Correct option is C
The correct answer is (c).
Introduction
- Chemical precipitation is a widely utilized chemical treatment method for managing liquid hazardous wastes.
- It involves the addition of chemical reagents to a liquid stream to alter the physical state of dissolved hazardous constituents, forcing them to drop out of solution as solid, settleable particles.
Information Booster
- This process alters the chemical equilibrium, transforming soluble toxic metals (like lead, cadmium, or chromium) into insoluble salts, usually hydroxides or sulfides.
- For example, adding lime (calcium hydroxide) raises the pH and precipitates heavy metals into a sludge that can be physically removed and safely landfilled.
- It is a cornerstone technology in the treatment of highly toxic industrial effluents from electroplating, mining, and battery manufacturing facilities.
- The efficiency of precipitation is highly dependent on precise pH control and the presence of complexing agents.
- The chemical precipitation was one of the earliest engineered methods adopted during the Industrial Revolution to prevent heavy metals from utterly destroying riverine ecosystems.
- Sedimentation (A) is a purely physical treatment method utilizing gravity to settle suspended solids; no chemical alteration occurs.
- Electrodialysis (B) is a physical-chemical membrane process where an electrical potential drives ions through a semi-permeable membrane, primarily used for desalination, not bulk chemical transformation.
- Resin adsorption (D), or ion exchange, is a physical-chemical mass transfer process where pollutants adhere to a solid matrix; it captures ions but does not precipitate them through a chemical reagent reaction.
- For context, the global tightening of clean water acts in the 1970s forced industries to adopt advanced precipitation techniques over mere dilution.
English
10 Questions
20 Marks
12 Mins
