Application of Activated Carbon Adsorbents Prepared from Prickly Pear Fruit Seeds and a Conductive Polymer Matrix to Remove Congo Red from Aqueous Solutions

Abdelkader El Kebir,Abdelghani Benyoucef,Saadia Lahreche,M’Hamed Kaid,Imane Moulefera,Lilia Sabantina

doi:10.3390/fib10010007

Abstract

The present work was aimed to evaluate the adsorption properties of activated carbons based on prickly pear seeds (PPS) and conductive polymer matrix based on polyaniline (PANI) for the removal of anionic Congo red (CR) dye from aqueous solutions. The adsorbent was prepared by polymerization of aniline in the presence of activated PPS by phosphoric acid and sodium hydroxide. The samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and the Brunauer–Emmett–Teller (BET) methods. The adsorption kinetics were studied using UV-visible (UV/Vis) spectroscopy. The characterization data suggest that the adsorption of the Congo red dye is enhanced because PANI chain molecules, which are especially accountable for removal through π–π interaction and H–bonding with the CR, are adsorbed/tethered onto the acid-activated PPS (PPSH), and thus surmount the mass transfer limitation by being best exposed to the CR-adsorbed molecule. The adsorption kinetics follows the pseudo-second order process. The correlation coefficients (R2) for Langmuir, Freundlich and Tempkin showed that the adsorption values obey Freundlich and Tempkin isotherm models. Moreover, the isotherm was most accurately described by the Freundlich model, and the maximum removal percentage was calculated to be 91.14% under optimized conditions of pH 6.6, 1 g/L of adsorbent dosage, and an initial CR dye concentration of 20 mg·L−1. Importantly, the hybrid adsorbent exhibited the highest adsorption capacity (80.15%) after five cycles of the adsorption–desorption process. Thermodynamic parameters, such as entropy changes, enthalpy changes and Gibbs free energy, were also evaluated. These results indicated that the PANI matrix can generally be better utilized for the removal of Congo red dye when appropriately dispersed on the surface of suitable support materials. These results provide a new direction to promote the separable adsorbents with increasing performance for adsorption of dye impurities from wastewater.

Highlights

Dyeing effluents from textile finishing or printing industries pose a major environmental risk due to the pollution of freshwater with toxic and hazardous substances, which are dangerous to aquatic ecosystems and humans, as well as depleting drinking water resources [1,2]
PANI was semi-crystalline in nature, as shown by three peaks centered at 2θ = 16.45◦ (011), 20.22◦ (020), and 25.87◦ (200), which was Fibers 2022, 10, x FOR PEER REVIEdWue to the presence of benzenoid with the quinonoid group in the polymer chain [43]6.oTf 2h0e characteristic peaks of two constituents were observed in the X-ray diffraction (XRD) patterns of PANI@PPSH3PO4 was converted into solid carbon (PPSH), indicating that the hybrid material was successfully synthesized
PANI chains were grown on the surface of the PPSH support by in situ polymerization to significantly improve the Congo red (CR) removal capacity

Summary

Introduction

Dyeing effluents from textile finishing or printing industries pose a major environmental risk due to the pollution of freshwater with toxic and hazardous substances, which are dangerous to aquatic ecosystems and humans, as well as depleting drinking water resources [1,2]. This problem is becoming more significant as the discharge of dyeing effluents has increased significantly in recent years [3]. There is an urgent need for an effective method to remove dyes in a cost-effective, environmentally friendly, and selective manner

Methods

Results

Conclusion