Green synthesis of a bifunctional Fe-montmorillonite composite during the Fenton degradation process and its enhanced adsorption and heterogeneous photo-Fenton catalytic properties

A novel Fe-MMT-I composite was synthesized during the degradation of rhodamine B (RhB) through Fenton's method, which could degrade RhB (concentration as high as 1000 mg L), reuse iron sludge and obtain a highly efficient bifunctional composite at the same time. X-ray diffraction analysis confirmed the existence of FeOOH in the composite. It is interesting to observe that the introduction of RhB leads to more FeOOH inserted into the layer of MMT, which enhanced both the adsorption and heterogeneous photo-Fenton activities of the composite. The Fe-MMT-I was efficient for the adsorption of RhB over a wide pH range (2.06-9.72). The Fe-MMT-RhB still exhibited a high adsorption capacity toward RhB even after five recycles using the heterogeneous Fenton method to regenerate the spent adsorbent. Furthermore, the Fe-MMT-I composite showed high efficiency for photo-Fenton discoloration of RhB with a wide operating pH range (2.01-11.67). Photoluminescence measurement and a leaching test demonstrated that the discoloration of RhB by the composite could be attributed to the synergetic effects of the enhanced adsorption power of the composite and the hydroxyl radicals initiated through the heterogeneous photo-Fenton process. This green method could lead to the construction of combined homogeneous and heterogeneous Fenton processes, which gives new insight into fabricating novel bifunctional composites for environmental remediation.