Synthesis of PNIPAM/magnetite/multiamine-functionalized mesoporous silica composite and investigation of temperature of its aggregation and adsorption

A new adsorbent comprising of poly (N-isopropylacrylamide) (PNIPAM), magnetite, and multiamine-functionalized mesoporous silica (multiamine-PMMS) was synthesized in this study. The structure of the multiamine-PMMS sample was analyzed by X-ray diffraction (XRD), thermogravimetry (TG), and nitrogen adsorption measurements. It was found that the multiamine-PMMS sample contained magnetite (approximately 8.4 wt%) and PNIPAM (approximately 5 wt%). The multiamine-PMMS sample tended to aggregate above the lower critical solution temperature (LCST) of approximately 32 degrees C for PNIPAM; this aggregation caused the recovery ratio using a magnet at 45 degrees C to increase by approximately 30 wt% compared to that at room temperature (below the LCST). Five minutes after the precipitation test, the turbidity of the supernatant solution reached a range of 220-230 nephelometric turbidity units (NTU) at room temperature; however, it steeply decreased to approximately 60 NTU at 45 degrees C. Saturated adsorption amounts of methyl orange (MO) for the multiamine-PMMS samples calculated by the Langmuir adsorption model were 0.33, 0.53, and 0.71 mmol/g. In addition, the MO adsorption rate was considerably high, and equilibrium was reached in 10 min for all multiamine-PMMS samples.

Automated summary

A new adsorbent consisting of poly(N-isopropylacrylamide) (PNIPAM), magnetite, and multiamine-functionalized mesoporous silica (multiamine-PMMS) was synthesized and characterized in this study. The multiamine-PMMS sample showed enhanced recovery ratio and adsorption performance at a specific temperature, with satisfactory adsorption capacity and kinetics for methyl orange.