Effect of a catalyst on the kinetics of reduction of celestite (SrSO4) by active charcoal

Abstract

Reduction of celestite (SrSO 4 ) powder with particles of active charcoal has been studied extensively in the absence and presence of catalysts. The optimum temperature at the charging zone has been optimized to get a maximum water-soluble strontium sulfide value. The strontium value has been analyzed using a chemical method, which was verified by the instrumental method using an inductively coupled plasma-optical emission spectrophotometer (ICP-OES). The conversion-time data have been analyzed by using a modified volume-reaction (MVR) model, and the effect of the catalyst on kinetic parameters has been elucidated. It was found that potassium carbonate, potassium dichromate, sodium carbonate, and sodium dichromate catalysts were found to enhance the reaction rate quite satisfactorily in the reduction of the celestite (SrSO 4 ).

Heat treatment and substrate dependant properties of titania thin films with high copper loading

“…One effective method proposed to enhance the absorption properties of titania is to dope it with anions or cations . The key idea here is that doping modifies the electronic structure, which would effectively shrink the band gap.…”

Dry mechanochemical conversion of SrSO4 to SrCO3

“…In the black ash process, SrSO 4 is reduced with coke (or coal) at temperatures generally over than 1000 • C to produce water soluble SrS [3,4]. The sulfide is then leached in hot water and strontium carbonate is precipitated using soda ash, ammonium bicarbonate and/or CO 2 [3,5,6].…”

“…This equates to a net free energy change of −22.3 kJ mol −1 at 298 K which is why dry milling will also induce the reaction. SrSO 4 + Na 2 CO 3 = SrCO 3 + Na 2 SO 4 (1)…”

Carbothermic reduction of mechanically activated celestite

“…Fundamental conditions of the carbothermic reduction have been investigated and discussed in detail by and Sonawane et al (2000). The first chemical reaction occurring at low temperatures (N400°C) is the solid-state reaction given as,…”

“…92 (2009) j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i j m i n p ro above 777°C under the influence of CO and the outcome of this reduction depends on the CO 2 − CO concentration ratio in the gas phase. and then Sonawane et al (2000) studied the reduction reaction using a stoichiometric amount of carbon and through intermediate temperatures ranging from 600°C to 700°C at the loading zone and from 1200°C to 1300°C at the discharging zone of a rotary kiln. Due to the high discharging-zone temperature, the process has some disadvantages: (1) high electric energy requirement, (2) sintering of the reactants and products, and (3) difficulties in the selection of the material of construction for the reactor system for a commercial plant.…”