Nitrogen-Rich Polyaniline-Based Activated Carbon for Water Treatment: Adsorption Kinetics of Anionic Dye Methyl Orange

Abstract

In the present work, a nitrogen-rich activated carbon (PAnAC) was prepared using polyaniline (PAn) as a precursor to represent one possible conversion of nitrogen-containing polymeric waste into a valuable adsorbent. PAnAC was fabricated under the chemical activation of KOH and a PAn precursor (in a 4:1 ratio) at 650 °C and was characterized using FTIR, SEM, BET, TGA, and CHN elemental composition. The structural characteristics support its applicability as an adsorbent material. The adsorption performance was assessed in terms of adsorption kinetics for contact time (0–180 min), methyl orange (MO) concentration (C0 = 50, 100, and 200 ppm), and adsorbent dosages (20, 40, and 80 mg per 250 mL batch). The kinetic results revealed a better fit to a pseudo-second-order, specifically nonlinear equation compared to pseudo-first-order and Elovich equations, which suggests multilayer coverage and a chemical sorption process. The adsorption capacity (qe) was optimal (405.6 mg/g) at MO C0 with PAnAC dosages of 200 ppm and 40 mg and increased as MO C0 increased but decreased as the adsorbent dosage increased. The adsorption mechanism assumes that chemisorption and the rate-controlling step are governed by mass transfer and intraparticle diffusion processes.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers

“…Figure 4 shows the spectra of the investigated polymers (PPy and poly(An-co-Py), polymer-based activated carbons before (PPyAC and PnyAC) and after (PPyAC-MO and PnyAC-MO) the adsorption of MO and MO dye. PAn-based spectra have been reported in Al-Odayni et al [17]. The spectra of MO, PPy, PAn, PPyAC, PAnAC, PPyAC-MO and PAnAC-MO were consistent with the literature [4,17,[36][37][38].…”

“…The result of the elemental analysis is presented in Table 1. Evidently, the ACs' structure has retained a high content of heteroatoms N and O [4,17,34], providing the product with some essential functional groups representing part of the adsorbent active sites. Moreover, the PAnAC adsorbent has the highest O and N content, followed by the copolymer-based one (PnyAC), suggesting high active sites and potentially explaining the obtained high adsorption capacity of PAnAC.…”

“…The surface texture was observed with SEM at an accelerating voltage of 5 kV, as shown in Figure 3. The micrographs of the as-synthesized PAnAC [17], PPyAC, and PnyAC have revealed a rough surface with peel-like structures. Furthermore, the surface combined with pores of relatively large and irregular shape and with an average diameter of about 3-5 µm.…”

“…Nitrogen (N)-containing polymers such as acrylonitrile-based thermoplastic (e.g., styrene-acrylonitrile, acrylonitrile butadiene-styrene), carriers such as polydopamine, conducting polymers (i.e., polyaniline (PAn), polypyrrole (PPy)), nylons (e.g., polyamides), etc., represent examples of N-rich precursors [12][13][14][15] from, e.g., wastes that can be converted into N-containing carbons. For instance, N-containing carbons based on conducting polymers have shown an exciting performance as adsorbents [13,16,17] for dye removal from wastewater. However, the end properties of activated carbons, including N-doped ones, depend on various factors such as the carbon source, the activator and the activation process [18].…”

“…However, the end properties of activated carbons, including N-doped ones, depend on various factors such as the carbon source, the activator and the activation process [18]. Notably, activation using inorganic bases such as potassium hydroxide (KOH) has been reported to be efficient in producing effective adsorbents [4,17].…”