Bifunctional MnFe2O4/chitosan modified biochar composite for enhanced methyl orange removal based on adsorption and photo-Fenton process

A novel composite of chitosan modified biochar (CPB) and MnFe2O4 (MnFe2O4@CPB) was prepared successfully through mild chemical co-precipitation method which worked efficiently for methyl orange (MO) removal in adsorption and photo-Fenton processes. The morphology, structure, and magnetism of MnFe2O4@CPB were well characterized using SEM, XRD, XPS, FTIR, BET, and VSM. Due to hydrogen bonding forces and pi-pi interactions between MO and MnFe2O4@CPB, under the same condition, the adsorption capacity of MnFe2O4@CPB was 1.48, 1.06 and 7.90 times of original biochar, CPB and MnFe2O4, respectively. Moreover, MnFe2O4@CPB could degrade 99.50 % of MO in visible LED light/H2O2 system under the synergetic effect of MnFe2O4 and CPB. Herein, the abundant surface functional groups of CPB (especially amino groups and C-O) offered reaction sites for H2O2 and then generated hydroxyl radicals ((OH)-O-center dot). The redox catalytic cycles of Fe (II)/Fe (III) and Mn (III)/Mn (II) were realized under visible LED light, which enabled MnFe2O4@CPB to maintain great removal performance in five recycle tests. Besides, the good reusability and easy separation from water of MnFe2O4@CPB were proved. The degradation pathways of MO were proposed by high resolution mass spectrometry (HRMS) and four main reaction ways were analyzed. Based on these excellent properties, MnFe2O4@CPB would become a promising bifunctional material in wastewater treatment.