Pretreatment of date syrup with sulfuric acid, tricalcium phosphate, tricalcium phosphate with hydrochloric acid, potassium ferrocyanide, and EDTA to increase the production of citric acid was investigated. Among the above techniques used for the removal of heavy metals, 2% tricalcium phosphate treatment gave better results regarding citric acid concentration (55 +/- 1.5 g l(-1)), citric acid yield (50 +/- 1.5%), and sugar utilization (73.3 +/- 1%). The optimum pH for citric acid production was 6.5. The addition of 4% (v/v) methanol in the date syrup solution treated with 2% tricalcium phosphate increased the concentration of citric acid from 55 to 90 g l(-1).