*Article* **Basic Blue Dye Adsorption from Water Using Polyaniline**/**Magnetite (Fe 3 O 4) Composites: Kinetic and Thermodynamic Aspects**

### **Amir Muhammad 1, Anwar-ul-Haq Ali Shah 1,\*, Salma Bilal 2,3,\* and Gul Rahman 1**


Received: 4 May 2019; Accepted: 28 May 2019; Published: 30 May 2019

**Abstract:** Owing to its exciting physicochemical properties and doping–dedoping chemistry, polyaniline (PANI) has emerged as a potential adsorbent for removal of dyes and heavy metals from aqueous solution. Herein, we report on the synthesis of PANI composites with magnetic oxide (Fe3O4) for e fficient removal of Basic Blue 3 (BB3) dye from aqueous solution. PANI, Fe3O4, and their composites were characterized with several techniques and subsequently applied for adsorption of BB3. E ffect of contact time, initial concentration of dye, pH, and ionic strength on adsorption behavior were systematically investigated. The data obtained were fitted into Langmuir, Frundlich, Dubbanin-Rudiskavich (D-R), and Tempkin adsorption isotherm models for evaluation of adsorption parameters. Langmuir isotherm fits closely to the adsorption data with R<sup>2</sup> values of 0.9788, 0.9849, and 0.9985 for Fe3O4, PANI, and PANI/Fe3O4 composites, respectively. The maximum amount of dye adsorbed was 7.474, 47.977, and 78.13 mg/g for Fe3O4, PANI, and PANI/Fe3O4 composites, respectively. The enhanced adsorption capability of the composites is attributed to increase in surface area and pore volume of the hybrid materials. The adsorption followed pseudo second order kinetics with R<sup>2</sup> values of 0.873, 0.979, and 0.999 for Fe3O4, PANI, and PANI/Fe3O4 composites, respectively. The activation energy, enthalpy, Gibbs free energy changes, and entropy changes were found to be 11.14, −32.84, −04.05, and −0.095 kJ/mol for Fe3O4, 11.97, −62.93, −07.78, and −0.18 kJ/mol for PANI and 09.94, −74.26, −10.63, and −0.210 kJ/mol for PANI/Fe3O4 respectively, which indicate the spontaneous and exothermic nature of the adsorption process.

**Keywords:** Basic Blue 3 dye (BB3), polyaniline/Fe3O4 composite; Freundlich; Langmuir; Tempkin and Dubbanin-Radushkavitch adsorption isotherm
