# Preparation of magnetic activated carbon fibers@Fe3O4 by electrostatic self-assembly method and adsorption properties for methylene blue

## TL;DR

This paper describes a method to create magnetic activated carbon fibers that efficiently adsorb methylene blue and can be easily separated using a magnetic field.

## Contribution

A novel electrostatic self-assembly method to prepare magnetic activated carbon fibers with high adsorption capacity and easy separation.

## Key findings

- The ideal loading conditions for MACF@Fe3O4 were a mass ratio of 1:1, 20 min, pH 9.36, and 22.5°C.
- MACF@Fe3O4 achieved a 97.29% adsorption rate and a maximum capacity of 12.1616 mg·g−1 for methylene blue.
- The adsorption process followed pseudo-first-order and pseudo-second-order kinetics at different time intervals.

## Abstract

Nano-Fe3O4 was loaded onto coconut-based activated carbon fibres (CACF) using an electrostatic self-assembly method. The effects of the mass ratio of CACF to nano-Fe3O4, loading time, pH and temperature on the loading effect were investigated and ideal loading conditions were determined. To study the adsorption performance of MACF@Fe3O4 for methylene blue, the effects of the initial concentration, pH and time on the adsorption were investigated and the working conditions of adsorption were established. MACF@Fe3O4 was systematically characterized. Adsorption kinetics were investigated under ideal conditions. The ideal loading conditions for MACF@Fe3O4 were as follows: mass ratio of 1:1, 20 min, pH 9.36, 22.5°C. The saturation magnetization of MACF@Fe3O4 was 48.2263 emu·g−1, which could be quickly separated under an external magnetic field. When the dosage was 0.010 g, the adsorption rate reached 97.29% and the maximum adsorption capacity was 12.1616 mg·g−1. The adsorption process conformed to pseudo-first-order kinetics during the first 15 min and pseudo-second-order kinetics during 20–120 min. The equations were ln(Qe-Qt)=2.2394-0.0689t and tQt=0.0774 + 0.5295t, respectively. The isothermal adsorption model showed that MACF@Fe3O4 was more in line with the Langmuir model, indicating that the adsorption process was mainly monolayer adsorption. The thermodynamic analysis results showed that the adsorption process of MB by MACF@Fe3O4 was an endothermic process. In this study, MACF@Fe3O4 with high adsorption capacity and easy separation from coconut palm fibres has good application prospects in the field of adsorption, which can promote the high-value utilization of coconut palms.