Polyaniline-Coated Glucose-Derived Carbon Spheres for Efficient Adsorption of 2,4- Dichlorophenoxyacetic Acid

Polyaniline coated carbon sphere (CS-PANI), an efficient adsorbent is designed and synthesized through a two-step process. The carbon spheres (CSs) were derived from glucose via a hydrothermal method followed by in-situ polymerization of polyaniline (PANI) on the carbon sphere surfaces forming CS-PANI with enhanced adsorption properties. This adsorbent is effectively used to remove herbicide 2, 4-dichlorophenoxyacetic acid (2, 4-D) from aqueous medium. Furthermore, by varying aniline concentration during synthesis, two different composites, CS-PANI-1 and CS-PANI-2 are synthesized maintaining CS to aniline mass ratios 2:1 and 1:1 respectively. Synthesized materials are characterized by PXRD, FTIR, EDX and techniques. Adsorption studies with both the adsorbents are performed with various optimized parameters such as pH of medium, contact time, solution temperature, adsorbent dosage, and initial 2, 4-D concentrations. Both the composites show enhanced performance in removal of 2, 4-D in comparison to pure CS. Additionally, CS-PANI-2 shows better performance compared to CS-PANI-1 suggesting the effect of amount of PANI on the overall performance of the composites. The Langmuir adsorption capacity of CS-PANI-1 and CS-PANI-2 are 15.49 mg g ^-1 and 69.01 mg g ^-1 , respectively at pH 3.0. The adsorption kinetics is found favourable for pseudo-second-order for both CS-PANI samples and the adsorption process follows Freundlich isotherm model more suitably. The mass transfer mechanism obeys Weber-Morris mechanism rather than Boyd mass transfer model. The positive ∆H° and negative ∆G° values indicate that the 2, 4-D sorption on CS-PANI samples are endothermic and spontaneous. Thus, CS-PANIs could be applied as efficient and potential adsorbents for the removal of 2, 4-D from aqueous medium and by tailoring the PANI component, the adsorption performance can be enhanced and optimized.