Alkali Solution Erodes Shale: Influencing Factors and Structural Damage Characteristics

Table 3

Chemical reaction formula of minerals and sodium hydroxide solution.

Mineral	Chemical reaction formula	References
Quartz	SiO2(s) + NaOH + H2O = NaH3SiO4	[17, 18]
Feldspar	Al2O3 + 2NaOH = 2NaAlO2 + H2O	[8, 19]
	SiO2 + 2NaOH = Na2SiO3 + H2O
Dolomite	CaMg(CO3)2 + 2Na^+ + 2OH^− = CaCO3 + Mg(OH)2 + Na2CO3	[8, 20]
Smectite	A12Si4O10(OH)2 + 10H2O = 2Al(OH)3 + 2Si(OH)4	[21]
	5A12Si4O10(OH)2 + 12Na^+ + 2Al(OH)3 + 12OH^− + 10H2O = 4Na3A13Si5O16·6H2O
Kaolinite	A12Si2O5(OH)4 + 5H2O = 2Al(OH)3 + 2Si(OH)4	[22, 23]
	A12Si2O5(OH)4 + 2Na^+ + 2OH^− + 4Si(OH)4 = 2NaA1Si3O3 + 11H2O
	A12Si2O5(OH)4 + 2Na^+ + 2OH^− + 2Si(OH)4 = 2NaA1Si2O6·H2O + 5H2O
Illite	(K, H3O^+)(Al, Mg, Fe)2[(Si, Al)4O10](OH)2 + OH^− → Al(OH)3 + K^+ + Fe^2+ + Mg^2+ + SiO3^2−	[19]
Chlorite	Y3[Z4O10](OH)2 + Y3(OH)6 + OH^− → Al(OH)3 + Fe^2+ + Fe^3+ + Mg^2+ + B^3+ + SiO3^2− + K^+(Y—Mg, Al, Fe; Z—Si, Al, Fe^3+, B^3+)	[19]
Pyrite	FeS2 + 2OH^− → Fe(OH)2 + SO4^2− + 14e (electrochemical reaction)	[24]