Coprecipitation of phosphate with calcite in the presence of photosynthesizing green algae

The results of phosphate coprecipitation on calcite, occurring in a solution of calcium bicarbonate, in the presence of photosynthesizing algae are presented. The precipitation experiments were carried out at 20 degrees C in an illuminated culture apparatus with continuous recordings of pH and conductivity. The alga used in the experiment was the unicellular green alga Chlorococcum sp. The results are analysed using chemical kinetic models and are compared to phosphate coprecipitation occurring in abiotic conditions. The calculated values of the maximum surface density of coprecipitated phosphate are in good agreement with those from abiotic conditions, which indicates that the same mechanism is in operation. (C) 1997 Elsevier Science Ltd.