Characterization of a Novel Biodegradable Material to Reduce Emission of Ammonia
A novel biodegradable ammonia control material was developed from steam exploded corn cob and its adsorption capacity was studied by packed column and titration method. The packed column studies showed that the maximum absorption capacities of the raw corn cob (RCC) and the steam exploded corn cob (SECC) were 10.45 mg NHB3B/gRCC and 59.80 mg NHB3B/gSECC respectively. However, the titration of the water slurries with a NHB4BOH showed that the capacity of the SECC was 14.4 times that of RCC. The large difference between the packed column (SECC/RCC = 5.7) and the slurry titration (SECC/RCC = 14.4) was probably because: (1) the initial ammonia reaction products blocked the pores of the SECC and reduced diffusion into the pore structure; (2) the ammonia gas flow rates were too high and therefore the gas did not penetrate the pores; (3) the gas contact time was below the equilibrium value; and (4) since interior pore surface area is usually larger than the external surface area of a particle, it appears the low column SECC/RCC ratio is due to reactions on the SECC particle surface whereas the slurry result was a combination of both.
Fourier Transform Infrared, FTIR spectroscopy was conducted on RCC, SECC, ammonia adsorbed on RCC and ammonia adsorbed on SECC in the range 4000–700 cmP-1P. The FTIR bands in the region between 1500 and 2000 cmPâ 1P showed a considerable difference between RCC and SECC. When SECC was treated with ammonia, the carboxylic functional group peak at 1700 cmP-1P was reduced and a new peak was observed at 1584 cmP-1P. The adsorption, desorption test and the heat of adsorption results suggested combined physisorption and chemisorption of ammonia on SECC but chemisorption was found to play an important role in ammonia removal. The BET specific surface area of RCC was 3.4 m2/g whilst that SECC was less than 1 m2/g. Although SECC had a low surface area compared with RCC its adsorption capacity was found to be greater than that of RCC meaning the adsorption process is chemically controlled. Also, the pore size distribution showed that RCC exhibited both macroporosity and mesoporosity whilst SECC showed only mesoporosity. It is interesting to note that upon steam exploding RCC, the macropores within RCC collapsed to form more mesopores in SECC. The high uptake of SECC was determined to be its small pore width compared to that RCC.
Simultaneous Differential Scanning Calorimetry, DSC and Thermal Gravimetric Analyzer, TGA, was used to determine the heat of adsorption of ammonia on SECC. The heat of adsorption of ammonia on SECC was 33.00 kJ per mole of NHB3B. This study shows that SECC could be potentially used to remove NHB3B from various emission sources.