Amino-functionalized polyacrylonitrile/bentonite composite membranes for effective decontamination of Pb2+ and Congo Red

Abstract

The synthesis of three amino-functionalized polyacrylonitrile/bentonite (PAN/BT) composite membranes and the removal strategies of Pb2+ and Congo Red (CR) from water were put forward. The successful synthesis of PAN/BT was confirmed by scanning electron microscopy, X-ray energy spectrum, differential thermogravimetric analysis, specific surface area and contact angle tests. In addition, although having a similar composition to PAN/BT, the functionalized membrane materials have more N-H and C = N groups and stronger wettability. The influences of the optimal contaminant type, adsorbent dosage, temperature, contaminant concentration and contact time on the adsorption process of the modified membrane materials were systematically investigated. The adsorption processes were in good agreement with the Langmuir model, in which the theoretical maximum adsorption capacities of γ-aminopropyl triethoxysilane (KH550)-modified PAN/BT (K-PAN/BT), diethylenetriamine (DETA)-modified PAN/BT (D-PAN/BT) and hydroxylamine hydrochloride (NH3OHCl)-modified PAN/BT (N-PAN/BT) for Pb2+ were 200.1, 332.9 and 182.8 mg/g, and the theoretical maximum adsorption of CR was 346.9, 156.2 and 579.2 mg/g, respectively, which were higher than 88 and 149 mg/g of bentonite, exhibiting excellent component synergy. The adsorption equilibrium was reached within 100 min for both Pb2+ and CR, and the adsorption processes were in accordance with the pseudo-second-order kinetics, involving chelation, cation exchange and ‘π-π’ interactions. It is worth mentioning that the N-PAN/BT membranes can remove high concentrations of anionic and cationic dyes with a difference of up to 100 times, with selective adsorption potential and excellent contaminant indicating ability, which has an application prospect in the field of environmental protection.