mercury (Hg)

Mercury (Hg) is a heavy metal — the only metallic element liquid at room temperature — used in fluorescent and CFL lamps (2-25 mg per tube), tilt switches in older thermostats and washing machine balance switches, LCD backlight cold-cathode fluorescent lamps (CCFLs), and in some legacy dental and medical devices. Its vapour is highly toxic to the central nervous system; chronic low-dose inhalation causes tremor, irritability, memory impairment and renal damage; bioaccumulation in aquatic food chains converts inorganic mercury to methylmercury, the form responsible for the Minamata Bay disaster (1956) that killed over 1,800 people in Japan.

The global regulatory response is the Minamata Convention on Mercury (2013, in force 2017), to which India is a signatory (signed 2014, ratified 2018). The Convention phases out mercury-added products: most fluorescent lamps for general lighting (compact CFLs, linear T5/T8 fluorescent) face progressive bans starting 2025-2027 in many parties to the Convention; LCD backlight CCFLs are obsolete since LED backlight adoption around 2010; mercury thermometers and sphygmomanometers are phased out in India under the Mercury (Manufacture, Storage and Disposal) regulations. The transition to LED lighting has dramatically reduced mercury volume in the consumer e-waste stream, but the installed base of legacy fluorescent lighting will continue to enter recycling for the next 5-10 years.

Mercury exposure during recycling occurs through three pathways. Mechanical breakage — uncontrolled shredding of fluorescent tubes vaporises mercury into the workshop air at concentrations potentially 100-1000x the occupational limit (0.025 mg/m³ time-weighted average). Acid leaching — hydrometallurgy on PCBs containing mercury switches dissolves mercury into the leach solution, requiring sulphide precipitation and dedicated hazardous waste disposal. Combustion — incinerating lamp fragments in uncontrolled-temperature open burning releases mercury vapour directly to atmosphere; high-temperature incinerators (above 850°C with activated carbon scrubbing) capture 95-99% but require specialised equipment.

For Indian lamp recyclers, the dedicated technology is end-cap crusher with mercury capture — the tube is broken inside a sealed chamber, glass and phosphor are separated, mercury vapour is condensed in a low-temperature trap (sulphur-impregnated activated carbon at 0-5°C captures 99%+), and recovered mercury is bottled for storage or controlled disposal. A standard unit handles 500-2,000 tubes per hour at capex Rs 30-80 lakh. Recovered mercury is hazardous waste; India has no domestic mercury reuse market (Minamata phase-out), so storage at TSDF or export to a hazardous-waste incinerator (CPCB-approved overseas, since India has no high-temperature mercury incinerator) is the disposal pathway. The Toxics Link 2018 report on lamp recycling in India estimated only 1-2% of fluorescent tubes are processed through dedicated recovery; the remainder break in dustbins, sweepers' carts or municipal landfills, exposing waste workers and groundwater.