Study On Supported-Gas-Membrane Process For Removal And Recovery Of Aliphatic Amines From Aqueous Streams

Environmental problems caused by aliphatic amines are long-standing focus ongreen environmental protection in our country, and which cause a very serious impacton the natural environment and human health. The traditional methods for the removalof waste water solution of amine and related pollutants have a variety of drawbacks,such as occupying large area, huge energy consumption, enormous cost of investmentand construction, easy to cause secondary air and water pollution, etc. This researchsolved the problems discussed above perfectly by supported-gas-membrane (SGM)process, showed superior prospects for development.Removal of aliphatic amines of low molecular weight from their individualaqueous solutions was investigated theoretically and experimentally by using hollowfiber supported-gas-membrane (SGM) process. Aqueous solutions contained200–5000mg·L-1of amine as feeds were tested, respectively. And aqueous solution of10%wt sulfuric acid was used as absorbing solution. Amines such as methylamine,dimethylamine, trimethylamine, ethylamine, diethylamine and triethylamine, as wellas ammonia, were tested for SGM process. The experimental data indicated that theoverall mass transfer coefficient was a strong function of polarity of amine, or ofamine/water volatility, and it was in an order: isopropylamine> trimethylamine>tertbutylamine> ammonia> triethylamine> diethylamine> propylamine>ethylamine> dimethylamine> methylamine.The influences of feed-in temperature and concentration, feed flow rate, and theconcentration of NaOH pre-added to the feed, on mass transfer coefficients were alsoinvestigated. Among these operating factors, feed-in temperature and NaOHconcentration were crucial. Increasing feed-in temperature and NaOH concentrationled to significant increase of mass transfer coefficient，especially when amineconcentration in the feed was low. Mathematical model incorporating laminar flow,ion and molecular diffusion, dissociation equilibrium and vapor-liquid equilibriumwere established and solved numerically. When surface tension of the feed solutionwas>55mN/m, the SGM process indicated a good stability in a test period of at least30days. While>95%of amine was removed, amine could be enriched for10-20times in the absorbing solution. Thus, this SGM-based separation process is suitable to remove, to recover, and to concentrate amines from their aqueous solutions.