1. Development of Iron Loaded Algae Derived Carbon for Arsenite Removal from Water
Joshua Gomez, Chemical Engineering.
Meng Zhou, mentor, Chemical Engineering.
Dr. Shuguang Deng, mentor, professor, Chemical Engineering.
Introduction
Discussion
Having potable water is essential to sustain a healthy life, but in many cases people can not access potable water. Arsenic contamination in water is very common around the world, especially along the border region in Columbus, New Mexico and Puerto Palomas, Mexico because these cities lie on the edge of the aquifer where they attain water. The health risks associated with arsenic are commonly recognized causing skin damage, problems with the circulatory system, and also increases the risk of developing cancer. There are many solutions to this problem, such as reverse osmosis, evaporation, and adsorption, but the cost is always and issue. In this project, carbon impregnated carbon was produced for the purpose of adsorbing arsenite from water. The physical properties of the iron impregnated carbon were measured and recorded.
Overall, the carbon that was activated with FeCl3 performed the best. The iron activated carbon had the highest yield, highest adsorption capacity, and highest percent adsorbed overall. The adsorption that took place with the carbon activated with potassium hydroxide and the commercial carbon was purely physical, which is why the adsorption capacity for arsenic was low. On the other hand, the carbon activated with FeCl3 experienced chemical adsorption due to the iron ions. The positive charge on the iron ions bonds with the negative arsenic ions. The FeAC showed from the washed sample that it had a very high surface area and pore volume. The surface area and pore volume of the unwashed sample shows that iron coats the surface of the carbon. This is showed further by the x-ray diffraction pattern where the peaks match that of FeCl2 displaying that the iron had been reduced to 2+ . The SEM images show that the carbon is uniform and sponge like.
Objective
The aim of this project was to experimentally find an optimum synthesis method that will produce a carbon material excellent for removing arsenite from water.
Results
Materials and methods
Chlorella algae and ferric chloride were mixed together in a solution of varying ratios of 3 grams of algae to 6 grams of ferric chloride (1:2) and 3 grams of algae to 12 grams of ferric chloride (1:3). This solution was then heated to 80°C for 3 hours to create a slurry. This slurry was then pyrolyzed in a Lindberg Blue M quarts tube furnace under a nitrogen atmosphere at 500°C and 600°C for 2 hours. The resulting iron impregnated carbon (FeAC) was then washed with deionized water. Carbon made with potassium hydroxide (KOHAC) was prepared in a similar manner to compare properties but washed with hydrochloric acid. Batch shaker experiments were executed using FeAC, KOHAC, and commercial activated carbon at 25°C with 100 mL of 0.1, 0.2, 0.5, 0.8 and 1 mg/L of arsenite solutions for 24 hours to test adsorption effectiveness of each carbon. Concentrations of all solution were measured using an inductively coupled mass spectrometer. The FeAC was then analyzed for surface area and pore size qualities using an ASAP The texture of the FeAC was observed using a scanning electron microscope, and the main phase of the carbon was found using x-ray diffraction.
Fig.1 Scanning Electron Microscope images Fe-AC
500 °C
Fe/ADC
600 °C
FeCl2/ADC
BET surface area (m^2/g)
Average pore size (nm)
8.6408
6.5769
Pore volume
(cm^3/g)
0.0394
0.0476
N2 adsorption and desorption isothermal
@ 77K for unwashed Fe-AC
Mass of adsorbent
Fig.2 X-ray diffraction Pattern of FeAC
500 °C
Fe/ADC (after washing)
600 °C
ADC (after washing
BET surface area (m^2/g)
Average pore size (nm)
7.8704
7.9340
Pore volume
(cm^3/g)
0.3362
0.3305
Conclusions
From the experiments, it can be concluded that the carbon that was activated with Ferric chloride can be a very effective adsorbent of arsenite from water. For the low cost and ease of synthesis, if further investigation is done on the optimization of algae derived carbon activated, this adsorbent can be deemed critical for the adsorption of arsenite from water for the improvement of the health of communities all over the world.
N2 adsorption and desorption isothermal
@ 77K for washed Fe-AC
Adsorption Capacity
Acknowledgments
My sincerest gratitude goes to everyone who guided me and helped me during this project. Mark Chidester from the water quality lab at NMSU greatly helped me through my mass spectrometer analysis and I am very appreciative for that. I would like to thank NM AMP for the support they have given me. Meng Zhou played a large role in this project by mentoring and directing me. Finally, I would like to thank Dr. Shuguang Deng for his amazing support, advice, guidance, and mentoring.
NSF HRD #
Second Shaker Experiments to determine trend.