Research Article

Dissolution, Solubility, and Stability of the Basic Ferric Sulfate-Arsenates [Fe(SO4)x(AsO4)y(OH)z·nH2O] at 25–45°C and pH 2–10

Table 5

Experimental data and solubility determination for the basic ferric sulfate-arsenate FeSAsOH-4 [Fe(SO4)0.28(AsO4)0.74(OH)0.22·0.28H2O and FeAsO4·0.75H2O mixture].

Temp (°C)Initial pHTime (h)Dissolution data (mmol/L)Fe(SO4)0.28(AsO4)0.74(OH)0.22·0.28H2OFeAsO4·0.75H2O
pHFeSO4AsO4log_IAPMean log_IAPlog_IAPMean log_IAP

25a257601.960.1318780.2823860.054991−22.66−22.64−23.89−23.87
64801.970.1334900.2716270.054323−22.64±0.02−23.86±0.02
72001.970.1339370.2766170.054857−22.63−23.86
79201.970.1338480.2753700.054257−22.63−23.86

25657603.200.0005660.3407040.005979−24.39−24.40−25.53−25.54
64803.200.0005480.3378970.005991−24.40±0.01−25.54±0.01
72003.200.0005360.3388320.006026−24.41−25.55
79203.200.0005390.3375850.006021−24.41−25.55

251057603.200.0004680.3173140.006248−24.47−24.48−25.59−25.61
64803.200.0004570.3138840.006032−24.49±0.01−25.62±0.02
72003.200.0004610.3134160.006066−24.48−25.61
79203.200.0004580.3123250.006059−24.49−25.61

25b257601.950.1329530.2819190.055792−22.67−22.66−23.91−23.90
64801.950.1394880.2837900.055591−22.65±0.01−23.89±0.01
72001.940.1411000.2800470.055925−22.66−23.90
79201.940.1400250.2833220.055391−22.67−23.91

35257601.940.1952660.3895090.031099−22.66−22.66−24.03−24.03
64801.950.2012640.3838960.030899−22.63±0.03−24.00±0.03
72001.930.1997420.3821810.030565−22.68−24.05
79201.930.2003690.3824920.030565−22.68−24.05

45257601.890.2751270.4849370.024692−22.67−22.64−24.12−24.09
64801.900.2889140.4872760.024359−22.63±0.03−24.09±0.03
72001.900.2915110.4846250.024359−22.63−24.08
79201.900.2899890.4886800.024626−22.62−24.08

a,b Dissolution tests in duplicate.