Adsorption performance of magnetic metal–organic framework composites for Congo red and amino black 10B

Azo dyes have posed a serious threat to the ecological environment and human health owing to the high toxicity. Exploring efficient materials to reduce or even eliminate azo dyes is of vital importance. In this study, functionalized Fe 3 O 4 nanoparticles, Terephthalic acid and FeCl 3 ·6H 2 O were impregnated in N , N -Dimethylformamide to fabricate magnetic metal–organic framework composite Fe 3 O 4 @MOF-235. The material was then characterized and used as an adsorbent to remove Congo red and amino black 10B in water. The material presented excellent selective adsorption ability for Congo red and amino black 10B with an adsorption amount of 114.42 and 39.48 mg g −1 , respectively, when the pH range was 5–8. The adsorption of Congo red and amino black 10B by composites followed pseudo-second-order kinetic and Langmuir models ( R 2 > 0.99), and was a spontaneous process. The Fe 3 O 4 @MOF-235 showed favorable stability and reusability, and the maximum adsorption capacity for Congo red and amino black 10B in real water was basically unaffected. The adsorption mechanism was through the interactions (i.e. hydrophobic action, π–π stacking action and electrostatic action) between Fe 3 O 4 @MOF-235 and the azo dyes. In a word, the as-prepared composites demonstrated high potential as an azo dye adsorbent.