Aluminum hydroxide and hydrochloric acid

Hydrochloric acid is an aqueous solution of hydrogen chloride and is a strong acid. Hydrochloric acid is also a strong reducing agent that reacts with oxides and reduces metal ions. Aluminum hydroxide is the hydroxide of aluminum and has amphoteric reaction. Aluminum hydroxide is alkaline when it reacts with acid and acidic when it reacts with strong acid to produce aluminum and water. Next, let's take a closer look at the reaction between aluminum hydroxide and hydrochloric acid.

1. Reaction of aluminum hydroxide with acid: Al(OH)3+3HCl → AlCl3+3H2O

Al(OH)3+3H+ →Al3++3H2O

2. Production method

Alkaline solution is added to aluminum sulfate solution under stirring to generate precipitate which is then washed, filtered, low-temperature dried and crushed to obtain the finished product. The dehydrated paste can also be used directly as a product. The concentration, temperature, reaction temperature control, and drying temperature of the solution during preparation affect the product quality.

Aluminum sulfate is produced by reacting sulfuric acid with aluminum powder or aluminum ash, and then undergoes double decomposition reaction with ammonium bicarbonate to produce aluminum hydroxide. Alternatively, sodium aluminate solution and aluminum sulfate solution are neutralized to pH 6.5 to generate aluminum hydroxide precipitate, which is then washed with water, filtered, dried at 70-80°C, and crushed to obtain aluminum hydroxide. Its reaction formula:

3. Alumina has:

(1) Blowing carbon dioxide into a sodium aluminate aqueous solution at 40-60°C and pH>12; placing the sodium aluminate aqueous solution at room temperature without or with alumina seed;

(2) Al(OC2H5)3 and 1% to 20% ethanolamine NH2C2H4OH coexist, hydrolyze at 20 to 60°C, and mature the resulting gel for several months.

4. Bayerite has:

1) Blowing carbon dioxide into the sodium aluminate aqueous solution at room temperature;

2) Aluminum amalgam hydrolyzes at room temperature;

(3) Al(OC2H5)3 hydrolyzes below 70°C;

(4) A method in which an aqueous solution of aluminum chloride is neutralized with an alkali metal hydroxide or ammonia. Boehmite can be prepared by hydrothermally treating aluminum hydroxide in an aqueous solution of aluminum hydroxide or a weak alkaline aqueous solution at 150-300°C; aluminum amalgam can be oxidized with boiling water, etc. The stable range of diaspore is 275-425℃, and the water vapor pressure is above 140atm (1atm=98.066kPa). It is reported that diaspore can be obtained by hydrothermal treatment of aluminum hydroxide, or by hydrothermal treatment of ρ alumina and χ alumina produced by vacuum dehydration of diaspore.

Laboratory preparation

Chemical equation: 2Al+3H2SO4 (dilute) = Al2(SO4)3+3H2↑

2Al+2NaOH+6H2O=2Na[Al(OH)4]+3H2↑

Al2(SO4）3+6Na[Al(OH)4]+12H2O=8Al(OH)3↓+3Na2(SO4） or

Al2(SO4）3+6NH3.H2O=2Al(OH)3↓+3(NH4）2SO4

Ionic formula: 2Al+6H+=2Al3++3H2↑

2Al3++2OH-+6H2O=2[Al(OH)4]-+3H2↑

Al3++3[Al(OH)4]-+6H2O=4Al(OH)3↓

Or Al3++3NH3·H2O=Al(OH)3↓+3NH4+

①Al(OH)3 is an amphoteric hydroxide, which can react with both strong acids and strong bases at room temperature:

Al(OH)3+3HCl=AlCl3+3H2O Al(OH)3+3H+=Al3++3H2O

Al(OH)3+NaOH=Na[Al(OH)4] Al(OH)3+OH－=[Al(OH)4]－

②Al(OH)3 is easily decomposed into Al2O3 when heated: 2Al(OH)3==Al2O3+3H2O (rule: insoluble alkali will decompose when heated)

③ Preparation of Al(OH)3:

a. Prepare Al(OH)3 by reacting soluble aluminum salt with ammonia water

AlCl3+3NH3·H2O=Al(OH)3↓+3NH4Cl

Al2(SO4）3+6NH3·H2O=2 Al(OH)3↓+3(NH4）2SO4（Al3++3NH3·H2O=Al(OH)3↓+3NH4+）

Because strong alkali (such as NaOH) easily reacts with Al(OH)3, the laboratory does not use strong alkali to prepare Al(OH)3, but uses ammonia water.

b. Sodium tetrahydroxyaluminate reacts with excess carbon dioxide

Na[Al(OH)4]+CO2(over)=NaHCO3+Al(OH)3↓

Excess carbon dioxide does not react with aluminum hydroxide, ensuring that all [Al(OH)4]- is converted into aluminum hydroxide