title: Sulphate removal from sodium sulphate-rich brine and recovery of barium as a barium salt mixture.
abstract: Sulphate removal from sodium sulphate-rich brine using barium hydroxide and recovery of the barium salts has been investigated. The sodium sulphate-rich brine treated with different dosages of barium hydroxide to precipitate barium sulphate showed sulphate removal from 13.5 g/L to less than 400 mg/L over 60 min using a barium to sulphate molar ratio of 1.1. The thermal conversion of precipitated barium sulphate to barium sulphide achieved a conversion yield of 85% using coal as both a reducing agent and an energy source. The recovery of a pure mixture of barium salts from barium sulphide, which involved dissolution of barium sulphide and reaction with ammonium hydroxide resulted in recovery of a mixture of barium carbonate (62%) and barium hydroxide (38%), which is a critical input raw material for barium salts based acid mine drainage (AMD) desalination technologies. Under alkaline conditions of this barium salt mixture recovery process, ammonia gas is given off, while hydrogen sulfide is retained in solution as bisulfide species, and this provides basis for ammonium hydroxide separation and recovery for reuse, with hydrogen sulfide also recoverable for further industrial applications such as sulfur production by subsequent stripping.
authors.affiliation: Natural Resources and Environment, Council for Scientific and Industrial Research, Pretoria, South Africa. vvravikumar@yahoo.com
authors.forename: Viswanath R K
authors.initials: VR
authors.lastname: Vadapalli
authors.forename: John N
authors.initials: JN
authors.lastname: Zvimba
authors.forename: Jean
authors.initials: J
authors.lastname: Mulopo
authors.forename: Solly
authors.initials: S
authors.lastname: Motaung
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001464:Barium / Q000737:chemistry / Q000302:isolation & purification*; D017609:Barium Compounds / Q000737:chemistry; D001466:Barium Sulfate / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D013431:Sulfates / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D017609:Barium Compounds; D002254:Carbonates; D013431:Sulfates; C012036:sodium sulfate; C012766:barium hydroxide; D001464:Barium; D001466:Barium Sulfate; C006685:barium carbonate; D000641:Ammonia