Method for suppressing the leachability of certain metals like tungsten and lead

• Main Authors: STEVENS, HENRY J, MORGAN, RICKY D, LUNK, HANS-JOACHIM
• Format: Patent
• Language: English; French; German
• Published: 17.09.2008
• Subjects: CASTING; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS; CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING ORPROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; FERROUS OR NON-FERROUS ALLOYS; FIRE-FIGHTING; HUMAN NECESSITIES; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; LIFE-SAVING; MAKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; METALLURGY; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLICMATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASSC23 AND AT LEAST ONEPROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25; NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; PERFORMING OPERATIONS; POWDER METALLURGY; PRETREATMENT OF RAW MATERIALS; PRODUCTION AND REFINING OF METALS; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS; WORKING METALLIC POWDER

The interaction of Sn, Sb and Pb with tungsten in contact with an aqueous medium has a synergistic effect in which the leachability of each metal is suppressed. This means that tungsten has the ability to suppress the leachability of these same metals, in particular lead. For example, tungsten may be added to the lead-contaminated soil in order to suppress lead contamination of the ground water by forming lead tungstate which has a very low solubility. The method may also be useful in processing tungsten powder and protecting tungsten metal powder compacts.