In Situ Construction Of Nanometer Zero-valent Iron Composites And Deep Adsorption Of Selenium And Tellurium In Photovoltaic Waste

As one of the most potential environmental remediation materials,Nano-zero-valent iron(NZVI)particles with small particle size,large specific surface area,active chemical properties,strong reduction capacity and environmental safety,have shown unique advantages in solving heavy metal pollution and various organic pollution in water and attract much attention around the world.The preparation processes of NZVI mainly include liquid phase reduction and hydrogen reduction method.In this paper,NZVI and its composites were prepared by using these two methods to study the adsorption property of selenium and tellurium from solutions.1.In this paper,the rod-shaped FeOOH was firstly prepared,and then the rod-shaped NZVI was obtained by reduction under continuous hydrogen flow.The physical and chemical properties of magnetic NZVI were characterized by SEM,TEM,XRD,XPS and BET.The results showed that rod-shaped NZVI was successfully prepared with a specific surface area of 64.43 m~2/g and an average pore diameter of 2.80 nm.After adsorption,XPS data showed that the surface of NZVI was covered by tellurium,which proved its good adsorption property.The effects of initial solution concentration,NZVI dosage,pH,interfering ions,time,temperature and other parameters were also studied and due to the high reactivity of NZVI,the final maximum adsorption capacity was 190 mg/g,and the adsorption efficiency can reach to about 90%.In addition,the material can realize magnetic separation under the action of external magnetic field,so as to recycle and recycle the material.2.Porous NZVI/LDOs composites with both physical and chemical adsorption effects were synthesized combining layered double oxides(LDOs)with NZVI by liquid phase reduction method.The morphology and crystal structure of the composites were determined by SEM,TEM,XRD and BET.It was found that NZVI particles were uniformly distributed on the surface of LDOs,and the specific surface area and pore size were expanded to 134.04 m~2/g and 10.15 nm respectively.By controlling the factors of pH,interfering ions,concentration and temperature,the maximum adsorption quantity of the composites for tellurium can reach 500 mg/g under the optimal adsorption conditions,and the removal rate can reach about 95%.The introduction of LDOs can effectively solve the agglomeration problem of NZVI particles and maximize the adsorption capacity.3.NZVI/C composites were obtained by hydrogen reduction method.It realizes the controllable preparation of the ordered rod-shaped nanometer zero-valent iron arrays on the fibers,solving the agglomeration problem of nanometer zero-valent iron.More importantly,this method can be extended to various fiber materials and is expected to achieve large-scale industrial production.4.Multi-walled carbon nanotubes were used as raw materials,and carbon nanotube films were prepared by re-assembly after mixed acid etching for the base material.The liquid-phase reduction method was used to attach nano-zero-valent iron particles to the surface of carbon nanotube films to obtain dynamic NZVI/ACNTs hybrid films.After an adsorption cycle,the hybrid membrane can be recovered by simple acid treatment and reused.