Efficient activation of persulfate by a magnetic recyclable rape straw biochar catalyst for the degradation of tetracycline hydrochloride in water.

A recyclable magnetic rape straw biochar (MRSB) catalyst was synthesized by a high value-added and energy-saving method using abandoned rape straw as the raw material. The MRSB catalyst showed high catalytic activity and recyclability for activating persulfate (PS) to degrade tetracycline hydrochloride (TC) in water. The Fe3O4 in the MRSB greatly promoted the activation of PS. More importantly, the MRSB catalyst exhibited high catalytic performance over a wide pH range (2.99-11.01) for activating PS to degrade TC in water. Moreover, MRSB still had good catalytic activity for TC degradation after 8 recycling cycles and was easily separated by an external magnetic field for reuse. The electron spin resonance (ESR) analysis indicated that the generation of the sulfate radicals (SO4-), hydroxyl radicals (OH) and superoxide radicals (O2-) was greatly promoted in the MRSB/PS system. As a result, MRSB exhibited 13.24-fold higher reaction rate for activating PS than those of rape straw biochar (RSB). Both radical mechanism and non-radical mechanism existed in the MRSB/PS system, and SO4- and singlet oxygen (1O2) played a determinative role. This study might give a new way to reuse abandoned rape straw and synthesize new recyclable catalysts for activating PS to degrade organic pollutants in water.