High-efficiency adsorption removal of CR and MG dyes using AlOOH fibers embedded with porous CoFeO nanoparticles.

Owing to the toxicity and difficulty in degradation, how to the effective separation for the residual dyes in the aqueous solution is still an issue with great challenge in the area of environmental protection. Now, to high-efficiency removal of organic dyes from the aqueous solution, we design a unique AlOOH/CoFeO adsorbent with porous CoFeO nanoparticles embedded on the AlOOH fibers using a simple hydrothermal technique and calcination process. The structural properties and surface characteristics of the AlOOH/CoFeO composites are detailedly analyzed by XRD, FTIR, XPS, TEM and SEM. Here, the high S and specific porous structure are beneficial to improve the adsorption performance of AlOOH/CoFeO adsorbents. Especially, when the molar ratio of AlOOH to CoFeO in the AlOOH/CoFeO fibers is 1:1, an optimal performance on adsorbing anionic Congo red (CR) and cationic methyl green (MG) dyes can be obtained at pH = 6.29, where the corresponding maximum adsorption capacities reach up to 565.0 and 423.7 mg g, respectively. Factors leading to the change in the ability of adsorbing CR and MG dyes are systematically discussed, including contact time, temperature, initial concentrations, and pH values of the solutions. Meanwhile, the uptake of CR and MG dyes can best conform to Langmuir isotherm model and pseudo-second-order adsorption kinetics. The thermodynamic analysis verifies that the dye adsorption process is spontaneous and endothermic. Moreover, from the point view of practical application, the good reusability further makes the as-synthesized magnetic AlOOH/CoFeO composite be a perfect adsorbent with efficiently removing both anionic and cationic dyes from aqueous solutions.