Effect of Secondary Precipitated Carbonate Minerals in the Chemical Behavior of Soil Iron


A carbonate minerals precipitation lab experiment was conducted using saline solution of Calcium / Magnesium chlorides in different rates of Ca/Mg at (100/0,75/25,50/50 و 25/75and,0/100) in two concentrations of 20,100 mmol.l-1 ,and Sodium bicarbonate as a source of carbonate in two concentrations of 26, 130 mmol.l-1 .precipitation process was contacted following two methodologies , the first one is the direct precipitation method (MI) where high concentrations of bicarbonates were used , the second one is the gradual precipitation method (M2) where low concentrations were used , as they were added as drops in a fixed rate with time . the third treatment was using calcium and magnesium solutions only (M3) to know the effect of atmosphere in the formation of precipitates. After precipitation process was completed, Iron was added in five concentrations of (0,5,10,15, and 20) µg ml-1.ml to study the adsorption isotherms . Results showed that the rate of bonding energy was (2247,1498, and 192) µg.gmsoil-1 of M1,M2, andM3 treatment respectively. Also bounding energy was decreased with time in M1 and M2 treatment where they were 1.9, 1.73, 0.926, 1.34, 0.70,and 0.41 ml. µgFe+2. during periods of 6 , 12 ,and 24 hours restively ,while it has increased in M3 treatment at 0.363 ,0.474 , and 0.570 ml. µgmFe+2. results also showed a decrease in bonding energy rates with an increase in Magnesium rates at (2.49 ,1.93 ,1.40 ,0.76 , 0.43, 1.79 ,1.06 , 0.59, 0.38 , 0.27, 0.68, 0.58, 0.44, 0.37,and 0.28) ml. µgFe+2.Differences in precipitation mechanism affected the rates of released Iron , where it increased in the direct precipitation method rather than the gradual precipitation at 23.3 % and this rate also increased with the increase of magnesium rates in M1 as compared to M2 at (41.8 ,23.3 ,40.9 ,11.8 , and 13.5)% of treatments (100/0,75/25,50/50, 25/75, and 0/100respectively) .