Influence of Selected Conditions on the Efficiency of Carbonate Precipitation of Cu(II), Ni(II), Pb(II) and Zn(II) Ions

Optimal process conditions for carbonate precipitation of selected heavy metal ions were tested in laboratory conditions using Na2CO3. To the prepared synthetic monocomponent and binary multicomponent solutions of heavy metals with initial concentrations of 500 mg/L, Na2CO3 was added in certain doses at selected mixing speeds (0, 100, 300 and 800 rpm) and mixing time (0, 15, and 30 minutes). The results show the removal efficiency at optimal mixing speeds for monocomponent metal solutions were: Cu(II) 96.394% (300 rpm), Ni(II) 94.594% (0 rpm and 800 rpm), Pb(II) 75.968% (0 rpm ), Zn (II) 99.311% (0 rpm). In binary multicomponent mixtures Cu(II)-Ni(II) and Pb(II)-Zn(II) the removal efficiency results at optimal mixing speeds were: Cu(II) 96.394% (100 rpm), Ni(II) 95.528% (800 rpm), Pb(II) 99.536% (300 rpm), Zn(II) 98.945% (100 rpm). Also, the results of the efficiency of heavy metal removal due to the influence of the contact time of the precipitant and heavy metal ions in monocomponent solutions show the following values: Cu(II) 99.940% (0 min), Ni(II) 94.612 % (0 min), Pb(II) 77.925 % (15 min), Zn(II) 99.324% (30 min), while in binary multicomponent mixtures Cu(II)-Ni(II) and Pb(II)-Zn(II) they were for Cu(II) 96.247% (30 min), Ni(II) 95.521% (0 min), Pb(II) 99.350% (30 min) and Zn(II) 98.944% (0 min). Examination of the influence of the mixing speed of monocomponent solutions showed that the efficiency of removing heavy metal ions was in most cases the best without mixing. Effect of metal-precipitant contact time on the efficiency of heavy metal ion removal showed that in half of the examined metals, the optimal values ​​were chosen as the best (0 and 30 min). It can be concluded that this method based on chemical precipitation using Na2CO3 with optimal parameters such as contact time and mixing speed, can be used in the treatment of industrial wastewater.