Synthesis, characterization and thermochemistry of a Pb-jarosite

Abstract

The enthalpy of formation from the elements of a well-characterized synthetic Pb-jarosite sample corresponding to the chemical formula (H 3 O) 0.74 Pb 0.13 Fe 2.92 (SO 4 ) 2 (OH) 5.76 (H 2 O) 0.24 was measured by high temperature oxide melt solution calorimetry. This value (DH f = À3695.9 ± 9.7 kJ/mol) is the first direct measurement of the heat of formation for a lead-containing jarosite. Comparison to the thermochemical properties of hydronium jarosite and plumbojarosite end-members strongly suggests the existence of a negative enthalpy of mixing possibly related to the nonrandom distribution of Pb 2+ ions within the jarosite structure. Based on these considerations, the following thermodynamic data are proposed as the recommended values for the enthalpy of formation from the elements of the ideal stoichiometric plumbojarosite Pb 0.5 Fe 3 (SO 4 ) 2 (OH) 6 : DG f = À3118.1 ± 4.6 kJ/mol, DH f = À3603.6 ± 4.6 kJ/mol and S°= 376.6 ± 4.5 J/(mol K). These data should prove helpful for the calculation of phase diagrams of the Pb-Fe-SO 4 -H 2 O system and for estimating the solubility product of pure plumbojarosite. For illustration, the evolution of the estimated solubility product of ideal plumbojarosite as a function of temperature in the range 5-45°C was computed (Log(K sp ) ranging from À24.3 to À26.2). An Eh-pH diagram is also presented.

Synthesis, characterization and thermochemistry of synthetic Pb–As, Pb–Cu and Pb–Zn jarosites

“…c !H ds (SO 3(g) ) as determined by Majzlan et al (2002). Forray et al (2010)., b Drouet and Navrotsky (2003)., c Robie and Hemingway (1995). d Majzlan et al (2002), e SGTE (1999), f Nordstrom and Archer (2003).…”

“…These cycles involves the enthalpy of drop solution of lead carbonate PbCO 3 (Forray et al, 2010), ZnO, and CuO as well as other thermodynamic data taken from the literature (Robie and Hemingway, 1995;SGTE, 1999;Majzlan et al, 2002;Drouet and Navrotsky, 2003;Nordstrom and Archer, 2003) and listed in Table 5. Application of these thermodynamic cycles leads to the heat of formation, from the elements (!Hº f ) -3691.2 ± 8.6 kJ/mol for the synthetic Pb-As jarosite, -3653.6 ± 8.2 kJ/mol for the synthetic Pb-Cu jarosite and -3669.4 ± 8.4 kJ/mol for the synthetic Pb-Zn jarosite.…”

Investigation of thermal decomposition of jarosite tailing waste

“…Thus, the recycling and reuse of ammonium jarosite is of incredible importance. Nowadays, jarosite has been in the headlines of many researchers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] aiming at its use in sulfoaluminate cement production [2], ordinary Portland cement production [7], brick production [5] or silver recovery [8]. Jarosite structure can accommodate many other elements [10][11][12][13][14].…”

“…[7,8]. The thermal decomposition of natural and synthetic jarosite produced by zinc industry has been studied for some time [6,[12][13][14], with the use of thermogravimetric analysis and infrared spectroscopy [12][13][14][15][16]. In general, jarosite is known as hydrous mineral with approximately 10 mass% H 2 O in the form of OHgroups [10].…”

Kinetic Analysis of the Decomposition of the KFe3(SO4)2-x(CrO4)x(OH)6Jarosite Solid Solution in Ca(OH)2Medium

“…This characteristic makes minerals such as jarosite ideal to incorporate undesirable metallic elements that are also potentially dangerous for the environment. 27 The ion substitutions that alter the parameters of the unit cell of the ideal jarosite have been shown regarding the influence of dissolution and solubility rates. The substitution of H 3 O and Na in site A significantly increases the jarosite solubility compared to jarosite with K, while the substitution of chromate by sulfate decreases the solubility of potassium jarosite.…”