The Preparation Of Ni/Fe Bimetallic Nanomaterial And Their Application For The Treatment Of Environmental Pollutants

Halogenated organics,like chlorophenols, poly brominated diphenyl ethers, can be propagated to the atmosphere, water, soil through various ways in industrial production as reaction intermediates, organic solvent and important chemical raw materials, which has polluted the ecological environment seriously. At present, the studies of reductive dechlorination by zero metal materials are receiving more and more attention. Among them, due to the low cost and excellent oxidation reduction potential, zero-valent iron (ZVI) pays more attention. But, the catalytic efficiency of single ZVI for hydrogenation is very low. How to improve the reaction efficiency of ZVI becomes the focus of the research direction. The addition of catalytic Ni can enhance the catalytic activity of ZVI for hydrodechlorination significantly. Therefore, Ni/Fe bimetal nanomaterial is the reinforcement of single ZVI and it has very important meanings to study the preparation and application. The preparation of Ni/Fe bimetal with supporting materials as template is the immobilization of metallic nano-materials. It can minimize the adverse effect of aggregation of nano-materials during use, which can lead to the low catalytic activity. In addition, because of the large specific surface area of supporting materials, it can increase the catalytic activity by more catalytic sites.This study has prepared highly active and stable Ni/Fe bimetal nanomaterial by a new way (simultaneous ball milling and in-situ chemical deposition) and has studied the application for environmental pollution treatment. The preparation methods of Ni/Fe bimetal in this study can industrial scale-up and the bimetal catalytic material has higher catalytic activity than the similar materials in hydrodechlorination, which has most realistic value and applied widely. This study has achieved the immobilization of Ni/Fe bimetal. It can minimize the aggregation and wastage in the course use. The main conclusions are as follows:1. This study puts forward a new way to prepared bimetal nano-materials, simultaneous ball milling and in-situ chemical deposition (B&C). This method combines the strengths of ball milling and chemical deposition. The bimetal catalytic material has higher catalytic activity than the similar materials in hydrodechlorination. This method has universality and easy to industrial scale-up.2. The catalytic activity of Ni/Fe-B&C can be increased significantly by increasing the milling time. Ni/Fe-B&C prepared for 4h has the most catalytic rate in the dechlorination experiment in this study.3. The introduction of catalytic Ni significantly increased the catalytic activity of iron base materials for dechlorination. But the activity decreases when the Ni contents is more than 25% in the bimetal. Therefore, Ni/Fe-B&C has the highest catalytic activity when the Ni content is about 25%.4. The high catalytic activity of Ni/Fe-B&C is because of the small and homogeneous Ni particles in the bimetal as the catalytic sites on one hand. On the other hand, the lattice imperfection found by milling in the material can increase the catalytic activity too. The dechlorination rate increase as defect level increase.5. Cation exchange resin immobilized bimetallic nickel-iron nanoparticles were used to minimize aggregation and environmental leaking risks of nano-materials. The reaction rate of resin-bound nZVI is ～55% higher than that of dispersed nZVI.6. We had successfully prepared montmorillonoid immobilized bimetallic nickel-iron nanoparticles and the dry in-situ reduction by hydrogen can reduce the cost and easy to industrial scale-up. The best preparation temperature is 400℃ and the best Ni content is about 17.7%.