Efficient Adsorption of Anionic Dyes by Ammoniated Waste Polyacrylonitrile Fiber: Mechanism and Practicability

Adsorption is one of the commonly used methods in wastewater treatment, but it has the problem of high cost and a complicated production process. In this paper, a low-cost and efficient decolorizing adsorbent was successfully prepared based on waste polyacrylonitrile fiber (PANF). The waste PANF was ammoniated by propylene diamine derivates (PANA_MF), and benzylamine (PANA_BMF) and quaternary ammonium ions (PANQ_MF) were introduced for PANA_MF to regulate hydrophilicity and hydrophobicity. With acidic red 249 as the model anionic dye, influences of the adsorption center structure, the degree of modification, the concentration of acid, the dye structure, and the auxiliary agent in the solution on the dye adsorption performance were studied. Isothermal models, kinetic models, reusability, and continuous application ability of the fiber adsorbent were discussed. PANA_MF, PANA_BMF, and PANA_QF exhibit excellent adsorption performance compared to the common adsorbent. After protonation, the saturation adsorption value can reach 2051.3 mg/g for PANA_MF. PANA_MF also exhibited excellent reusability, and the adsorption capacity after being reused eight times still can keep 72.7% of that for the first time. The adsorption of the anionic dye for PANA_MF is a chemisorption process, and the rate-determining step is changed from the diffuse step to the adsorption on the surface with the adsorption time. PANA_MF can also be used in the continuous flow process, and the absorption amount is similar to that in the batch adsorption, which shows excellent commercial application potential.