Study on the Impact Factors of COD Throughput in Corncob Extract

[ Objectivel The study aims to discuss the impact factors of COD （chemical oxygen demand） throughput in corncob extract. [ Method ] Firstly, as the variations of the mass concentration of corncob, temperature, time and pH, the throughput of COD in corncob extract were analyzed respectively. Afterwards, through the orthogonal test, the best conditions for extracting organic matter from corncob were determined. [ Result] The single-factor tests showed that there was a linear relationship between the mass concentration of corncob and COD of corncob extract when the mass concentration of the corncob was lower than 50 g/L; COD of corncob extract was higher under acidic or alkaline conditions. The optimum con- ditions for extracting organic compounds from corncob were as follows： temperature was 35 ℃, mass concentration was 40 g/L, pH =3, and ex- tracting time was 3 hours; under this conditions, the mass of COD released from a unit mass of corncob reached 0.056 2 g. [ Conclusien] The re- search could decrease the treatment cost of wastewater from uranium mining in mines and make corncob more useful.

Thermodynamics of Zn(Ⅱ)-NaOH-H_2O system

According to the principles of simultaneous equilibrium and electronic charge neutrality, the thermodynamics of Zn（II）-NaOH-H2O system was studied in this paper. Varying the concentration of sodium hydroxide, in range of 0- 400 g/L, the distribution law of all zinc species and the mathematical model of equilibrium concentration of zinc in the system were obtained. The relative errors between theoretic calculation and the experimental values of total concentration of zinc were analyzed, and the absolute average error is only 0.129 8%. The mathematical model and the thermodynamic data are believable.