Correct option is A
The correct answer is (a).
Introduction
Slaked lime (Calcium Hydroxide, Ca(OH)2) is an alkaline substance extensively used to neutralize acidic hazardous wastes.
This neutralization process is most efficiently conducted in a Continuously Stirred Tank Reactor (CSTR) to ensure complete mixing and consistent chemical reactions.
Information Booster
- A Continuously Stirred Chemical Reactor (CSTR) utilizes mechanical agitation to maintain uniform composition and temperature throughout the reaction vessel.
- When slaked lime is introduced to acidic waste streams in a CSTR, it rapidly raises the pH, initiating neutralization.
- This process often results in the precipitation of toxic heavy metals (like lead, copper, or zinc) out of the liquid phase, forming stable, insoluble metal hydroxides.
- The continuous stirring prevents the heavy, dense lime slurry and precipitated solids from settling at the bottom, ensuring maximum chemical contact.
- It is a cornerstone technology in effluent treatment plants (ETPs) for metallurgical and chemical industries.
- The use of lime for sanitation and acid neutralization dates back centuries, but its application in engineered CSTRs scaled up during the industrial revolution.
- An immobilized stirred tank is typically used in biochemical engineering where enzymes or cells are fixed to a substrate; it is not suited for harsh, precipitating chemical neutralizations.
- Fluidized-bed reactors suspend solid fuels or catalysts in upward-flowing gas or liquid, commonly used for combustion or advanced catalytic cracking, not standard acidic liquid neutralization.
- An Air lift fermenter relies on gas injection rather than mechanical impellers for mixing, primarily used in aerobic biological processes (like yeast production), not for heavy chemical waste treatment.
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