Electrochemical Oxidation of the Sulfide Ion in Synthetic Geothermal Brines in Batch Cells Using Coke Electrodes

Abstract

The oxidation of the sulfide ion occurs efficiently in batch cells at massive coke electrodes. At all currents studied, the products included a low yield of elemental sulfur, which deposited on the anode; the yields of sulfate were also low, except at the highest current. The remaining products were soluble organosulfur species, indicating that the coke anodes acted sacrificially. The reaction displayed unusual kinetic behavior with respect to the disappearance of sulfide: a two-stage reaction was observed in which the loss of sulfide was faster in the early stages of reaction, while elemental sulfur deposited on the anode. A subsequent slower current-controlled reaction was associated with the formation of the remaining products.

Study on the phase equilibrium of the quaternary systems Na+ (K+)//H2PO4−, Cl−, SO42−–H2O at 313.15 K

“…4 shows a comparison of the equilibrium phase diagrams for the quaternary system at (298. 15 (1) Solubility of NaH 2 PO 4 in water increased significantly than the other two salts, which results in the invariant point move down from F 1 to E. At each temperature, the crystalline region of NaH 2 PO 4 Á2H 2 O is smaller than that of Na 2 SO 4 and NaCl.…”

“…15 According to the calculated Jänecke dry-salt index, the water diagram of the system at 313.15 K is shown in Fig. 5, with the Jänecke index of water used as ordinate, and the Jänecke index of NaH 2 PO 4 used as abscissa.…”

“…Sulfate ion concentration in liquids and their corresponding wet solid phases was obtained by means of barium sulfate turbidimetry [15]. The relative standard uncertainty of this determination is 0.02 [16].…”

Stable (solid+liquid) phase equilibrium for the ternary systems (K2SO4+KH2PO4+H2O), (K2SO4+KCl+H2O) at T=313.15K

“…The H 2 PO 4 -concentration was determined by the quinoline phosphomolybdate gravimetric method [17][18][19] with a standard uncertainty of 0.004 in mass fraction. The sulfate ion concentration was obtained by means of barium sulfate turbidimetry [20,21] with a standard uncertainty of 0.002 in mass fraction. The Cl À concentration was determined by Volhard method [22,23] with a standard uncertainty of 0.005 in mass fraction.…”

Electrochemical removal of sulfur pollution

“…In addition, electrochemical treatment can allow for on-site recovery of sulfur compounds (e.g. elemental sulfur (S 0 ) and sulfuric acid (H 2 SO 4 )), or electrolysis side products (H 2 gas, caustic soda (NaOH), see Figure 8.3) (Dutta et al, 2008;Rabaey et al, 2006;Vaiopoulou et al, 2016), ultimately resulting in the minimization of the operational costs (Chatzisymeon et al, 2013;Pikaar et al, 2015;Rankin et al, 2010).…”