**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

**151**

that of ANI.

self-assembly route.

in **Figure 5d**.

**Figure 5.**

*(c) spherical [30] and (d) tubular [2].*

*Polyaniline-Based Nanocomposites for Environmental Remediation*

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

*SEM images of different structures of PANI nanocomposites (a) fibres [28], (b) smooth surface [29],* 

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 6a**–**d**). 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

**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

*DOI: http://dx.doi.org/10.5772/intechopen.82384*

#### **Figure 5.**

*Trace Metals in the Environment - New Approaches and Recent Advances*

intermediate referred to as *p*-aminodiphenylamine (PADPA) [25, 26]. These

**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

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

processes are also accompanied by the elimination of two protons.

*2.2.3 Step 3: chain propagation*

*Formation of a trimer and polymer formation [27].*

**150**

so on.

**Figure 4.**

**Figure 3.**

*Formation of a dimer [25, 27].*

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

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**.

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 6a**–**d**). 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.

**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.

#### **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.**

*Some of PANI nanocomposites and their reported structures.*
