Ultra-rapid removal of cationic organic dyes by novel single- and double-stranded DNA immobilized on quaternary ammonium magnetic chitosan

Water pollution caused by dyes is a major environmental hazard. Dye-bearing effluents if not treated effectively and released to the waters, it will block penetration of sunlight, disturb aquatic photosynthesis and decrease dissolved oxygen. Aquatic life will be in danger and its normal growth will be hindered. Eventually, dyes will enter human body through food chains and damaging human health due to its toxic, carcinogenic and mutagenic nature. However, few effective and simple approaches for removal of contamination have been reported. Therefore, in this study, novel single- and double-stranded DNA immobilized on quaternary ammonium magnetic chitosan (ssDNA-QMC and dsDNA-QMC, respectively) were prepared using a simple method with high stability at a wide range of pH values and ionic strengths and used for magnetic removal of acridine orange (AO), ethidium bromide (EtBr), and methylene blue (MB). The as-prepared ssDNA-QMC and dsDNA-QMC were characterized using a surface ζ-potential analyzer, Fourier transformed infrared spectrofotometer, scanning electron microscope equipped with an energy dispersive X-ray spectrofotometer, and superconducting quantum interference device magnetic property measurement system. The ssDNA-QMC and dsDNA-QMC only required 5 min to reach the equilibrium stage, and the results followed a pseudo-second order kinetics model. Langmuir maximum capacities were 92.950 μmol.g^-1 AO, 50.980 μmol.g^-1 EtBr, and 64.743 μmol.g^-1 MB for ssDNA-QMC and 159.095 μmol.g^-1 AO, 79.976 μmol.g^-1 EtBr, and 93.809 μmol.g^-1 MB for dsDNA-QMC. The simple preparation, high stability, and ultra-rapid removal of this approach highlighted the promising applications of ssDNA-QMC and dsDNA-QMC for magnetic removal of cationic dyes in polluted water.