[Diffusion coefficients of ammonia, nitrate and nitrite in cell-free and cell-containing PVA gel membranes]

The cell-free PVA gel membrane and cell-containing PVA gel membrane were prepared by iterative freezing and thawing, and the diffusion coefficients of ammonia, nitrate and nitrite in PVA gel membranes were determined. The effect of the conditions of preparing PVA gel membranes and cell concentration on the diffusion coefficients of ammonia in PVA gel membranes were investigated. The results shown the diffusion coefficients of ammonia in PVA gel membranes decreased while the iteration times of freezing-thawing or PVA concentration or cell concentration increased. The diffusion coefficients of ammonia, nitrate and nitrite in cell-free PVA gel membranes (PVA concentration was 15%) were 0.69 x 10(-9) m2/s, 0.52 x 10(-9) m2/s, and 0.56 x 10(-9) m2/s, respectively. The diffusion coefficients of ammonia, nitrate and nitrite in cell-containing PVA gel membranes (the cell concentration was 60 g/L) were 0.55 x 10(-9) m2/s, 0.46 x 10(-9) m2/s, and 0.45 x 10(-9) m2/s, respectively.