Preparation of polyaniline iron oxide composite (PANI/Fe3O4) for enhanced Congo red removal performance

Hollow Polyaniline Microsphere/MnO2/Fe3O4 Nanocomposites in Adsorptive Removal of Toxic Dyes from Contaminated Water

“…Subsequently, the cationic MG dye comprising positively charged =N + iminium ions is easily adsorbed onto the negatively charged surface of PNHM/MnO 2 /Fe 3 O 4 at a higher pH range through electrostatic attraction . In contrast, the CR anionic dye with two negatively charged sulfonate groups in its structure could interact with the positively charged −NH + – centers of PANI present in PNHM/MnO 2 /Fe 3 O 4 at lower pH through the electrostatic attraction . Further, the O 1s high-resolution XPS spectra in Figure c show the presence of O–Mn–O (529.7 eV).…”

“…The influence of PNHM/MnO 2 /Fe 3 O 4 dose on the % removal and adsorption capacity of MG and CR dyes was studied by varying the PNHM/MnO 2 /Fe 3 O 4 dosage from 0.25 to 5 g/L at a fixed initial dye concentration of 20 mg/L and pH ∼6.75 at 300 ± 3 K. The experimental results are displayed in Figure d, revealing that the % removal of MG and CR dyes improved by increasing the adsorbent dosage. This enhanced adsorption efficiency could be accountable for the more number of available active sites on PNHM/MnO 2 /Fe 3 O 4 with the rise of adsorbent dosage . Gradually, the saturation of MG and CR dyes removal % reached ∼88 and ∼98% at the adsorbent dose of 1 g/L.…”

“…However, a decrease of adsorption capacity on increasing the adsorbent dose is also observed. This phenomenon is likely due to the achievement of the equilibrium point, after which the increase in adsorbent dose is not desirable …”

“…The % removal of MG and CR dyes decreased from 88 to 65% and 98 to 54%, respectively, as the initial dye concentration increased from 20 to 100 mg/L. Such phenomena are ascribed to the reverse relationship between the initial dye concentration and the free active sites present on the surface of the adsorbent at a constant adsorbent dose …”

“…). − Among these, the adsorption process has gained considerable attention because of its simple operation, wide range of applications, cost-effectiveness, high removal capacity, high selectivity, recycling facilities, etc . Considering the factors mentioned above, the present work is focused on the adsorptive removal of cationic methyl green (MG) and anionic Congo red (CR), owing to their excessive use in industrial and biological sectors as well as their ecotoxicological effects. − Further, the performance of the adsorbent is determined based on the desired characteristics of an efficient adsorbent, including simple synthesis routes, nontoxicity, high adsorption capacity, and recycling ability . Therefore, various adsorbents such as activated carbon, carbon nanotubes, graphene oxides, natural clay materials, layered double hydroxides, metal-organic frameworks, metal oxides, conducting polymers, and their hybrids have been used as adsorbents for the removal of dyes from aqueous media. , Among these, conducting polymer-based adsorbents are of prime interest owing to their diverse physicochemical properties, low cost, and wide applications in various fields, including environmental remediation, electromagnetic shielding instruments, extraction, and electrochemical applications. ,, …”