What are the four uses of hydrated lime?

The chemical name of hydrated lime is calcium hydroxide,which is a white powdery solid obtained by"digesting"quicklime with water.It is inexpensive and has unique properties.It has been widely used in ancient times and still plays an indispensable role in many fields today.The following are four important and common uses of hydrated lime:
Usage 1:The"Centennial Foundation Stone"of the Construction Industry
This is the ancient and classic use of hydrated lime,mainly used for preparing building mortar.
How to apply:Mix hydrated lime,sand,and water in a certain proportion to form lime mortar.In the past,this was the main material for masonry bricks and wall plastering.
Working Principle:
Good workability:Lime mortar has excellent water retention and plasticity,making it easier for workers to operate and smoother for masonry.
Auto healing:Calcium hydroxide in mortar slowly absorbs carbon dioxide from the air,regenerating strong calcium carbonate and precipitating moisture.This process is called"carbonization",which increases the strength of mortar over time and allows calcium carbonate to precipitate from small cracks,achieving"automatic healing".

Modern development:Although modern ordinary Portland cement mortar has become mainstream,traditional lime mortar still holds an irreplaceable position in ancient building restoration,historical preservation,and some special projects due to its compatibility and breathability.

Usage 2:A versatile player in the field of environmental protection
Hydrated lime is a key chemical agent in wastewater treatment and exhaust gas purification.
Wastewater treatment:
Neutralizing acidic wastewater:Hydrated lime is a strong alkali that can effectively neutralize acidic wastewater discharged from mines,electroplating plants,and chemical plants,preventing pipeline corrosion and water acidification.
Phosphorus removal:It can react with phosphate ions in water to form insoluble calcium phosphate precipitates,thereby removing eutrophic substances from the water and preventing eutrophication.
Sterilization and disinfection:Its alkaline environment can effectively kill pathogens and viruses.

Flue gas desulfurization:In the flue gas treatment of coal-fired power plants and waste incineration plants,hydrated lime slurry is sprayed into the flue gas,which can react with sulfur dioxide(SO₂)in the flue gas to produce calcium sulfate(gypsum),thereby significantly reducing the emission of the main pollutant causing acid rain.

Usage Three:"Soil Doctor"for Agricultural Production
Lime is one of the economical and effective materials for improving acidic soils.
How to apply:Farmers sprinkle hydrated lime powder on fields with high acidity and mix it with the soil through tillage.
Working Principle:
Neutralizing acidity:The alkalinity of hydrated lime can neutralize hydrogen and aluminum ions in the soil,effectively increasing the pH value of the soil and improving soil acidification caused by acid rain or long-term fertilization.
Increasing nutrients:After the soil acidity decreases,nutrients that were originally fixed will be released and become easily absorbed by crops.
Improving structure:It can also promote the formation of soil aggregate structure,making the soil more loose and breathable,which is beneficial for crop root growth and water and fertilizer maintenance.
Usage Four:"Special Additives"for Industry and Food
The use of hydrated lime has also penetrated into some unexpected fields.
Sugar industry:Lime milk needs to be added in the production process of sucrose or beet sugar.It can neutralize organic acids in sugar juice,precipitate impurities,and coagulate colloids for subsequent filtration and purification,thereby producing pure white sugar.

Century egg processing:When making Century egg,soda ash,salt,tea,etc.will be mixed with hydrated lime to form mud,and wrapped around the duck egg.The strong alkaline environment provided by hydrated lime is the key to solidifying proteins,forming unique flavors and patterns.

Disinfection and sterilization:Due to its strong alkalinity,a certain concentration of lime water or lime milk can be used to brush trees,walls of farms,septic tanks,and around sewers,playing a role in sterilization and preventing the spread of pests and diseases.
From buildings that provide shelter for humans from wind and rain,to safeguarding the soil,water,and air that we rely on for survival;From ancient craftsmanship to modern industrial assembly lines,hydrated lime silently serves human society with its simple yet powerful chemical properties.These four uses are just a microcosm of their contributions,truly embodying the scientific charm of"turning decay into magic",and are a truly"treasure"material.