(371d) Textile Dye Removal from Water Using Catalytic Nanoparticle-Carbon Composites

Authors: 
Watson, S., University of Arkansas
Greenlee, L. F., University of Arkansas
Shinn, S., University of Arkansas
Herring, A. M., Colorado School of Mines
Kuo, M. C., Colorado School of Mines
In recent years, increasing consumer spending and new emerging markets in the world trade have caused a boom in production in the textile industry. With this growth comes the contamination of the environment through substances called azo dyes. In the presence of digestive tracts, these azo dyes can cleave creating aromatic amines, which, in some cases have been proven to be carcinogenic. Also, the azo dyes often cannot be completely filtered out of water naturally due to their highly hydrophilic nature and very small size. Studies have shown that metal nanoparticles reduce the concentration of these azo dyes in aqueous solution to a certain extent, but many studies have focused on precious metals such as gold, copper, and palladium. Due to the cost of these metals, there is interest in developing reactive nanoparticles that are based entirely on non-precious metal combinations. For this study, we have chosen to focus on iron-nickel bimetallic nanoparticles.

In this study, our research focuses on demonstrating the effectiveness of bimetallic iron-nickel nanoparticles in the treatment of Orange G azo dye for different molar ratios of nickel to iron and for the case where these nanoparticles are deposited onto a high surface area carbon support material. If reactive nanoparticles are to be used in realistic treatment scenarios, the nanoparticles must be immobilized within a treatment system, and high surface area carbon materials are a potentially ideal choice for immobilization. Carbons, such as activated carbon, are often used in water treatment to adsorb and remove water contaminants and thus may serve not only as an immobilization strategy but as an additional available surface for adsorptive contaminant removal.

In our experimental work, nanoparticles were created by using an aqueous nanoparticle synthesis technique and using an alloyed nanoparticle morphology. The process uses an iron sulfate heptahydrate salt along with a stabilizer (ATMP) and a nickel chloride hexahydrate salt with its respective stabilizer (PVP). These metals are mixed under argon gas, then reduced using sodium borohydride. This procedure results in the formation of nanoparticles and hydrogen gas. The nanoparticles are then added to an aqueous solution of Orange G in a batch reactor setup and mixed while samples are taken at specific time intervals to evaluate Orange G removal. Our results thus far indicate a strong correlation between the decrease in Orange G concentration and the molar ratio of nickel to iron. Experiments performed with monometallic nanoparticles (10 g/L iron and 10 g/L nickel) showed little to no decrease in Orange G concentration while the bimetallic counterparts showed promising results in decreasing the concentration of Orange G. Results showed that at a lower molar ratio of nickel to iron increased the effectiveness of the bimetallic nanoparticles in decreasing the concentration of Orange G. In comparison to nanoparticles alone, nanoparticles were deposited onto several high surface area carbon support materials and tested in the same batch reactor setup for removal of Orange G. Preliminary results suggest that nanoparticle immobilization onto carbon results in an increase in the rate of removal of Orange G and an increase in the overall amount of Orange G removed.

In this talk, we will present results for immobilized iron-nickel nanoparticles on several key high surface area carbon support materials. In particular, two types of commercially-available activated carbons will be compared to several novel surface-functionalized carbons. The novel carbon materials are functionalized with specific heteropolyacids thought to have potential oxidizing capabilities in aqueous solution. Results for immobilized nanoparticles will be compared to results for non-immobilized nanoparticles in a batch reactor setup. The influence of nickel to iron molar ratio on Orange G removal for both immobilized and non-immobilized nanoparticles will be discussed. Characterization results for nanoparticle and nanoparticle-carbon composite morphology, composition and phase will be presented. Characterization methods include electron microscopy, power x-ray diffraction, and x-ray photoelectron spectroscopy. Finally, a comparison of the different tested carbon support materials will demonstrate that there are differences in Orange G dye removal depending on what carbon support is chosen for nanoparticle immobilization.