A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can be used to hydrothermal synthesize ZSM-5 zeolite without impurity phase contamination

which was confirmed by XRD

TG

SEM

BET and EDS characteristic techniques. It was found that with the increase of SiO

2

/Al

2

O

3

ratio and the extension of reaction time

the crystal type transform from the orthorhombic to the monoclinic phase. The impurity fluorine content of the recovered SiO

2

from H

2

SiF

6

has great influence on the hydrothermal process for ZSM-5 crystal structure formation. Moreover

the increase of fluorine ions content in the hydrothermal process can control the crystal morphology and size of synthesized ZSM-5. Catalytic properties of synthesized HZSM-5 with different SiO

2

/Al

2

O

3

ratio in transalkylation of toluene and 1

2

4-trimethylbenzene show good and stable catal

ytic performance. The ZSM-5 synthesized with recovered silica source exhibits similar catalyst life as the performance of small particle size HZSM-5

because the ZSM-5 synthesized with the silica source from industrial hexafluorosilicic acid prefers a thin disk crystal along the b axis direction

which shortens the diffusion distance of generated products.