Removal of Heavy Metals Using Chemicals Precipitation


The single component and multi-component hydroxide precipitation andadsorption were studied for different heavy metals namely Iron (III), Chromium(III), Copper (II), Lead (II), Nickel (II), and Cadmium (II) from aqueous solutions.By using the jar tester Magnesia (MgO) was used as a precipitator at differentdoses and compared with other chemicals like lime (CaO) and caustic soda(NaOH). The treatment involves the addition of either magnesia or lime-watersuspensions (combined with cationic polyelectrolyte, CPE) in various doses, 1.0 –5.0 g/l for the metal samples to study the effect of varying doses on the treatmentefficiency. The results show that the percent removal of metal ions increases toabout 99 % with increasing the MgO dose to some limits. The optimum values ofMgO doses were found to be 1.5-3.0 g/l. The pH value ranges are 9.5 to 10 withMgO precipitant and pH of 11.5 to 12 with CaO precipitant. In the jar experimentthe rotation speed, N, 180-200 rpm, (G of 460-480 s-1) of mixing for two minuteswas the most favorable speed of rapid mixing and the slow mixing speed of 15-30rpm, G of (14-35 s-1), for twenty minutes gave the best results.At the best operatingconditions of the pilot plant, the removal efficiency of metal ions was more than97% at doses of MgO (1.0-4.0 g/l).