ECOLOGICAL TREATMENT OF MEA AQUEOUS SOLUTION USING A HYDROPONIC METHOD

摘要

In the CO _( 2 ) chemical absorption process, a CO _( 2 ) absorbent may be released into air directly through absorbent volatilization and discharged into water body through absorbent leakage, with both leading to the potential pollutions of the air and water environment. In the present study, a new ecological treatment of monoethanolamine (MEA), a widely used solvent in the chemical absorption process, was proposed using lettuce hydroponics. An aqueous MEA solution was firstly CO _( 2 ) -saturated to reduce its pH value to about 7, and then the CO _( 2 ) -rich MEA solution was mixed with a chemical nutrition solution to act as the hydroponic liquid for lettuce cultivation. The feasibility of ecological treatment of MEA by lettuce hydroponics was investigated in terms of the phytotoxicity of MEA and characteristics of the hydroponic lettuce, followed by screening the optimal MEA concentration. The results showed that the phytotoxicity of MEA increases with MEA concentration. Generally, the phytotoxicity of MEA is relatively low. The MEA concentration causing 50% inhibition rate of root growth (EC _( 50 ) ) is about 0.012 mol/L, implying that the maximum MEA concentration suitable for ecological treatment should be less than 0.012 mol/L. In terms of the external quality, agronomic trait and physiological characteristic of hydroponic lettuce cultivated in hydroponic liquids containing MEA, the growth of lettuce is improved at some MEA concentrations when compared to the lettuce cultivated in a chemical nutrition liquid, including more active lettuce life, stronger substance assimilation capacity, higher apparent quality and lettuce yield. In short, ecological treatment of MEA on the basis of the hydroponic method is feasible, and the promising concentration of MEA is 0.001 mol-MEA/L.