title: Reduction-melting combined with a Na₂CO₃ flux recycling process for lead recovery from cathode ray tube funnel glass.
abstract: With large quantity of flux (Na2CO3), lead can be recovered from the funnel glass of waste cathode-ray tubes via reduction-melting at 1000°C. To reduce flux cost, a technique to recover added flux from the generated oxide phase is also important in order to recycle the flux recovered from the reduction-melting process. In this study, the phase separation of sodium and the crystallization of water-soluble sodium silicates were induced after the reduction-melting process to enhance the leachability of sodium in the oxide phase and to extract the sodium from the phase for the recovery of Na2CO3 as flux. A reductive atmosphere promoted the phase separation and crystallization, and the leachability of sodium from the oxide phase was enhanced. The optimum temperature and treatment time for increasing the leachability were 700°C and 2h, respectively. After treatment, more than 90% of the sodium in the oxide phase was extracted in water. NaHCO3 can be recovered by carbonization of the solution containing sodium ions using carbon dioxide gas, decomposed to Na2CO3 at 50°C and recycled for use in the reduction-melting process.
authors.affiliation: Headquarters for Innovative Society-Academic Cooperation, University of Fukui, Bunkyo 3-9-1, Fukui 910-8507, Japan. Electronic address: t-okada@u-fukui.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okada
authors.affiliation: Headquarters for Innovative Society-Academic Cooperation, University of Fukui, Bunkyo 3-9-1, Fukui 910-8507, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Yonezawa
mesh_terms: D001272:Atmosphere; D002245:Carbon Dioxide / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry*; D055984:Cathode Ray Tube; D003460:Crystallization; D059029:Electronic Waste; D005898:Glass; D006358:Hot Temperature; D007477:Ions; D007854:Lead / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D011208:Powders; D059027:Recycling / Q000379:methods*; D012037:Refuse Disposal / Q000379:methods*; D017640:Silicates / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D017670:Sodium Compounds / Q000737:chemistry; D012995:Solubility; D013690:Television / Q000295:instrumentation; D013997:Time Factors
chemical_list: D002254:Carbonates; D007477:Ions; D010087:Oxides; D011208:Powders; D017640:Silicates; D017670:Sodium Compounds; D002245:Carbon Dioxide; D007854:Lead; C096707:sodium oxide; C005686:sodium carbonate; D012964:Sodium; C005691:sodium silicate
keywords: Cathode-ray tube; Crystallization; Phase separation; Reduction–melting; Sodium recovery