N, Debnath S, Pillay K, Maity A. Efficient removal of reactive black from aqueous solution using polyaniline coated ligno-cellulose composite as a potential adsorbent. Journal of Molecular Liquids. 2015;209:387-396. DOI: 10.1016/j.molliq.2015.05.051
  73. 73.Debnath S, Ballav V, Maity A, Pillay K. Efficient removal of reactive black from aqueous solution using polyaniline coated ligno-cellulose composite as a potential adsorbent. International Journal of Biological Macromolecules. 2015;72:732-739. DOI: 10.1016/j.ijbiomac.2014.09.018
  74. 74.Shariri R, Mahmoodi NO. Synthesis and characterization of polypyrrole, polyaniline nanoparticles and their nanocomposite for removal of azo dyes; sunset yellow and Congo red. Journal of Cleaner Production. 2018;179:235-245. DOI: 10.1016/j.jclepro.2018.01.03
  75. 75.Bhaumik M, McCrindle RI, Maity A. Enhanced adsorptive degradation of Congo red in aqueous solutions using polyaniline/Fe0 composite nanofibers. Chemical Engineering Journal. 2015;260:716-729. DOI: 10.1016/j.cej.2014.09.014
  76. 76.Janaki V, Vijayaraghavan K, Oh B, Lee K, Muthuchelian K, Ramasamya AK, et al. Starch/polyaniline nanocomposite for enhanced removal of reactive dyes from synthetic effluent. Carbohydrates Polymers. 2012;90:1437-1444. DOI: 10.1016/j.carbpol.2012.07.012

Written By

Thabiso C. Maponya, Mpitloane J. Hato, Thabang R. Somo, Kabelo E. Ramohlola, Mogwasha D. Makhafola, Gobeng R. Monama, Arjun Maity, Kwena D. Modibane and Lebogang M. Katata-Seru

Submitted: April 6th, 2018Reviewed: November 4th, 2018Published: November 11th, 2019