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Original, impacts, abatement and management

Chromium. Original, impacts, abatement and management. Content. 1. Original and Impact Chromium emission through industry go to air, water, soil (region matter) Human health effect 2. Management and Abatement Regulation (emission standard) Source reduction Treatment.

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Original, impacts, abatement and management

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  1. Chromium Original, impacts, abatement and management

  2. Content 1. Original and Impact Chromium emission through industry go to air, water, soil (region matter) Human health effect 2. Management and Abatement Regulation (emission standard) Source reduction Treatment

  3. 1. Original and Impact Chromium Chemistry • Chromium can exist in oxidation state ranging from -2 to +6 • Chromium most frequently found in +3, +6

  4. Industrial Sources US EPA defines 27 industrial sources of Chromium • Textiles • Electroplating • Organic chemicals • Inorganic chemicals • Petroleum refining • Iron and steel manufacturing • Nonferrous metal manufacturing • Steam electric • Ferroalloy • Leather tanning and finishing • Rubber • Timber products processing • Metal finishing • Nonferrous metals forming • Mineral mining • Paving and roofing • Paint formulating • Ink formulating • Gum and wood • Carbon black • Battery manufacturing • Coil coating • Porcelain enameling • Aluminum forming • Copper forming • Electrical and electronic components. • Asbestos

  5. Impacts Emission pathway Atmosphere: mostly as fine dust, particles as Cr+6 from electroplating as Cr+3 from combustion, ore processing, settle over land and water. Surface waters: Electroplating leather tanning, and textile industries Most Cr(+3) insoluble and settle down Cr (+6) soluble but then reduce to Cr (+3) Soil: Disposal of chromium- products, coal ash from electric utilities etc… Cr (+3) mostly as insoluble carbonate and oxide immobile Its solubility may increase when organic matters available

  6. Human health impact • Chromium (III) is much less toxic than Chromium (VI) , major target organ = respiratory tract by inhalation exposure Acute effect • Inhalation: - Irritation and ulceration of the nasal septum - Respiratory sensitization (asthma) etc. • Ingestion: - Gastrointestinal effects (abdominal pain, vomiting, and hemorrhage) - Affect kidney & liver function etc. • Dermal contact: Skin burns etc. Chronic effect • Inhalation: Perforations and ulcerations of the septum, bronchitis, pneumonia, asthma, etc. • Ingestion: Gastrointestinal effects etc. • Dermal contact: Contact dermatitis, sensitivity, and ulceration of the skin etc. Cancer risk:EPA has classified chromium (VI) as a Group A, known human carcinogen by the inhalation route of exposure.

  7. 2. Management and Abatement Regulation and standard AMBIENT AIR QUALITY STANDARD US EPA • The maximum 24‑hour Total Chromium concentration at any location≤ 0.3 µg/m3 • The annual geometric mean of the Total Chromium concentrations at any location≤ 0.05 µg/m3 WATER QUALITY STANDARD US EPA • Drinking Water (MAC) ≤ 0.05 mg/l • Bottled Drinking Water (MAC)≤ 0.05 mg/l SOIL QUALITY STANDARD US EPA • For habitat and agriculture≤ 300 mg/kg NOTE:MAC= Maximum Allowable Concentration These standard only used for Hexavalent Chromium

  8. AIR EMISSION STANDARDUS EPA Regulation and standard WASTEWATER EMISSION STANDARD US EPA NOTE:These emission standard only used for Chromium Plating Industry

  9. Source reduction Recycle Treat Dispose Pollution Prevention Source reduction Product change Process change • Input material changes • Technology change • Improved operating practice

  10. Electroplating industries

  11. Source reduction Electroplating Alternative Nickel plating, Chemical Vapor Deposition, Surface Hardening, Thermal Spraying, Physical Vapor Drag-out Reduction: Use optimum temperature, chemical concentration, Use drain board, Space Chromium recover Evaporate, Reverse osmosis Good surface prepare:Surface clean, dry Process Bath Maintenance:Remove bath contaminant by filtration etc…. Oil, water, sludge, degreaser Water, heat caustic soda, Degrease Alkaline Water Water Rinse Water Water, NaOH, heat Anodic Cleaning Waste water Wet scrubber … Mist of Cr+6 Water, Chromic acid, sulfate, fluoride, Chromium bath Waste water Waste water Cr+6 Sludge Rinse 1 Water Waste water Cr+6 Rinse 2 Waste water Cr+6 Water …

  12. Treatment technologies Wastewater • Physical treatment Membrane technologies, carbon adsorption, filtration, ion exchange and sedimentation etc,. • Chemical treatment Chemical oxidation, chemical precipitation, chromium reduction, coagulation and flocculation. • Biological treatment Using specific microorganisms Air(mist, dust) Using wet scrubber • Sludge (management as hazardous waste) • using precipitation with lime as reducing agent • incineration : Cr(3) to oxide form

  13. Treatment technologies Chemical precipitation • Conversion of Chrome from Cr (VI) to Cr (III) that is insoluble at higher pH levels and easy to remove from water (by precipitation or physical / chemical methods). • Using SO2 , NaHSO3 , Na2S2O5 , etc. as reducing agents Stage 1: 3SO2 + 2H2Cr2O4 + 3H2O Cr2(SO4)3 + 5H2O Stage 2: Cr2(SO4)3 + 3Ca(OH)22Cr(OH)3 + 3CaSO4

  14. Treatment technologies Chromium waste treatment using chemical precipitation in Electroplating industry

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