Materials synthesized from coal gangue and their heavy metal adsorption performance.

Material	Raw material	Heavy metal ion	Maximum adsorption capacity (mg g−1)	Ref.
NaX zeolite	Coal gangue	Cu2+	45.1	53
		Co2+	44.5
NaX zeolite	Coal gangue	Cd2+	38.6	50
Coal gangue microspheres	Coal gangue	Cu2+	6.5	57
		Pb2+	18.9
Hollow gangue microsphere/geopolymer	Hollow gangue microspheres, geopolymer matrix	Cu2+	17.5	58
		Cd2+	18.2
		Zn2+	14.3
		Pb2+	138.8
Zeolite-activated carbon composite	Coal gangue, bamboo	Cu2+	104.9	55
Coal–analcime composite	Coal gangue, coal	Pb2+	268	56
Zeolite-activated carbon	Coal gangue, coal	Cu2+	111.3	54