Copolymer-type magnetic graphene oxide with dual-function for adsorption of variety of dyes

Background: To solve the dye pollution, graphene oxide (GO) is an excellent substrate for developing novel adsorbents, meanwhile surface-initiated atom transfer radical polymerization (SI-ATRP) is a progressive modification to significantly promote density of functional groups and magnetic adsorbents can efficiently simple adsorption process. Therefore, our effort has been made to develop an ideal dye absorptive material with: (i) the high adsorption capacity, (ii) the high selectivity, (iii) the favorable regeneration and reuse and (iv) the simple and fast adsorption treatment. Methods: Cationic and anionic monomers (sodium 4-styrenesulfonate, Nass and methacryloyloxyethyl trimethyl ammonium chloride, DMC) were grafted onto polydopamine coated magnetic GO (Fe3O4@GO@PDA) by SI-ATRP, obtaining copolymer brush-type Fe3O4@GO@PDA@poly(NASS-co-DMC) adsorbent with dual function of sulfonic acid and tertiary amino groups. The adsorption properties of methylene blue (MB), basic fuchsin (BF), acidic fuchsin (AF), acidic chrome blue K (AK), rhodamine B (RhB) and congo red (CR) were studied. The selectivity of adsorbents was explored in mixed AF/MB solution, and further highlighted by using it to detect of MB and AF in lake water. The recycling and stability were tested by adsorption-desorption experiments in detail. Significant findings: The adsorption capacities of MB, BF, AF, AK, RhB and CR reached 170.3, 289.7, 330.5, 148.7, 170.4 and 230.5 mgmiddotg(-1), respectively, that was found fits well with Langmuir adsorption isotherm and pseudosecond-order kinetic model. The responsible adsorption mechanisms are dominated by electrostatic interaction, hydrogen bond interaction and pi-pi stacking. Moreover, the adsorption selectivity of Fe3O4@GO@PDA@poly(NASS-co-DMC) could be adjustable by the regulating the ratio of NASS to DMC, and at 4:1, 1:1 and 1:4 of NASS to DMC, adsorbent generated the different recoveries in detection of MB and AF. Furthermore, the adsorbent was recycled multiple times still remained an excellent removal efficiency and structural stability. These findings demonstrates the developed dual-function adsorbent can be applied in the treatment and detection of wastewater containing both cationic and anionic dyes.